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Articles 31 - 60 of 253

Full-Text Articles in Mechanical Engineering

High Throughput Mechanical Testing Platform And Application In Metal Additive Manufacturing And Process Optimization, Ke Huang, Chris Kain, Nathalia Diaz-Vallejo, Yongho Sohn, Le Zhou Jun 2021

High Throughput Mechanical Testing Platform And Application In Metal Additive Manufacturing And Process Optimization, Ke Huang, Chris Kain, Nathalia Diaz-Vallejo, Yongho Sohn, Le Zhou

Mechanical Engineering Faculty Research and Publications

Agility of additive manufacturing (AM) warrants a development of an equally agile, high-throughput properties evaluation technique that can efficiently assess properties of AM specimens as functions of materials and process variables. High throughput (HTP) tensile testing rig has been developed, enabled by miniature sample design and Python based control codes for a full automation of testing and data processing. The rig is capable of testing 60 specimens per hour, much faster than conventional tensile testing. To luminate the merit of its use, an efficient process optimization workflow based on HTP testing is proposed and demonstrated on laser powder bed fusion …

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Additive Manufacturing And Mechanical Properties Of The Dense And Crack Free Zr-Modified Aluminum Alloy 6061 Fabricated By The Laser-Powder Bed Fusion, Abhishek Mehta, Le Zhou, Thinh Huynh, Sharon Park, Holden Hyer, Shutao Song, Yunali Bai, D. Devin Imholte, Nicolas E. Woolstenhulme, Daniel M. Wachs, Yongho Sohn May 2021

Additive Manufacturing And Mechanical Properties Of The Dense And Crack Free Zr-Modified Aluminum Alloy 6061 Fabricated By The Laser-Powder Bed Fusion, Abhishek Mehta, Le Zhou, Thinh Huynh, Sharon Park, Holden Hyer, Shutao Song, Yunali Bai, D. Devin Imholte, Nicolas E. Woolstenhulme, Daniel M. Wachs, Yongho Sohn

Mechanical Engineering Faculty Research and Publications

For additive manufacturing such as laser powder bed fusion (LPBF), commercial aluminum alloy (AA) 6061 is typically considered unsuitable due to formation of solidification cracking and/or excessive porosity. In this study, to improve buildability/printability of AA6061, 1 wt% of Zr was alloyed to produce Zr-modified AA6061 by LPBF. Powders of unmodified and Zr-modified AA6061 were produced by gas atomization, and utilized as a feed-stock for the LPBF to fabricate specimens for microstructural examination and mechanical testing. The as-built unmodified AA6061 exhibited poor printability due to formation of cracks and porosity in the microstructure regardless of LPBF parameters. However, the Zr-modified …

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High Strength We43 Microlattice Structures Additively Manufactured By Laser Powder Bed Fusion, Holden Hyer, Le Zhou, Qingyang Liu, Dazhong Wu, Shutao Song, Yuanli Bai, Brandon Mcwilliams, Kyu Cho, Yongho Sohn May 2021

High Strength We43 Microlattice Structures Additively Manufactured By Laser Powder Bed Fusion, Holden Hyer, Le Zhou, Qingyang Liu, Dazhong Wu, Shutao Song, Yuanli Bai, Brandon Mcwilliams, Kyu Cho, Yongho Sohn

Mechanical Engineering Faculty Research and Publications

WE43 is a high strength, high creep resistant Mg-alloy containing Y, Nd, and Zr, and has potential for many lightweight structural applications in the automotive, aerospace, and biomedical industries. Additive manufacturing technology such as laser powder bed fusion (LPBF) brings an opportunity to produce complex geometries such as lattice structures. In this study, fabrication, compressive behavior, and fracture modes of 24 different microlattice structures were investigated by varying unit cell type, strut diameter, and number of unit cells. These complex lattice structures were produced by LPBF using the parameter set: laser power = 200 W, scan speed = 1100 mm/sec, …

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In Situ Tem Characterization Of Microstructure Evolution And Mechanical Behavior Of The 3d-Printed Inconel 718 Exposed To High Temperature, Supriya Koul, Le Zhou, Omar Ahmed, Yongho Sohn, Tengfei Jiang, Akihiro Kushima Apr 2021

In Situ Tem Characterization Of Microstructure Evolution And Mechanical Behavior Of The 3d-Printed Inconel 718 Exposed To High Temperature, Supriya Koul, Le Zhou, Omar Ahmed, Yongho Sohn, Tengfei Jiang, Akihiro Kushima

Mechanical Engineering Faculty Research and Publications

This in situ transmission electron microscopy work presents a nanoscale characterization of the microstructural evolution in 3D-printed Inconel 718 (IN718) while exposed to elevated temperature and an associated change in the mechanical property under tensile loading. Here, we utilized a specially designed specimen shape that enables tensile testing of nano-sized thin films without off-plane deformations. Additionally, it allows a seamless transition from the in situ heating to tensile experiment using the same specimen, which enables a direct correlation of the microstructure and the mechanical property of the sample. The method was successfully used to observe the residual stress relaxation and …

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Composition-Dependent Solidification Cracking Of Aluminum-Silicon Alloys During Laser Powder Bed Fusion, Holden Hyer, Le Zhou, Abhishek Mehta, Sharon Park, Thinh Huynh, Shutao Song, Yuanli Bai, Kyu Cho, Brandon Mcwilliams, Yongho Sohn Apr 2021

Composition-Dependent Solidification Cracking Of Aluminum-Silicon Alloys During Laser Powder Bed Fusion, Holden Hyer, Le Zhou, Abhishek Mehta, Sharon Park, Thinh Huynh, Shutao Song, Yuanli Bai, Kyu Cho, Brandon Mcwilliams, Yongho Sohn

Mechanical Engineering Faculty Research and Publications

Consistent manufacturing of volumetrically dense engineering components, free of solidification cracks by laser powder bed fusion (LPBF), has been demonstrated for Al-Si alloys such as AlSi10Mg and Al12Si. The success in LPBF of these alloys is attributed to the near eutectic composition with a small freezing range. To illuminate this observation, cracking susceptibility was examined from Scheil-Gulliver solidification modeling by calculating the hot cracking susceptibility, |dT/dfS1/2|. To validate the findings from hot cracking susceptibility calculations, six binary Al-Si alloys, whose compositions were strategically chosen at hypo-, near-, and hyper-eutectic compositions, were gas atomized into alloy powders, and …

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A Hybrid Droplet Vaporization-Adaptive Surrogate Model Using An Optimized Continuous Thermodynamics Distribution, Simcha L. Singer, Michael Hayes, Alanna Y. Cooney Mar 2021

A Hybrid Droplet Vaporization-Adaptive Surrogate Model Using An Optimized Continuous Thermodynamics Distribution, Simcha L. Singer, Michael Hayes, Alanna Y. Cooney

Mechanical Engineering Faculty Research and Publications

Liquid transportation fuels are composed of hundreds of species, necessitating the use of surrogates in CFD simulations. Surrogates composed of a few species are often formulated to emulate the combustion properties targets (CPTs) of pre-vaporized fuels but fail to reproduce their vaporization behavior, implying that such surrogates cannot replicate the CPTs in the presence of preferential vaporization. The prevailing approach to this problem proposes a physical–chemical surrogate formulated to match the fuel’s distillation curve in addition to its CPTs. However, the physical–chemical surrogate approach requires more species, may not reproduce the instantaneous (distillation-resolved) CPTs, and is not well-suited to conditions …

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Microstructural Development In As Built And Heat Treated In625 Component Additively Manufactured By Laser Powder Bed Fusion, Holden Hyer, Ryan Newell, Dan Matejczyk, Sinsar Hsie, Mason Anthony, Le Zhou, Cathy Kammerer, Yongho Sohn Feb 2021

Microstructural Development In As Built And Heat Treated In625 Component Additively Manufactured By Laser Powder Bed Fusion, Holden Hyer, Ryan Newell, Dan Matejczyk, Sinsar Hsie, Mason Anthony, Le Zhou, Cathy Kammerer, Yongho Sohn

Mechanical Engineering Faculty Research and Publications

The RL10 engine program is exploring the use of IN625 Ni-base superalloy components that are additively manufactured using laser powder bed fusion (LPBF). IN625 alloy powders are commercially available for LPBF to produce dense, complex parts/components. In this study, IN625 components, with both simple and complex geometries with overhangs, were manufactured via LPBF, and subjected to a heat-treatment consisting of a stress relief, hot isostatic pressing (HIP), and a solution anneal. The microstructure was examined with optical, scanning electron, and transmission electron microscopy. Changes in phase constituents and microstructure were documented as a function of heat treatment and component geometry …

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Effects Of Alloy Composition And Solid-State Diffusion Kinetics On Powder Bed Fusion Cracking Susceptibility, Holden Hyer, Le Zhou, Abhishek Mehta, Yongho Sohn Feb 2021

Effects Of Alloy Composition And Solid-State Diffusion Kinetics On Powder Bed Fusion Cracking Susceptibility, Holden Hyer, Le Zhou, Abhishek Mehta, Yongho Sohn

Mechanical Engineering Faculty Research and Publications

Laser powder bed fusion (LPBF) has demonstrated its unique ability to produce customized, complex engineering components. However, processing of many commercial Al-alloys by LPBF remains challenging due to the formation of solidification cracking, although they are labelled castable or weldable. In order to elucidate this divergence, solidification cracking susceptibility from the steepness of the solidification curves, specifically |dT⁄dfs1⁄2|, as the fraction solidified nears 1 towards complete solidification, was calculated via Scheil–Gulliver model as a function of solute concentration in simple binary Al-Si, Al-Mg, and Al-Cu systems. Introduction of “diffusion in solid” into Scheil–Gulliver model resulted in a …

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Addressing The Practical Limitations Of Volatile Organic Compound Sensors Through An Oscillator-Based Sensing Array, Allison K. Murray, Joseph R. Meseke, Nikhil Bajaj, Jeffrey F. Rhoads Jan 2021

Addressing The Practical Limitations Of Volatile Organic Compound Sensors Through An Oscillator-Based Sensing Array, Allison K. Murray, Joseph R. Meseke, Nikhil Bajaj, Jeffrey F. Rhoads

Mechanical Engineering Faculty Research and Publications

This work demonstrated the development of an array of oscillator-based sensors for the detection of volatile organic compounds (VOCs). A field-programmable gate array (FPGA) was leveraged to monitor the oscillation frequency of 16 sensing elements in parallel. It was shown that three functional chemistries can be deposited via inkjet printing to detect several analytes selectively. These unique response characteristics allowed for the creation of a linear regression model that relates the shifts in oscillation frequencies to the concentration of specific analytes. This approach utilized a single array with sufficient elements to incorporate intentional redundancies. Ultimately, this work demonstrated a low-cost …

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A New Line-By-Line Methodology Based On The Spectral Contributions Of The Bands, Felipe R. Coelho, Aline Ziemniczak, Somesh Roy, Francis H.R. França Jan 2021

A New Line-By-Line Methodology Based On The Spectral Contributions Of The Bands, Felipe R. Coelho, Aline Ziemniczak, Somesh Roy, Francis H.R. França

Mechanical Engineering Faculty Research and Publications

This study presents a new methodology to solve thermal radiation in participating gases, the spectrally reduced integration (SRI), which employs a non-uniform spectral discretization to considerably reduce the computational cost of the line-by-line (LBL) solution while still maintaining good levels of accuracy. This non-uniform spectral mesh is generated from discretization schemes based on the spectral contributions of the bands, which apply less or more refined spectral resolution depending on the importance of the bands to the radiative transfer. Based on this methodology, several schemes were initially proposed and evaluated for a homogeneous H2O-CO2 mixture test case. Results …

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Globally Optimal Passive Compliance Control For Tasks Having Multiple Homotopy Classes, Jacob J. Rice, Joseph M. Schimmels Dec 2020

Globally Optimal Passive Compliance Control For Tasks Having Multiple Homotopy Classes, Jacob J. Rice, Joseph M. Schimmels

Mechanical Engineering Faculty Research and Publications

Redundant serial manipulators with variable stiffness actuators (VSAs) are capable of passive compliance control, in which the elastic behavior of the end-effector is controlled for robust interaction with a stiff environment. This paper addresses the problem of finding the globally optimal joint manipulation path (sequence of joint positions and compliances) that yields a desired task manipulation path (sequence of end-effector positions and compliances) when there is one degree of redundancy. The space of admissible joint paths can be very complex, with multiple bifurcations resulting in multiple homotopy classes of joint paths. Bifurcations due to singularities in the combined kinematic and …

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Modifying The Surface Chemistry And Nanostructure Of Carbon Nanotubes Facilitates The Detection Of Aromatic Hydrocarbon Gases, John N. Hodul, Allison K. Murray, Nikhil F. Carneiro, Joseph R. Meseke, Jacob Morris, Xinping He, Dimitry Zemlyanov, George T.-C. Chiu, James E. Braun, Jeffrey F. Rhoads, Bryan W. Boudouris Oct 2020

Modifying The Surface Chemistry And Nanostructure Of Carbon Nanotubes Facilitates The Detection Of Aromatic Hydrocarbon Gases, John N. Hodul, Allison K. Murray, Nikhil F. Carneiro, Joseph R. Meseke, Jacob Morris, Xinping He, Dimitry Zemlyanov, George T.-C. Chiu, James E. Braun, Jeffrey F. Rhoads, Bryan W. Boudouris

Mechanical Engineering Faculty Research and Publications

The benzene, toluene, and xylene (BTX) compounds currently utilized in many building materials and paints have been linked to deleterious health effects, and thus, monitoring the presence of these compounds is of increasing importance with respect to public health. As such, there is a critical need for next-generation low-cost, selective, and sensitive indoor BTX sensors. Current BTX detection systems require multicomponent, complex devices or require high power input to achieve BTX detection at meaningful concentrations, but this long-standing paradigm can be altered through the introduction of tailored nanomaterials. Specifically, we demonstrate a selective BTX resonant mass sensor platform that leverages …

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Anomalous Growth Of Al8Mo3 Phase During Interdiffusion And Reaction Between Al And Mo, Abhishek Mehta, Le Zhou, Dennis D. Keiser Jr., Yongho Sohn Oct 2020

Anomalous Growth Of Al8Mo3 Phase During Interdiffusion And Reaction Between Al And Mo, Abhishek Mehta, Le Zhou, Dennis D. Keiser Jr., Yongho Sohn

Mechanical Engineering Faculty Research and Publications

No abstract provided.

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Understanding The Laser Powder Bed Fusion Of Alsi10mg Alloy, Holden Hyer, Le Zhou, Sharon Park, Guilherme Gottsfritz, George Benson, Bjorn Tolentino, Brandon Mcwilliams, Kyu Cho, Yongho Sohn Aug 2020

Understanding The Laser Powder Bed Fusion Of Alsi10mg Alloy, Holden Hyer, Le Zhou, Sharon Park, Guilherme Gottsfritz, George Benson, Bjorn Tolentino, Brandon Mcwilliams, Kyu Cho, Yongho Sohn

Mechanical Engineering Faculty Research and Publications

We examine the microstructural characteristics of LPBF AlSi10Mg produced by using a wide range of LPBF processing parameters with independently varied laser power, hatch spacing, scan speed, slice thickness, and the normalized energy density. The lower energy density produced lack of fusion flaws from residual interparticle spacing, while the higher energy density produced spherical pores from trapped gas. The highest density (> 99%) samples were produced by using an energy density of 32 to 54 J/mm3. Within this energy density range, use of smaller slice thicknesses increased the processing window that would produce dense AlSi10Mg samples. A cellular …

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Multi-Homotopy Class Optimal Path Planning For Manipulation With One Degree Of Redundancy, Jacob J. Rice, Joseph M. Schimmels Jul 2020

Multi-Homotopy Class Optimal Path Planning For Manipulation With One Degree Of Redundancy, Jacob J. Rice, Joseph M. Schimmels

Mechanical Engineering Faculty Research and Publications

Redundant manipulators have an infinitely large set of joint paths that yield a desired end-effector path in the task space. A unique joint path can be obtained by minimizing a global cost function. Prior optimal control methods minimize a global cost function to find a local minimum within a homotopy class. Many possible locally optimal joint paths are in different homotopy classes. This paper presents an algorithm that effectively searches the solution space and finds many locally optimal paths in all relevant homotopy classes. The path with the lowest cost is very likely the globally optimal path. The algorithm is …

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Process-Dependent Composition, Microstructure, And Printability Of Al-Zn-Mg And Al-Zn-Mg-Sc-Zr Alloys Manufactured By Laser Powder Bed Fusion, Le Zhou, Holden Hyer, Saket Thapliyal, Rajiv S. Mishra, Brandon Mcwilliams, Kyu Cho, Yongho Sohn Jun 2020

Process-Dependent Composition, Microstructure, And Printability Of Al-Zn-Mg And Al-Zn-Mg-Sc-Zr Alloys Manufactured By Laser Powder Bed Fusion, Le Zhou, Holden Hyer, Saket Thapliyal, Rajiv S. Mishra, Brandon Mcwilliams, Kyu Cho, Yongho Sohn

Mechanical Engineering Faculty Research and Publications

Additive manufacturing (AM) technology for metallic alloys such as laser powder bed fusion (LPBF) brings tremendous opportunities for development of novel alloys specifically designed for AM that would desensitize the inherent process variability and requires a refined understanding of processing–structure–property relationship that would contribute to future alloy development. In this study, two different alloys, Al-6Zn-2Mg and Al-6Zn-2Mg-0.7Sc-0.3Zr in wt. pct, representing traditional and AM-specific novel aluminum alloys, respectively, were manufactured by LPBF technique using pre-alloyed gas atomized powders. The Al-Zn-Mg ternary alloys exhibited cracks at various LPBF processing parameters, primarily along the grain boundaries of the large columnar grains that …

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Mechanical Analysis And Modeling Of Porous Thermal Barrier Coatings, Shiyu Cui, Wenping Liang, Luis Saucedo Mora, Qiang Miao, Joseph P. Domblesky, Hao Lin, Lijia Yu May 2020

Mechanical Analysis And Modeling Of Porous Thermal Barrier Coatings, Shiyu Cui, Wenping Liang, Luis Saucedo Mora, Qiang Miao, Joseph P. Domblesky, Hao Lin, Lijia Yu

Mechanical Engineering Faculty Research and Publications

Thermal barrier coatings (TBCs) are applied to the surface of components that are used in gas turbines and aircraft engines in order to increase the heat load. In this study, the cross-sectional microstructures of TBCs were investigated via scanning electron microscopy. After calculating the porosity and the pore size distribution, a two-dimensional finite element model with four different porosities (0, 1, 3, and 5%) were established. A stochastic method was used to generate a randomly distributed porous structure. Based on the results of FE analysis and nanoindentation tests, It was found that, at a high porosity (>3%), radial cracks …

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Additive Manufacturing Of Dense We43 Mg Alloy By Laser Powder Bed Fusion, Holden Hyer, Le Zhou, George Benson, Brandon Mcwilliams, Kyu Cho, Yongho Sohn May 2020

Additive Manufacturing Of Dense We43 Mg Alloy By Laser Powder Bed Fusion, Holden Hyer, Le Zhou, George Benson, Brandon Mcwilliams, Kyu Cho, Yongho Sohn

Mechanical Engineering Faculty Research and Publications

WE43 is a high-strength, corrosion-resistant Mg-alloy containing rare earths such as Y and Nb, and has potential for many lightweight structural or bioresorbable prosthetic applications. In this study, additive manufacturing of dense WE43 alloy by laser powder bed fusion (LPBF) from gas atomized powders has been accomplished through studies involving single track scan of wrought WE43, parametric variation of LPBF, microstructural analysis and mechanical testing, both in compression and tension. The Archimedes method and image analyses from optical micrographs were employed to document the LPBF of dense (>99 % relative density) WE43 using optimum parameters of 200 W laser …

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Detailed Modeling Of A Small-Scale Turbulent Pool Fire, Bifen Wu, Somesh Roy, Xinyu Zhao Apr 2020

Detailed Modeling Of A Small-Scale Turbulent Pool Fire, Bifen Wu, Somesh Roy, Xinyu Zhao

Mechanical Engineering Faculty Research and Publications

Turbulent pool fires have been studied as a canonical configuration in fire science with wide interest. A numerical study of a small-scale turbulent heptane pool fire is conducted in the present study to understand the interactions and coupling among turbulence, chemistry, soot, and radiation in pool fires. A Monte Carlo ray tracing based radiation solver, with line-by-line spectral models for five gaseous species and soot, is coupled with a fireFOAM-based reacting flow solver to describe the dynamics of the target fire. A 33-species skeletal mechanism is employed to describe the finite-rate chemistry. A two-equation soot model with C2H …

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An Integrated Computational Materials Engineering-Anchored Closed-Loop Method For Design Of Aluminum Alloys For Additive Manufacturing, Saket Thapliyal, Mageshwari Komarasamy, Shivakant Shukla, Le Zhou, Holden Hyer, Sharon Park, Yongho Sohn, Rajiv S. Mishra Mar 2020

An Integrated Computational Materials Engineering-Anchored Closed-Loop Method For Design Of Aluminum Alloys For Additive Manufacturing, Saket Thapliyal, Mageshwari Komarasamy, Shivakant Shukla, Le Zhou, Holden Hyer, Sharon Park, Yongho Sohn, Rajiv S. Mishra

Mechanical Engineering Faculty Research and Publications

A closed-loop approach based on integrated computational material engineering was used to design, fabricate and characterize an Al–1.5Cu–0.8Sc–0.4Zr (wt%) alloy for laser powder bed fusion additive manufacturing (AM). Finalization of composition and prediction of solidification behavior and mechanical properties were done using calculation of phase diagrams (CALPHAD) and analytical tools. The microstructure of the printed alloy in as-built condition consisted of crack-free regions with fine-equiaxed grains which was consistent with CALPHAD results. Yield strength (YS) of ~349 ± 8 MPa was also in more than 90% agreement with predicted YS. The findings demonstrate an efficient methodology for application-based alloy design …

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A Quasi-Monte Carlo Solver For Thermal Radiation In Participating Media, Joseph Farmer, Somesh Roy Feb 2020

A Quasi-Monte Carlo Solver For Thermal Radiation In Participating Media, Joseph Farmer, Somesh Roy

Mechanical Engineering Faculty Research and Publications

The Monte Carlo (MC) method is the most accurate method for resolving radiative heat transfer in participating media. However, it is also computationally prohibitive in large-scale simulations. To alleviate this, this study proposes a quasi-Monte Carlo (QMC) method for thermal radiation in participating media with a focus on combustion-related problems. The QMC method employs low-discrepancy sequences (LDS) in place of the traditional random numbers. Three different low-discrepancy sequences – Sobol, Halton, and Niederreiter – were examined as part of this work. The developed QMC method was first validated against analytical solutions of radiative heat transfer in several one-dimensional configurations. Then …

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Effect Of O2 Concentration In Ambient Mixture And Multiphase Radiation On Pollutant Formation In Ecn Spray-A, Khaled Mosharraf Mosharraf Mukut, Somesh Roy Jan 2020

Effect Of O2 Concentration In Ambient Mixture And Multiphase Radiation On Pollutant Formation In Ecn Spray-A, Khaled Mosharraf Mosharraf Mukut, Somesh Roy

Mechanical Engineering Faculty Research and Publications

The present study investigates the formation and evolution of soot and NOX in a high-pressure constant-volume combustion chamber. This work focuses on the effect of multiphase thermal radiation and O2 dilution in ambient/exhaust gases, some- times also referred to as exhaust gas recirculation(EGR), qualitatively and quantitatively. The spray-A case (n-dodecane as fuel) from Engine Combustion Network (ECN) is used as the target condition. Two different soot modeling approaches have been considered: a semi-empirical two-equation model and a detailed method of moments with interpolative closure (MOMIC) model. A multiphase photon Monte Carlo (PMC) solver with line-by-line (LBL) spectral data …

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Investigation Of Through Thickness Microstructure And Mechanical Properties In Friction Stir Welded 7n01 Aluminum Alloy Plate, Xingxin Zhao, Zhiyong Yang, Joseph P. Domblesky, Jianmin Han, Zhiqiang Li, Xiaolong Liu Jul 2019

Investigation Of Through Thickness Microstructure And Mechanical Properties In Friction Stir Welded 7n01 Aluminum Alloy Plate, Xingxin Zhao, Zhiyong Yang, Joseph P. Domblesky, Jianmin Han, Zhiqiang Li, Xiaolong Liu

Mechanical Engineering Faculty Research and Publications

An on-going problem in friction stir welded (FSW) joints used in the high-speed train sector is that the microstructure and mechanical properties can significantly vary in thick sections. Because inhomogeneous properties can reduce weld efficiency and degrade service performance, it is of some interest to understand how inhomogeneous properties can develop in FSW welds made from precipitation hardening alloys such as 7N01. In the current study, butt welds were made using 12 mm thick plates and then sectioned perpendicular to the weld line. Five 2.2 mm thick slices were cut from a section and used to measure tensile properties access …

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Crack Propagation And Microstructural Transformation On The Friction Surface Of A High-Speed Railway Brake Disc, Zhizhong Wang, Jianmin Han, Joseph P. Domblesky, Zhiqiang Li, Xinguang Fan, Xiaolong Liu Jun 2019

Crack Propagation And Microstructural Transformation On The Friction Surface Of A High-Speed Railway Brake Disc, Zhizhong Wang, Jianmin Han, Joseph P. Domblesky, Zhiqiang Li, Xinguang Fan, Xiaolong Liu

Mechanical Engineering Faculty Research and Publications

While brake disc wear represents a significant problem in high-speed rail systems, the progressive development of fatigue cracks during successive braking cycles also plays a great role in braking integrity. The modified microstructure consisting of a white etching layer (WEL) containing nanosized ferrite was observed on the friction surface of worn brake discs. In order to analyze how sequential thermal and mechanical stress affected crack propagation and microstructure evolution in brake discs, successive braking cycles were simulated on a full-scale braking bench test rig. Crack initiation and propagation mechanisms were proposed based on the experimental results, i.e., (i) occurrence of …

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Micro-Ct-Based Approaches For Quantifying The Morphology Of Pulverized Char Particles, Scott Jorgensen, Simcha L. Singer May 2019

Micro-Ct-Based Approaches For Quantifying The Morphology Of Pulverized Char Particles, Scott Jorgensen, Simcha L. Singer

Mechanical Engineering Faculty Research and Publications

Morphological analysis of pulverized coal char particles using two-dimensional (2-D) cross-sectional imaging has been widely employed, but its accuracy has not been adequately assessed. In this study, pulverized coal char particles are imaged in three dimensions (3-D) using high-resolution X-ray microcomputed tomography (micro-CT). Particle volume, macropore volume, and macroporosity are measured in three dimensions and analyzed as a function of distance from the particle center using averaging at each radial location. A technique for extracting each particle’s average wall thickness, another morphological parameter used for classification, is also presented based on micro-CT imaging. When applied to pulverized bituminous coal char …

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High Fidelity Dynamic Modeling And Nonlinear Control Of Fluidic Artificial Muscles, Jonathon Earl Slightam Apr 2019

High Fidelity Dynamic Modeling And Nonlinear Control Of Fluidic Artificial Muscles, Jonathon Earl Slightam

Dissertations (1934 -)

A fluidic artificial muscle is a type of soft actuator. Soft actuators transmit power with elastic or hyper-elastic bladders that are deformed with a pressurized fluid. In a fluidic artificial muscle a rubber tube is encompassed by a helical fiber braid with caps on both ends. One of the end caps has an orifice, allowing the control of fluid flow in and out of the device. As the actuator is pressurized, the rubber tube expands radially and is constrained by the helical fiber braid. This constraint results in a contractile motion similar to that of biological muscles. Although artificial muscles …

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Partial Pressures And High-Temperature Thermodynamic Properties For The Germanium-Tellurium System, Robert F. Brebrick Apr 2019

Partial Pressures And High-Temperature Thermodynamic Properties For The Germanium-Tellurium System, Robert F. Brebrick

Mechanical Engineering Faculty Research and Publications

Our earlier optical density measurements over Ge-Te compositions are reanalyzed. Spectral characteristics of the GeTe(g) spectrum are determined from measurements with a 1 at.% Te sample near 1200 K. Beers law constants for GeTe(g) are established by requiring consistency between spectroscopic results for the dissociation of GeTe(g) into Ge(g) and Te2(g) and our description in terms of the partial pressure of Te2 and the partial optical density of GeTe over Ge saturated GeTe(c). Between 870 and 997 K the partial pressures over Ge saturated GeTe(c) are ln P(Te2,atm) = − 24,800/T + 17.600 and ln …

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Shock Compaction Of Graphene Doped Yttria Stabilized Zirconia: An Experimental And Computational Study, Christopher Rueben Johnson Apr 2019

Shock Compaction Of Graphene Doped Yttria Stabilized Zirconia: An Experimental And Computational Study, Christopher Rueben Johnson

Master's Theses (2009 -)

Yttria stabilized zirconia (YSZ) is a broadly used ceramic due to its impeccable hardness and thermal stability. Limitations of the material, however, subsist within its fracture toughness. Literature indicates that shock consolidation may enable production of composite YSZ and graphene mixtures with improved fracture toughness and other material properties while maintaining the material’s nanostructure dimensionality. Therefore, investigation of the compaction phenomena at non-equilibrium states will provide informative results to be used in the fabrication of bulk graphene-YSZ composites. Computational molecular dynamics (MD) simulations and impact experiments are conducted to explore and characterize the dynamic response of the YSZ variants. Molecular …

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Geometry Based Synthesis Of Planar Compliances With Redundant Mechanisms Having Five Compliant Components, Shuguang Huang, Joseph M. Schimmels Apr 2019

Geometry Based Synthesis Of Planar Compliances With Redundant Mechanisms Having Five Compliant Components, Shuguang Huang, Joseph M. Schimmels

Mechanical Engineering Faculty Research and Publications

In this paper, a geometric approach to the passive realization of any planar compliance with a redundant compliant mechanism is presented. The mechanisms considered are either simple serial mechanisms consisting of five elastic joints or simple parallel mechanisms consisting of five springs. For each type of mechanism, realization conditions to achieve a given compliance are derived. The physical significance of each condition is identified and graphically interpreted. Geometry based synthesis procedures to achieve any given compliance are developed for both types of mechanisms. Since each realization condition imposes restrictions solely on the mechanism geometry, the procedures allow one to choose …

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Analysis Of The Forming Characteristics For Cu/Al Bimetal Tubes Produced By The Spinning Process, Kai Jin, Qiwei Yuan, Jie Tao, Joseph P. Domblesky, Xunzhong Guo Mar 2019

Analysis Of The Forming Characteristics For Cu/Al Bimetal Tubes Produced By The Spinning Process, Kai Jin, Qiwei Yuan, Jie Tao, Joseph P. Domblesky, Xunzhong Guo

Mechanical Engineering Faculty Research and Publications

Tube spinning technology represents a process with high forming precision and good flexibility and is increasingly being used in the manufacture of bimetal composite tubular structures. In the present study, a forming analysis of clad tube and base tube in spinning process was conducted through numerical simulations and experiments. There was an equivalent stress transition on the interface since the stress transmission was retarded from clad tube to base tube. The yield strength became a main consideration during a design bimetal composite tube. Meanwhile, the strain distributions in axial direction, tangential direction, and radial direction were also investigated to determine …

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