Mechanical Engineering Commons^™

The Effect Of A Powered Ankle Foot Orthosis On Walking In A Stroke Subject: A Case Study, Ali Pourghasem, Ismail Ebrahimi Takamjani, Mohammad Taghi Karimi, Mohammad Kamali, Mohammad Jannesari, Iman Salafian

Department of Mechanical and Materials Engineering: Faculty Publications

[Purpose] Standing and walking are impaired in stroke patients. Therefore, assisted devices are required to restore their walking abilities. The ankle foot orthosis with an external powered source is a new type of orthosis. The aim of this study was to evaluate the performance of a powered ankle foot orthosis compared with unpowered orthoses in a stroke patient.

[Subjects and Methods] A single stroke subject participated in this study. The subject was fitted with three types of ankle foot orthosis (powered, posterior leg spring, and carbon ankle foot orthoses). He was asked to walk with and without the three types …

Microstructural Analysis Of Thermoelastic Response, Nonlinear Creep, And Pervasive Cracking In Heterogeneous Materials, Alden C. Cook

Electronic Theses and Dissertations

This dissertation is concerned with the development of robust numerical solution procedures for the generalized micromechanical analysis of linear and nonlinear constitutive behavior in heterogeneous materials. Although the methods developed are applicable in many engineering, geological, and materials science fields, three main areas are explored in this work. First, a numerical methodology is presented for the thermomechanical analysis of heterogeneous materials with a special focus on real polycrystalline microstructures obtained using electron backscatter diffraction techniques. Asymptotic expansion homogenization and finite element analysis are employed for micromechanical analysis of polycrystalline materials. Effective thermoelastic properties of polycrystalline materials are determined and compared …

Self-Patterning Gd Nano-Fibers In Mg-Gd Alloys, Yangxin Li, Jian Wang, Kaiguo Chen, Meiyue Shao, Yao Shen, Li Jin, Guo-Zhen Zhu

Department of Mechanical and Materials Engineering: Faculty Publications

Manipulating the shape and distribution of strengthening units, e.g. particles, fibers, and precipitates, in a bulk metal, has been a widely applied strategy of tailoring their mechanical properties. Here, we report self-assembled patterns of Gd nano-fibers in Mg-Gd alloys for the purpose of improving their strength and deformability. 1-nm Gd nano-fibers, with a 〈c〉-rod shape, are formed and hexagonally patterned in association with Gd segregations along dislocations that nucleated during hot extrusion. Such Gd-fiber patterns are able to regulate the relative activities of slips and twinning, as a result, overcome the inherent limitations in strength and ductility of Mg alloys. …

Single Site Robotc Device And Related Systems And Methods, Jack Mondry, Shane M. Farritor, Eric Markvicka, Thomas Frederick, Joseph Bartels

Department of Mechanical and Materials Engineering: Faculty Publications

The embodiments disclosed herein relate to various medical device components, including components that can be incor porated into robotic and/or in vivo medical devices. Certain embodiments include various medical devices for in vivo medical procedures.

Finite Element Simulation Of Pzt-Aided Interrogation Of Composite Laminates Exhibiting Damage, Amany Micheal, Yehia Bahei-El-Din

Centre for Advanced Materials

Piezoelectricity has proved effective in capturing changes in structures caused by various damage mechanisms. In one approach, piezoelectric wafer active sensors (PWAS) are mounted on the surface of the host structure and utilized as both actuators and sensors to interrogate the structure and monitor its health. This is achieved by subjecting the PWAS to a transient electric pulse and reading the resulting voltage. Changes in the stiffness of the substrate due to structural damage affect the response of the PWAS, which could be correlated to integrity of the structure. Applying this technique to fibrous composite laminates encounters particular challenges due …

Video Capture And Post-Processing Technique For Approximating 3d Projectile Trajectory, Chase M. Pfeifer, Judith M. Burnfield, Guilherme M. Cesar, Max H. Twedt, Jeff A. Hawks

Department of Mechanical and Materials Engineering: Faculty Publications

In this paper we introduce a low-cost procedure and methodology for markerless projectile tracking in three-dimensional (3D) space. Understanding the 3D trajectory of an object in flight can often be essential in examining variables relating to launch and landing conditions. Many systems exist to track the 3D motion of projectiles but are often constrained by space or the type of object the system can recognize (Qualisys, Göteborg, Sweden; Vicon, Oxford, United Kingdom; Opti-Track, Corvallis, Oregon USA; Motion Analysis, Santa Rosa, California USA; Flight Scope, Orlando, Florida USA). These technologies can also be quite expensive, often costing hundreds of thousand dollars. …

Simulation Of Superplastic Forming Of Circular Edge-Welded Envelopes, Olga Tulupova

The 8th International Conference on Physical and Numerical Simulation of Materials Processing

No abstract provided.

Flow Stress And Microstructure Models Of Alloys, Lars-Erik Lindgren

The 8th International Conference on Physical and Numerical Simulation of Materials Processing

No abstract provided.

Thermal Analysis Of Continuous And Patterned Multilayer Films In The Presence Of A Nanoscale Hot Spot, Jia-Yang Juang, Jinglin Zheng

Department of Mechanical and Materials Engineering: Faculty Publications

Thermal responses of multilayer films play essential roles in state-of-the-art electronic systems, such as photo/micro-electronic devices, data storage systems, and silicon-on-insulator transistors. In this paper, we focus on the thermal aspects of multilayer films in the presence of a nanoscale hot spot induced by near field laser heating. The problem is set up in the scenario of heat assisted magnetic recording (HAMR), the next-generation technology to overcome the data storage density limit imposed by superparamagnetism. We characterized thermal responses of both continuous and patterned multilayer media films using transient thermal modeling. We observed that material configurations, in particular, the thermal …

Case Study Of Quantifying Energy Loss Through Ceiling-Attic Recessed Lighting Fixtures Through 3d Numerical Simulation, Ri Na, Shengmao Lin, Zhigang Shen, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Abstract Air leakage through recessed lighting fixtures has been identified as a common issue that causes extra energy consumption in residential buildings. However, few quantitative studies in this area were found. As such, a preliminary assessment of the magnitude of this type of energy loss was conducted by using three-dimensional (3D) transient computational fluid dynamics (CFD) models. A hypothetical layout of recessed lighting fixtures was designed with boundary conditions of four different seasons, which were obtained from recorded roof/attic temperature data sets. The results of the study indicate that leakage of recessed lighting fixtures could be a significant channel of …

Compositionally Graded Bulk Heterojunction Devices And Methods Of Manufacturing The Same, Jinsong Huang, Zhengguo Xiao

Department of Mechanical and Materials Engineering: Faculty Publications

Systems and methods are described to form compositionally graded BHJ structures utilizing solvent-fluxing techniques. In implementations, the systems and methods described herein involve a high boiling point additive, a solution of a polymer donor and an acceptor, a substrate material, a working solvent, and a flux solvent for formation of compositionally graded BHJ structures.

Bioink Properties Before, During And After 3d Bioprinting, Katja Hölzl, Shengmao Lin, Liesbeth Tytgat, Sandra Van Vlierberghe, Linxia Gu, Aleksandr Ovsianikov

Department of Mechanical and Materials Engineering: Faculty Publications

Bioprinting is a process based on additive manufacturing from materials containing living cells. These materials, often referred to as bioink, are based on cytocompatible hydrogel precursor formulations, which gel in a manner compatible with different bioprinting approaches. The bioink properties before, during and after gelation are essential for its printability, comprising such features as achievable structural resolution, shape fidelity and cell survival. However, it is the final properties of the matured bioprinted tissue construct that are crucial for the end application. During tissue formation these properties are influenced by the amount of cells present in the construct, their proliferation, migration …

Optical Patterning Of Trapped Charge In Nitrogen-Doped Diamond, Harishankar Jayakumar, Jacob Henshaw, Siddharth Dhomkar, Daniela Pagliero, Abdelghani Laraoui, Neil B. Manson, Remus Albu, Marcus W. Doherty, Carlos A. Meriles

Department of Mechanical and Materials Engineering: Faculty Publications

The nitrogen-vacancy (NV) centre in diamond is emerging as a promising platform for solid-state quantum information processing and nanoscale metrology. Of interest in these applications is the manipulation of the NV charge, which can be attained by optical excitation. Here, we use two-colour optical microscopy to investigate the dynamics of NV photo-ionization, charge diffusion and trapping in type-1b diamond. We combine fixed-point laser excitation and scanning fluorescence imaging to locally alter the concentration of negatively charged NVs, and to subsequently probe the corresponding redistribution of charge. We uncover the formation of spatial patterns of trapped charge, which we qualitatively reproduce …

Contribution Of Fiber Undulation To Mechanics Of Three-Dimensional Collagen-I Gel, Shengmao Lin, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

The collagen-I gel is extensively used as a scaffold material in tissue engineering due to its ability to mimic the extracellular matrix (ECM). In this study, the mechanics of collagen-I gel is investigated using a numerical model of three-dimensional collagen network. The resulted mechanical behavior was validated against the published experimental data. Results illustrated that fiber alignment was dominated in the low strain region, and its transition to stretching dominated phenomena at higher strain led to the strain stiffening of collagen gel. The collagen undulation at the microscopic level was found to delay the initiation of strain stiffening

Effects Of Electrode Off Centre On Trapped Thickness-Shear Modes In Contoured At-Cut Quartz Resonators, Junjie Shi, Cuiying Fan, Minghao Zhao, Jiashi S. Yang

Department of Mechanical and Materials Engineering: Faculty Publications

We investigated thickness-shear vibrations of a contoured, AT-cut quartz resonator with a pair of electrodes displaced from the resonator centre. The scalar differential equations by Stevens and Tiersten for thickness-shear vibrations of electroded and unelectroded quartz plates were employed. Based on the variational formulation of the scalar differential equations established in a previous paper and the variation-based Ritz method with trigonometric functions as basis functions, free vibration resonance frequencies and trapped thickness-shear modes were obtained. The effects of the electrode off centre on resonance frequencies and mode shapes were examined. When the electrode off centre is about one hundredth of …

Experimental Building Demonstration Model With Viscous Fluid Dampers, Blake Thomas Reeve, Brianna Jean Kufa, Aden Malek Stepanians, Sophie Carmion Ratkovich

Architectural Engineering

The Architectural Engineering major places a heavy emphasis on structural dynamics and the role of wind and seismic loading in building analysis and design. Buildings of high importance that are critical to community function, such as hospitals, often utilize supplemental damping devices like supplemental viscous fluid dampers or base isolators to reduce the overall demands on the structural system. The design and analysis of these dampers are typically not taught at the undergraduate level, and is frequently performed by mechanical engineers, in lieu of structural engineers.

To better understand and research building behavior with supplemental damping devices, our multi-disciplinary team …

Focal Adhesion Kinase Regulation In Stem Cell Alignment And Spreading On Nanofibers, Mohammad Nahid Andalib, Jeong Soon Lee, Ligyeom Ha, Yuris A. Dzenis, Jung Yul Lim

Department of Mechanical and Materials Engineering: Faculty Publications

While electrospun nanofibers have demonstrated the potential for novel tissue engineering scaffolds, very little is known about the molecular mechanism of how cells sense and adapt to nanofibers. Here, we revealed the role of focal adhesion kinase (FAK), one of the key molecular sensors in the focal adhesion complex, in regulating mesenchymal stem cell (MSC) shaping on nanofibers. We produced uniaxially aligned and randomly distributed nanofibers from poly(L-lactic acid) to have the same diameters (about 130 nm) and evaluated MSC behavior on these nanofibers comparing with that on flat PLLA control. C3H10T1/2 murine MSCs exhibited upregulations in FAK expression and …

Design Of A Folding V-Scraper With Roller For Orchard Applications, Chase Ulrich

BioResource and Agricultural Engineering

This senior project discusses the design of a folding 15 ft. wide leveler for orchard use. This design utilized a category 2 three-point hitch to connect the implement to a tractor. The folding mechanism uses the tractors hydraulic system to actuate the folding movement using hydraulic cylinders. The blades, when wings in operational position, are rigid with one another after some assembly. When the implement is folded the width is reduced to nine feet.

Haul Truck Tires Recycling, Jessica N. Lizarazu

Chemical Engineering Undergraduate Honors Theses

The disposal of large Off-the-Road (OTR) tires is an increasingly important concern. These tires can weigh up to 8,450 pounds with an overall diameter and width of approximately 140.7 inches and 45.1 inches respectively. OTR tires are used for mining vehicles such as haul trucks, wheel loaders, backhoes, graders, and trenchers. These new tires cost between $38,000 and $50,000 each, depending on multiple factors including oil prices and the cyclical nature of the industry. Haul trucks contain six tires per vehicle, and mines replace these tires around every 9-12 months. Statistics regarding discarded OTR tires are not provided by the …

Heating Element Including Carbon Nanotube (Cnt) Layer, Santhosh Kumar Loganathan, Virginie Rollin, Daewon Kim

Publications

Apparatus , materials , and techniques and techniques herein can include providing a deposited layer comprising a com posite material including carbon nanotubes ( CNTs ) . Accord ing to various examples , the composite can be applied to a substrate such as using a solution containing CNTs and other constituents such as sulfur . The solution can be spray applied to a substrate , or spin - coated upon a substrate , such as to provide a uniform , conductive , and optically - transpar ent film layer . In one application , such a film layer can be …

Ramifications Of Projectile Velocity On The Ballistic Dart Penetration Of Sand, Peter Anthony Sable

Master's Theses (2009 -)

With the advent of novel in-situ experimental measurement techniques, highly resolved quantitative observations of dynamic events within granular media can now be made. In particular, high speed imagery and digital analysis now allow for the ballistic behaviors of sand to be examined not only across a range of event velocities but across multiple length scales. In an attempt to further understand the dynamic behavior of granular media, these new experimental developments were implemented utilizing high speed photography coupled with piezo-electric stress gauges to observe visually accessible ballistic events of a dart penetrating Ottawa sand. Projectile velocities ranged from 100 to …

Method For Hyper-Polarizing Nuclear Spns At Arbtrary Magnetic Felds, Carlos A. Meriles, Daniela Pagliero, Abdelghani Laraoui

Department of Mechanical and Materials Engineering: Faculty Publications

A method of dynamically polarizing the nuclear spin host of nitrogen-vacancy (NV) centers in diamond is provided. The method uses optical, microwave and radio-frequency pulses to recursively transfer spin polarization from the NV electronic spin. Nitrogen nuclear spin initialization approaching 80% at room temperature is demonstrated both in ensemble and single NV centers without relying on level anti-crossings. This makes the method applicable at arbitrary magnetic fields.

Characterizing The Boundary Lateral To The Shear Direction Of Deformation Twins In Magnesium, Y. Liu, N. Li, S. Shao, M. Gong, J Wang, R.J. Mccabe, Y. Jiang, C.N. Tome

Department of Mechanical and Materials Engineering: Faculty Publications

The three-dimensional nature of twins, especially the atomic structures and motion mechanisms of the boundary lateral to the shear direction of the twin, has never been characterized at the atomic level, because such boundary is, in principle, crystallographically unobservable.We thus refer to it here as the dark side of the twin. Here, using high-resolution transmission electron microscopy and atomistic simulations, we characterize the dark side of {1012} deformation twins in magnesium. It is found that the dark side is serrated and comprised of {1012} coherent twin boundaries and semi-coherent twist prismatic–prismatic {2110} boundaries that control twin growth. The conclusions of …

The Design And Construction Of A Torque Measuring Arm For An Air Motor, Logan Dearinger

All Undergraduate Projects

There is a system efficiency lab that sits in the thermodynamics lab of the Mechanical Engineering Technologies department. To expand this lab, a torque measuring device was needed to measure the torsional force that the pump exerts on the air motor. The expansion of this lab is important to give a better understanding of how the different mechanical parts effect the efficiency of the overall system. The first step in the expansion process was the design of a suitable torque measuring device. The most efficient design was a simple one with minimal moving parts. When the air motor is energized …

Stress-Dependent Ultrasonic Scattering In Polycrystalline Materials, Christopher M. Kube, Christopher A Turner

Department of Mechanical and Materials Engineering: Faculty Publications

Stress-dependent elastic moduli of polycrystalline materials are used in a statistically based model for the scattering of ultrasonic waves from randomly oriented grains that are members of a stressed polycrystal. The stress is assumed to be homogeneous and can be either residual or generated from external loads. The stress-dependent elastic properties are incorporated into the definition of the differential scattering cross-section, which defines how strongly an incident wave is scattered into various directions. Nine stress-dependent differential scattering cross-sections or scattering coefficients are defined to include all possibilities of incident and scattered waves, which can be either longitudinal or (two) transverse …

Active Stiffening Of F-Actin Network Dominated By Structural Transition Of Actin Filaments Into Bundles, Shengmao Lin, Xinwei Han, Gary C.P. Tsui, David Hui, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Molecular motor regulated active contractile force is key for cells sensing and responding to their mechanical environment, which leads to characteristic structures and functions of cells. The F-actin network demonstrates a two-order of magnitude increase in its modulus due to contractility; however, the mechanism for this active stiffening remains unclear. Two widely acknowledged hypotheses are that active stiffening of F-actin network is caused by (1) the nonlinear force-extension behavior of cross-linkers, and (2) the loading mode being switched from bending to stretching dominated regime. Direct evidence supporting either theory is lacking. Here we examined these hypotheses and showed that a …

Low Temperature Solution-Processed Sb:Sno2 Nanocrystals For Efficient Planar Perovskite Solar Cells, Yang Bai, Yanjun Fang, Yehao Deng, Qi Wang, Jingjing Zhao, Xiaopeng Zheng, Yang Zhang, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Inorganic metal oxide electron-transport layers (ETLs) have the potential to yield perovskite solar cells with improved stability, but generally need high temperature to form conductive and defect-less forms, which is not compatible with the fabrication of flexible and tandem solar cells. Here, we demonstrate a facile strategy for developing efficient inorganic ETLs by doping SnO₂ nanocrystals (NCs) with a small amount of Sb using a low-temperature solution-processed method. The electrical conductivity was remarkably enhanced by Sb-doping, which increased the carrier concentration in Sb:SnO₂ NCs. Moreover, the upward shift of the Fermi level owing to doping results in improved …

Development Of A Synthetic Gene Network To Modulate Gene Expression By Mechanical Forces, Zoltan Kis, Tania Rodin, Asma Zafar, Zhangxing Lai, Grace Freke, Oliver Fleck, Armando Del Rio Hernandez, Leila Towhidi, Ryan M. Pedrigi, Takayuki Homma, Rob Krams

Department of Mechanical and Materials Engineering: Faculty Publications

The majority of (mammalian) cells in our body are sensitive to mechanical forces, but little work has been done to develop assays to monitor mechanosensor activity. Furthermore, it is currently impossible to use mechanosensor activity to drive gene expression. To address these needs, we developed the first mammalian mechanosensitive synthetic gene network to monitor endothelial cell shear stress levels and directly modulate expression of an atheroprotective transcription factor by shear stress. The technique is highly modular, easily scalable and allows graded control of gene expression by mechanical stimuli in hard-to-transfect mammalian cells. We call this new approach mechanosyngenetics. To insert …

Experimental Explanation Of The Formation Mechanism Of Surface Mound-Structures By Femtosecond Laser On Polycrystalline Ni60Nb40, Edwin Peng, A. Tsubaki, Craig A. Zuhlke, Meiyu Wang, Ryan Bell, Michael J. Lucis, Troy P. Anderson, Dennis R. Alexander, George Gogos, Jeffrey E. Shield

Department of Mechanical and Materials Engineering: Faculty Publications

Femtosecond laser surface processing (FLSP) is an emerging technique for creating functionalized surfaces with specialized properties, such as broadband optical absorption or superhydrophobicity/ superhydrophilicity. It has been demonstrated in the past that FLSP can be used to form two distinct classes of mound-like, self-organized micro/nanostructures on the surfaces of various metals. Here, the formation mechanisms of below surface growth (BSG) and above surface growth (ASG) mounds on polycrystalline Ni₆₀Nb₄₀ are studied. Cross-sectional imaging of these mounds by focused ion beam milling and subsequent scanning electron microscopy revealed evidence of the unique formation processes for each class of …

Mechanically Activated Combustion Synthesis Of Molybdenum Borosilicides For Ultrahigh-Temperature Structural Applications, Alan Alberto Esparza Hernandez

Open Access Theses & Dissertations

The desire to improve the efficiency of power generation gas-turbines has led to a relentless quest for new, ultrahigh-temperature structural materials to replace the current nickel-based superalloys. These materials have reached the maximum allowable operating temperature determined by the melting temperature of these alloys, which is about 1150 °C. These materials could be replaced by molybdenum silicides and borosilicides based on Mo5SiB 2 (T2) phase due to their high melting point and mechanical properties. A major challenge, however, is to simultaneously achieve high oxidation resistance and acceptable mechanical properties at elevated temperatures. One novel approach to improve these properties is …