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Articles 61 - 90 of 253

Full-Text Articles in Mechanical Engineering

Shattered Rim And Shelling Of High-Speed Railway Wheels In The Very-High-Cycle Fatigue Regime Under Rolling Contact Loading, Tao Cong, Jianmin Han, Jianmin Han, Joseph P. Domblesky, Xiaolong Liu Mar 2019

Shattered Rim And Shelling Of High-Speed Railway Wheels In The Very-High-Cycle Fatigue Regime Under Rolling Contact Loading, Tao Cong, Jianmin Han, Jianmin Han, Joseph P. Domblesky, Xiaolong Liu

Mechanical Engineering Faculty Research and Publications

Due to the improvement of the wear property, rolling contact fatigue including shattered rim and shelling are the main failure causes of the high-speed railway wheels. In this paper, shattered rim and shelling occurred on the service wheels of the China Railway High-speed (CRH) trains were systematically investigated. The recorded data of the last ten years CRH operation indicated that all shattered rims and shelling were detected with serving >106 km (corresponding to the fatigue life 107–109 cycles) which is very-high-cycle fatigue (VHCF). The crack initiationregion of shattered rim located at the depth of 10–25 mm …

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A Detailed Modeling Study Of Radiative Heat Transfer In A Heavy-Duty Diesel Engine, Chandan Paul, Sebastian Ferreyro Fernandez, Daniel C. Haworth, Somesh Roy, Michael F. Modest Feb 2019

A Detailed Modeling Study Of Radiative Heat Transfer In A Heavy-Duty Diesel Engine, Chandan Paul, Sebastian Ferreyro Fernandez, Daniel C. Haworth, Somesh Roy, Michael F. Modest

Mechanical Engineering Faculty Research and Publications

In recent years, the importance of radiative heat transfer in combustion has been increasingly recognized. Detailed models have become available that accurately represent the complex spectral radiative properties of reacting gas mixtures and soot particles, and new methods have been developed to solve the radiative transfer equation (RTE). At the same time, the trends toward higher operating pressures and higher levels of exhaust-gas recirculation in compression-ignition engines, together with the demand for higher quantitative accuracy from in-cylinder CFD models, has led to renewed interest in radiative transfer in engines. Here an in-depth investigation of radiative heat transfer is performed for …

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Investigation Of Void Formation In Friction Stir Welding Of 7n01 Aluminum Alloy, Xingxin Zhao, Jianmin Han, Joseph P. Domblesky, Zhiyong Yang, Zhiqiang Li, Xiaolong Liu Jan 2019

Investigation Of Void Formation In Friction Stir Welding Of 7n01 Aluminum Alloy, Xingxin Zhao, Jianmin Han, Joseph P. Domblesky, Zhiyong Yang, Zhiqiang Li, Xiaolong Liu

Mechanical Engineering Faculty Research and Publications

Friction Stir Welding (FSW) is a solid state joining process that is widely used to produce high integrity aluminum weldments for a variety of industries. While extensive work has been conducted to understand flow behavior, much less research has been performed to identify how void defects form and how to predict them. In the present study, the relationship between rotation speed, plasticized region, and defect formation was investigated. To analyze how tunneling and cavity type void defects form during FSW, a 3-D Computational fluid dynamics(CFD) model based on the Fluent software code was used to simulate butt welding. The CFD …

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Effect Of Diffusion Distance On Evolution Of Kirkendall Pores In Titanium-Coated Nickel Wires, Aaron R. Yosta, Dinc Erdeniz, Ashley E. Paz Y Puente, David C. Dunanda Jan 2019

Effect Of Diffusion Distance On Evolution Of Kirkendall Pores In Titanium-Coated Nickel Wires, Aaron R. Yosta, Dinc Erdeniz, Ashley E. Paz Y Puente, David C. Dunanda

Mechanical Engineering Faculty Research and Publications

Microtubes of near-equiatomic nickel-titanium (NiTi) alloys can be created via the Kirkendall effect during NiTi interdiffusion, when nickel wires are surface-coated with titanium via pack cementation and subsequently homogenized. This study explores the effect of diffusion distance upon Kirkendall microtube formation in NiTi by considering a range of Ni wire diameters. For Ni wire diameters of 25, 50 and 100 μm, titanized at 925 °C for 0.5, 2, and 8 h to achieve average NiTi composition, partial interdiffusion occurs concurrently with Ti surface deposition, resulting in concentric shells of NiTi2, NiTi and Ni3Ti around a Ni …

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An Efficient Monte Carlo-Based Solver For Thermal Radiation In Participating Media, Joseph Farmer, Somesh Roy Jan 2019

An Efficient Monte Carlo-Based Solver For Thermal Radiation In Participating Media, Joseph Farmer, Somesh Roy

Mechanical Engineering Faculty Research and Publications

Monte Carlo-based solvers, while well-suited for accurate calculation of complex thermal radiation transport problems in participating media, are often deemed computationally unattractive for use in the solution of real-world problems. The main disadvantage of Monte Carlo (MC) solvers is their slow convergence rate and relatively high computational cost. This work presents a novel approach based on a low-discrepancy sequence (LDS) and is proposed for reducing the error bound of a Monte Carlo-based radiation solver. Sobols sequence – an LDS generated with a bit-by-bit exclusive-or operator – is used to develop a quasi-Monte Carlo (QMC) solver for thermal radiation in this …

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A Hybrid Droplet Vaporization-Chemical Surrogate Approach For Emulating Vaporization, Physical Properties, And Chemical Combustion Behavior Of Multicomponent Fuels, Alanna Y. Cooney, Simcha L. Singer Jan 2019

A Hybrid Droplet Vaporization-Chemical Surrogate Approach For Emulating Vaporization, Physical Properties, And Chemical Combustion Behavior Of Multicomponent Fuels, Alanna Y. Cooney, Simcha L. Singer

Mechanical Engineering Faculty Research and Publications

The complex nature of multicomponent aviation fuels presents a daunting task for accurately simulating combustion behavior without incurring impractical computational costs. To reduce computation time, chemical fuel surrogates comprised of only a few species are used to emulate the combustion of complex pre-vaporized fuels. These surrogates are often unable to match the vaporization behavior and physical properties of the real fuel and fail to capture the effect of preferential vaporization on combustion behavior. Therefore, a computationally efficient, hybrid droplet vaporization-chemical surrogate approach has been developed which emulates both the physical and chemical properties of a multicomponent kerosene fuel. The droplet …

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Structure And Growth Of Core–Shell Nanoprecipitates In Al–Er–Sc–Zr–V–Si High-Temperature Alloys, Wahaz Nasim, Saegh Yazdi, Ruben Santamarta, Jahanzaib Malik, Dinc Erdeniz, Bilal Mansoor, David N. Seidman, David C. Dunand, Ibrahim Karaman Jan 2019

Structure And Growth Of Core–Shell Nanoprecipitates In Al–Er–Sc–Zr–V–Si High-Temperature Alloys, Wahaz Nasim, Saegh Yazdi, Ruben Santamarta, Jahanzaib Malik, Dinc Erdeniz, Bilal Mansoor, David N. Seidman, David C. Dunand, Ibrahim Karaman

Mechanical Engineering Faculty Research and Publications

Lightweight Sc-containing aluminum alloys exhibit superior mechanical performance at high temperatures due to core–shell, L12-ordered trialuminide nanoprecipitates. In this study, the structure of these nanoprecipitates was studied, using different transmission electron microscopy (TEM) techniques, for an Al–Er– Sc–Zr–V–Si alloy that was subjected to a two-stage overaging heat treatment. Energy-dispersive X-ray spectroscopy of the spherical Al3(Sc, Zr, Er ,V) nanoprecipitates revealed a core–shell structure with an Sc- and Er-enriched core and a Zr-enriched shell, without a clear V outer shell. This structure is stable up to 72% of the absolute melting temperature of Al for extended periods …

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Experimental And Modeling Study Of Compressive Creep In 3d-Woven Ni-Based Superalloys, Hoon-Hwe Cho, Dinc Erdeniz, Keith W. Sharp, David C. Dunand Aug 2018

Experimental And Modeling Study Of Compressive Creep In 3d-Woven Ni-Based Superalloys, Hoon-Hwe Cho, Dinc Erdeniz, Keith W. Sharp, David C. Dunand

Mechanical Engineering Faculty Research and Publications

Micro-architectured Ni-based superalloy structures, with Ni-20Cr-3Ti-2Al (wt.%) composition and γ/γ′-microstructure, are created by a multi-step process: (i) non-crimp orthogonal 3D-weaving of ductile, 202 μm diameter Ni-20%Cr wires, (ii) gas-phase alloying with Al and Ti, (iii) simultaneous transient-liquid phase (TLP) bonding between wires and homogenization within wires via interdiffusion, (iv) solutionizing to create a single-phase solid solution, and (v) aging to precipitate the γ′ phase. The creep behavior of these 3D-woven γ/γ′ nickel-based superalloys is studied under uniaxial compression via experiments at 825 °C and via finite element (FE) analysis, using a 3D model of the woven structures obtained …

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Pore-Resolving Simulation Of Char Particle Gasification Using Micro-Ct, Greg Hingwah Fong, Scott Jorgensen, Simcha L. Singer Jul 2018

Pore-Resolving Simulation Of Char Particle Gasification Using Micro-Ct, Greg Hingwah Fong, Scott Jorgensen, Simcha L. Singer

Mechanical Engineering Faculty Research and Publications

Understanding the interaction between transport, reaction and morphology at the scale of individual char particles is important for optimizing solid fuel gasification and combustion processes. However, most particle-scale models treat porous char particles as an effective porous continuum, even though the presence of large, irregular macropores, voids and fractures render such upscaled treatments mathematically invalid, and the models non-predictive. A new modeling framework is therefore proposed to elucidate the impact of morphology on char particle gasification and combustion. A pore-resolving, transient, three-dimensional simulation for gasification of a realistic coal char particle is developed based on X-ray micro-computed tomography (micro-CT). The …

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Control Design And Implementation Of An Active Transtibial Prosthesis, Joseph Klein Jul 2018

Control Design And Implementation Of An Active Transtibial Prosthesis, Joseph Klein

Master's Theses (2009 -)

Prior work at Marquette University developed the Marquette Prosthesis, an active transtibial prosthesis that utilized a torsional spring and a four-bar mechanism. The controls for the Marquette Prosthesis implemented a finite state control algorithm to determine the state of gait of the amputee along with two lower level controllers, a PI moment controller to control the moment during stance and a PID position controller to control the position during stance. The Marquette Prosthesis was successful in mimicking the gait profile presented by Winter. However, after completing human subject testing, the Marquette Prosthesis was insufficient in trying to match the gait …

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Effects Of Nb And Ta Additions On The Strength And Coarsening Resistance Of Precipitation-Strengthened Al-Zr-Sc-Er-Si Alloys, Dinc Erdeniz, Anthony De Luca, David N. Seidman, David C. Dunand Jul 2018

Effects Of Nb And Ta Additions On The Strength And Coarsening Resistance Of Precipitation-Strengthened Al-Zr-Sc-Er-Si Alloys, Dinc Erdeniz, Anthony De Luca, David N. Seidman, David C. Dunand

Mechanical Engineering Faculty Research and Publications

A dilute Al-0.07Zr-0.02Sc-0.005Er-0.06Si (at.%) alloy was microalloyed with 0.08 at.% Nb or Ta. Atom-probe tomography reveals that, upon aging, Nb and Ta partition to the coherent L12-Al3(Zr,Sc,Er) nanoprecipitates (with average concentrations of 0.2 and 0.08 at.%, respectively), with both segregating at the matrix/nanoprecipitate heterophase interface. This is consistent with the Nb- and Ta-modified alloys exhibiting, as compared to the unmodified alloy: (i) higher peak microhardness, from a higher nanoprecipitate volume fraction and/or latticeparameter mismatch; and (ii) improved aging resistance, from slower nanoprecipitate coarsening due to the small diffusivities of niobium and tantalum in aluminum. Analogous results …

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Soot And Spectral Radiation Modeling For High-Pressure Turbulent Spray Flames, Sebastian Ferreyro Fernandez, C. Paul, A. Sircar, A. Imren, D. C. Haworth, Somesh Roy, Michael F. Modest Apr 2018

Soot And Spectral Radiation Modeling For High-Pressure Turbulent Spray Flames, Sebastian Ferreyro Fernandez, C. Paul, A. Sircar, A. Imren, D. C. Haworth, Somesh Roy, Michael F. Modest

Mechanical Engineering Faculty Research and Publications

A transported probability density function (PDF) method and a photon Monte Carlo/line-by-line (PMC/LBL) spectral model are exercised to generate physical insight into soot processes and spectral radiation characteristics in transient high-pressure turbulent n-dodecane spray flames, under conditions that are relevant for compression-ignition piston engines. PDF model results are compared with experimental measurements and with results from a locally well-stirred reactor (WSR) model that neglects unresolved turbulent fluctuations in composition and temperature. Computed total soot mass and soot spatial distributions are highly sensitive to the modeling of unresolved turbulent fluctuations. To achieve reasonable agreement between model and experiment and to capture …

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Computational Methods For Modeling Multicomponent Droplet Vaporization, Alanna Y. Cooney Apr 2018

Computational Methods For Modeling Multicomponent Droplet Vaporization, Alanna Y. Cooney

Master's Theses (2009 -)

Computational fluid dynamics (CFD) models for combustion of multicomponent hydrocarbon fuels must often prioritize computational efficiency over model complexity, leading to oversimplifying assumptions in the sub-models for droplet vaporization and chemical kinetics. Therefore, a computationally efficient hybrid droplet vaporization-chemical surrogate approach has been developed which emulates both the physical and chemical properties of a multicomponent fuel. For the droplet vaporization/physical portion of the hybrid, a new solution method is presented called the Coupled Algebraic-Direct Quadrature Method of Moments (CA-DQMoM) with delumping which accurately solves for the evolution of every discrete species in a vaporizing multicomponent fuel droplet with the computational …

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Geometric Construction-Based Realization Of Spatial Elastic Behaviors In Parallel And Serial Manipulators, Shuguang Huang, Joseph M. Schimmels Mar 2018

Geometric Construction-Based Realization Of Spatial Elastic Behaviors In Parallel And Serial Manipulators, Shuguang Huang, Joseph M. Schimmels

Mechanical Engineering Faculty Research and Publications

This paper addresses the realization of spatial elastic behavior with a parallel or a serial manipulator. Necessary and sufficient conditions for a manipulator (either parallel or serial) to realize a specific elastic behavior are presented and interpreted in terms of the manipulator geometry. These conditions completely decouple the requirements on component elastic properties from the requirements on mechanism kinematics. New construction-based synthesis procedures for spatial elastic behaviors are developed. With these synthesis procedures, one can select each elastic component of a parallel (or serial) mechanism based on the geometry of a restricted space of allowable candidates. With each elastic component …

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Mechanical Behavior Of Three-Dimensional Braided Nickel-Based Superalloys Synthesized Via Pack Cementation, Nicolas Lippitz, Dinc Erdeniz, Keith W. Sharp, David C. Dunand Mar 2018

Mechanical Behavior Of Three-Dimensional Braided Nickel-Based Superalloys Synthesized Via Pack Cementation, Nicolas Lippitz, Dinc Erdeniz, Keith W. Sharp, David C. Dunand

Mechanical Engineering Faculty Research and Publications

Braided tubes of Ni-based superalloys are fabricated via three-dimensional (3-D) braiding of ductile Ni-20Cr (wt pct) wires followed by post-textile gas-phase alloying with Al and Ti to create, after homogenization and aging, γ/γ′ strengthened lightweight, porous structures. Tensile tests reveal an increase in strength by 100 MPa compared to as-braided Ni-20Cr (wt pct). An interrupted tensile test, combined with X-ray tomographic scans between each step, sheds light on the failure behavior of the braided superalloy tubes.

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An Efficient Coal Pyrolysis Model For Detailed Tar Species Vaporization, Jianqing Li, Simcha L. Singer Mar 2018

An Efficient Coal Pyrolysis Model For Detailed Tar Species Vaporization, Jianqing Li, Simcha L. Singer

Mechanical Engineering Faculty Research and Publications

An accurate and computationally efficient model for the vaporization of many tar species during coal particle pyrolysis has been developed. Like previous models, the molecular fragments generated by thermal decomposition are partitioned into liquid metaplast, which remains in the particle, and vapor, which escapes as tar, using a vapor-liquid equilibrium(VLE) sub-model. Multicomponent VLE is formulated as a rate-based process, which results in an ordinary differential equation (ODE) for every species. To reduce the computational expense of solving many ODEs, the model treats tar and metaplast species as a continuous distribution of molecular weight. To improve upon the accuracy of …

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Modeling Multicomponent Fuel Droplet Vaporization With Finite Liquid Diffusivity Using Coupled Algebraic-Dqmom With Delumping, Alanna Y. Cooney, Simcha L. Singer Jan 2018

Modeling Multicomponent Fuel Droplet Vaporization With Finite Liquid Diffusivity Using Coupled Algebraic-Dqmom With Delumping, Alanna Y. Cooney, Simcha L. Singer

Mechanical Engineering Faculty Research and Publications

Multicomponent fuel droplet vaporization models for use in combustion CFD codes often prioritize computational efficiency over model complexity. This leads to oversimplifying assumptions such as single component droplets or infinite liquid diffusivity. The previously developed Direct Quadrature Method of Moments (DQMoM) with delumping model demonstrated a computationally efficient and accurate approach to solve for every discrete species in a well-mixed vaporizing multicomponent droplet. To expand the method to less restrictive cases, a new solution technique is presented called the Coupled Algebraic-Direct Quadrature Method of Moments (CA-DQMoM). In contrast to previous moment methods for droplet vaporization, CA-DQMoM solves for the evolution …

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Experimental Validation Of An Unscented Kalman Filter For Estimating Transient Engine Exhaust Composition With Fourier Transform Infrared Spectroscopy, David Wilson, Casey Allen Jan 2018

Experimental Validation Of An Unscented Kalman Filter For Estimating Transient Engine Exhaust Composition With Fourier Transform Infrared Spectroscopy, David Wilson, Casey Allen

Mechanical Engineering Faculty Research and Publications

Fourier transform infrared (FTIR) spectroscopy is a prevalent technique for measuring the comprehensive chemical composition of engine emissions. However, its applicability to transient emissions is limited due to recirculation of exhaust from past engine cycles within a FTIR gas cell and nonstationarity of the infrared beam intensity. An unscented Kalman filter is developed to overcome these limitations and obtain accurate, time-resolved estimations of engine exhaust composition from FTIR measurements. Residence time distribution within the FTIR gas cell is modeled using the well-mixed assumption, while the Fourier transform of an interferogram generated from a linearly evolving, uniformly broadened absorption line is …

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A Degradation Function Consistent With Cocks–Ashby Porosity Kinetics, John A. Moore Jan 2018

A Degradation Function Consistent With Cocks–Ashby Porosity Kinetics, John A. Moore

Mechanical Engineering Faculty Research and Publications

The load carrying capacity of ductile materials degrades as a function of porosity, stress state and strain-rate. The effect of these variables on porosity kinetics is captured by the Cocks–Ashby model; however, the Cocks–Ashby model does not account for material degradation directly. This work uses a yield criteria to form a degradation function that is consistent with Cocks–Ashby porosity kinetics and is a function of porosity, stress state and strain-rate dependence. Approximations of this degradation function for pure hydrostatic stress states are also explored.

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Development Of A Multiphase Photon Monte Carlo Method For Spray Combustion And Its Application In High-Pressure Conditions, Somesh Roy, Jian Cai, Michael F. Modest Dec 2017

Development Of A Multiphase Photon Monte Carlo Method For Spray Combustion And Its Application In High-Pressure Conditions, Somesh Roy, Jian Cai, Michael F. Modest

Mechanical Engineering Faculty Research and Publications

In this work the development of a multiphase photon Monte Carlo (PMC) method with a focus on resolving radiative heat transfer in combustion simulations is presented. The multiphase PMC solver can account for description of participating media in both Lagrangian and Eulerian frameworks. The solver is validated against exact solutions in several one-dimensional configurations. The developed solver is then applied to Diesel spray combustions, where liquid spray droplets are assumed to be cold, nonemitting, large, and isotropically scattering. Several formulations for radiative properties of the Diesel spray are first explored. The PMC solver has then been coupled with the multiphase …

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A Comparison Of Sensitivity Metrics For Two-Stage Ignition Behavior In Rapid Compression Machines, David Wilson, Casey Allen Nov 2017

A Comparison Of Sensitivity Metrics For Two-Stage Ignition Behavior In Rapid Compression Machines, David Wilson, Casey Allen

Mechanical Engineering Faculty Research and Publications

A rapid compression machine (RCM) multi-zone model is used to simulate the ignition of primary reference fuel (PRF) mixtures that exhibit two-stage ignition behavior. Sensitivity coefficients for each reaction in the PRF mechanism are calculated from four different metrics: (1) first-stage energy release, (2) first-stage pressure rise, (3) first-stage ignition delay time, and (4) total ignition delay time. The sensitivity coefficients are used to provide four unique rankings, and the rankings are compared using Spearman’s rank correlation coefficient. Special emphasis is given to comparing the rankings based on first-stage energy release and total ignition delay time. The level of agreement …

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Hip Joint Function In People With Femoroacetabular Impingement Syndrome, Philip Malloy Oct 2017

Hip Joint Function In People With Femoroacetabular Impingement Syndrome, Philip Malloy

Dissertations (1934 -)

Femoroacetabular impingement syndrome (FAIS) is a clinical hip disorder that represents symptomatic contact between the proximal femur and rim of the acetabulum during normal hip range of motion. FAIS has been described as a precursor to hip joint osteoarthritis (OA), and results in physical impairments and functional limitations in young individuals and active adults. Despite tremendous growth in arthroscopic hip surgery for FAIS, little is known about how this disorder affects dynamic hip joint function. The purpose of this dissertation was to investigate hip joint function, during clinical and functional activities, both before and after arthroscopic hip surgery for FAIS. …

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Performance Analysis Of Constant Speed Local Abstacle Avoidance Controller Using A Mpc Algorithym On Granular Terrain, Nicholas Haraus Oct 2017

Performance Analysis Of Constant Speed Local Abstacle Avoidance Controller Using A Mpc Algorithym On Granular Terrain, Nicholas Haraus

Master's Theses (2009 -)

A Model Predictive Control (MPC) LIDAR-based constant speed local obstacle avoidance algorithm has been implemented on rigid terrain and granular terrain in Chrono to examine the robustness of this control method. Provided LIDAR data as well as a target location, a vehicle can route itself around obstacles as it encounters them and arrive at an end goal via an optimal route. This research is one important step towards eventual implementation of autonomous vehicles capable of navigating on all terrains. Using Chrono, a multibody physics API, this controller has been tested on a complex multibody physics HMMWV model representing the plant …

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Construction And Characterization Of A Single Stage Dual Diaphragm Gas Gun, Nathaniel Steven Helminiak Oct 2017

Construction And Characterization Of A Single Stage Dual Diaphragm Gas Gun, Nathaniel Steven Helminiak

Master's Theses (2009 -)

In the interest of studying the propagation of shock waves, this work sets out to design, construct, and characterize a pneumatic accelerator that performs high-velocity flyer plate impact tests. A single stage gas gun with a dual diaphragm breach allows for a non-volatile, reliable experimental testing platform for shock phenomena. This remotely operated gas gun utilizes compressed nitrogen to launch projectiles down a 14 foot long, 2 inch diameter bore barrel, which subsequently impacts a target material of interest. A dual diaphragm firing mechanism allows the 4.5 liter breech to reach a total pressure differential of 10ksi before accelerating projectiles …

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The Effects Of A Reduced Force Aerial Bucket Control On Upper Extremity Muscular Demands As Assessed With Surface Electromyography, Casey D. Garces Oct 2017

The Effects Of A Reduced Force Aerial Bucket Control On Upper Extremity Muscular Demands As Assessed With Surface Electromyography, Casey D. Garces

Master's Theses (2009 -)

A common control for operating aerial bucket trucks for utility companies in North America is called a pistol grip control. Based upon many anecdotal reports of forearm muscle fatigue from workers using this control, Prof. Richard Marklin began an EPRI-sponsored study in 2016 using EMG to determine muscle fatigue of workers while they used the pistol grip. Muscle activity recorded by EMG is a measure of the magnitude of muscle force under controlled conditions. This study confirmed the reports of muscle fatigue in extensor digitorum communis (EDC) muscle in the right forearm. The next phase of the study was to …

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Design Of A Passive Ankle Prosthesis With Energy Return That Increases With Increasing Walking Velocity, Alexander J. Folz Oct 2017

Design Of A Passive Ankle Prosthesis With Energy Return That Increases With Increasing Walking Velocity, Alexander J. Folz

Master's Theses (2009 -)

Patients who undergo a transtibial (below the knee) amputation are often met with a difficult decision: selection of a prosthesis. Limitations of currently available prostheses motivate work on a new solution, the EaSY Walk, a passive device that mimics two key aspects of the natural ankle: non-linear rotational stiffness through implementation of a stiffening flexure mechanism and rotational work output that varies as a function of walking velocity to propel the user forward. To achieve the latter, a strategy to convert the maximum available translational energy acquired from deflection along the leg into rotational energy about the ankle joint through …

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A Bayesian Estimation Model For Transient Engine Exhaust Characterization Using Fourier Transform Infrared Spectroscopy, David Wilson, Casey Allen Sep 2017

A Bayesian Estimation Model For Transient Engine Exhaust Characterization Using Fourier Transform Infrared Spectroscopy, David Wilson, Casey Allen

Mechanical Engineering Faculty Research and Publications

Comprehensive emissions models extensively use engine exhaust data from vehicle experiments to represent the relationship between fuel composition and pollutants. However, the predicted emissions from these models often neglect the effects of transients and speed-load history. Fourier transform infrared (FTIR) spectroscopy is a high frequency measurement technique capable of comprehensive speciation. However, due to long residence times of exhaust within a FTIR spectrometer gas cell, FTIR measurements are contaminated by the effects of historical emissions, precluding the attainment of time-resolved engine exhaust data. This work presents a Bayesian estimation model for processing FTIR measurements to obtain accurate estimations of instantaneous …

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Run-Out Based Crossed Roller Bearing Life Prediction By Utilization Of Accelerated Testing Approach And Fe Numerical Models, Luca Quagliato, Dongwook Kim, Nara Lee, Soyoung Hwang, Joseph P. Domblesky, Naksoo Kim Sep 2017

Run-Out Based Crossed Roller Bearing Life Prediction By Utilization Of Accelerated Testing Approach And Fe Numerical Models, Luca Quagliato, Dongwook Kim, Nara Lee, Soyoung Hwang, Joseph P. Domblesky, Naksoo Kim

Mechanical Engineering Faculty Research and Publications

Surface wear and spalling phenomena are the most important factors affecting roller bearing performance and operational lifetime, in terms of number of cycles the bearing can operate. Although bearing life has been traditionally defined by the onset of spalling, as specified by international standard ISO 281, this definition does not always reflect the real operational conditions, since bearing wear can also represent a failure criterion when excessive run-out occurs. In such cases, bearing life needs to be predicted according to the amount of bearing run-out resulting from wear due to load and number of cycles. In the current study, the …

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Applied Force And Semg Muscle Activity Required To Operate Pistol Grip Control In An Electric Utility Aerial Bucket, Richard W. Marklin Jr., Jonathaon E. Slightam, Mark L. Nagurka, Trent M. Wolff, Casey D. Garces, Lovely Krishen Sep 2017

Applied Force And Semg Muscle Activity Required To Operate Pistol Grip Control In An Electric Utility Aerial Bucket, Richard W. Marklin Jr., Jonathaon E. Slightam, Mark L. Nagurka, Trent M. Wolff, Casey D. Garces, Lovely Krishen

Mechanical Engineering Faculty Research and Publications

Electric utility line workers report high levels of fatigue in forearm muscles when operating a conventional pistol grip control in aerial buckets. This study measured the applied force and surface electromyographic (sEMG) signals from four upper extremity muscles required to operate the pistol grip control in two tasks. The first task was movement of the pistol grip in six directions (up/down, forward/rearward, clockwise/counter-clockwise), and the second task was movement of the bucket from its resting position on the truck bed to an overhead conductor on top of a 40 ft tall pole. The force applied to the pistol grip was …

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Effect Of Multiphase Radiation On Coal Combustion In A Pulverized Coal Jet Flame, Bifen Wu, Somesh Roy, Xinyu Zhao, Michael F. Modest Aug 2017

Effect Of Multiphase Radiation On Coal Combustion In A Pulverized Coal Jet Flame, Bifen Wu, Somesh Roy, Xinyu Zhao, Michael F. Modest

Mechanical Engineering Faculty Research and Publications

The accurate modeling of coal combustion requires detailed radiative heat transfer models for both gaseous combustion products and solid coal particles. A multiphase Monte Carlo ray tracing (MCRT) radiation solver is developed in this work to simulate a laboratory-scale pulverized coal flame. The MCRT solver considers radiative interactions between coal particles and three major combustion products (CO2, H2O, and CO). A line-by-line spectral database for the gas phase and a size-dependent nongray correlation for the solid phase are employed to account for the nongray effects. The flame structure is significantly altered by considering nongray radiation and …

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