Mechanics of Materials Commons^™

Plastic Deformation Of Astm A36 Steel Using Two-Stage Light Gas Gun, Shawoon Kumar Roy

College of Engineering: Graduate Celebration Programs

To characterize material deformation in high velocity impact. To validate material models for computation simulation purposes.

This ongoing research is an attempt to study the plastic deformation of A36 steel plate (0.5” thick) under hypervelocity impact. Plastic deformation of the target plate was simulated using finite element software LS-DYNA.

High-Resolution Correlation Spectroscopy Of 13c Spins Near A Nitrogen-Vacancy Centre In Diamond, Abdelghani Laraoui, Florian Dolde, Christian Burk, Friedemann Reinhard, Jorg Wrachtrup, Carlos A. Meriles

Department of Mechanical and Materials Engineering: Faculty Publications

Spin complexes comprising the nitrogen-vacancy centre and neighbouring spins are being considered as a building block for a new generation of spintronic and quantum information processing devices. As assembling identical spin clusters is difficult, new strategies are being developed to determine individual node structures with the highest precision. Here we use a pulse protocol to monitor the time evolution of the 13C ensemble in the vicinity of a nitrogenvacancy centre. We observe long-lived time correlations in the nuclear spin dynamics, limited by nitrogen-vacancy spin–lattice relaxation. We use the host 14N spin as a quantum register and demonstrate that hyperfine-shifted resonances …

Thickness-Shear Vibration Of A Rectangular Quartz Plate With Partial Electrodes, Huijing He, Jiashi Yang, John A. Kosinski, Ji Wang

Department of Mechanical and Materials Engineering: Faculty Publications

We study free vibration of a thickness-shear mode crystal resonator of AT-cut quartz. The resonator is a rectangular plate partially and symmetrically electroded at the center with rectangular electrodes. A single-mode, three-dimensional equation governing the thickness-shear displacement is used. A Fourier series solution is obtained. Numerical results calculated from the series show that there exist trapped thickness-shear modes whose vibration is mainly under the electrodes and decays rapidly outside the electrodes. The effects of the electrode size and thickness on the trapped modes are examined.

Room-Temperature Organic Ferromagnetism In The Crystalline Poly(3-Hexylthiophene): Phenyl-C61-Butyric Acid Methyl Ester Blend Film, Bin Yang, Zhengguo Xiao, Yongbo Yuan, Tanjore V. Jayaraman, Jeffrey E. Shield, Ralph Skomski, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Pronounced ferromagnetism was observed in a crystalline blend film of conjugated polymer poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) by using magnetic force microscopy measurements. A substantial room-temperature saturation magnetization of about 0.65 emu g−1 was measured by an alternating gradient field magnetometer. Multiple experimental evidences demonstrate the charge transfer from the P3HT to the PCBM and the formation of P3HT crystal domain are expected to be two critical factors for the originals of room-temperature organic ferromagnetism.

Structure And Properties Of Cocoons And Silk Fibers Produced By Attacus Atlas, Narendra Reddy, Yi Zhao, Yiqi Yang

Department of Textiles, Merchandising and Fashion Design: Faculty Publications

Silk fibers in the three layers of Attacus atlas (A. atlas) cocoons have morphological structure and tensile properties similar to that of Bombyx mori silk. Attempts are being made to produce silk for commercial applications from cocoons of relatively unknown wild insects due to the unique properties of the fibers and as a source of income and employment. In this research, A. atlas cocoons were used to study the chemical composition, morphology, physical structure and tensile properties of the silk fibers in the cocoons and ability of the fibers to support the attachment and proliferation of mouse fibroblast cells. It …

A Mathematical Evaluation Of Hemodynamic Parameters After Carotid Eversion And Conventional Patch Angioplasty, Alexey Kamenskiy, Iraklis I. Pipinos, Yuris A. Dzenis, Prateek K. Gupta, Syed A. Jaffar Kazmi, Jason N. Mactaggart

Department of Mechanical and Materials Engineering: Faculty Publications

Carotid endarterectomy has a long history in stroke prevention, yet controversy remains concerning optimal techniques. Two methods frequently used are endarterectomy with patch angioplasty (CEAP) and eversion endarterectomy (CEE). The objective of this study was to compare hemodynamics-related stress and strain distributions between arteries repaired using CEAP and CEE. Mathematical models were based on in vivo three-dimensional arterial geometry, pulsatile velocity profiles, and intraluminal pressure inputs obtained from 16 patients with carotid artery disease. These data were combined with experimentally derived nonlinear, anisotropic carotid artery mechanical properties to create fluid-structure interaction models of CEAP and CEE. These models were then …

Effects Of Mode Coupling On The Admittance Of An At-Cut Quartz Thickness-Shear Resonator, Huijing He, Jiashi Yang, Wei-Ping Zhang, Ji Wang

Department of Mechanical and Materials Engineering: Faculty Publications

We study the effects of couplings to flexure and face-shear modes on the admittance of an AT-cut quartz plate thickness-shear mode resonator. Mindlin’s two-dimensional equations for piezoelectric plates are employed. Electrically forced vibration solutions are obtained for three cases: pure thickness-shear mode alone; two coupled modes of thickness shear and flexure; and three coupled modes of thickness shear, flexure, and face shear. Admittance is calculated and its dependence on the driving frequency and the length/thickness ratio of the resonator is examined. Results show that near the thickness-shear resonance, admittance assumes maxima, and that for certain values of the length/thickness ratio, …

A Comparative Study Of The Dry And Wet Nano-Scale Electro-Machining, M. P. Jahan, K. R. Virwani, Kamlakar P. Rajurkar, A. P. Malshe

Department of Mechanical and Materials Engineering: Faculty Publications

In recent years, a nano-electromachining (nano-EM) process based on a scanning tunneling microscope (STM) platform has been demonstrated. Nano-EM is capable of machining nano-features, under both, liquid dielectric (wet nano-EM) and air dielectric (dry nano-EM) media. The objective of this paper is to present a comparative study between the wet and dry nano-EM processes based on process mechanism, machining performance, consistency and dimensional repeatability of these two processes. The comparison of the two processes has been conducted at near field nano-EM, where the gap between the tool electrode and workpiece is 2 nm and the machining is performed at room …

Inducing Neurite Outgrowth By Mechanical Cell Stretch, Suzanne Higgins, Jeong Soon Lee, Ligyeom Ha, Jung Yul Lim

Department of Mechanical and Materials Engineering: Faculty Publications

Establishing extracellular milieus to stimulate neuronal regeneration is a critical need in neuronal tissue engineering. Many studies have used a soluble factor (such as nerve growth factor or retinoic acid [RA]), micropatterned substrate, and electrical stimulation to induce enhanced neurogenesis in neuronal precursor cells. However, little attention has been paid to mechanical stimulation because neuronal cells are not generally recognized as being mechanically functional, a characteristic of mechanoresponsive cells such as osteoblasts, chondrocytes, and muscle cells. In this study, we performed proof-of-concept experiments to demonstrate the potential anabolic effects of mechanical stretch to enhance cellular neurogenesis. We cultured human neuroblastoma …

Systems Biology Of The Functional And Dysfunctional Endothelium, Jennifer Frueh, Nataly Maimari, Takayuki Homma, Sandra M. Bovens, Ryan M. Pedrigi, Leila Towhidi, Rob Krams

Department of Mechanical and Materials Engineering: Faculty Publications

This review provides an overview of the effect of blood flow on endothelial cell (EC) signalling pathways, applying microarray technologies to cultured cells, and in vivo studies of normal and atherosclerotic animals. It is found that in cultured ECs, 5–10% of genes are up- or down-regulated in response to fluid flow, whereas only 3–6% of genes are regulated by varying levels of fluid flow. Of all genes, 90%are regulated by the steady part of fluid flow and 10% by pulsatile components. The associated gene profiles show high variability from experiment to experiment depending on experimental conditions, and importantly, the bioinformatical …

Orientation Controllable Epitaxial Vapor-Liquid-Solid Semiconductor Nanowire Synthesis On Silicon Substrate, Sung Hwan Chung

Open Access Dissertations

Semiconductor nanowires synthesized via the vapor-liquid-solid (VLS) mechanism have attracted extensive research interest in recent years owing to their unique structure as a promising candidate for the future electronic devices. Germanium and silicon nanowires, in particular, are compatible with the current silicon-based technology via direct assembly. However, one of the main challenges for the successful nanowire application in large-scale is the lack of the method for obtaining nanowires in desired positions and directions. Therefore, the comprehensive, systematic understanding of epitaxial nanowire growth and the more suitable method to align nanowires on novel structure are required. In this work, the synthesis …

Structural, Optical And Electrical Properties Of Yttrium-Doped Hafnium Oxide Nanocrystalline Thin Films, Abhilash Kongu

Open Access Theses & Dissertations

Hafnium oxide (HfO2) has emerged as the most promising high-k dielectric for Metal-Oxide-Semiconductor (MOS) devices and has been highlighted as the most suitable dielectric materials to replace silicon oxide because of its comprehensive performance. In the present research, yttrium-doped HfO2 (YDH) thin films were fabricated using RF magnetron sputter deposition onto Si (100) and quartz with a variable thickness. Cross-sectional scanning electron microscopy coupled with Filmetrics revealed that film thickness values range from 700 A° to 7500 A°. Electrical properties such as AC Resistivity and current-voltage (I-V) characteristics of YDH films were studied. YDH films that were relatively thin (<1500 A°) crystallized in monoclinic phase while thicker films crystallized in cubic phase. The band gap (Eg) of the films was calculated from the optical measurements. The band gap was found to be ∼5.60 eV for monoclinic while it is ∼6.05 eV for cubic phase of YDH films. Frequency dependence of the electrical resistivity (ρac) and the total conductivity of the films were measured. Resistivity decreased (by three orders of magnitude) with increasing frequency from 100 Hz to 1 MHz, attributed due to the hopping mechanism in YDH films. Whereas, while ρac∼1Ω-m at low frequencies (100 Hz), it decreased to ∼ 104 Ω-cm at higher frequencies (1 MHz). Aluminum (Al) metal electrodes were deposited to fabricate a thin film capacitor with YDH layer as dielectric film thereby employing Al-YDH-Si capacitor structure. The results indicate that the capacitance of the films decrease with increasing film thickness. A detailed analysis of the electrical characteristics of YDH films is presented.

Experimental Study On The Fabrication Of Advanced Materials For Energy Applications Using High Energy Mechanical Milling, Ashvin Kumar Narayana Swamy

Open Access Theses & Dissertations

The reaction of aluminum (Al) powder with water has the potential for on demand hydrogen generation. Conventional Al powders, however, react with water slowly due to a highly protective oxide layer on the particle surface. Current methods for Al activation involve harmful and expensive materials. The nano-scale Al powders also remain very expensive and have problems such as a large amount of oxide on the surface. The use of aluminum in an energy generation cycle is also hindered by the fact that, although Al is the most abundant metal in the Earth's crust, its recovery from ore consumes a lot …

Rbd2po4: Room Temprature Synthesis, Chemical And Structural Stablity Upon Heating, Masoud Mollaee

Open Access Theses & Dissertations

Monoclinic RbD2PO4 polycrystals were synthesized via the room temperature crystallization of RbH2PO4 dissolved in D2O. Powder x-ray diffraction (XRD) data collected at T=25 ºC indicate that this deuterated compound crystallizes in space group P21/m with unit cell parameters a=7.688í?, b=6.192í?, c=4.781í? and β=109.02°, and is isomorphic with the intermediate-temperature phase of its hydrogenated counterpart rubidium dihydrogen phosphate (RDP). We found no evidence of previously reported [Phase Transitions 80, 17 (2007)] polymorphic phase transition in rubidium dideuterium phosphate (DRDP) upon heating from room temperature to 210 ºC. All lattice parameters vary smoothly within this temperature range, demonstrating that the P21/m phase …

Effect Of Hafnium-Incorporation On The Microstructure And Dielectric Properties Of Cobalt Ferrite Ceramics, Stephen Josiah Wells

Open Access Theses & Dissertations

The effect of hafnium ion (Hf⁴⁺) incorporation in cobalt ferrite (CFO) was studied. Samples of Hf substituted CFO ceramic (CoFe_2-xHf_xO₄), were synthesized in the laboratory with hafnium concentrations ranging from x=0.000 to x=0.200. X-ray diffraction scans show that the Hafnium CFO crystalizes in the inverse spinel phase. Inclusion of hafnium causes lattice expansion, increasing the lattice parameter from 8.374 í? for pure CoFe2O4 to 8.391 í? for the highest concentration of hafnium tested (x=0.020). The dielectric properties of CFO are greatly enhanced by inclusion of hafnium. The enhancement is due to the …

Microstructure And Properties For Titanium Aluminide Superalloy Prototypes Fabricated By Electron Beam Melting And Thermally Processed, Jennifer Hernandez

Open Access Theses & Dissertations

Gamma TiAl has been considered to be an ideal replacement for Ni-base superalloy aerospace applications, particularly in weight-critical applications. While bulk, fully dense gamma-TiAl is 50% less dense than Ni-base superalloys, it also has excellent mechanical properties at high temperature (up to ~800°C). Pre alloyed (Ti-48Al-2Cr-2Nb) powder was used to fabricate solid, fully dense (3.85 g/cm3) components and foam components with densities ranging from 0.33 g/cm³ to 0.46 g/cm³ by electron beam melting (EBM). A 10:1 blend of 2-phase TiAl (Ti-48Al-2Cr-2Nb in ^a/_o) : Inconel 625 (Ni-22Cr-6Mo-2Nb in ^a/_o) pre-alloyed powders produced …

Reducing Metal Alloy Powder Costs For Use In Powder Bed Fusion Additive Manufacturing: Improving The Economics For Production, Fransisco Medina

Open Access Theses & Dissertations

Titanium and its associated alloys have been used in industry for over 50 years and have become more popular in the recent decades. Titanium has been most successful in areas where the high strength to weight ratio provides an advantage over aluminum and steels. Other advantages of titanium include biocompatibility and corrosion resistance. Electron Beam Melting (EBM) is an additive manufacturing (AM) technology that has been successfully applied in the manufacturing of titanium components for the aerospace and medical industry with equivalent or better mechanical properties as parts fabricated via more traditional casting and machining methods. As the demand for …

Process Study And Control Of Electron Beam Melting Technology Using Infrared Thermography, Jorge Mireles

Open Access Theses & Dissertations

An IR camera was installed in an Arcam A2 system (Arcam AB, Mölndal, Sweeden) and layer-by-layer image acquisition was achieved. The camera's capability to detect manufacturing defects was evaluated by implementing computer vision techniques using LabVIEW measurement and programming software (National Instruments, Austin, TX). Thermal maps acquired by the IR camera allowed layer-by-layer part temperature to be recorded. A core objective of this research was to study the impact of processing temperature on EBM-fabricated Ti-6Al-4V parts and achieve controlled mechanical properties. In this research, build variations were achieved by modifying parameters that change processing temperature from the standard processing temperature. …

Review Of Electrochemical And Electrodischarge Machining, Kamlakar P. Rajurkar, M. M. Sundaram, A. P. Malshe

Department of Mechanical and Materials Engineering: Faculty Publications

Electrochemical and electro-discharge machining processes are the two major electro-machining processes with unique capabilities. Electrical Discharge Machining (EDM) and Electrochemical Machining (ECM) offer a better alternative or sometimes the only alternative in generating accurate 3-D complex shaped macro, micro and nano features and components of difficult–to-machine materials. Technological advances reported in electrochemical and electro discharge machining processes, which reflect the state of the art in academic and industrial research and applications, are briefly reviewed in this paper.

Wire Electro-Discharge Machining Of Titanium Alloy, Farnaz Nourbakhsh, Kamlakar P. Rajurkar, Ajay P. Malshe, Jian Cao

Department of Mechanical and Materials Engineering: Faculty Publications

This paper presents an experimental investigation of wire electro-discharge machining (WEDM) of titanium alloy. The objective is to investigate the effect of seven process parameters including pulse width, servo reference voltage, pulse current, and wire tension on process performance parameters (such as cutting speed, wire rupture and surface integrity). A Taguchi L18 design of experiment (DOE) has been applied. All experiments have been conducted using Charmilles WEDM. It was also found that the cutting speed increases with peak current and pulse interval. Surface roughness was found to increase with pulse width and decrease with pulse interval. The Analysis of Variance …