Mechanical Engineering Commons^™

Warpage And Shape Distortion In Laser Metal Sintering, Xuan Wang

Industrial and Manufacturing Engineering

Selective Laser Sintering (SLS) is the primary method to fabricate metal and ceramic components in additive manufacturing. Due to the anisotropy of powder material, the sintering rate difference will inevitably causes shape change, distortion , and other defects of sintered parts. In this paper, a continuum model was developed to simulate the SLS process. The developed model has been successful to predict sintering kinetics. The impact of processing parameters, such as laser power, scanning speed, hatching distance, and particle size has been studied . The proposed method provides an innovative tool to optimize SLS process parameters.

Mechanical Properties Of Intermetallic Compounds In Electrodeposited Multilayered Thin Film At Small Scale By Nanoindentation

Faculty of Engineering University of Malaya

Mechanical properties of intermetallic compounds (IMCs) which were formed in electrodeposited Cu/Sn and Cu/Ni/Sn multilayered thin film have been investigated. The layers of Cu, Sn and Ni were formed by electrodeposition technique using copper pyrophosphate, tin methanesulfonic and nickel Watts baths, respectively. After synthesis, samples were subjected to high temperature aging at 150 degrees C for 168 h. Two different types of intermetallics Cu3Sn and Cu6Sn5 were formed in Cu/Sn. After adding ultra-thin layer of Ni (70 nm) in between Cu and Sn layers, (Cu, Ni)(6)Sn-5 was formed after aging at similar condition to that of Cu/Sn. Tin whisker growth …

Computational Fluid Dynamics Applied To The Analysis Of Blood Flow Through Central Aortic To Pulmonary Artery Shunts, Carey Celestin Jr

University of New Orleans Theses and Dissertations

This research utilizes CFD to analyze blood flow through pathways representative of central shunts, commonly used as part of the Fontan procedure to treat cyanotic heart disease. In the first part of this research, a parametric study of steady, Newtonian blood flow through parabolic pathways was performed to demonstrate the effect that flow pathway curvature has on wall shear stress distribution and flow energy losses. In the second part, blood flow through two shunts obtained via biplane angiograms is simulated. Pressure boundary conditions were obtained via catheterization. Results showed that wall shear stresses were of sufficient magnitude to initiate platelet …

Effects Of Biomass Moisture Content On Volatile Flame Length During Cofiring With Coal, Matthew Pollard

McKelvey School of Engineering Theses & Dissertations

Cofiring biomass with coal can contribute to meeting Renewable Portfolio Standards (RPS) and reduce pollutant emissions. The physical characteristics and composition of biomass can vary significantly, which can affect the combustion characteristics. When cofiring biomass with coal, these differences can impact the structure of the volatile flame, the region where combustion of volatiles dominates. The length and location of the volatile flame is important to flame stability and determines the location and extent of volatile release. This has an effect on pollutant emissions, such as NOx (nitrogen oxides). Previously, the effects of parameters such as cofiring ratio, particle size, and …

Numerical Simulation And Optimization Of Carbon Dioxide Utilization For Enhanced Oil Recovery From Depleted Reservoirs, Razi Safi

McKelvey School of Engineering Theses & Dissertations

Due to concerns about rising CO₂ emissions from fossil fuel power plants, there has been a strong emphasis on the development of a safe and economical method for Carbon Capture Utilization and Storage (CCUS). One area of current interest in CO₂ utilization is the Enhanced Oil Recovery (EOR) from depleted reservoirs. In an Enhanced Oil Recovery system, a depleted or depleting oil reservoir is re-energized by injecting high-pressure CO₂ to increase the recovery factor of the oil from the reservoir. An additional benefit beyond oil recovery is that the reservoir could also serve as a long-term storage …

Maximum Energy Efficiency Cost Effectiveness In New Home Construction, Florida Solar Energy Center, Philip Fairey

FSEC Energy Research Center®

EnergyGauge® USA (v.4.0.00) is used to examine the cost effectiveness of high performance homes that are improved to significantly exceed the minimum requirements of the 2015 IECC. The objective of the study is to determine the maximum level of energy efficiency that can be considered cost effective to the consumer. For these purposes, it is the cost effectiveness of the entire package of measures that is considered by the analysis rather than the cost effectiveness of individual measures. Optimization and rank ordering of the individual improvement measures in the package is not considered by the analysis.

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The Microstructure And The Electrochemical Behavior Of Cobalt Chromium Molybdenum Alloys From Retrieved Hip Implants, Christopher P. Emerson

FIU Electronic Theses and Dissertations

Because of their excellent mechanical, tribological, and electrochemical properties, Cobalt Chromium Molybdenum alloys have been used as the material for both the stem and head of modular hip implants. Corrosion is one mechanism by which metal debris, from these implants, is generated, which can lead to adverse events that requires revision surgery. Manufacturing process such as wrought, as-cast, and powder metallurgy influences the microstructure, material properties, and performance of these implants

The current research focuses on analyzing the microstructure of CoCrMo alloys from retrieved hip implants with optical and scanning electron microscopy. Additionally, energy disperse spectroscopy was utilized to determine …

Fiber Optic Bandage, Logan Mcneil, Cameron Pilkey, Brittani Erwin, Adam Wojnar

Faculty Publications and Other Works -- Biomedical and Diagnostic Sciences

The purpose of this document is to show the report for the Fiber optic device formulated through the biomedical engineering department with a senior design group. A growing issue in medical technology is open wound care. Particularly prevalent in diabetics, open wound care is expensive and time consuming. Certain wavelengths of light have not only shown to have germicidal properties, but also allow cell growth and regeneration. The following design was founded around these ideas, and an initial design was developed. The design centered around using fiber optics as a means of replacing a wet bandage in a normal wound …

College Of Engineering Senior Design Competition Spring 2015, University Of Nevada, Las Vegas

Fred and Harriet Cox Senior Design Competition Projects

Part of every UNLV engineering student’s academic experience, the senior design project stimulates engineering innovation and entrepreneurship. Each student in their senior year chooses, plans, designs, and prototypes a product in this required element of the curriculum. A capstone to the student’s educational career, the senior design project encourages the student to use everything learned in the engineering program to create a practical, real world solution to an engineering challenge. The senior design competition helps focus the senior students in increasing the quality and potential for commercial application for their design projects. Judges from local industry evaluate the projects on …

Mushy Zone Equilibrium Solidification Of A Semitransparent Layer Subject To Radiative And Convective Cooling, Chengcai Yao, Benjamin Chung, Guo-Xiang Wang

Dr. Guo-Xiang Wang

Equilibrium solidification in a semitransparent planar layer is studied using an isothermal mushy zone model. The layer is made up of a pure material being emitting, absorbing and isotropically scattering and is subject to radiative and convective cooling. The model involves solving simultaneously the transient energy equation and the radiation transport equation. An implicit finite volume scheme is employed to solve the energy equation, with the discrete ordinate method being used to deal with the radiation transport. A systematical parametric study is performed and the effects of various materials optical properties and processing conditions are investigated. It is found that …

Thermal Analysis On Planar Interface Stability In Solidification Of Semitransparent Materials, Guo-Xiang Wang, Chengcai Yao, Benjamin Chung

Dr. Guo-Xiang Wang

Significant melt undercooling may be developed in the melt in front of the solid/liquid interface during solidification of semitransparent materials because of internal radiative heat transfer with the environment. A nonequilibrium plana interface solidification model has been developed recently to permit the melt undercooling near the interface. A thermal analysis is presented for the stability of such a planar interface. . .

Thermomechanical Design Criteria For Ceramic-Coated Surfaces, Robert L. Mullen, J. Padovan, Minel J. Braun, Benjamin T.F. Chung, G. Mcdonals, Robert C. Hendricks

Dr. Benjamin T.F. Chung

Some early history of ceramic applications is presented. Finite element modeling of components to determine service and fabrication loads found inelastic behavior and residual stresses to be significant to component life. Inelastic behavior mitigates peak strains but enhances residual strains. Results of furnace, Mach 0.3 burner, and engine tests are discussed and categorized into design criteria (loading, geometry, fabrication, materials, analysis, and testing). These design rules and finite element analyses are brought to bear on two test cases: turboshaft engine seals, and rocket thrust chambers.

Thermomechanical Design Criteria For Zr02-Y203 Coated Surfaces, J. Padovan, Benjamin T.F. Chung, Glen E. Mcdonald, Robert C. Hendricks

Dr. Benjamin T.F. Chung

Thermocycling of ceramic-coated turbomachine components produces high thermomechanical stresses that are mitigated by plasticity and creep but aggravated by oxidation, with residual stresses exacerbated by all three. These residual stresses, coupled with the thermocyclic loading, lead to high compressive stresses that cause the coating to spall. In the paper a ceramic-coated gas path seal is modeled with consideration given to creep, plasticity, and oxidation. The resulting stresses and possible failure modes are discussed.

Towards A Dynamic Clamp For Neurochemical Modalities, C. M. Rivera, H.-J. Kwon, A. Hashmi, Gu Yu, J. Zhao, J. Gao, J. Xu, Wei Xue, A. G. Dimitrov

Henry M. Rowan College of Engineering Faculty Scholarship

The classic dynamic clamp technique uses a real-time electrical interface between living cells and neural simulations in order to investigate hypotheses about neural function and structure. One of the acknowledged drawbacks of that technique is the limited control of the cells’ chemical microenvironment. In this manuscript, we use a novel combination of nanosensor and microfluidic technology and microfluidic and neural simulations to add sensing and control of chemical concentrations to the dynamic clamp technique. Specifically, we use a microfluidic lab-on-a-chip to generate distinct chemical concentration gradients (ions or neuromodulators), to register the concentrations with embedded nanosensors and use the processed …

Response Of Endothelial Cells To Quantified Hemodynamic Shear Stress, Hamed Avari

Electronic Thesis and Dissertation Repository

Cardiovascular diseases (CVDs) are the number one cause of death globally. Arterial endothelial cell (EC) dysfunction plays a key role in many of these CVDs, such as atherosclerosis. Blood flow-induced wall shear stress (WSS), among many other pathophysiological factors, is shown to significantly contribute to EC dysfunction.

The present dissertation is an in vitro investigation of quantified WSS on ECs to quantitatively analyze the EC morphometric parameters, as well as cytoskeletal remodeling.

A hemodynamic facility based on the parallel plate flow chamber (PPFC) concept. The Laser Doppler Velocimetry (LDV) method with a custom set-up was implemented to suit the needs …

Evaluating The Optical Properties Of Tio2 Nanofluid For A Direct Absorption Solar Collector

Faculty of Engineering University of Malaya

Recent studies specify that designated nanofluids may increase the proficiency of direct absorption solar thermal collectors. To determine the efficiency of nanofluids in solar applications, their capability to change light energy to thermal energy must be identified (i.e., the absorption spectrum of the solar material). In view of that, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (200- 1100nm). In the first decade of nanofluid research, most of the focus was on measuring and modeling the fundamental thermophysical properties of nanofluids (i.e., thermal conductivity, density, viscosity, and convection coefficients). …

Experimental And Numerical Investigation Of Heat Transfer In Cnt Nanofluids

Faculty of Engineering University of Malaya

Nanofluids with their enhanced thermal conductivity are believed to be a promising coolant in heat transfer applications. In this study, carbon nanotube (CNT) nanofluids of 0.01wt%, stabilised by 1.0wt% gum arabic were used as a cooling liquid in a concentric tube laminar flow heat exchanger. The flow rate of cold fluid varied from 10 to 50g/s. Both experimental and numerical simulations were carried out to determine the heat transfer enhancement using CNT nanofluids. Computational fluid dynamics (CFD) simulations were carried out using Fluent v 6.3 by assuming single-phase approximation. Thermal conductivity, density and rheology of the nanofluid were also measured …

Investigating Cavitation Peening Parameters For Fatigue Performance Using Designed Experiment, Mohammadsadegh Mobin, Afshan Roshani, Mahmood Mobin, Ali Rastegari

Mohammadsadegh Mobin

Mechanical surface enhancement techniques such as cavitation peening (CP) have various design parameters which can affect the fatigue performance of the part. In this study, a full factorial design of experiment is applied to investigate the effects of cavitation peening process parameters on the fatigue performance of carburized steel. These parameters include standoff distance, cavitation number, nozzle size, and exposure time. The response variables considered in this experiment include residual stress, surface roughness and austenitic ratio. Results obtained from full factorial design of experiment method were compared with the results from literature which applied Taguchi method. The comparison revealed that …

Metacomposites Protection System Against Primary Blast Injury, Kwek Tan, C. Sun

Dr. Kwek-Tze Tan

There is an increasing use of improvised explosive devices (IEDs) in terrorist and insurgent activities. Exposure to blast is becoming more frequent. Blast related injuries can be inflicted at various levels. Primary blast injury results from blast wave-induced changes in atmospheric pressure, causing organs and tissues to rupture due to shearing and stretching at different rates. Secondary blast injury results from objects put in motion by the blast wind impacting a person. Tertiary blast injury results from a person being blown into solid objects by the blast wind. This paper deals with the protection system against primary blast injury by …

Influence Of Stitch Density And Stitch Thread Thickness On Compression After Impact Strength Of Stitched Composites, Kwek Tan, N. Watanabe, Y. Iwahori, T. Ishikawa

Dr. Kwek-Tze Tan

This study aims to investigate the influence of stitch density and stitch thread thickness on compression after impact (CAI) strength of stitched composites. Unstitched laminated composites and specimens stitched with varying stitch density and stitch thread thickness are subjected to impact damage and then compressive loading. It is shown that stitched composites have higher CAI strength than unstitched counterpart due to smaller impact-induced delamination area, where local buckling occurs during compressive failure. However, it is revealed that the effectiveness of stitching in suppressing delamination growth and inhibiting sublaminate buckling under compressive loading is intimately related to stitch density. It is …