Browsing by Subject "mechanical engineering"
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Item Freeform Fabrication of Zirconium Diboride Parts Using Selective Laser Sintering(2008-09-10) Leu, Ming C.; Adamek, Erik B.; Huang, Tieshu; Hilmas, Greg E.; Dogan, FaithUsing the Selective Laser Sintering (SLS) process, both flexural test bars and 3D fuel injector components have been fabricated with zirconium diboride (ZrB2) powder. Stearic acid was selected as the binder. Values of SLS process parameters were chosen such that the green parts could be built with sharp geometrical features and that the sintered parts could have good mechanical properties. After binder burnout and sintering, the SLS fabricated ZrB2 test bars achieved 80% theoretical density, and the average flexural strength of the sintered samples was 195 MPa. These values demonstrate the feasibility of the SLS process for freeform fabrication of 3D parts with the ultra high temperature ceramic.Item Layer-to-Layer Height Control for Laser Metal Deposition(2008-09-10) Tang, Lie; Ruan, Jianzhoung; Sparks, Todd E.; Landers, Robert G.; Liou, FrankA Laser Metal Deposition (LMD) height controller design methodology is presented in this paper. The height controller utilizes the Particle Swarm Optimization (PSO) algorithm to estimate model parameters between layers using measured temperature and track height profiles. The process model parameters for the next layer are then predicted using Exponentially Weighted Moving Average (EWMA). Using the predicted model, the powder flow rate reference profile, which will produce the desired layer height reference, is then generated using Iterative Learning Control (ILC). The model parameter estimation capability is tested using a four-layer deposition. The results demonstrate the simulation based upon estimated process parameters matches the experimental results quite well. Simulation study also shows that the methodology described above works well in producing the reference layer height.Item Material Spreading and Compaction in Power-Based Solid Freeform Fabrication Methods: Mathematical Modeling(2008-09-10) Shanjani, Yaser; Toyserkani, EhsanIn this study, the spreading and compaction of powder by a counter-rotating roller, in the solid freeform fabrication (SFF) process, is modeled and characterized. The effect of layer thickness, roller diameter, amount of loose powder, and its initial density on the powder bed’s relative density and roller compaction pressure is investigated.Item Modeling and Experimental Results of Concentration with Support Material in Rapid Freeze Prototyping(2008-09-10) Bryant, Frances D.; Leu, Ming C.Ice structures with complex geometries and overhung areas are created by the Rapid Freeze Prototyping (RFP) process in a sufficiently cool environment by freezing water into ice as the main material in conjunction with a eutectic dextrose-water solution as the sacrificial support material. The supported areas in an ice structure are removed via an increase in temperature in a separate environment after the structure is completely fabricated. To understand to what extent these two materials mix during fabrication, two methods of modeling the concentration changes that occur near the interface of the main and support materials have been developed. The simulation results based on these models along with some experimentally measured data are presented in this paper.Item News-Bulletin of the University of Texas, Number 334(University of Texas at Austin, 1914-05-10) University of Texas at AustinItem Peristaltic transport due to finite amplitude bending and contraction waves(Journal of Fluid Mechanics, 1979) Wilson, Dennis E.; Panton, Ronald L.; Panton, Ronald L.Item Study on the Influence of Rapid Prototyping Parameters on Product Quality in 3D Printing(2008-09-10) Arumaikkannu, G.; Anilkumar, N.; Saravanan, R.This work aims at evaluating the relative significance of the input parameters on the product quality produced by Z510 3DP rapid fabricator. Taguchi’s L18 orthogonal array was employed to investigate the possible process parameters including binder setting saturation value (shell & core), layer thickness, and build orientation. Using a surface profilometer and CMM, a series of measurements in evaluating the 3DP products surface finish and dimensional accuracy has been carried out. Nonlinear regression model was developed and a statistical analysis was done to determine the significant factors affecting the product quality of the fabricated products. Optimal process parameter settings were proposed using Particle Swarm Optimization technique. The results were validated by conducting the confirmatory experiments.Item University Interscholastic League Beginners' Slide Rule Manual(University of Texas at Austin, 1970-03-01) Brown, Otto G.; Rylander, H. Grady