ccm/sff-papers · Datasets at Hugging Face

['Eiamsa-ard, Kunnayut', 'Nair, Hari Janardanan', 'Ren, Lan', 'Ruan, Jianzhong', 'Sparks, Todd', 'Liou, Frank W.']

2020-02-24T15:12:39Z

8/3/05

Mechanical Engineering

null

['https://hdl.handle.net/2152/80079', 'http://dx.doi.org/10.26153/tsw/7100']

eng

2005 International Solid Freeform Fabrication Symposium

Open

Gas Tungsten Arc Welding

Part Repair using a Hybrid Manufacturing System

Conference paper

https://repositories.lib.utexas.edu//bitstreams/ca2d785e-91d6-476b-b017-d49f48daf254/download

null

Nowadays, part repair technology is gaining more interest from military and industries due to the benefit of cost reducing as well as time and energy saving. Traditionally, part repair is done in the repair department using welding process. The limitations of the traditional welding process are becoming more and more noticeable when the accuracy and reliability are required. Part repair process has been developed utilizing a hybrid manufacturing system, in which the laser aided deposition and CNC cutting processes are integrated. Part repair software is developed in order to facilitate the users. The system and the software elevate the repair process to the next level, in which the accuracy, reliability, and efficiency can be achieved. The concept of repair process is presented in this paper. Verification and experimental results are also discussed.

null

['Grose, J.', 'Liao, A.', 'Tasnim, F.', 'Foong, C.S.', 'Cullinan, M.A.']

2024-03-26T20:08:29Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124387', 'https://doi.org/10.26153/tsw/50995']

en_US

2023 International Solid Freeform Fabrication Symposium

Open

['microscale selective laser sintering', 'heat zones', 'additive manufacturing']

PART SCALE SIMULATION OF HEAT AFFECTED ZONES FOR PARAMETER OPTIMIZATION IN A MICROSCALE SELECTIVE LASER SINTERING SYSTEM

Conference paper

https://repositories.lib.utexas.edu//bitstreams/19f30244-c06c-40a1-b18a-9c1c76fb04e1/download

University of Texas at Austin

The Microscale Selective Laser Sintering (μ-SLS) system can produce feature sizes on the order of a single micrometer, far smaller than existing metal additive technologies. Despite this advantage, there are challenges in producing reliable small-scale parts due to unwanted heat transfer in the nanoparticle bed. To address this issue, a multiscale Finite Element thermal model has been developed to predict the temperature changes that occur during sintering within the particle bed. Nanoscale particle models are used to quantify material property changes experienced by particle groups that undergo laser sintering. This work processes the property relationships developed by the particle models and integrates comprehensive property functions into the partscale model to capture the nuanced thermal evolution that occurs during sintering. The multiscale model predicts the extent of heat spread and part formation during sintering to optimize input laser parameters, reduce unwanted heat spread, and improve the minimum feature resolution of printable parts.

null

['Peng, Hao', 'Go, David B.', 'Billo, Rick', 'Gong, Shan', 'Ravi Shankar, M.', 'Aboud Gatrell, Bernice', 'Budzinski, Joseph', 'Ostiguy, Pierre', 'Attardo, Ross', 'Tomonto, Charles', 'Neidig, Joel', 'Hoelzle, David']

2021-10-26T19:15:12Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89561

eng

2016 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'DMLS', 'thermal distortion', 'thermal stress', 'part orientation', 'support structure', 'quasi-static loading']

Part-Scale Model for Fast Prediction of Thermal Distortion in DMLS Additive Manufacturing Part 2: A Quasi-Static Thermomechanical Model

Conference paper

https://repositories.lib.utexas.edu//bitstreams/851e07fe-5648-437b-82de-7db495fdb7ba/download

University of Texas at Austin

The direct metal laser sintering (DMLS) additive manufacturing process can quickly produce complex parts with excellent mechanical properties. However, thermal stress accumulated in the layer-by-layer build cycles of DMLS may induce part distortion and even cause the failure of the whole build process. This paper is the second part of two companion papers that present a part-scale model for fast prediction of temperature history and part distortion in DMLS. In this paper, a quasi-static thermomechanical (QTM) model is built to estimate the thermal distortion of entire parts in DMLS. Firstly, the thermal contraction in each build cycle is modeled as a quasi-static loading process; the final thermal stress accumulated in the parts is the superposition of thermal stress generated in each build cycle. Secondly, the stress relaxation process after the parts are cut off from the substrate is modeled, and final distortion of the parts is predicted with thermal stress calculated from the thermal contraction processes. In comparison to existing transient thermomechanical models, the QTM can predict thermal distortion in DMLS with much faster computational speed, and a comparison against experiment shows less than 10% error.

null

['Johnston, Scott', 'Anderson, Rhonda', 'Storti, Duane']

2019-11-21T18:25:31Z

2003

Mechanical Engineering

null

['https://hdl.handle.net/2152/78558', 'http://dx.doi.org/10.26153/tsw/5614']

eng

2003 International Solid Freeform Fabrication Symposium

Open

Steel Components

Particle Size Influence Upon Sintered Induced Strains Within 3DP� Stainless Steel Components

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5fff2f6b-f754-4851-83ba-d93f5abbaa7e/download

null

Three-dimensional printing (3DP™ 1 ) is a layer-by-layer manufacturing process whereby a three-dimensional (3D) component is created by the distribution of a liquid binder onto a powder media. A 3DP™ process using stainless steel powder as its printing media requires post-printing thermal processing for debinding and sintering of the printed green component. To minimize dimensional distortion while increasing structural integrity of the green component, 3DP™ thermal post-processing is designed to produce only neck growth between particles, defined as initial stage sintering. The accepted theoretical model governing initial stage sintering strain for spherical powder particles provides a qualitative account of strain development with respect to time and temperature variance; however, the model does not produce an accurate quantitative account for the magnitude of the strain when compared to dimensional experimental results. The theoretical model indicates that powder particle size is the dominant parameter governing sintering strain. The purpose of this study is to introduce an effective particle size into the theoretical model, thus enabling the application of the theoretical model to estimate dimensional change for components produced by 3DP™. Dimensional sintering experimentation has been performed using 3DP™ test specimens with spherical powder particles having mean diameters of 20 Pm, 80 Pm, and 200 Pm. Experimental results and progress on the theoretical model are discussed.

Financial support for this work is provided by the Office of Naval Research, Contract #N00014-C-00-0378.

null

['Sellers, R.', 'Gould, B.', 'Wolff, S.']

2021-12-06T23:17:52Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90713', 'http://dx.doi.org/10.26153/tsw/17632']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'directed energy deposition', 'Ti-6Al-4V', 'x-ray imaging', 'thermal imaging', 'molybdenum', 'surface energy']

Particle-Melt Pool Interactions in Multi-Material Laser Based Directed Energy Deposition

Conference paper

https://repositories.lib.utexas.edu//bitstreams/ec057e63-1558-4e2d-a9ec-ffa02f738b85/download

University of Texas at Austin

Laser based metal directed energy deposition (DED) is an additive manufacturing process that is currently on the rise in the industry. However, there is still a knowledge gap in the understanding of fundamental interactions between particles and the melt pool in the DED process and how to change the parameters to alter microstructure. This work utilized synchronized in-situ thermal and X-ray imaging to understand the anomalous behavior of molybdenum powder binding onto a Ti-6Al-4V substrate as fundamental understanding for layer-by-layer processing. Using these visual techniques, particle velocity, mass, surface energy, kinetic energy, contact area, and temperature were observed and calculated. The correlation is shown and recorded to understand the wettability of particles and why some will bounce off of the substrate while others enter the melt pool. This work will allow for the manipulation of particle-melt pool interactions in DED which will help reproduce and build better parts more efficiently

null

['Moser, D.', 'Cullinan, M.', 'Murthy, J.']

2021-10-26T18:42:10Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89553

eng

2016 International Solid Freeform Fabrication Symposium

Open

['melt modeling', 'selective laser melting', 'discrete element model', 'powder particles']

Particle-Scale Melt Modeling of the Selective Laser Melting Process

Conference paper

https://repositories.lib.utexas.edu//bitstreams/85151f2f-d375-4bb0-842e-3d13f94b88c5/download

University of Texas at Austin

In this work, a melting model is developed and implemented to simulate the melting of powder particles for Selective Laser Melting (SLS). A hybrid continuum-discrete methodology is used to model the melting process. A Discrete Element Model (DEM) is used to generate random packing structures of spherical particles. These structures are then placed on top of a background mesh in the OpenFOAM finite volume library. The radiation transport equation (RTE) is solved on the mesh to simulate the effect of laser heating. Heat sources generated by the RTE are introduced into the energy equation, which is also solved on the mesh. Once particle melting occurs, the resulting flow is solved for on the mesh. Computation of properties in the mesh cells is accomplished using volume averaging between the solid, liquid, and background gas phases. The resulting total melt pool depth and width is calculated and results compared against previously published experimental results and good agreement is obtained. Relations are then developed for the melt fraction of the powder as a function of the average temperature of the powder. These relations can be used as bulk properties in the enthalpy model for part-scale simulations.

null

['Narahara, Hiroyuki', 'Kawaguchi, Shinichiro', 'Suzuki, Hiroshi']

2019-10-23T15:03:35Z

2002

Mechanical Engineering

null

['https://hdl.handle.net/2152/76753', 'http://dx.doi.org/10.26153/tsw/3842']

eng

2002 International Solid Freeform Fabrication Symposium

Open

Stereolithography

Parts Design and Manufacturing Process Support System Based on Stereolithography Manufacturing Knowledge Database

Conference paper

https://repositories.lib.utexas.edu//bitstreams/20b73d3a-8a66-41ce-8b1c-6016905470b1/download

null

Although rapid prototyping technology has a strong point that complex parts can be manufactured easily, it is difficult to satisfy further higher precision if designer isn't familiar with the technological know-how of the manufacture. This research aims to develop a design support system for realizing higher precision of RP easily in consideration of manufacturing know-how. The function of this system is as follows: the knowledge of manufacturing know-how such as the preferred manufacturing direction for higher precision is stored in database. The complex shape of solid form is analyzed in the middle of design stage, and then preferred manufacturing processes or compositions are advised by this system.

null

['Chen, Xi', 'Zhang, Haiou', 'Hu, Jiannan', 'Xiao, Yu']

2021-11-18T18:18:38Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90454', 'http://dx.doi.org/10.26153/tsw/17375']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['infrared thermography', 'stack temperature field', 'pixel width curve', 'defect detection', 'wire arc additive manufacturing']

A Passive On-Line Defect Detection Method for Wire and Arc Additive Manufacturing Based on Infrared Thermography

Conference paper

https://repositories.lib.utexas.edu//bitstreams/789b20d5-44ce-486c-8899-859e72bff663/download

University of Texas at Austin

According to the additive manufacturing process, this paper comes up with a passive infrared thermography non-destructive testing method based on the stack temperature field and pixel width curve. The temperature field of the arc-melting layer is collected in real-time, and the multi-frame temperature data stream is stacked for maximum value, and the region where the maximum value is greater than 800 °C is intercepted to obtain the current molten layer profile. The AlexNet model is used to classify the profile of molten layers, such as normal, deviation, flow and hump. Determine whether the current layer has a shape defect based on the model and the pixel width curve and the processing such as milling and repair welding will be taken in time. This method detects in real-time during the manufacturing process which will cause irreversible losses, and the current layer detection information is also the basis for adjusting the processing parameters of the next layer and realizes the closed-loop feedback of the additive manufacturing process.

null

['Geuy, Michael', 'Martin, Jay', 'Simpson, Timothy', 'Meisel, Nicholas']

2024-03-26T20:10:36Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124388', 'https://doi.org/10.26153/tsw/50996']

en_US

2022 International Solid Freeform Fabrication Symposium

Open

['robotic material extrusion', 'non-planar', 'additive manufacturing']

PATH PLANNING FOR NON-PLANAR ROBOTIC ADDITIVE MANUFACTURING

Conference paper

https://repositories.lib.utexas.edu//bitstreams/b76e63c0-fb07-46a6-980f-28c5b3965e90/download

University of Texas at Austin

As material extrusion additive manufacturing continues to mature, there is increasing need for an extrusion path planning (“slicing”) method that takes full advantage of the abilities of manydegree-of-freedom systems like those used in Robotic Material Extrusion (RoMEX). These systems can create engineering parts with complex geometries and improved mechanical properties by utilizing non-planar curved layers, part-region-specific extrusion parameters, and support-free printing. This paper explores the application of 3D surfaces (demonstrated here with an upward pointing cone) as the basis of non-planar layer generation without the need to decompose the object into regions. Creation of these toolpaths incorporates key principles from planar, multi-planar, and active-Z path generation methods with attention paid to variable layer thickness, extrusion angle control, and overhang angle. The primary result of this work is a method for the generation of curved extrusion paths forming layers of arbitrary shape for arbitrary part geometry, based on a novel combination of existing best practices present throughout the available literature.

null

['Frank, Matthew C.', 'Joshi, Ashish', 'Anderson, Donald D.', 'Thomas, Thaddeus P.', 'Rudert, M. James', 'Tochigi, Yuki', 'Marsh, J. Lawrence', 'Brown, Thomas D.']

2021-10-01T00:28:23Z

2010

Mechanical Engineering

null

['https://hdl.handle.net/2152/88309', 'http://dx.doi.org/10.26153/tsw/15250']

eng

2010 International Solid Freeform Fabrication Symposium

Open

['rapid machining', 'rapid prototyping', 'bone implants', 'surface texturing']

Patient-Specific Bone Implants using Subtractive Rapid Prototyping

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5dcf002c-7b7d-4e7e-8fe1-8eb5d1442222/download

null

This research involves the development of rapid manufacturing for patient-specific bone implants using a Subtractive Rapid Prototyping process. The geometry of segmental defects in bone, resulting from traumatic injury or cancerous tumor resection, can be reverse-engineered from medical images (such as CT scans), and then accurate defect fillers can be automatically generated in advanced synthetic or otherwise bioactive/biocompatible materials. This paper presents a general process planning methodology that begins with CT imaging and results in the automatic generation of process plans for a subtractive RP system. This work uniquely enables the rapid manufacturing of implant fillers with several key characteristics including; suitable bio-compatible materials and custom surface characteristics on specified patches of the filler geometry. This work utilizes a PLY input file, instead of the more common STL, since color texture information can be utilized for advanced process planning depending on whether the surface is fracture, periosteal or articular in origin. The future impact of this work is the ability to create accurate filler geometries that improve initial fixation strength and stability through accurate mating geometry, fixation planning and inter-surface roughness conditions. Keywords: Rapid Machining, Rapid Prototyping, Bone Implants, Surface Texturing

null

['Himmer, T.', 'Stiles, E.', 'Techel, A.', 'Beyer, E.']

2020-02-20T19:37:32Z

2005

Mechanical Engineering

null

https://hdl.handle.net/2152/80042

eng

2005 International Solid Freeform Fabrication Symposium

Open

Precise Cast Prototyping

PCPro a Novel Technology for Rapid Prototyping and Rapid Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5973798d-595a-4c02-bb1c-d470d020c73d/download

null

PCPro stands for Precise Cast Prototyping, which is a combination of casting technologies and milling. This method was developed at Fraunhofer IWS in Dresden, Germany. It is patented in Germany [1] and is applied in the USA under US 10/794,936. The main goal for this development was to shorten the process chain for making plastic prototypes accompanied by higher quality. The casting technology was integrated in a machining center in order to enable a high degree of automation and to avoid an external casting system. This means that Rapid Manufacturing can be easily implemented using such an automated combination of casting and machining. This article describes the PCPro method by means of the fabrication of sample parts. The advantages and the limitations in comparison to common Rapid Prototyping and Rapid Manufacturing process chains will be discussed. In addition, the manufacturing of a prototype machine is presented.

null

['Luo, M.', 'Tian, X.', 'Shang, J.', 'Zhu, W.', 'Li, D.']

2021-11-11T15:33:23Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90221', 'http://dx.doi.org/10.26153/tsw/17142']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['PEEK', 'interlaminar shear strength', 'crystallinity', 'laser device', 'heat treatment', 'in-situ', 'fused deposition modeling']

PEEK High Performance Fused Deposition Modeling Manufacturing with Laser In-Situ Heat Treatment

Conference paper

https://repositories.lib.utexas.edu//bitstreams/97730456-cd5c-4b4d-986d-2fb757658379/download

University of Texas at Austin

Because of the thermal resistance, high mechanical properties, biocompatibility, PEEK have increasingly extended their application in medicals, aircraft, industrial fields and so on. In FDM, a low crystallinity can be got to limit volume contraction to avoid weak interlaminar bonding, which results in the conflict between high interlaminar bonding and crystallinity. In this study, a CO2 laser device was adopted to improve both the interlaminar shear strength and the crystallinity of PEEK part synchronously in FDM. A series of test was then successively implemented. And after the observation and the analysis of the results, an obvious improvement was got that its interlaminar shear strength could improve over 45%, while its crystallinity could improve over double times for PEEK. Additionally, the process suggests a much potential in developing the gradient distribution of the crystallinity or stiffness in multi-function integration manufacturing for PEEK-like semi-crystalline materials.

null

['Seppälä, J.', 'Rockel, D.', 'Hupfer, A.']

2021-10-18T20:08:46Z

2014

Mechanical Engineering

null

https://hdl.handle.net/2152/89226

eng

2014 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'design method', 'aircraft engine', 'aircraft engine components']

Performance and Functionality Based Design Methods for Improved and Novel Aircraft Engine Components for Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/9a11931a-e8d3-4eea-a9a8-9a2d9cd9d995/download

University of Texas at Austin

For aircraft engine manufacturers the technology of AM appears promising. AM provides the opportunity for a highly flexible and a cost effective part production. Furthermore AM offers new potentials and possibilities for lightweight designs. The implementation and applications of AM can be divided in three different strategic application levels. The first level includes manufacturing simple existing parts; these kinds of parts are already in production. In the second level, new design tools, such as structural optimization, are used to improve an existing part by benefiting from the new design freedom but without changing its functionality. The third level includes novel parts with new functionality. This paper presents design methods for AM parts for the second and third level: performance and solution based approach, respectively. Also the safety classification of engine parts is looked into. Step-by-step design methods are presented, accompanied by case studies that demonstrate improvement to the initial design: a light weight, topology optimized turbine guide vane (level two) and an aircraft engine casing design that has an improved tip clearance behavior under transient operating cycles (level three).

null

['Lane, B.', 'Grantham, S.', 'Yeung, H.', 'Zarobila, C.', 'Fox, J.']

2021-11-03T21:54:08Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89944

eng

2017 International Solid Freeform Fabrication Symposium

Open

['process monitoring', 'sensors', 'metrology testbed', 'additive manufacturing', 'National Institute Standards and Technology', 'NIST']

Performance Characterization of Process Monitoring Sensors on the NIST Additive Manufacturing Metrology Testbed

Conference paper

https://repositories.lib.utexas.edu//bitstreams/7fc4b220-4e14-477d-b545-6fd3da83b43c/download

University of Texas at Austin

Researchers and equipment manufacturers are developing in-situ process monitoring techniques with the goal of qualifying additive manufacturing (AM) parts during a build, thereby accelerating the certification process. Co-axial melt pool monitoring (MPM) is one of the primary in-situ process monitoring methods implemented on laser powder bed fusion (LPBF) machines. A co-axial MPM system is incorporated on the Additive Manufacturing Metrology Testbed (AMMT) at the National Institute of Standards and Technology (NIST); a custom LPBF and thermophysical property research platform where one of many research goals is to advance measurement science of AM process monitoring. This paper presents the methods used to calibrate and characterize the spatial resolution of the melt pool monitoring instrumentation on the AMMT. Results from the measurements are compared to real melt pool images, and analysis is provided comparing the effect on spatial resolution limits on image analysis.

null

['Bitragunta, Venkata Sivaram', 'Sparks, Todd', 'Liou, Frank']

2021-10-20T20:19:39Z

2015

Mechanical Engineering

null

https://hdl.handle.net/2152/89352

eng

2015 International Solid Freeform Fabrication Symposium

Open

['blown direct metal deposition process', 'perturbation frequency', 'disk feeders', 'deposit quality', 'surface roughness']

Performance Metric for Powder Feeder Systems in Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/a4134f18-1bc5-49ca-a375-e1803860f1b7/download

University of Texas at Austin

null

This paper describes experiments that were carried out to determine the significance between measured surface roughness values of the deposits over theoretically calculated performance metric values.

null

['Jarrett, David O.', 'Gibert, James M.', 'Fadel, Georges M.']

2021-10-05T19:55:21Z

2012

Mechanical Engineering

null

['https://hdl.handle.net/2152/88421', 'http://dx.doi.org/10.26153/tsw/15360']

eng

2012 International Solid Freeform Fabrication Symposium

Open

['ultrasonic additive manufacturing', 'metal matrix composites', 'steel wire reinforcements', 'aluminum matrix']

Performance of Stainless Steel AlSi 304 Wire Reinforced Metal Matrix Composites Made Using Ultrasonic Additive Manufacturing in Bending

Conference paper

https://repositories.lib.utexas.edu//bitstreams/bfcc0cbf-c171-48a7-a69f-35e85859ade3/download

University of Texas at Austin

Ultrasonic additive manufacturing (UAM) is a solid-state additive and subtractive manufacturing process that utilizes ultrasonic energy to produce layered metallic parts. The process is easily extended to create advanced multi-material structures, e.g., metal matrix composites, functionally graded metallic components, and shape memory alloys. This research utilizes a three point bending test to compare the elastic modulus in metal matrix composites (MMC’s) specimens consisting of stainless steel wire reinforcements with an aluminum matrix to unreinforced test specimens; both specimens are produced by UAM. In the MMC the volume fraction of wire is relatively low, 0.77%, yet yields an average increase in modulus of 8.9%.

null

['Yuan, Xiao', 'Zhang, Jing', 'Zahiri, Behnam', 'Khoshnevis, Behrokh']

2021-11-01T22:05:21Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89773

eng

2016 International Solid Freeform Fabrication Symposium

Open

['contour crafting', 'additive manufacturing', 'sulfur concrete', 'space colonization']

Performance of Sulfur Concrete in Planetary Applications of Contour Crafting

Conference paper

https://repositories.lib.utexas.edu//bitstreams/68a911f7-14a9-4638-9444-fb0fea81bbe1/download

University of Texas at Austin

Sulfur concrete is a high potential composite material which meets NASA’s ISRU (In-Situ Resource Utilization) requirements for some Lunar and most Martian structure construction by means of Contour Crafting (CC). The performance of sulfur concrete is sensitive to its ingredients and to the variables in the thermal process used for applying the material. The sulfur concrete extrusion process is implemented on a mini-scale auger extruder and a novel full-scale extruder. An experiment is designed to study the factors that influence the workability of sulfur concrete. The research result may be instrumental for improving the workability of sulfur concrete, which also has significant terrestrial applications.

null

['Marchal, V.', 'Peryaut, F.', 'Zhang, Y.', 'Labed, N.']

2021-12-07T17:47:46Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90734', 'http://dx.doi.org/10.26153/tsw/17653']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['continuous fiber printing', 'periodic homogenization', 'elastic properties']

A Periodic Homogenization Model Including Porosity to Predict Elastic Properties of 3D-Printed Continuous Carbon Fiber-Reinforced Composites

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6b65890f-e579-4801-bbe5-a0f17124286d/download

University of Texas at Austin

Adding continuous carbon fiber into the Fused Filament Fabrication (FFF) process is critical to get reinforced composite structures with improved mechanical properties. However, it remains difficult for the designer to create optimized complex composite structures. Indeed, performing numerical simulations on these materials require to know their elastic coefficients, which are difficult to determine. Using a model of periodic homogenization which considers both the fiber content and the porosity, would be a quick solution to predict the mechanical properties of the printed composite. Based on material studies and validated mechanical tests, this simulation model allows the use of a homogeneous material to replace the composite material for the finite element analysis. This will greatly reduce the number of elements required in the model, leading to a big decrease of the computation cost. Hence, the numerical model has potential to perform simulation-driven design processes, such as generative design.

null

['Shigueoka, M.O.', 'de M. Junqueira, S.L.', 'Alves, T.A.', 'Volpato, N.']

2021-11-30T21:37:01Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90557', 'http://dx.doi.org/10.26153/tsw/17476']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['porous media', 'permeability', 'material extrusion']

Permeability Analysis of Polymeric Porous Media Obtained by Material Extrusion Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d9686b1b-9e1c-45ed-85d2-14360a3d9a7d/download

University of Texas at Austin

Porous media (PM) are used in many applications, and their geometry and hydraulic properties are essential in flow analysis, especially in geology (oil and gas) and medical (tissue engineering) applications. Additive Manufacturing (AM) enables the production of planned porosity and the material extrusion AM allows working with process parameters to produce lattice type geometries, without the need to have a 3D model of the internal porous structure. This work presents a preliminary study on the permeability of some PM designs obtained in PLA using an in-house process-planning software. Two main filling variations of the raster strategies were studied, one considering the displacement of staggered layers and the other involving a new joined filaments proposal. The permeability obtained experimentally is compared with numerical outputs. The results indicate that both filling strategies influence the PM permeability, but this was more significant with the joined filaments approach.

null

['Yardimci, M. Atif', 'Guceri, Selcuk I', 'Danforth, Stephen C.']

2018-10-10T15:50:28Z

1995

Mechanical Engineering

doi:10.15781/T2NV99W2B

http://hdl.handle.net/2152/68757

eng

1995 International Solid Freeform Fabrication Symposium

Open

['FDM', 'stereolithography', 'laser-based methods']

A Phenomenological Numerical Model For Fused Deposition Processing of Particle Filled Parts

Conference paper

https://repositories.lib.utexas.edu//bitstreams/11db4dba-a999-4e4c-9eb9-fa2a30d6ad37/download

null

Fused Deposition ModelingTM utilizes the simple idea of melting, extrusion and resolidification of thermoplastic filaments. The introduction of particulate materials, especially ceramics and metals, will widen the range of capabilities of the process. The present study is directed to the development of a family of numerical models for the FDM and Fused Deposition of Ceramics processes. These models in turn would help to predict the operation windows of the FDM/FDC. Time-dependent mesh generation and parameter file generation are incorporated into the developed two-dimensional model. Finite element method is used in order to address heat transfer issues regarding the solidification ofthe thermoplastic binder

null

['Steinchen, W.', 'Kramer, B.', 'Kupfer, G.']

2018-11-02T13:53:40Z

1995

Mechanical Engineering

doi:10.15781/T2Z02ZV09

http://hdl.handle.net/2152/69327

eng

1995 International Solid Freeform Fabrication Symposium

Open

['stereolithography', 'photoelastic', '3D Systems']

Photoelastic Investigation Using New STL-Resins

Conference paper

https://repositories.lib.utexas.edu//bitstreams/41508cf2-e773-46dc-a1c0-b0fd47b5d9b2/download

null

Stereolithography is not only ideal to study the function and the design of a simple or complex component, but also for stress and strain analysis by means of photoelasticity. The basis for using Stereolithograpy components is the biremngent property of the photoPOIYffiers, which has been discovered in 1991 in the Lab ofPhotoelasticity and Holography [5]. Therefore, a few acrylate and epoxy resins develoPed by Ciba-Geigy were calibrated and compared with the most commonly used resin, Araldite B (manufactured by Ciba-Geigy, too). The experience shows that static and dynamic photoelastic investigations by using the new STL-resins are possible. The time saving for photoelastic investigations amountsto values about 10 months and the cost saving is equivalent to 90010.

null

['Kim, Young Hyun', 'Lim, Jong Seon', 'Lee, In Hwan', 'Kim, Ho-Chan']

2021-09-29T17:08:09Z

2009

Mechanical Engineering

null

['https://hdl.handle.net/2152/88190', 'http://dx.doi.org/10.26153/tsw/15131']

eng

2009 International Solid Freeform Fabrication Symposium

Open

['photopolymer solidification', 'stereolithography process', 'laser exposure conditions']

Photopolymer Solidification for Inclined Laser Exposure Conditions

Conference paper

https://repositories.lib.utexas.edu//bitstreams/768b557a-5ded-4a09-aded-aff72b5fdc38/download

University of Texas at Austin

It has been reported that the photopolymer solidification in the stereolithogrpahy process is mainly depended on the laser exposure conditions such as laser power and scanning speed. However, they were focused on the vertical laser exposure conditions. In this research, we developed a mathematical model for the photopolymer solidification under the inclined laser beam exposure condition. Using the developed mathematical model, the photopolymer solidifications were simulated for various inclined laser exposure conditions. Developed mathematical model was in good agreement with the experimental result. This research can be applied to improve the surface roughness in the stereolithogrpahy process.

null

['Chartoff, Richard P.', 'Du, Jin']

2018-11-02T16:30:30Z

1995

Mechanical Engineering

doi:10.15781/T2NG4HB5D

http://hdl.handle.net/2152/69337

eng

1995 International Solid Freeform Fabrication Symposium

Open

['UV laser beam', 'SLA process', 'stereolithography resins']

Photopolymerization Reaction Rates By Reflectance Real Time Infrared Spectroscopy: Application To Stereolithography Resins

Conference paper

https://repositories.lib.utexas.edu//bitstreams/bc98602e-3357-48c2-96c3-7232419a8769/download

null

An advanced real time infrared technique for studying the isothermal in-situ cure of ultra-fast photopolymerization reactions has been developed. The method, referred to as reflectance real time infrared (RRTIR), involves time resolved IR analysis by reflected IR radiation while a resin sample is being exposed to a UV laser beam. The effect of factors such as chemical composition, radiation intensity, and temperature on reaction rate were determined for multifunctional acrylate resins exposed to a HeCd laser (325 nm). Isothermal cure profiles were monitored quantitatively through disappearance of the 810 cm-1 acrylate IR absorbance band. The dark reaction after the UV radiation was turned off also was monitored. The RRTIR method is shown to be highly effective for quantifying photopolymerization reactions in the millisecond time range. The rate data indicate that quantitative comparisons between reactivities and conversions for different stereolithography resins are possible using this method under conditions that simulate the SLA process. Also, the data show conclusively that the reaction continues for long periods of time after initial laser exposure. This is expected to be a significant factor in the development of warpage and curl during the SLA building process.

null

['Olubummo, Adekunle', 'Zhao, Lihua', 'Hartman, Aja', 'Tom, Howard', 'Zhao, Yan', 'Wycoff, Kyle']

2024-03-25T22:29:25Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124322', 'https://doi.org/10.26153/tsw/50930']

en_US

2023 International Solid Freeform Fabrication Symposium

Open

['nickel dithiolene', '3D printing', 'bleaching', 'additive manufacturing']

Photothermal Bleaching of Nickel Dithiolene for Bright Multi-colored 3D Printed Parts

Conference paper

https://repositories.lib.utexas.edu//bitstreams/889a6490-9196-488f-96bd-8c61f249ceb7/download

University of Texas at Austin

HP’s Multi Jet Fusion is a powder bed fusion 3D printing technology that utilizes a carbon-based radiation absorber in combination with a near infrared (NIR) light source to facilitate the fusion of polymer powder in a layer-by-layer fashion to generate 3D parts. Most available carbon-based and NIR radiation absorbers have an intrinsic dark color, which as a result will only produce black/gray and dark colored parts. However, there are many applications that require variable color, including prosthetics, medical models, and indicators, among others. To create white, bright colored, and translucent parts with MJF, a visibly transparent and colorless radiation absorber is required. In this paper, we designed an activating fusing agent (AFA) that contains a red, strong NIR absorbing dye that turns colorless after harvesting irradiation energy during the MJF 3D printing process and provide a bright colored part when working with other color agents.

null

['Hong, Zhen', 'Wang, Zhiping', 'Deng, Sihao', 'Zhang, Yicha', 'Bernard, Alain']

2021-12-06T23:30:01Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90717', 'http://dx.doi.org/10.26153/tsw/17636']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['toolpath optimization', 'profile-based sweep', 'hybrid additive manufacturing', 'HAM']

Physical Deposition Profile Based Toolpath Generation and Optimization for Additive Volume Building in Hybrid Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d6e54ab1-a349-4cd1-bf1c-50d5bcbb2bf5/download

University of Texas at Austin

In hybrid additive manufacturing (HAM), toolpaths affect the volume building and removing during the sequential or iterative hybrid processing since they control the deposition nozzle or cutting tools. In sequential hybrid additive manufacturing, toolpaths for additive manufacturing module define the volume directly determines of the shape accuracy and volume building time. In this paper, we report a new toolpath generation and optimization method for a developing cold spraying - based HAM process’s additive processing module. This method adopts a valid physical deposition profile to set scanning parameters and then applies an evolutionary optimization algorithm to minimize the total scanning length for building a set of ordered disconnected volumes on a predefined base. The propose method is illustrated by a complex tree shape model and validated by three selected numerical examples. It has potential to help save spraying raw materials and time as well as improve shape accuracy.

null

['Ahn, S.', 'Murphy, J.', 'Ramos, J.', 'Beaman, J.J.']

2019-10-18T16:22:43Z

2001

Mechanical Engineering

null

['https://hdl.handle.net/2152/76252', 'http://dx.doi.org/10.26153/tsw/3341']

eng

2001 International Solid Freeform Fabrication Symposium

Open

Melting

Physical Modeling for Dynamic Control of Melting Process in Direct-SLS

Conference paper

https://repositories.lib.utexas.edu//bitstreams/33ba8a4c-e37a-40ac-a0bd-ba5a22ff1340/download

null

During the melting process by laser irradiation, it is essential to understand the phase change processes to get high quality Direct SLS parts especially when highorder scanning paths are needed. This process is a transient three -dimensional heat conduction problem with a moving heat source and a moving phase boundary. The process can be simplified to a one-dimensional moving boundary model using appropriate assumptions. To implement a real-time control strategy, approximate solutions were found using three methods. Experiments using a CW CO2 laser were performed on low carbon steelsamples to verify the models’ results. By using first order differential equations derived from the model, multi-input multi-output (MIMO) control strategies can be applied.

null

['Awenlimobor, Aigbe', 'Wang, Zhaogui', 'Smith, Douglas E.']

2021-12-07T17:53:08Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90736', 'http://dx.doi.org/10.26153/tsw/17655']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['fiber simulation', 'fiber motion', 'finite element analysis', 'large-scale additive manufacturing', 'polymer deposition', 'printed beads']

Physical Modeling: Simulation of Micro-Void Development within Large Scale Polymer Composite Deposition Beads

Conference paper

https://repositories.lib.utexas.edu//bitstreams/63bc40c1-0aca-4ba8-b1cb-9f1ffeeeb583/download

University of Texas at Austin

Short carbon fiber composites are used in large-scale polymer deposition additive manufacturing due to their increased stiffness and strength and reduced thermal expansion and print distortion. While much attention has been given to interlayer properties, less is known about bead microstructure, including the effect that suspended fibers have on porosity. This paper develops a model for single fiber motion in a purely viscous flow that is simulated with a custom finite element fiber suspension analysis. Our fiber simulation is based on Jeffrey’s model assumptions where translational and rotational velocities which zero applied forces and moments are computed. Velocity gradients along streamlines within the flow of polymer melt through a large-scale polymer deposition additive manufacturing flow field serve as input. The pressure distribution around a fiber is computed along the flow path including the die swell expansion at the nozzle exit. The simulation provides insight into micro-void formation within printed beads.

null

['Mensch, Cole', 'Zhou, Wenchao', 'Sha, Zhenghui']

2024-03-26T21:37:31Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124422', 'https://doi.org/10.26153/tsw/51030']

en_US

2023 International Solid Freeform Fabrication Symposium

Open

['job placement', 'cooperative 3D printing', 'additive manufacturing']

PHYSICAL VALIDATION OF JOB PLACEMENT OPTIMIZATION IN COOPERATIVE 3D PRINTING

Conference paper

https://repositories.lib.utexas.edu//bitstreams/3326e1ee-4481-4086-8d8c-bd3722f3a487/download

University of Texas at Austin

Cooperative 3D printing (C3DP) is an emerging technology designed to overcome the limitations of traditional 3D printing, including speed and scalability. C3DP achieves this by partitioning prints into smaller jobs, e.g., chunks, and assigning them to a team of mobile 3D printers that work cooperatively in parallel allowing for autonomous additive manufacturing of large objects via a swarm-based system. Our prior work established a framework for optimizing job placement by connecting geometric partitioning algorithms with path planning and scheduling algorithms. However, this framework was not physically validated. In this paper, we present the first physical validation of the job placement algorithm by chunking and printing two objects using the proposed algorithm. The objects used in the test cases vary in size and complexity, from a small and simple object to a large object with intricate geometry. We demonstrate that our optimized placement algorithm provides results comparable to the physical C3DP system, providing a significant step forward in the practical implementation of C3DP technology.

null

['Gao, Fuquan', 'Sonin, Ain A.']

2018-05-03T19:22:52Z

1993

Mechanical Engineering

doi:10.15781/T2NV99T9T

http://hdl.handle.net/2152/65063

eng

1993 International Solid Freeform Fabrication Symposium

Open

['Department of Mechanical Engineering', 'digital microfabrication', '3D']

The Physics of Digital Microfabrication with Molten Microdrops

Conference paper

https://repositories.lib.utexas.edu//bitstreams/fede82b5-2da5-4d1a-b317-b1065f811e8a/download

null

Precise deposition of molten microdrops under controlled thermal conditions provides a means of 3D "digital microfabrication" , microdrop by microdrop, under complete computer control, much in the same way as 2D hard copy is obtained by ink-jet printing. This paper describes some results from a study of the basic modes of microdrop deposition and solidification (Gao & Sonin, 1993). The conditions required controlled deposition are discussed, and some experimental results and theoretical analyses are given for various basic deposition modes. These include columnar (Le. drop-on-drop) deposition at low and high frequencies, sweep deposition of continuous beads on flat surfaces, and repeated sweep deposition for buildup of larger objects or materials.

null

['Boulger, Alex M.', 'Chesser, Phillip C.', 'Post, Brian K.', 'Roschli, Alex', 'Hilton, Joshua', 'Welcome, Connor', 'Tsiamis, Nikolaos Y.', 'Love, Lonnie J.', 'Gaul, Katherine T.', 'Rhyne, Breanna J.']

2021-11-15T22:09:41Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90288', 'http://dx.doi.org/10.26153/tsw/17209']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['pick and place', 'fiducials', 'robotic actuator', 'big area additive manufacturing']

Pick and Place Robotic Actuator for Big Area Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d8b01f83-cb7d-42eb-92de-e0d9dc58da64/download

University of Texas at Austin

Oak Ridge National Laboratory’s Manufacturing Demonstration Facility has created a system that works in tandem with an existing large-scale additive manufacturing (AM) system to ‘pick and place’ custom components into a part as it is printed. Large-scale AM leaves a layered surface finish and is typically post-processed through 5-axis CNC machining. Each surface must be accurately recorded into a laser tracking system. This process can be simplified with the use of fiducials, small location indicators placed on the surface of a part. Additionally, the ability to monitor an AM tool via wireless sensors is advantageous to gauge part health as it is fabricated and later used. The ‘pick and place’ system allows thermocouples, fiducials, and other sensors to be accurately placed throughout the tool as it is fabricated. This solution has the potential to reduce time, labor, and cost associated with fabricating, post-processing, and using AM parts.

null

Marusak, Ronald E.

2018-05-03T17:09:40Z

1993

Mechanical Engineering

doi:10.15781/T2H98ZX0J

http://hdl.handle.net/2152/65041

eng

1993 International Solid Freeform Fabrication Symposium

Open

['ink-jet printing', 'TAB', 'metal printer']

Picoliter Solder Droplet Dispensing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/531cddb4-6ef3-45b5-8df9-c252c5a89703/download

null

A device based on ink-jet printing technology was used to produce and place molten solder droplets, approximately 25-125pm in diameter, onto substrates. The advantages of an ink-jet based system are direct production of metallic objects, no postcure, low cost, and the repeatability and resolution for small feature sizes. This paper describes the device, the supporting hardware, and experimental procedures. Results show that bump size can be varied by placing in quick succession, multiple droplets as well as by resizing the device and by altering the signal.

null

['Evans, Emmeline', 'McComb, Christopher']

2021-12-01T21:35:24Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90621', 'http://dx.doi.org/10.26153/tsw/17540']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['3D printing', 'PLA claves', 'wooden claves', 'claves', 'vibrations', 'frequency']

Pitch Imperfect: Designing 3D Printed Claves to Mimic the Sounds of Their Wooden Counterparts

Conference paper

https://repositories.lib.utexas.edu//bitstreams/2ac836af-02e2-4a05-9430-43252e09f864/download

University of Texas at Austin

Despite the benefits afforded students by music education, public schools operating on insufficient budgets often cut music programs to reduce expenses. Students deserve access to high quality instruments, regardless of socioeconomic status or district funding. Therefore, the goal of this research is to develop 3D printed, PLA claves that reproduce the sound of wooden claves. This study examined clave vibration by approximating claves as damped, simply supported, thin beams. The frequency predictions obtained from that model are compared to experimental results obtained by recording clave prototypes and analyzing the resulting frequency spectra. Results indicate that while it is technically feasible to 3D print a correctly pitched PLA clave, the design would not be suitable for an education instrument.

null

['Ghazanfari, Amir', 'Li, Wenbin', 'Leu, Ming C.', 'Landers, Robert G.']

2021-10-21T18:23:53Z

2015

Mechanical Engineering

null

https://hdl.handle.net/2152/89419

eng

2015 International Solid Freeform Fabrication Symposium

Open

['horizontal staircase effect', 'freeform extrusion fabrication', '3D parts', 'adaptive rastering']

Planning Freeform Extrusion Fabrication Processes with Consideration of Horizontal Staircase Effect

Conference paper

https://repositories.lib.utexas.edu//bitstreams/3331da7f-664d-44b2-93b6-8975c2bea16a/download

University of Texas at Austin

An algorithm has been developed to estimate the “horizontal” staircase effect and a technique is proposed to reduce this type of geometrical error for freeform extrusion fabrication processes of 3D “solid” parts. The adaptive rastering technique, proposed in this paper, analyzes the geometry of each layer and changes the width of each line of the raster adaptively in order to reduce the staircase error and increase the productivity simultaneously. For each line, the maximum width that results in a staircase error smaller than a predefined threshold is determined for decreasing the fabrication time or increasing the dimensional accuracy, or both. To examine the efficacy of the proposed technique, examples are provided in which staircase errors and fabrication times are compared between uniform and adaptive rastering methods for each part. The results show a considerable improvement in accuracy and/or fabrication time for all parts studied when using the adaptive rastering technique.

null

['Yan, Jingyuan', 'Battiato, Ilenia', 'Fadel, Georges M.']

2021-10-26T18:18:58Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89549

eng

2016 International Solid Freeform Fabrication Symposium

Open

['functionally graded material', 'direct metal deposition', '2D model', 'thin-walled parts', 'process parameters']

Planning the Process Parameters During Direct Metal Deposition of Functionally Graded Thin-Walled Parts Based on a 2D Model

Conference paper

https://repositories.lib.utexas.edu//bitstreams/e5f3cff5-ec38-4fca-bbe9-1d3aea69e161/download

University of Texas at Austin

The need for functionally graded material (FGM) parts has surfaced with the development of material science and additive manufacturing techniques. Direct Metal Deposition (DMD) processes can locally deposit different metallic powders to produce FGM parts. Yet inappropriate mixing of materials without considering the influence of varying dilution rates and the variation of material properties can result in inaccurate material composition ratios when compared to the desired or computed compositions. Within such a context, this paper proposes a 2D simulation based design method for planning the process parameters in the DMD manufacturing of designed thin-walled parts. The proposed scheme is illustrated through two case studies, one of which is a part with one-dimensional varying composition and the other with two dimensional variation. Using the proposed method, the process parameters can be planned prior to the manufacturing process, and the material distribution deviation from the desired one can be reduced.

null

['Holzman, Noah', 'Francis, Lorraine']

2021-11-02T19:17:04Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89870

eng

2017 International Solid Freeform Fabrication Symposium

Open

['pneumatic system', 'direct write 3D printing', 'direct write printing']

Pneumatic System Design for Direct Write 3D Printing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/86da84df-3e20-405e-95aa-066bcb5d3a0c/download

University of Texas at Austin

Direct write 3D printing methods are interesting due to the diverse palette of materials available for the process. In this work, a pneumatic system for direct write printing is built using off-the-shelf hardware and synchronized with an open-source firmware for motion control. The time to steady-state pressure of the system is found to be ~150 ms for the range of pressures tested; this delay can lead to defects on the start of a path. Proof of concept is established by printing with a high viscosity, room temperature curing silicone using a 410 µm nozzle and 300 µm layer height. Test prints show a high degree of dimensional accuracy and consistent layer height over 10s of layers.

null

['Lao, S. C.', 'Koo, J. H.', 'Yong, W.', 'Lam, C.', 'Zhou, J.', 'Moon, T.', 'Piccione, P. M.', 'Wissler, G.', 'Pilato, L.', 'Luo, Z. P.']

2020-03-10T17:16:43Z

2008

Mechanical Engineering

null

['https://hdl.handle.net/2152/80232', 'http://dx.doi.org/10.26153/tsw/7251']

eng

2008 International Solid Freeform Fabrication Symposium

Open

selective laser sintering

Polyamide 11-Carbon Nanotubes Nanocomposites: Preliminary Investigation

Conference paper

https://repositories.lib.utexas.edu//bitstreams/c2ad1caf-162c-42b1-afeb-96024e104446/download

null

The objective of this research is to develop an improved polyamide 11 (PA11) polymer with enhanced flame retardancy, thermal, and mechanical properties for selective laser sintering (SLS) rapid manufacturing. In the present study, a nanophase was introduced into polyamide 11 via twin screw extrusion. Arkema Rilsan® polyamide 11 molding polymer pellets were used with 1, 3, 5, and 7 wt% loadings of Arkema’s GraphistrengthTM multi-wall carbon nanotubes (MWNTs) to create a family of PA11-MWNT nanocomposites. Transmission electron microscopy and scanning electron microscopy were used to determine the degree and uniformity of dispersion. Injection molded test specimens were fabricated for physical, thermal, mechanical properties, and flammability measurements. Thermal stability of these polyamide 11-MWNT nanocomposites was examined by TGA. Mechanical properties such as ultimate tensile strength, rupture tensile strength, and elongation at rupture were measured. Flammability properties were also obtained using the UL 94 test method. All these different methods and subsequent polymer characteristics are discussed in this paper.

null

['Lao, S.C.', 'Kan, M.F.', 'Lam, C.K.', 'Chen, D.Z.', 'Koo, J.H.', 'Moon, T.', 'Londa, M.', 'Takatsuka, T.', 'Kuramoto, E.', 'Wissler, G.', 'Pilato, L.', 'Luo, Z.P.']

2021-09-30T18:25:10Z

2010

Mechanical Engineering

null

['https://hdl.handle.net/2152/88270', 'http://dx.doi.org/10.26153/tsw/15211']

eng

2010 International Solid Freeform Fabrication Symposium

Open

['multifunctionial polyamide 11 polymer', 'enhanced properties', 'selective laser sintering', 'rapid manufacturing', 'nanotechnology', 'multi-wall carbon nanotubes', 'nanocomposites']

Polyamide 11-Carbon Nanotubes Nanocomposites: Processing, Morphological, and Property Characterization

Conference paper

https://repositories.lib.utexas.edu//bitstreams/7981e45c-bc53-4824-bfc8-1261c74c17dc/download

University of Texas at Austin

The objective of this research is to develop a multifunctional polyamide 11 (PA11) polymer with enhanced electrical, thermal, mechanical, and flammability properties for selective laser sintering (SLS) rapid manufacturing through the use of nanotechnology. In the present study, a nanophase was introduced into PA11 powder via rotation & revolution and twin screw extrusion techniques to disperse the MWNTs in the PA11 pellet. Arkema Rilsan® polyamide 11 molding polymer pellets were used with 1, 3, 5, and 7 wt% loadings of Arkema’s Graphistrength™ multi-wall carbon nanotubes (MWNTs) to create a family of PA11-MWNT nanocomposites using twin screw extrusion technique. Arkema Rilsan® polyamide 11 powders were blended with 5 wt% loading of Graphistrength™ MWNTs using the rotation & revolution technique to create another set of PA11-MWNT nanocomposites. Transmission electron microscopy and scanning electron microscopy were used to determine the degree and uniformity of dispersion of MWNTs in the PA11 polymer. Injection and compression molded test specimens were fabricated for physical, electrical, thermal, mechanical, and flammability properties characterization. Thermal stability of these polyamide 11-MWNT nanocomposites was examined by TGA. Kinetic parameters were calculated using isoconversion technique. Electrical properties were measured using ASTM D257. Mechanical properties such as ultimate tensile strength, rupture tensile strength, and elongation at rupture were measured. Flammability properties were obtained using the UL 94 test method. All these different test methods and subsequent polymer characteristics are discussed in this paper.

null

['Koo, J. H.', 'Lao, S.', 'Ngyuen, K.', 'Cheng, J.', 'Pilato, L.', 'Wissler, G.', 'Ervin, M.']

2020-03-02T14:37:01Z

2006

Mechanical Engineering

null

['https://hdl.handle.net/2152/80127', 'http://dx.doi.org/10.26153/tsw/7148']

eng

2006 International Solid Freeform Fabrication Symposium

Open

Wide angle X-ray diffraction

Polyamide Nanocomposites for Selective Laser Sintering

Conference paper

https://repositories.lib.utexas.edu//bitstreams/26576f56-0c88-4d2a-97cf-40e9b13605fe/download

null

Current polyamide 11 and 12 are lacking in fire retardancy and high strength/high heat resistance characteristics for a plethora of finished parts that are desired and required for performance driven applications. It is anticipated that nanomodification of polyamide 11 and 12 will result in enhanced polymer performance, i.e., fire retardancy, high strength and high heat resistance for polyamide 11 and 12. It is expected that these findings will expand the market opportunities for polyamide 11 and 12 resin manufacturers. The objective of this research is to develop improved polyamide 11 and 12 polymers with enhanced flame retardancy, thermal, and mechanical properties for selective laser sintering (SLS) rapid manufacturing (RM). A nanophase was introduced into the polyamide 11 and 12 via twin screw extrusion to provide improved material properties of the polymer blends. Arkema RILSAN® polyamide 11 molding polymer pellets and Degussa VESTAMID® L1670 polyamide 12 were examined with three types of nanoparticles: chemically modified montmorillonite (MMT) organoclays, surface modified nanosilica, and carbon nanofibers (CNFs) to create polyamide 11 and 12 nanocomposites. Wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) were used to determine the degree of dispersion. Injection molded test specimens were fabricated for physical, thermal, mechanical properties, and flammability tests. Thermal stability of these polyamide 11 and 12 nanocomposites was examined by TGA. Mechanical properties such as tensile, flexural, and elongation at break were measured. Flammability properties were also obtained using the Cone Calorimeter at an external heat flux of 50 kW/m2. TEM micrographs, physical, mechanical, and flammability properties are included in the paper. Polyamide 11 and 12 nanocomposites properties are compared with polyamide 11 and 12 baseline polymers. Based on flammability and mechanical material performance, selective polymers including polyamide 11 nanocomposites and control polyamide 11 were cryogenically ground into fine powders and fabricated into SLS parts.

null

['McMorrow, Brain', 'Chartoff, Richard', 'Lucas, Pierre', 'Richardson, Wade']

2020-02-20T21:07:06Z

2005

Mechanical Engineering

null

https://hdl.handle.net/2152/80055

eng

2005 International Solid Freeform Fabrication Symposium

Open

Solid Freeform Fabrication

Polymer Matrix Nanocomposites by Inkjet Printing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/263bc2e5-d492-4c9d-8fcc-25e9f0f719c0/download

null

This paper describes work on a continuing project to form functional composites that contain ceramic nanoparticles using a Solid Freeform Fabrication (SFF) inkjet printing method. The process involves inkjet deposition of monomer/particle suspensions in layers followed by curing each layer in sequence using UV radiation. The reactive monomer is hexanediol-diacrylate (HDODA); the polymer forming reaction proceeds by a free radical mechanism. The liquid monomer containing nanoparticles is essentially a printing ink formulation. Successfully suspending the particles in the monomer is critical. We have developed a surface treatment method for forming stable suspensions of the nanoparticles so that they remain discrete throughout the processing sequence. The SFF process involves careful control of the polymer cure so that the interface between layers is seamless and residual stresses in the composites are eliminated. An immediate use for such composites is in optical applications as gradient refractive index lenses (GRIN). GRIN lenses have planar surfaces, eliminating the need for costly grinding and polishing. The planar surfaces also eliminate optical aberrations that result at the edges of spherical lenses and diminish the accuracy of focus. If the appropriate nanoparticles are fully dispersed they will modify the polymer's refractive index without interfering with light transmission. The effect is additive with volume concentration. Using 'inks' of different compositions in a multiple nozzle inkjet printer allows the formation of composites with precise composition gradients. Since an object is built one planar layer at a time, changes can be made readily both within each layer and from layer to layer. Inkjet printing with picoliter resolution is ideal for this task. Working with SiC nanoparticles in HDODA as a model system for demonstrating the inkjet deposition process, nanocomposite films with a linear concentration gradient varying from 0 to 4.5% (wt) were fabricated on Silicon wafers. These composites are 30 layer films, which total 140µm in thickness. Each layer in the composite is about 5 µm in thickness. Analytical methods for characterizing the dispersion of the nanoparticles in the composite and some of the salient optical properties of the composites also were established. The status of the program is reviewed in this paper.

null

['Hüsler, A.', 'Wildman, R.D.', 'Alexander, M.R.']

2021-10-21T21:01:10Z

2015

Mechanical Engineering

null

https://hdl.handle.net/2152/89447

eng

2015 International Solid Freeform Fabrication Symposium

Open

['inkjet printing', 'polymer particle formation', 'biodegradable', 'photocrosslinkable']

Polymer Particle Formation Using Inkjet Printing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/040f3941-ac50-4924-9dc6-ffa69644d183/download

University of Texas at Austin

Exciting advances have been made in biomaterials research, through both relating material properties to cell response and discovery of new materials via high throughput screening. This area of research is still hindered though by the paucity of information on the physicochemical parameters governing the response of cells to a broad range of materials. Herein, a combinatorial library of biodegradable, photocrosslinkable and microparticle-forming polymers is generated by transforming a macro-performed pipetting experiment into a micro-sized piezoelectric inkjet printing. Physiochemical properties such as density, polymerization rate, surface tension, viscosity and solubility have been shown to be critical for successful single and multiple polymer structured microparticles. The vision is to mature this effort for applications that require biocompatibility such as drug delivery and cell carriers in regenerative medicine strategies to engineer cell functions.

null

['Cruz, Fabio', 'Lanza, Silvia', 'Boudaoud, Hakim', 'Hoppe, Sandrine', 'Camargo, Mauricio']

2021-10-21T20:38:07Z

2015

Mechanical Engineering

null

https://hdl.handle.net/2152/89441

eng

2015 International Solid Freeform Fabrication Symposium

Open

['polymer recycling', 'additive manufacturing', '3D printers', 'filament extruders', 'open source']

Polymer Recycling and Additive Manufacturing in an Open Source Context: Optimization of Processes and Methods

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5aa71bbe-b1be-479b-abd1-66ef9fe48ccd/download

University of Texas at Austin

Polymer recycling is a way to reduce environmental impacts of accumulation of polymeric waste materials. However, low recycling rates are often observed in conventional centralized recycling plants mainly to the challenge of collection and transportation for high-volume low-weight-polymers in conventional centralized recycling plants. As the democratization of open-source 3D printers is going forward thanks to initiatives such as FabLab environments, there is a growing interest on how to use this technology to improve the efficiency of use of raw materials. Studies have been proposed in order to recycle waste polymer into open-source 3D printer feedstock. The recycling of high-density polyethylene (HDPE) issued from bottles of used milk jugs through use of an open-source filament fabricator system called RecycleBot has been evaluated. In this study, we propose an evaluation of the mechanical recyclability of Polylactic Acid (PLA), material widely used in the open-source 3D printing context, in order to establish the viability of this recycled material to be used in the open-source 3D printers. The degradation of the material’s mechanical and rheological properties after a number of cycles of multiple extrusion and printing processes is evaluated. The characterization of recycled raw materials for open-source 3D printing has implications not only to reduce the environmental impact of polymers waste, but also it will allow us to understand the technical requirements and challenges for development of open-source filament recycle machine/process. The coupling of open-source 3D printers and filament extruders can offer the bases of a new distributed polymer recycling paradigm, which reverses the traditional paradigm of centralizing recycling of polymers where is often uneconomic and energy intensive due to transportation embodied energy. Moreover, this characterization also will allow the exploration of new source of materials and new composite materials for open-source 3D printing, in order to improve the quality of products made by this technology.

null

['Johnson, David M.', 'Beck, Victor', 'Valente, Michael', 'Völkel, Armin', 'Chang, Norine', 'Jose, Arun', 'Lancaster, Cory', 'Biegelsen, Dave', 'Elrod, Scott']

2021-10-28T20:51:51Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89697

eng

2016 International Solid Freeform Fabrication Symposium

Open

['polymer spray deposition', 'electrostatic patterning', 'aerosol-based deposition', 'additive manufacturing', 'PARC']

Polymer Spray Deposition: A Novel Aerosol-Based, Electrostatic Digital Deposition System for Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/48c62ab7-2eb1-45dd-ba4a-9b82325b236f/download

University of Texas at Austin

In order to address some of the shortcomings from traditional additive manufacturing methods, PARC, a Xerox Company, is developing a new additive manufacturing method for polymers that uses electrostatic patterning in combination with a new method of creating aerosols to directly pattern a wide range of thermoplastics with high resolution. Our aerosol technology takes advantage of the non-Newtonian nature of polymers to create monodisperse small droplets. In addition, we leverage ionographic printing techniques to pattern thick substrates and create digital thin films. This technology can bring 3D printing of polymers into a performance range where the technology can be used to replace more traditional techniques such as injection molding and machining.

null

Lee, Biing-Lin

2018-04-12T18:45:35Z

1991

Mechanical Engineering

doi:10.15781/T2XP6VM3G

http://hdl.handle.net/2152/64284

eng

1991 International Solid Freeform Fabrication Symposium

Open

['SLS', 'BFGoodrich R&D Center', 'CAD systems', 'CAM systems', 'CAE systems']

Polymeric Powder Material Technology for Selective Laser Sintering: The Overall View

Conference paper

https://repositories.lib.utexas.edu//bitstreams/7e666990-692c-4e65-b7d6-9c570d562bcd/download

null

This paper de.als with polymeric POwder technology relating to the conversion of raw polymeric materialsintoSelective LaserSinteringi(SLS) mtlterials. Generally, all SLS·polymeric powders go through similarexperiencesinmaterial- SLS interaction, such· as powderfeeding andsintering. The·desirtlblematerial - SLS interaction can be. achieved by a set of unit oPerations that converts a raw materialforSLS fabrication. The unit operations are: compounding, size reduction, attrition, size enlargement, and poWder mixing.

null

['Rauniyar, Santosh K.', 'Chou, Kevin']

2021-11-30T20:57:06Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90545', 'http://dx.doi.org/10.26153/tsw/17464']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['laser powder bed fusion', 'Ti64 alloy', 'porosity', 'computed tomography', 'CT']

Porosity Analysis and Pore Tracking of Metal AM Tensile Specimen by Micro-CT

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6442a179-04e5-426c-af38-9e55f3bdd15b/download

University of Texas at Austin

In this study, the porosity of Ti-6Al-4V (Ti64) tensile specimen fabricated by laser powder bed fusion (L-PBF) with varying three process conditions was investigated. The variation included the energy density in fabrication (3 levels), the build location (3 levels) and the build orientation (2 levels) for a constant scan speed of 600 mm/s. The tensile specimens were scanned using a micro-CT system before and after tensile testing. The porosity of the specimens varied significantly according to the energy density and the build direction, but only a minor effect of the location change was observed. The fractured specimens showed a significant increase, more than nine percent increase in the pore volume in all cases, for the pore volume as well as the porosity percentage. Also, few large pores were tracked in some of the fractured samples and compared with the as-built counterpart to observe the change in pore morphology.

null

['Nagahama, Takaya', 'Mizoguchi, Takashi', 'Yonehara, Makiko', 'Kyogoku, Hideki']

2021-11-18T01:06:31Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90384', 'http://dx.doi.org/10.26153/tsw/17305']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['selective laser melting', 'process parameters', 'H13 tool steel', 'mechanical properties']

The Porosity and Mechanical Properties of H13 Tool Steel Processed by High-Speed Selective Laser Melting

Conference paper

https://repositories.lib.utexas.edu//bitstreams/b8e7165d-9b08-4579-9e01-ae118a38efdd/download

University of Texas at Austin

Additive Manufacturing (AM) technology has the advantages of complicated geometry fabrication and integration of multiple parts. Selective Laser Melting (SLM), which is one of the AM technologies, generally takes longer manufacturing time than other manufacturing methods. In this research, the process parameters, which can achieve high-speed additive manufacturing of H13 tool steel, are investigated using a SLM machine with a 1 kW multi-mode fiber laser. As a result, the optimal process window has been determined in the process map of the laser power and the scan speed. High laser power in the process window is estimated to increase the manufacturing speed by 50 % of that with the conventional parameters. The specimen manufactured with the optimal parameters has a tensile strength of 1500 MPa, which is equivalent to the bulk samples.

null

['Khanzadeh, Mojtaba', 'Bian, Linkan', 'Shamsaei, Nima', 'Thompson, Scott M.']

2021-10-28T20:17:21Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89688

eng

2016 International Solid Freeform Fabrication Symposium

Open

['laser based additive manufacturing', 'porosity', 'porosity detection', 'melt pool', 'melt pool morphology', 'clustering', 'laser engineered net shaping']

Porosity Detection of Laser Based Additive Manufacturing Using Melt Pool Morphology Clustering

Conference paper

https://repositories.lib.utexas.edu//bitstreams/a26db74a-d6a2-4e60-91ba-6a4c8e0c987a/download

University of Texas at Austin

The microstructural and mechanical properties of Laser Based Additive Manufacturing (LBAM) are still inconsistent and unreliable, which is a major barrier that prevents Additive Manufacturing (AM) from entering main stream production. The key challenge is the lack of understanding for the underlying process-properties relationship. We monitor Laser Engineered Net Shaped (LENS) process using a state-of-art thermal image system, and the resulting high-speed Melt Pool (MP) data stream is used to characterize the complex thermo-physical process. We propose a novel method based on Self-Organizing Map to cluster the MPs based on their morphology and link MPs clusters’ characteristics to the porosity of fabricated parts, which is crucial to mechanical properties of parts. The results are validated using X-Ray tomography of Ti-64 thin-wall. Our approach identifies various patterns of MP morphology, which corresponds to different types of porosities. The proposed method can potentially be used to certify the part quality in a real-time and non-destructive manner.

null

['Qi, Ting', 'Zhu, Haihong', 'Yin, Jie', 'Chen, Baijin', 'Hu, Zhiheng', 'Zeng, Xiaoyun']

2021-11-02T14:47:26Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89815

eng

2017 International Solid Freeform Fabrication Symposium

Open

['porosity development', 'cracking behavior', '7xxx series', 'Al-Zn-Mg-Cu', 'selective laser melting']

Porosity Development and Cracking Behavior of Al-Zn-Mg-Cu Alloys Fabricated by Selective Laser Melting

Conference paper

https://repositories.lib.utexas.edu//bitstreams/77087821-3213-4c80-b723-8dce57f59ffe/download

University of Texas at Austin

Selective laser melting (SLM) of the 7xxx series Al alloy (Al-Zn-Mg-Cu) faces more challenge than other series aluminum alloy such as Al-Si system because of the high hot-cracking sensitivity. The porosity development and crack behavior of Al-Zn-Mg-Cu alloys fabricated at various scanning speeds in SLM process, as well as the influence of molten pool geometry were systematically investigated in this paper. Results show that the relative density over 99% can be achieved when the applied scanning speed is 150 mm/s. However, cracks are observed in almost all the as-deposited samples. The morphology, distribution and density of cracks were varied with the different molten pool geometry and scanning speed.

null

['Susan, D.F.', 'Puskar, J.D.', 'Brooks, J.A.', 'Robino, C.V.']

2019-09-20T15:16:27Z

2000

Mechanical Engineering

null

['https://hdl.handle.net/2152/75919', 'http://dx.doi.org/10.26153/tsw/3018']

eng

2000 International Solid Freeform Fabrication Symposium

Open

Porosity

Porosity in Stainless Steel LENS Powders and Deposits 50

Conference paper

https://repositories.lib.utexas.edu//bitstreams/bfb0e12f-fbc4-4372-8d00-1e2c3b6cf94b/download

null

Laser Engineered Net Shaping (LENS) utilizes a laser beam to melt fine powders to produce three-dimensional engineering structures line by line and layer by layer. When building these structures, defects including lack-of-fusion (LOF) at interlayer boundaries and intralayer porosity are sometimes observed. LOF defects can be minimized by adjusting processing parameters, but the sources of intralayer porosity are less apparent. In this paper, the amount and size distributions of 17-4PH and 304L powders and pores within the powder were characterized in parallel with the intralayer porosity in LENS deposits fabricated from the same materials. Intralayer porosity increased with increased powder porosity; but was not well correlated with deposition parameters. The results demonstrate the importance of careful characterization and specification of starting powders on the quality of the final LENS deposits.

null

['Kleszczynski, S.', 'Ladewig, A.', 'Friedberger, K.', 'zur Jacobsmühlen, J.', 'Merhof, D.', 'Witt, G.']

2021-10-19T20:33:42Z

2015

Mechanical Engineering

null

https://hdl.handle.net/2152/89333

eng

2015 International Solid Freeform Fabrication Symposium

Open

['Laser Beam Melting', 'part position', 'surface roughness']

Position Dependency of Surface Roughness in Parts from Laser Beam Melting Systems

Conference paper

https://repositories.lib.utexas.edu//bitstreams/9530c12b-cafb-4e85-ab74-bba6311060df/download

University of Texas at Austin

Laser Beam Melting is a promising Additive Manufacturing technology for the production of complex metal components. During batch production of multiple identical parts in a single build job, we observed parts with deviating surface roughness in certain areas, which all faced away from the laser. This suggests a dependency of surface roughness on the part position in the build chamber. In this work we systematically reproduce and analyze this effect. We place hollow pyramids with twelve faces and two different overhanging angles at nine positions on the substrate plate and build this setup twice, using an imaging setup for process documentation. Surface roughness is measured by contact profilometry on three lines for each pyramid face. Our experiments reproduce the effect. Based on these findings we present a hypothesis for the cause and show metallographic images to support our theory. As a consequence, the position relative to the laser should be considered in the design phase for parts with high surface quality requirements.

null

['King, B.A.', 'Rennie, A.E.W.', 'Taylor, J.P.', 'Bennett, G.R.']

2021-11-04T13:38:49Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89956

eng

2017 International Solid Freeform Fabrication Symposium

Open

['post processing treatment', 'post processing', 'nylon 12', 'laser sintering']

Post Processing Treatments on Laser Sintered Nylon 12

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f3f2281a-9361-4b1e-945b-68194a5ea51e/download

University of Texas at Austin

The laser sintering of polymers is an established process producing components with well-documented material properties. Whilst these properties are inferior to those of injection moulded nylon 12, they are suitable for prototyping and several specialist production applications. Broadening the applicability of the process to a wider range of manufacturing applications, can be accomplished by rendering the material properties of sintered nylon closer to those of injection moulded nylon. This paper reports on a series of post-processing treatments which have been carried out to enhance the mechanical properties of sintered nylon. The work has examined the effects of heat, pressure, infiltration with methyl methacrolate and combinations of these treatments. Results are reported on the impact of the treatments on the elongation and Ultimate Tensile Strength (UTS) of the test samples, with heated pressured samples improving UTS by 2MPa, and infiltrated parts increasing elongation by 5.2%.

null

['Rybalcenko, K.', 'Charlesworth, R.E.', 'Folgar, L.', 'Ioannides, G.', 'Crabtree, J.G.']

2021-12-01T21:24:39Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90618', 'http://dx.doi.org/10.26153/tsw/17537']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'post-process', 'COVID-19 nasopharyngeal swabs', 'COVID-19']

Post-Processing of Additively Manufactured Covid-19 Nasopharyngeal Swabs at Scale

Conference paper

https://repositories.lib.utexas.edu//bitstreams/5c116572-7f55-419b-842c-b77d761fb4ae/download

University of Texas at Austin

A methodology to post-process oral/respiratory Additively Manufactured medical components methods is presented. The system involves PostPro3D® smoothing machine by AMT, picking/racking module, industrial robot, conveyors and is used to smooth the surfaces of Covid-19 Nasopharyngeal Swabs manufactured at-scale using powder-based methods. The presented process for large scale postprocessing of Additively Manufactured articles has undergone all necessary medical verifications and has been already deployed in the field.

null

['Zarringhalam, Hadi', 'Hopkinson, Neil']

2019-11-21T18:39:19Z

2003

Mechanical Engineering

null

['https://hdl.handle.net/2152/78564', 'http://dx.doi.org/10.26153/tsw/5620']

eng

2003 International Solid Freeform Fabrication Symposium

Open

Polyamide

Post-Processing of DuraForm� Polyamide with Small-Scale Features

Conference paper

https://repositories.lib.utexas.edu//bitstreams/e3e191c3-b3f6-465f-b240-39e5c97d62c4/download

null

In recent years layer manufacturing processes have evolved from Rapid Prototyping (the production of pre-production prototypes) to Rapid Manufacture (the production of end use parts) where limitations of the processes do not affect end use. There is no doubt that applications for Rapid Manufacture will grow in coming years, however there are a number of current limitations that will need to be addressed so as to maximise the scope for Rapid Manufacturing applications. One of the main limitations for the adoption of Rapid Manufacturing is material properties of the parts produced. This research has looked at the possibility of increasing the range of material properties that may be achieved from parts made using current commercial Laser Sintering systems. A series of tensile and impact test parts were built using DuraformTM powder on a 3DSystems Vanguard machine. These parts were then subjected to various form of post-processing including thermal treatment and infiltration with polymer infiltrants. The parts were subjected to tensile and impact tests with results showing that thermal post-processing achieved preferable results when compared with infiltration. Heating above the glass transition temperature yielded superior results though as the melt temperature was approached issues of deformation arose. These initial results have formed the basis for further work to consider how material properties for Rapid Manufacture by Laser Sintering may be improved.

null

['Nelson, J.C.', 'Vail, N.K.']

2018-04-12T18:52:13Z

1991

Mechanical Engineering

doi:10.15781/T2SX64S93

http://hdl.handle.net/2152/64285

eng

1991 International Solid Freeform Fabrication Symposium

Open

['Department of Chemical Engineering', 'post-processing', 'polycarbonate', 'densification']

Post-Processing of Selective Laser Sintered Polycarbonate Parts

Conference paper

https://repositories.lib.utexas.edu//bitstreams/3a3ee1b1-e849-4428-95bf-23c29e9036d6/download

null

St\ldies were conducted·to det~rmine the effect of press\lre onpost-prpeessingofpolycarbonate coupons. No significant differences betweencou.pons processed at atmospheric •cQndidons.. andcouponsprpeessedin.vacuum were •observed. However, anisotropic shrinkage .was observedin.thez-directionnormal to thesintering plane. Thisphenomenawasfurtl1erinvestigated usingsYIllmetrical polycarbonatecubespr9(iuced by Selective LaserSintering using yariedlas~rpoweryariedpowderlayer thickness, and varied powder bed temperatures

null

['Xian, Y.', 'Rosen, D.W.']

2021-11-04T19:46:49Z

2017

Mechanical Engineering

null

['https://hdl.handle.net/2152/90014', 'http://dx.doi.org/10.26153/16935']

eng

2017 International Solid Freeform Fabrication Symposium

Open

['level set based topology optimization', 'part boundary', 'support materials', 'post-processing', '3D printing']

A Post-Processing Procedure for Level Set Based Topology Optimization

Conference paper

https://repositories.lib.utexas.edu//bitstreams/084febbc-8ff8-41e3-8b8a-c9f38838c30d/download

University of Texas at Austin

This paper addresses two issues: 1. Topology optimization yields designs that may require support structures if additively manufactured, which increase material and clean-up costs. 2. Topologically optimized designs consist of discretized geometry which makes subsequent engineering difficult, hence the increasing need to somehow render TO results to parameterized CAD models. This paper presents a procedure that, after a standard level set based topology optimization, firstly identifies certain regions on the part boundary that may require support materials or may cause staircase effect during 3D printing, then replaces these boundary segments with similar-shaped printable design features. Additionally, other boundary regions are fitted with simple geometric entities, so that the part boundary can be completely defined by geometric parameters of design primitives.

null

['Kruse, C.S.', 'Meile, D.H.', 'Salajeghe, R.', 'Spangenberg, J.']

2023-04-03T15:37:16Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117717', 'http://dx.doi.org/10.26153/tsw/44596']

eng

2022 International Solid Freeform Fabrication Symposium

Open

Additive manufacturing

Post-Processing Volumetric Additive Manufacturing (VAM) Components

Conference paper

https://repositories.lib.utexas.edu//bitstreams/b39d1f05-d96e-42f5-ac4c-72fafb26702d/download

null

Volumetric additive manufacturing, a new promising 3D-printing technology, has shown great potential to revolutionize the Additive Manufacturing industry. Within the field of Volumetric Additive Manufacturing, preliminary research has predominantly been focused on improving projection algorithms and optical systems as well as expanding its applicability to different materials, and little attention has therefore been paid to the post-processing phase of the printing process itself. As the surface of components produced by volumetric additive manufacturing using currently available photopolymer and published projection algorithms is not fully cured by the end of projection, it is highly susceptible to damage and deformation in the post-processing phase. In this study, a comparison has been made between the effects of different post-processing methods and techniques on the dimensions of the final post-processed components. The results show that it is a non-trivial task to maintain the surface quality and dimensions of components produced by volumetric additive manufacturing throughout post- processing, and it is therefore important to establish a well-defined method of post-processing that consistently yields satisfactory components.

null

['Raman, R.V.', 'Rele, S.V.', 'Anderson, R.L.']

2018-05-03T19:36:07Z

1993

Mechanical Engineering

doi:10.15781/T24X5507Z

http://hdl.handle.net/2152/65067

eng

1993 International Solid Freeform Fabrication Symposium

Open

['Ceracon Process', 'SFF', 'CAD', 'CAM']

Potential Application of Solid Free-Form Fabrication (SFF) Process in Ceracon P/M Forging

Conference paper

https://repositories.lib.utexas.edu//bitstreams/ed197074-363e-45d8-8b52-a0c5f4e8d2f6/download

null

The Ceracon Process is a patented[ll, low cost powder metallurgy process for achieving near-net-shape, full density parts. It. isasimple.·consolidation.technique which utilizes conventionalpowder metallurgyequipmenfand set-up. The Cetacon Process is a quasi-isostatic,hot consolidation technique, that utilizes a ceramic particulate material as a pressure transmitting medium instead ofagasmedia as is used in. hipping. Pressures up to 200 K.si can be used and a broad range ofmetallic, ceramic, and polymeric materials and composites have been successfully processed£2-6] .

null

['Buswell, R. A.', 'Soar, R.', 'Gibb, A.', 'Thorpe, A.']

2020-02-24T15:41:54Z

9/7/05

Mechanical Engineering

null

['https://hdl.handle.net/2152/80086', 'http://dx.doi.org/10.26153/tsw/7107']

eng

2005 International Solid Freeform Fabrication Symposium

Open

Freeform Construction

The Potential of Freeform Construction Processes

Conference paper

https://repositories.lib.utexas.edu//bitstreams/1bf0971e-f09d-46c1-9c27-3d511d19939f/download

null

The level of automation technology and processes control found in modern day construction lags significantly behind other industries such as automotive and aerospace. The construction industry has health and safety issues and still uses traditional methods of procurement. These problems are compounded by diminishing skills in the labour force. Methods of production must change if these issues are to be resolved and Freeform Construction is a collection of processes that could have potential impact. This paper outlines some of the major issues facing construction and sets a context with examples of digital fabrication in construction. Freeform Construction is defined and potential applications are presented and related to application scale. The viability of two potential applications are investigated in terms of cost.

null

['Binder, M.', 'Anstaett, C.', 'Horn, M.', 'Herzer, F.', 'Schlick, G.', 'Seidel, C.', 'Schilp, J.', 'Reinhart, G.']

2021-11-09T15:58:45Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90104', 'http://dx.doi.org/10.26153/tsw/17025']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['multi-material processing', 'laser-based powder bed fusion', 'LPBF', 'potentials', 'challenges']

Potentials and Challenges of Multi-Material Processing by Laser-Based Powder Bed Fusion

Conference paper

https://repositories.lib.utexas.edu//bitstreams/557451b0-7062-4aff-9ae2-972961fea417/download

University of Texas at Austin

Multi-material additive manufacturing offers a multitude of opportunities for increasing functional integration beyond the current state of the art. However, the real potential is only vaguely described and there are also challenges alongside the new opportunities. This paper presents a systematic collection of the challenges to be overcome by laser-based powder bed fusion before it can provide industrially relevant multi-material processes. Amongst others, parameter adaptation to avoid micro-cracking, relevant process monitoring technologies (e.g., thermography-based layer monitoring) and potential approaches for powder separation (e.g., using ferromagnetism) are described. Furthermore, to exploit the full potential of multi-material designs, possible concepts for the integration of fully functioning mechatronic devices into multi-material parts are also presented.

null

['Jahnke, U.', 'Lindemann, C.', 'Moi, M.', 'Koch, R.']

2021-10-12T18:58:27Z

8/16/13

Mechanical Engineering

null

['https://hdl.handle.net/2152/88720', 'http://dx.doi.org/10.26153/tsw/15654']

eng

2013 International Solid Freeform Fabrication Symposium

Open

['Additive Manufacturing', 'piracy', 'piracy prevention', 'plagiarism', 'product tagging']

Potentials of Additive Manufacturing to Prevent Product Piracy

Conference paper

https://repositories.lib.utexas.edu//bitstreams/ded408bc-d54b-4106-bb9c-45f1959f6dc3/download

University of Texas at Austin

Infringements of intellectual and industrial properties rights in terms of imitations of products are continuously increasing. Massive economic and reputational damages are consequences for concerned companies. One solution to this problem can be the use of Additive Manufacturing (AM) technologies. This production technology enables complex designed products and specific product properties due to the use of different manufacturing processes and materials, which can help preventing product piracy safety measures of products can highly benefit from these capabilities, which have not been possible yet. The layer wise process allows, for example, to implement identifiable marks under the parts surface and to adjust mechanical properties in a certain way. The use of AM can strongly reduce the economic efficiency of plagiarism. This paper will present approaches to product piracy prevention by the use of AM focusing on the tagging of products, preventive measures as well as the interplay of these types.

null

['Allison, Jared', 'Sharpe, Conner', 'Seepersad, Carolyn Conner', 'Kubiak, Steven']

2021-11-08T22:59:44Z

2017

Mechanical Engineering

null

['https://hdl.handle.net/2152/90068', 'http://dx.doi.org/10.26153/tsw/16989']

eng

2017 International Solid Freeform Fabrication Symposium

Open

['metrology', 'powder bed fusion', 'design for additive manufacturing', 'DFAM', 'test parts', 'design guidance', 'selective laser sintering']

Powder Bed Fusion Metrology for Additive Manufacturing Design Guidance

Conference paper

https://repositories.lib.utexas.edu//bitstreams/506b24c1-e3de-495e-9517-3124ce0758cc/download

University of Texas at Austin

Design for additive manufacturing (DFAM) guidelines are important for helping designers avoid iterations and fully leverage the design freedoms afforded by additive manufacturing (AM). Guidelines can be generated via metrology studies that use test parts to characterize statistically the geometric capabilities of specific AM processes. Towards that end, a test part is designed for polymer selective laser sintering (SLS) that incorporates an array of geometric features in an extremely compact volume, such that it can be easily inserted into existing builds. The part is then built in multiple materials, build orientations, and locations within the build chamber in a factorial-style study to assess the variation attributed to each processing parameter. Both part resolution and accuracy are investigated. Upon measurement of the test parts, tolerances and design allowables are established and compiled into a set of design guidelines for SLS. The guidelines are then made publicly accessible through an online web tool to be used by designers creating parts for polymer SLS.

null

['Nauka, Krzysztof', 'Niu, Michelle', 'Discekici, Emre', 'Hartman, Aja', 'Olubummo, Paul']

2023-01-20T14:03:56Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117255', 'http://dx.doi.org/10.26153/tsw/44136']

eng

2022 International Solid Freeform Fabrication Symposium

Open

ultraviolet light

Powder Bed Fusion of Polymers with Ultraviolet Light Emitting Diode Energy Sources

Conference paper

https://repositories.lib.utexas.edu//bitstreams/ee58827e-bfca-4d4e-a0ba-aec10f8d75ea/download

null

Powder bed 3D printing of polymers often uses broadband near-infrared (NIR) emitters and selectively printed fusing agents with absorption spectrum matching the emission of selected IR energy source. However, due to few available NIR absorbers that can be formulated into printable agent, printed 3D parts often have limited application due to regulatory concerns or unwanted color. Shifting the emitter’s spectrum to a narrow, near-ultraviolet band (wavelength > 350 nm) can provide more absorber candidates while minimizing the potential UV-induced damage. Choice of the printable absorber span from inorganic metal oxides (TiO2, ZnO, CeO, etc.) to organic absorbers that may include commercial UV absorbing ingredients used in paints, vitamins, food derivatives, cosmetic and pharmaceutical components. Some absorbers, being colorless or white, enable printing parts with the original polymer powder color or white base for desired coloring of the printed objects.

null

['Wang, Jiwen', 'Li, Xiaoxuan', 'Shaw, Leon L.', 'Marcus, Harris L.', 'Cameron, Thomas B.']

2019-10-18T16:55:53Z

2001

Mechanical Engineering

null

['https://hdl.handle.net/2152/76260', 'http://dx.doi.org/10.26153/tsw/3349']

eng

2001 International Solid Freeform Fabrication Symposium

Open

Prototyping

Powder Delivery in Dental Restoration Rapid Prototyping Process

Conference paper

https://repositories.lib.utexas.edu//bitstreams/8116c3e1-fbb8-4ac4-8f90-3794c02202c0/download

null

Rapid prototyping of dental restoration has been investigated for its potential to save time and cost. In this paper, a powder delivery system was developed to deliver dental porcelain powder accurately into 2-D shapes for dental restoration. Aqueous suspension of the porcelain was prepared as the vehicle for the powder delivery. An integrated dry and wet ball-milling process was developed to reduce the particle size and minimize agglomeration. The reduction in particle size and minimization of agglomeration increased the suspension stability. The optimization of the pH value of the suspension also provided an additional means to achieve the stability and reduce the viscosity of the suspension. With the optimization of the particle size, pH value and solid concentration in the suspension, desired powder shapes were successfully delivered.

The authors gratefully acknowledge financial support provided by the National Science Foundation under Grant No: DMI-9908249

null

Kumar, Ashok V.

2019-02-19T19:53:51Z

1998

Mechanical Engineering

null

['https://hdl.handle.net/2152/73439', 'http://dx.doi.org/10.26153/tsw/591']

eng

1998 International Solid Freeform Fabrication Symposium

Open

['SFF', 'functional structural components']

Powder Deposition and Sintering for a Two-Powder Approach to Solid Freeform Fabrication

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d40894c3-5410-47d3-bb08-a4e6dec8b021/download

null

A two-powder approach is presented where Fused Deposition modeling (FDM) is used to create a thin shell in the shape of the part to be fabricated. The shell is filled with powder of the part material and surrounded by a support powder that has a high sintering temperature. Upon compressing and sintering the shelVpowder system in a uniaxial hot press, the polymer shell burns out and the support powder compresses the part powder. The part powder consolidates into the desired part while the support material remains in powder form and can be easily removed. This paper presents results ofinitial experimental studies.

null

['Hossain, M.S.', 'Silva, D.F.', 'Vinel, A.', 'Liu, J.', 'Shamsaei, N.']

2021-12-01T22:42:45Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90643', 'http://dx.doi.org/10.26153/tsw/17562']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['LB-PBF', 'correlation coefficient', 'variance inflation factor', 'LASSO', 'random forest regression', 'stepwise regression']

Powder Features Affecting Structural and Mechanical Properties of Additively Manufactured Inconel 718: A Machine Learning Analysis

Conference paper

https://repositories.lib.utexas.edu//bitstreams/1c433f1d-1ef7-4f2f-97cc-65b242030cba/download

University of Texas at Austin

The aim of this paper is to select important Inconel 718 powder properties that can have significant effect on the structural and mechanical properties of Laser-Beam Powder Bed Fusion manufactured specimens. The dataset used was provided by NASA and contains powder rheological, morphological, and chemical composition properties. The output variables considered are melt pool depth, high cycle fatigue life, porosity volume fraction and porosity size. Initially, Pearson correlation coefficient matrix is used to reduce the number of predictor features. Several statistical and machine learning algorithms including stepwise regression, LASSO, and random forest regression are used to identify the powder properties that have the strongest impact on the selected outputs. The variables identified using the different statistical and machine learning techniques are similar, which increases the confidence of the findings.

null

['John Lee, Sang-Joon', 'Sachs, Emanuel', 'Cima, Michael']

2018-05-03T19:18:01Z

1993

Mechanical Engineering

doi:10.15781/T2XD0RF6D

http://hdl.handle.net/2152/65061

eng

1993 International Solid Freeform Fabrication Symposium

Open

['Department of Mechanical Engineering', 'Department of Materials Science and Engineering', 'Three Dimensional Printing', 'rapid prototyping']

Powder Layer Position Accuracy in Powder-Based Rapid Prototyping

Conference paper

https://repositories.lib.utexas.edu//bitstreams/31d6cd38-ff8c-4bd1-ac67-85ad75d6a710/download

null

['Wegner, A.', 'Ünlü, T.']

2021-10-27T22:40:31Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89636

eng

2016 International Solid Freeform Fabrication Symposium

Open

['laser sintering', 'aging effects', 'polypropylene', 'processing parameters']

Powder Life Cycle Analyses for a New Polypropylene Laser Sintering Material

Conference paper

https://repositories.lib.utexas.edu//bitstreams/1667ea16-c7ee-46b6-a61e-e7d2d2258d07/download

University of Texas at Austin

When processing polymers in laser sintering, material aging occurs. The consequences of these aging effects are changes of material and part properties. A reduction of surface quality and the occurrence of orange peel are often found when using a material of too high viscosity. These effects are well known when processing polyamide 12. For alternative materials there is only little knowledge on aging effects. Within the presented study effects of material aging and refreshing for a new developed polypropylene material are analyzed. Viscosity as well as powder flowability are characterized as material properties. Additionally, part properties in different orientations are studied for different aging states as well as refreshing levels. Tensile properties and part density are measured in order to analyze the influence of aging effects on part properties. Furthermore, the influence of different processing parameters on part quality is studied in order to establish fundamental process knowledge for the processing of the new polypropylene material.

null

['Hu, Q.J.', 'Fuh, J.Y.H.', 'Wong, Y.S.', 'Lu, L.', 'Choy, C.M.', 'Chen, Z.D.']

2019-10-22T18:31:45Z

2002

Mechanical Engineering

null

['https://hdl.handle.net/2152/76339', 'http://dx.doi.org/10.26153/tsw/3428']

eng

2002 International Solid Freeform Fabrication Symposium

Open

Metallurgy

Powder Metallurgy of M2 High-Speed Steel for Rapid Tooling Applications

Conference paper

https://repositories.lib.utexas.edu//bitstreams/2d6ade62-53ef-40ab-aa5d-8c91d792fb69/download

null

A rapid tooling method has been developed to make a metallic tooling by powder metallurgy [1]. It is an integration of two techniques: rapid prototyping and powder metallurgy. The main advantages of this rapid tooling technique over the conventional techniques were short production cycle, low investment and manufacture costs. The experiment reported was on the density, microstructure, hardness and shrinkage of M2 high-speed steel parts. The process included de-binding, sintering and tempering of M2 high-speed steel powder. The material used was water atomised M2 high-speed steel powder and was sintered in the temperature range of 1270-1310°C for one hour. The process is typically a liquid phase sintering and enables to obtain high brown densities. After sintering, the micro-structure of the high-speed steel consisted of 6-12% carbides, 15-30 % austenite and 60-80% martensite, and the parts were to be tempered. With sintering at 1300°C and tempering, the results showed that 96% density was obtained, the typical hardness of Hv0.2510 (HRc50) was achieved, the horizontal shrinkage of the brown part was controlled at 15%±1% and the vertical shrinkage was at 14%±1%. Sintering above the temperature of 1300°C resulted in increasing of the brown density, rapid growth in grain size and deformation occurred. Based on the combination of density, shrinkage and hardness, the optimal sintering temperature and tempering procedure were determined.

null

['Majewski, C.E.', 'Horsford, P.M.', 'Hopkinson, N.']

2021-09-29T14:49:37Z

9/18/09

Mechanical Engineering

null

['https://hdl.handle.net/2152/88187', 'http://dx.doi.org/10.26153/tsw/15128']

eng

2009 International Solid Freeform Fabrication Symposium

Open

['Elongation at Break', 'Laser Sintered parts', 'thermal pre-conditioning', 'powder pre-conditioning']

Powder Pre-Conditioning for the LS Process

Conference paper

https://repositories.lib.utexas.edu//bitstreams/18a490ae-f021-4c8f-9239-d5222583f19e/download

University of Texas at Austin

It has previously been shown that the use of recycled Nylon-12 powder leads to increased Elongation at Break (EaB) of Laser Sintered (LS) parts, possibly due to elevated powder temperature in the part bed causing increases in molecular weight. However, this increase in EaB often corresponds to a decrease in repeatability, likely to be through variations in powder history. The research presented here has shown that thermal pre-conditioning of virgin powder can increase EaB of LS parts, with no significant loss of repeatability. Materials analysis of the conditioned powder batches is also presented in order to quantify the differences in powder properties and to help explain the mechanisms involved.

null

['Chen, D.Z.', 'Lao, S.', 'Koo, J.H.', 'Londa, M.', 'Alabdullatif, Z.']

2021-09-30T15:51:40Z

2010

Mechanical Engineering

null

['https://hdl.handle.net/2152/88269', 'http://dx.doi.org/10.26153/tsw/15210']

eng

2010 International Solid Freeform Fabrication Symposium

Open

['nano-graphene platelets', 'polyamide 11', 'polymer nanocomposites', 'Selective Laser Sintering', 'powder-powder mixing techniques', 'twin-screw extrusion']

Powder Processing and Properties Characterization of Polyamide 11- Graphene Nanocomposites for Selective Laser Sintering

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6794958a-32a5-404c-b412-6e937ff3d98b/download

University of Texas at Austin

Nano-graphene platelets (NGPs) were added to polyamide 11 (PA11) powder in 1%, 3%, and 5% weight loading in an attempt to create electrostatic dissipative polymer nanocomposites (PNC) using SLS, a rapid manufacturing process. Powder-powder mixing techniques were explored as a potential replacement for twin-screw extrusion for dispersing nano-graphene platelets (NGPs) within a PA11 matrix. The Resodyn™ Resonant Acoustic Mixer as well as the Thinky™ mixer were studied as powder-powder mixing techniques. After mixing, the powder samples were pressed into thin-films for characterization on TGA, SEM, four-probe conductivity, and Raman spectroscopy. TGA results indicate a slight decrease in thermal stability with the addition of NGPs. This suggests an inadequate dispersion of NGP within the polymer matrix. SEM images support this hypothesis with evidence of artifacts, a sign of electron charging, as well as clusters of NGPs. The four-probe conductivity measurements indicate that all of the samples studied exceed the sensitivity range of the machines used, which is estimated to be 4.5x1010 Ω/=. This indicates that all of the samples are at least in the upper region of the range for electrostatic dissipation, if not out of it entirely. Further research will include twin-screw extrusion as well as surface functionalization of NGPs for better dispersion.

null

['Soltani-Tehrani, Arash', 'Shamsaei, Nima', 'Surya, Adapa Venkata', 'Mallory, Jaikp', 'Ramakrishnan, Ramesh']

2021-12-06T22:27:15Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90698', 'http://dx.doi.org/10.26153/tsw/17617']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'LB-PBF', 'L-PBF', 'tensile properties', 'Inconel 718', 'powder recycling', 'powder characterization']

Powder Reuse Effects on the Tensile Behavior of Additively Manufactured Inconel 718 Parts

Conference paper

https://repositories.lib.utexas.edu//bitstreams/3a028f4a-8e4a-4652-beb6-33c36af76d6f/download

University of Texas at Austin

Inconel 718 (IN718), with a wide range of applications in aerospace industries and good weldability, is a popular powder feedstock in the laser beam powder bed fusion (LB-PBF) additive manufacturing (AM) process. Due to fabrication, handling, and storage costs, powder feedstock is commonly reused several times. Therefore, it is important to understand how the mechanical properties of LB-PBF parts can be affected by powder reuse given that powder characteristics may change after repeated recycling. This study aims to investigate the effect of powder reuse on the tensile properties of LB-PBF IN718 parts. Powder characteristics such as cohesion and compressibility will be quantified in order to shed light on the variations observed in the part performances. In addition, by correlating the state of the reused powder with tensile properties, the most critical metrics for quality aspects in powder reuse will be determined.

null

['Klippstein, Helge', 'Schmid, Hans-Joachim']

2023-01-27T14:20:53Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117338', 'http://dx.doi.org/10.26153/tsw/44219']

eng

2022 International Solid Freeform Fabrication Symposium

Open

laser sintering

Powder Spread Flaws in Polymer Laser Sintering and Its Influences on Mechanical Performance

Conference paper

https://repositories.lib.utexas.edu//bitstreams/df87860b-1766-46d4-acf1-5bf45bf402fc/download

null

By monitoring the recoating process within polymer laser sintering production, it was shown that multiple powder-spread-flaws can be detected. Those groove-like flaws are expected to be the result of agglomerates jamming between the recoater and the last powder layer. This work is analyzing the interaction between powder-spread-flaws and part properties, showing the influence of the recoating process on the performance of laser sintering parts. Therefore, artificial powder-spread-flaws are applied to the build jobs of tensile test specimens which are measured and analyzed regarding the elongation at break, strength and fracture position. For the characteristics of the flaws, the artificial grooves are varied in depth and width. Furthermore, the position of the flaw is changed form mid part to close to surface areas. It was shown, that several flaws are visible at the part surface, resulting in stress concentration and reduced performance. But there are as well parts with flaw-layers, which are not visible after the build process on the part. Those parts can have significantly reduced mechanical properties as well.

null

['Klippstein, Helge', 'Heiny, Florian', 'Pashikanti, Nagaraju', 'Gessler, Monika', 'Schmid, Hans-Joachim']

2021-12-07T18:03:36Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90740', 'http://dx.doi.org/10.26153/tsw/17659']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['powder bed monitoring', 'process monitoring', 'powder spread', 'part properties', 'polymer laser sintering']

Powder Spread Process Monitoring in Polymer Laser Sintering and Its Influences on Part Properties

Conference paper

https://repositories.lib.utexas.edu//bitstreams/0f380a29-3310-4df7-8b2a-1c42df4217c5/download

University of Texas at Austin

Confidence in additive manufacturing technologies is directly related to the predictability of part properties, which is influenced by several factors. To gain confidence, online process monitoring with dedicated and reliable feedback is desirable for every process. In this project, a powder bed monitoring system was developed as a retrofit solution for the EOS P3 laser sintering machines. A high-resolution camera records each layer, which is analyzed by a Region Based Convolutional Neural Network (Mask R-CNN). Over 2500 images were annotated and classified to train the network in detecting defects in the powder bed at a very high level. Each defect is checked for intersection with exposure areas. To distinguish between acceptable imperfections and critical defects that lead to part rejection, the impact of these imperfections on part properties is investigated.

null

['Dobson, Sean', 'Vunnam, Swathi', 'Frankel, Dana', 'Sudbrack, Chantal', 'Starr, Thomas']

2021-11-18T00:11:21Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90365', 'http://dx.doi.org/10.26153/tsw/17286']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['selective laser melting', 'additive manufacturing', '17-4 PH stainless steel', 'microstructure', 'mechanical testing']

Powder Variation and Mechanical Properties for SLM 17-4 PH Stainless Steel

Conference paper

https://repositories.lib.utexas.edu//bitstreams/531d061d-2bc7-4d22-bea8-94cc0b4ef2e5/download

University of Texas at Austin

Chemical composition and atomizing gas of powders may affect properties of 17-4 PH fabricated via selective laser melting (SLM) process. This study investigates 17-4 PH stainless steel powders with various atomizing gases and compositions within 17-4 PH specification range. Material characterization demonstrated differences in flowability between the powders, but all produced fully dense parts. The as-built phase composition varied widely, with samples from Ar-atomized powders ranging from a mostly martensitic grain structure to containing a significant amount of δ-ferrite depending on their composition, whereas samples from N2 atomized powder contained largely austenite phase. After solutionizing and H900 hardening all Ar atomized powders produced homogeneous microstructure and improved mechanical properties meeting AMS 17-4 PH specification. The N2 atomized powder produced a martensitic microstructure with retained austenite and only ultimate strength meeting AMS specification.

null

['Glassshroeder, J.', 'Prager, E.', 'Zaeh, M.F.']

2021-10-13T21:36:39Z

2014

Mechanical Engineering

null

['https://hdl.handle.net/2152/88788', 'http://dx.doi.org/10.26153/tsw/15722']

eng

2014 International Solid Freeform Fabrication Symposium

Open

['powder-bed based 3D-printing', '3D printing', 'polymethyl methacrylate', 'PMMA', 'function integrated parts', 'base material', 'additive manufacturing']

Powder-Bed Based 3D-Printing of Function Integrated Parts

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f3de6502-2b43-47e1-88cc-db8a5724d7b9/download

University of Texas at Austin

null

['Sutton, Austin T.', 'Kriewall, Caitlin S.', 'Leu, Ming C.', 'Newkirk, Joseph W.']

2021-10-28T14:34:40Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89651

eng

2016 International Solid Freeform Fabrication Symposium

Open

['powder bed additive manufacturing', 'powder characterization', 'characterization techniques', 'part properties']

Powders for Additive Manufacturing Process: Characterization Techniques and Effects on Part Properties

Conference paper

https://repositories.lib.utexas.edu//bitstreams/1acd25b1-823f-4e27-8bd2-2c2b804070b3/download

University of Texas at Austin

Powder-bed based Additive Manufacturing is a class of Additive Manufacturing (AM) processes that bond successive layers of powder by laser melting to facilitate the creation of parts with complex geometries. As AM technology transitions from the fabrication of prototypes to end-use parts, the understanding of the powder properties needed to reliably produce parts of acceptable quality becomes critical. Consequently, this has led to the use of powder characterization techniques such as scanning electron microscopy (SEM), laser light diffraction, x-ray photoelectron spectroscopy (XPS), and differential thermal analysis (DTA) to both qualitatively and quantitatively study the effect of powder characteristics on part properties. Utilization of these powder characterization methods to study particle size and morphology, chemical composition, and microstructure of powder has resulted in significant strides being made towards the optimization of powder properties for powder-bed based AM processes. This paper reviews methods commonly used in characterizing metallic AM powders, and the effects of powder characteristics on the part properties in these AM processes.

null

['Jacobson, D. M.', 'Bennett, G.']

2020-03-05T20:08:27Z

2006

Mechanical Engineering

null

['https://hdl.handle.net/2152/80155', 'http://dx.doi.org/10.26153/tsw/7176']

eng

2006 International Solid Freeform Fabrication Symposium

Open

Direct Metal Laser Sintering

Practical Issues in the Application of Direct Metal Laser Sintering

Conference paper

https://repositories.lib.utexas.edu//bitstreams/118f6c81-e1d1-4ee4-ac64-033c7957ee7c/download

null

Direct Metal Laser Sintering (DMLS) was introduced to meet the objective of producing metal parts directly from CAD data. CRDM has accumulated six years of experience in applying this technique, mostly to prototyping parts for evaluation. For some applications, such as blow moulds, porosity generated in DMLS has proved to be beneficial, but for others a concession on tolerances or finish are necessary and/or complementary operations are required, which add to manufacturing time and cost. This paper examines such issues through some well chosen examples of parts to demonstrate both the strengths and weaknesses of the DMLS process.

null

['Klosterman, Don', 'Chartoff, Richard', 'Osborne, Nora', 'Graves, George', 'Lightman, Allan', 'Steidlel, Cheri']

2018-11-30T14:57:09Z

1997

Mechanical Engineering

doi:10.15781/T2C53FM75

http://hdl.handle.net/2152/70590

eng

1997 International Solid Freeform Fabrication Symposium

Open

['Material Selection', 'Rapid Prototype']

Pre-LOM, LOM, and Post-LOM Processes for the Fabrication of SiC and SiC/SiC Components

Conference paper

https://repositories.lib.utexas.edu//bitstreams/34b81d00-7cc0-4d87-a883-04fc2f747693/download

null

['Roschli, Alex', 'Post, Brian K.', 'Chesser, Phillip C.', 'Sallas, Matt', 'Love, Lonnie J.', 'Gaul, Katherine T.']

2021-11-09T19:20:54Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90140', 'http://dx.doi.org/10.26153/tsw/17061']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['precast concrete molds', 'big area additive manufacturing', 'conventional pattern making']

Precast Concrete Models Fabricated with Big Area Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/825ed515-8424-4d4d-8d0f-fd59b97acc7d/download

University of Texas at Austin

The traditional process of making precast concrete molds requires significant manual labor. The molds are made using hardwood, cost tens of thousands of dollars, and take weeks to build. Once built, a mold will last 5-10 pulls before becoming too heavily degraded to continue use. With additive manufacturing, the same mold can be built in eight hours, post-machined in eight hours, costs about $9000, and is projected to last nearly 200 pulls. Oak Ridge National Laboratory has been working with Big Area Additive Manufacturing (BAAM) to fabricate concrete molds for a new high-rise apartment complex in New York. The molded pieces will form structural window supports for the hundreds of windows in building façade. The magnitude of window molds is where additive manufacturing can shine when producing the geometry. This paper will discuss the methods and findings of using BAAM to replace conventional precast concrete pattern making.

null

['Jean, Daniel L.', 'Duty, Chad E.', 'Fuhrman, Brian T.', 'Lackey, W. Jack']

2019-09-20T18:13:15Z

2000

Mechanical Engineering

null

['https://hdl.handle.net/2152/75922', 'http://dx.doi.org/10.26153/tsw/3021']

eng

2000 International Solid Freeform Fabrication Symposium

Open

Deposition

Precision Carbon Deposition Using Pyrolytic Laser Chemical Vapor Deposition (LCVD) 73

Conference paper

https://repositories.lib.utexas.edu//bitstreams/09ab4a89-e6a2-489f-af3b-06e5c65a4a9f/download

null

Laser Chemical Vapor Deposition (LCVD) can be used to rapid prototype many different metals and ceramics. The spatial resolution is potentially very fine, depending on the accuracy of stage or laser movement, and the size of the laser spot used for the localized heating. This paper describes a set of experiments performed using an LCVD system powered with a 100 Watt CO2 laser. The laser was focused to 200 mm onto a graphite substrate to deposit pyrolytic carbon. The morphologies of the carbon deposits were studied while varying laser power, reagent concentration, scanning speeds, and scanning patterns.

null

['Li, L.', 'McGuan, R.', 'Kavehpour, P.', 'Candler, R.N.']

2021-11-09T15:22:00Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90092', 'http://dx.doi.org/10.26153/tsw/17013']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['metrology', 'additive manufacturing', 'high-speed optical scanning', 'in situ validation', 'scan while printing', 'geometric dimensioning and tolerating']

Precision Enhancement of 3D Printing via In Situ Metrology

Conference paper

https://repositories.lib.utexas.edu//bitstreams/9106a313-7ec3-4653-81ce-17e29fa75764/download

University of Texas at Austin

The field of additive manufacturing, especially 3D printing, has gained growing attention in the research and commercial sectors in recent years. Notwithstanding that the capabilities of 3D printing have moved on to enhanced resolution, higher deposition rate, and a wide variety of materials, the crucial challenge of verifying that the component manufactured is within the dimensional tolerance as designed continues to exist. This work developed and demonstrated an approach for layer-by-layer mapping of 3D printed parts, which can be used for validation of printed models and in situ adjustment of print parameters. A high-speed optical scanning system was integrated with a Fused Deposition Modeling type 3D printer to scan during the print process on demands.

null

['Wang, F.', 'Shor, L.', 'Darling, A.', 'Khalil, S.', 'Sun, W.', 'Güçeri, S.', 'Lau, A.']

2019-11-21T18:35:35Z

2003

Mechanical Engineering

null

['https://hdl.handle.net/2152/78562', 'http://dx.doi.org/10.26153/tsw/5618']

eng

2003 International Solid Freeform Fabrication Symposium

Open

Poly-e-Caprolactone

Precision Extruding Deposition and Characterization of Cellular Poly-e-Caprolactone Tissue Scaffolds

Conference paper

https://repositories.lib.utexas.edu//bitstreams/01596c97-57bc-4ff4-b2e3-662bf721f5dd/download

null

Successes in scaffold guided tissue engineering require scaffolds to have specific macroscopic geometries and internal architectures in order to provide the needed biological and biophysical functions. Freeform fabrication provides an effective process tool to manufacture many advanced scaffolds with designed properties. This paper reports our recent study on using a novel Precision Extruding Deposition (PED) process technique to directly fabricate cellular Poly-ε-Caprolactone (PCL) scaffolds. Scaffolds with a controlled pore size of 250 µm and designed structural orientations were fabricated. The scaffold morphology, internal micro-architecture and mechanical properties were evaluated using SEM, Micro-Computed Tomography (µ-CT) and the mechanical testing. Preliminary biological study was also conducted to investigate the cell responses to the as-fabricated tissue scaffolds. The results and the characterizations demonstrate the viability of the PED process to the scaffold fabrication as well as a good mechanical property, structural integrity, controlled pore size, pore interconnectivity, and the anticipated biological compatibility of the as-fabricated PCL scaffolds.

The authors acknowledge the NSF-0219176 project funding support to graduate students Andrew Darling and Saif Khalil, and the ONR research funding support to graduate student Lauren Shor.

null

['Shor, L.', 'Güçeri, S.', 'Sun, W.']

2020-02-27T20:11:25Z

2006

Mechanical Engineering

null

['https://hdl.handle.net/2152/80099', 'http://dx.doi.org/10.26153/tsw/7120']

eng

2006 International Solid Freeform Fabrication Symposium

Open

Precision Extrusion Deposition

Precision Extrusion Deposition of Polycaprolactone/Hydroxyapatite Tissue Scaffolds

Conference paper

https://repositories.lib.utexas.edu//bitstreams/9f9ddb22-d16a-4d7f-b2c9-884c884714a8/download

null

Freeform fabrication provides an effective process tool to manufacture advanced tissue scaffolds with specific designed properties. Our research focuses on using a novel Precision Extrusion Deposition (PED) process technique to directly fabricate Polycaprolactone (PCL) and composite PCL/ Hydroxyapatite (HA) tissue scaffolds. The scaffold morphology and the mechanical properties were evaluated using SEM and mechanical testing. In vitro biological studies were conducted to investigate the cellular responses of the composite scaffolds. Results and characterizations demonstrate the viability of the PED process as well as the good mechanical property, structural integrity, controlled pore size, pore interconnectivity, and the biological compatibility of the fabricated scaffolds.

null

['Jean, Daniel L.', 'Duty, Chad E.', 'Fuhrman, Brian T.', 'Lackey, W. Jack']

2019-03-08T17:47:07Z

1999

Mechanical Engineering

null

['https://hdl.handle.net/2152/73572', 'http://dx.doi.org/10.26153/tsw/714']

eng

1999 International Solid Freeform Fabrication Symposium

Open

['LCVD', 'materials']

Precision LCVD System Design with Real Time Process Control

Conference paper

https://repositories.lib.utexas.edu//bitstreams/9cab3350-dfe2-4c15-9e3c-202f0e25d526/download

null

A Laser Chemical Vapor Deposition (LCVD) system was designed using a fixed 100 Watt C02 laser focused on a moveable substrate. Temperature and height measurement devices monitor the reaction at the point of deposition to provide feedback for controlling the process. The LCVD system will use rapid prototyping technology to directly fabricate fully threedimensional ceramic, metallic, and composite parts of arbitrary shape. Potential applications include high temperature structures, electronic/photonic devices, and orthopaedic implants.

null

['Chadha, Charul', 'Patternson, Albert E.', 'Jasiuk, Iwona']

2021-12-01T23:32:39Z

2021

Mechanical Engineering

null

['https://hdl.handle.net/2152/90657', 'http://dx.doi.org/10.26153/tsw/17576']

eng

2021 International Solid Freeform Fabrication Symposium

Open

['part repair', 'adhesive strength', 'thermoplastics', 'polymer healing theory', 'fused filament fabrication']

Predict Adhesive Strength of Repair of Thermoplastic Component Based on Polymer Healing Theory

Conference paper

https://repositories.lib.utexas.edu//bitstreams/d7a47ff9-4220-492f-80e5-1f2e646dd671/download

University of Texas at Austin

Advancements in polymer technology have increased the production of high-valued parts using polymers. These parts are often produced in low volumes and have complex geometries, making them difficult to reproduce later, especially when original tooling is no longer available. Reproduction of these parts from scratch using additive manufacturing (AM) can be time-consuming and, at times, economically infeasible. This paper explores the application of fused filament fabrication (FFF-extrusion-based AM) to repair such parts and print broken features on damaged parts. Polymer healing theory is then employed to understand the effect of print speed on adhesive strength at the interface formed between the 3D printed repair geometry and the original damaged part. The theory was verified using three-point bending experiments. Results show that the adhesive strength at the interface is approximately proportional to print speed raised to power negative one-fifth fraction.

null

['Crockett, R.S.', "O'Kelly, J.", 'Calvert, P.D.', 'Fabes, B.D.', 'Stuffle, K.', 'Creegan, P.', 'Hoffman, R.']

2018-10-03T19:32:24Z

1995

Mechanical Engineering

doi:10.15781/T2833NH66

http://hdl.handle.net/2152/68683

eng

1995 International Solid Freeform Fabrication Symposium

Open

['polymerization', 'advanced ceramics research', 'CAD']

Predicting and Controlling Resolution and Surface Finish of Ceramic Objects Produced by Stereodeposition Processes

Conference paper

https://repositories.lib.utexas.edu//bitstreams/a1955181-4195-4051-af4c-99660961190d/download

null

Stereodeposition techniques are well suited for the Solid Freeform Fabrication of dense ceramic components. As opposed to forming a pattern in a particle bed or polymer bath, stereodeposition processes deposit material directly onto the previously created layer. The key to stereodeposition is a material's ability to be dispensed as a fluid, yet rapidly stiffen to hold the shape of the object. This is accomplished by either solidification of a thermoplastic binder upon cooling from a melt (Fused Deposition) or by polymerization of a binder (Reactive Stereodeposition). We are developing both techniques for the production of functional ceramic and engineering polymer objects. A key issue in developing a successful stereodeposition system is controlling the rate of bead transformation from liquid to solid. Control is critical to achieving high resolution and low surface roughness of the finished product, but is made complex by the large number of parameters involved. These include binder parameters (surface tension, gelling characteristics), slurry parameters (viscosity, particle loading and size distribution), and process parameters (deposition rate, temperature). Current efforts at the University of Arizona are focused on modeling and controlling the deposition and transformation of ceramic slurries used in the Reactive Stereodeposition process.

null

['Merschroth, Holger', 'Kniepkamp, Michael', 'Weigold, Matthias']

2021-11-16T16:07:30Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90327', 'http://dx.doi.org/10.26153/tsw/17248']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['neural networks', 'thermal history', 'temperature prediction', 'temperature control', 'laser power', 'laser-based powder bed fusion']

Predicting and Controlling the Thermal Part History in Powder Bed Fusion Using Neural Networks

Conference paper

https://repositories.lib.utexas.edu//bitstreams/596e094e-1370-4878-9f83-35d4f0279666/download

University of Texas at Austin

Laser-based powder bed fusion of metallic parts is used widely in different branches of industry. Although there have been many investigations to improve the process stability, thermal history is rarely taken into account. The thermal history describes the parts’ thermal situation throughout the build process as a result of successive heating and cooling with each layer. This could lead to different microstructures due to different thermal boundary conditions. In this paper, a methodology based on neural networks is developed to predict and control the parts’ temperature by adjusting the laser power. A thermal imaging system is used to monitor the thermal history and to generate a training data set for the neural network. The trained network is then used to predict and control the parts temperature. Finally, tensile testing is conducted to investigate the influence of the adjusted process on the mechanical properties of the parts.

null

['Kishore, Vidya', 'Ajinjeru, Christine', 'Liu, Peng', 'Lindahl, John', 'Hassen, Ahmed', 'Kunc, Vlastimil', 'Duty, Chad']

2021-11-04T14:50:06Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89975

eng

2017 International Solid Freeform Fabrication Symposium

Open

['sharkskin instability', 'sharksin', 'reinforced thermoplastics', 'extrusion additive manufacturing', 'big area additive manufacturing']

Predicting Sharkskin Instability in Extrusion Additive Manufacturing of Reinforced Thermoplastics

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f5b89d5e-eb9d-4c26-9ced-a10d8e7f2270/download

University of Texas at Austin

The development of large scale extrusion additive manufacturing systems such as the Big Area Additive Manufacturing (BAAM) system has enabled faster printing with throughput as high as 50 kg/h and the use of a variety of thermoplastics and composites with filler loading as high as 50%. The combination of high throughput and heavy reinforcements can give rise to a phenomenon known as “sharkskin” instability, which refers to extrudate surface distortions typically in the form of roughness or mattness, and is commonly observed in traditional extrusion processes. The onset of this instability depends upon the viscoelastic properties of the material and processing parameters such as throughput, shear rate, extruder die geometry, and temperature. For printed parts, such instabilities are undesirable and detrimental to mechanical properties. This work examines the effect of process parameters on the rheological properties of BAAM thermoplastics and composites to predict the occurrence of sharkskin during printing.

null

['Bartolai, Joseph', 'Simpson, Timothy W.', 'Xie, Renxuan']

2021-10-28T14:18:23Z

2016

Mechanical Engineering

null

https://hdl.handle.net/2152/89646

eng

2016 International Solid Freeform Fabrication Symposium

Open

['thermoplastic polymer', 'temperature history', 'rheological data', 'welding theory', 'mechanical strength', 'fused filament fabrication']

Predicting Strength of Thermoplastic Polymer Parts Produced Using Additive Manufacturing

Conference paper

https://repositories.lib.utexas.edu//bitstreams/fb496cc7-8b56-45b4-90e9-2b8646a9c46c/download

University of Texas at Austin

The weakest point in polymer parts produced by Fused Filament Fabrication (FFF) is the interface between adjacent layers and deposition toolpaths, or “roads”. We introduce a novel approach that uses the temperature history of these interfaces, polymer rheological data, and polymer welding theory to predict the mechanical strength of parts subjected to uniaxial tension. Interface temperature history data is collected in-situ using infrared imaging. Rheological data of the polycarbonate (PC) used to fabricate the parts in this study was determined experimentally. The prediction of strength of the interfaces was performed using polymer weld theory from the literature adapted to the PC feedstock used in this study. Understanding how the strength of the road and layer interfaces develop mechanical strength will lead to stronger FFF parts through intelligent toolpath optimization and temperature control.

null

['Peng, B.', 'Panesar, A.']

2024-03-26T20:12:23Z

2023

Mechanical Engineering

null

['https://hdl.handle.net/2152/124389', 'https://doi.org/10.26153/tsw/50997']

en_US

2023 International Solid Freeform Fabrication Symposium

Open

['PINN', 'metal additive manufacturing', 'temperature field']

Predicting Temperature Field for Metal Additive Manufacturing using PINN

Conference paper

https://repositories.lib.utexas.edu//bitstreams/bcd4f7b0-f922-4b28-ae01-954e237bfe79/download

University of Texas at Austin

Machine-learning-based methods are gaining traction as an alternative to numerical methods in many engineering applications. Physics-informed neural network (PINN), a self-supervised method, is particularly attractive with its unique capability of guiding the training with physical laws written in the forms of partial differential equations. Thermomechanical simulation for additive manufacturing (AM), a multi-scale, multi-physics problem could potentially benefit from the use of PINN, as demonstrated in some successful attempts in the literature. In this work, PINN is applied to different metal AM processes and several challenges that limit the robustness of PINN are observed. This paper aims to provide a summary of the observations and a preliminary attempt to account for such observations in order to pave the path for future work that aims to unleash the full promise of PINN in AM-related applications.

null

['Yadollahi, Aref', 'Mahtabi, Mohammad J.', 'Doude, Haley R.', 'Newman, James C. Jr']

2021-11-02T13:35:51Z

2017

Mechanical Engineering

null

https://hdl.handle.net/2152/89798

eng

2017 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'AM', 'laser powder bed fusion', 'L-PBF', 'fatigue-life prediction', 'crack growth', 'FASTRAN']

Prediction of Fatigue Lives in Additively Manufactured Alloys Based on the Crack-Growth Concept

Conference paper

https://repositories.lib.utexas.edu//bitstreams/ea52d9ee-d75b-43fd-a36a-709b137a60d1/download

University of Texas at Austin

This paper aims to predict the fatigue behavior of additively manufactured alloys using crack-growth data. Among different sources of damage under cyclic loadings, fatigue due to cracks originated from voids is the most life-limiting failure mechanism in powder-based metal additive manufacturing (AM) parts. Hence, the ability to predict the fatigue behavior of AM materials based on the void features is the first step toward improving AM part reliability. Test results from the literature on AM alloys are analyzed herein to model fatigue behavior based on the semi-circular surface flaws. The fatigue-life variations in the specimens are captured using the distribution of defect size. The results indicate that knowing the statistical distribution of the defect size can provide the opportunity of predicting the scatter in the fatigue-life of the AM materials, using an appropriate fatigue analysis code.

null

['Pal, Deepankar', 'Patil, Nachiket', 'Stucker, Brent E.']

2021-10-06T20:24:12Z

8/22/12

Mechanical Engineering

null

['https://hdl.handle.net/2152/88433', 'http://dx.doi.org/10.26153/tsw/15370']

eng

2012 International Solid Freeform Fabrication Symposium

Open

['Electron Beam Melting', 'Ti6Al4V', 'dislocation density based crystal plasticity framework', 'DDCP-FEM']

Prediction of Mechanical Properties of Electron Beam Melted Ti6Al4V Parts Using Dislocation Density Based Crystal Plasticity Framework

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6440965b-6508-4cc3-8af3-2b0ca0f6a7d8/download

University of Texas at Austin

Parts produced using Electron Beam Melting (EBM) with Ti6Al4V powders are generally tested for two important mechanical properties, namely tensile strength and fatigue life. The optimization of the process input parameters, such as part orientation, initial powder size and hatch pattern, for the abovementioned mechanical properties has been attempted using two numerical finite element methods. First, the dislocation density based crystal plasticity framework (DDCP-FEM) has been used to evaluate the localized stress-strain evolution, dislocation density evolutions and non-local deformations as a function of loading, sample geometry, microstructural phase, grain size and shape. This analysis has been compared against simulations based on continuum plasticity based finite element techniques. Though the localized evolutions as a function of microstructural attributes are missing in the continuum analysis, the low computational costs involved makes this technique an ideal candidate for spatial homogenization of the DDCP-FEM framework. The simulations conducted in the current work only validate the mechanical properties for tensile and fatigue specimens fabricated with known process parameters. These simulations will form the basis for future modeling efforts to optimize these parameters for required mechanical properties in service.

null

['Nasirov, A.', 'Hasanov, S.', 'Fidan, I.']

2021-11-18T17:49:40Z

2019

Mechanical Engineering

null

['https://hdl.handle.net/2152/90446', 'http://dx.doi.org/10.26153/tsw/17367']

eng

2019 International Solid Freeform Fabrication Symposium

Open

['classical laminate theory', 'multiscale modeling', 'mechanical properties', 'fused deposition modeling']

Prediction of Mechanical Properties of Fused Deposition Modeling Made Parts using Multiscale Modeling and Classical Laminate Theory

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6e52a5ab-6bc4-4bad-bf59-7e129d349bef/download

University of Texas at Austin

Fused deposition modeling (FDM) is one of the most popular additive manufacturing (AM) processes that works based on the layer-by-layer buildup of a 3D modeled part from polymers or fiber-reinforced polymer materials. In recent years, extensive research has been done to characterize the mechanical properties of FDM produced parts using classical laminate theory (CLT). However, considering the limitation of micromechanics approach to simple unit cells, there is a need to explore different techniques to alleviate those limitations. Taking into account the periodicity and multiscale nature of FDM infill patterns, one such technique is the asymptotic homogenization method used in this study to find mechanical properties. Moreover, the input of homogenized properties in CLT is discussed. Finally, both homogenization and CLT results are compared with experimental results.

null

['Klingbeil, N.W.', 'Brown, C.J.', 'Bontha, S.', 'Kobryn, P.A.', 'Fraser, H.L.']

2019-10-22T18:24:58Z

2002

Mechanical Engineering

null

['https://hdl.handle.net/2152/76336', 'http://dx.doi.org/10.26153/tsw/3425']

eng

2002 International Solid Freeform Fabrication Symposium

Open

Deposition

Prediction of Microstructure in Laser Deposition of Titanium Alloys

Conference paper

https://repositories.lib.utexas.edu//bitstreams/618984dc-95a3-4339-8014-3e68ffd6331a/download

null

Laser deposition of titanium alloys is under consideration for aerospace applications, and offers significant increases in efficiency and flexibility compared to conventional manufacturing methods. However, its ultimate success will depend on the ability to predict and control the microstructure and resulting mechanical properties of the deposit. In this study, both 2-D continuum finite element modeling and 3-D cellular automaton finite element modeling of a thinwall geometry are used to investigate the effects of deposition process variables on microstructure in laser deposited Ti-6Al-4V. Numerical results for cooling rate and thermal gradient obtained from the 2-D models are used to provide insight into grain size and morphology, while the 3-D cellular automaton models are used to provide direct predictions of deposited microstructure. The numerical model predictions are subsequently compared with observed microstructures in LENSTM deposited Ti-6Al-4V.

This work was supported by the Joint AFRL/DAGSI Research Program, project number ML-WSU-01-11, as well as by a grant from Wright State University and the Ohio Board of Regents.

null

['Tapia, G.', 'Elwany, A.H.']

2021-10-21T18:00:04Z

2015

Mechanical Engineering

null

https://hdl.handle.net/2152/89412

eng

2015 International Solid Freeform Fabrication Symposium

Open

['predictive models', 'porosity', 'Selective Laser Melting', 'Multivariate Adaptive Regression Splines']

Prediction of Porosity in SLM Parts Using a MARS Statistical Model and Bayesian Inference

Conference paper

https://repositories.lib.utexas.edu//bitstreams/dfe7c9fb-77e4-48e6-9669-b5d8653f97ca/download

University of Texas at Austin

Predictive models that establish a linkage between process parameters and part properties have been identified as a high priority research need in Additive Manufacturing. We work with a Multivariate Adaptive Regression Splines (MARS) statistical model to predict the porosity of parts produced using Selective Laser Melting (SLM) process as a function of process parameters. The proposed predictive model is validated through a case study on 17-4 PH stainless steel test coupons manufactured on a ProX 100 SLM system.

null

['Karamooz-Ravari, M.R.', 'Taheri Andani, M.']

2021-11-04T18:59:21Z

2017

Mechanical Engineering

null

['https://hdl.handle.net/2152/90005', 'http://dx.doi.org/10.26153/16926']

eng

2017 International Solid Freeform Fabrication Symposium

Open

['finite element method', 'TPMS', 'elastic response', 'cellular lattice structures', 'P-type', 'G-Type']

Prediction of the Elastic Response of TPMS Cellular Lattice Structures Using Finite Element Method

Conference paper

https://repositories.lib.utexas.edu//bitstreams/190a5e4d-379f-4f19-a4eb-d0c8ad9bc463/download

University of Texas at Austin

Cellular lattice structures are a group of porous materials in which the cells are regularly distributed. Since the morphology of the cells is complicated, the fabrication of them is challenging using conventional methods. However, with the advent of additive manufacturing technology, more attention is focused on these classes of materials because the regular geometry makes it possible to tailor the mechanical response of the structure. Among all kinds of cellular lattice structures, those based on triply periodic minimal surfaces are of great importance due to mechanical and biological properties. Since the fabrication of such structures is challenging and expensive, it is desirable to predict their mechanical response before fabrication. In this paper, finite element approach is employed to predict the elastic response of two well-known Schwarz minimal surfaces named P-Type and G-Type. To do so, first, the cloud points of the surfaces are generated using the implicit equation of the surface and are converted into solid finite element models. The results show that at the same value of porosity, the P-Type specimen provides a higher value of elastic modulus than G-Type one.

null

['Badrinarayan, B.', 'Barlow, J.W.']

2018-04-10T18:19:59Z

1990

Mechanical Engineering

doi:10.15781/T2FT8F24M

http://hdl.handle.net/2152/64244

eng

1990 International Solid Freeform Fabrication Symposium

Open

['Department of Chemical Engineering', 'Selective Layer Sintering', 'SLS']

Prediction of the Thermal Conductivity of Beds Which Contain Polymer Coated Metal Particles

Conference paper

https://repositories.lib.utexas.edu//bitstreams/f5a9391f-bd56-49a5-94c2-0a009af7a97e/download

null

Structural parts of ceramics or metals can, in principle, be made by laser sintering polymer coated ceramic or metal powders, followed by conventional methods for removing the binder and sintering in ovens. Understanding the laser sintering of coated materials requires knowledge of the behavior of beds containing composite particles. Many correlations for predicting the effective thermal conductivity of a bed of solid particles exist in literature, but little work has been done on beds of coated particles. We coated lead shots(high conductivity) with a styrene acrylic acid copolymer (low conductivity) to study the effect of coating thickness on the thermal conductivity. The thermal conductivity ofthe coated particle·hed was found to •drop rapidly in the beginning·· and then level off with increasing coating thickness. We also developed an equation that yields the equivalent conductivity of a coated spherical particle subjected to axial heat flow. The predicted results with the experimental measurements of bed conductivity obtained by an unsteady state method.

null

['Sih, Samuel Sumin', 'Barlow, Joel W.']

2018-11-08T15:23:40Z

1995

Mechanical Engineering

doi:10.15781/T2ZW19C17

http://hdl.handle.net/2152/69887

eng

1995 International Solid Freeform Fabrication Symposium

Open

['SFF', 'heat transfer', 'Powder beds']

The Prediction of the Thermal Conductivity of Powders

Conference paper

https://repositories.lib.utexas.edu//bitstreams/1f6eb687-8fdf-47df-abf4-3daa466f9e20/download

null

A revised view factor for the prediction of the thermal conductivity of powder beds at high temperatures that includes a radiation contribution to the conductivity is presented. Comparison of predictions by this equation with 424 measured values shows the predictions to be accurate to within a ±30% relative error.

null

['Nettekoven, A.', 'Fish, S.', 'Topcu, U.', 'Beaman, J.']

2021-11-16T15:02:24Z

2018

Mechanical Engineering

null

['https://hdl.handle.net/2152/90305', 'http://dx.doi.org/10.26153/tsw/17226']

eng

2018 International Solid Freeform Fabrication Symposium

Open

['additive manufacturing', 'iterative learning control', 'machine learning', 'intelligent control', 'artificial intelligence']

Predictive Iterative Learning Control with Data-Driven Model for Optimal Laser Power in Selective Laser Sintering

Conference paper

https://repositories.lib.utexas.edu//bitstreams/01599a8e-73d1-4970-9e86-79bc71858b32/download

University of Texas at Austin

Building high quality parts is still a key challenge for Selective Laser Sintering machines today due to a lack of sufficient process control. In order to improve process control, we propose a Predictive Iterative Learning Control (PILC) controller that minimizes the deviation of the postsintering temperature profile of a newly scanned part from a desired temperature. The controller does this by finding an optimal laser power profile and applying it to the plant in a feedforward manner. The PILC controller leverages machine learning models that accurately capture the process’ temperature dynamics based on in-situ measurement data while still guaranteeing low computational cost. We demonstrate the controller’s performance in regards to the control objective with heat transfer simulations by comparing the PILC-controlled laser power profiles to constant laser power profiles.

null

2019-09-25T15:54:41Z

2001

Mechanical Engineering

null

['https://hdl.handle.net/2152/75998', 'http://dx.doi.org/10.26153/tsw/3097']

eng

2001 International Solid Freeform Fabrication Symposium

Open

Preface

Conference paper

https://repositories.lib.utexas.edu//bitstreams/6e056690-14ae-4493-a7f0-3004de57a050/download

null

Laboratory for Freeform Fabrication and University of Texas at Austin

2023-01-19T17:33:19Z

2022

Mechanical Engineering

null

['https://hdl.handle.net/2152/117248', 'http://dx.doi.org/10.26153/tsw/44129']

eng

2022 International Solid Freeform Fabrication Symposium

Open

preface

Preface

Conference paper

https://repositories.lib.utexas.edu//bitstreams/1deb22c5-82b1-4b83-87c9-f4cd2a021472/download

null