Mechanics of Materials Commons^™

The Effect Of Cr, Si And B On The Oxidation Behavior On Three Nb-Based Alloys, David Alvarez

Open Access Theses & Dissertations

Nb-based alloys are of particular interest to replace the current Ni-based superalloys for high-temperature structural applications. One important limitation to improve the efficiency of gas-turbine engines is the temperature limit of current materials being used. By allowing the temperature to increase, the efficiency will increase. Nb-based alloys have high melting points and adequate mechanical properties but the oxidation resistance is still inadequate.

This research focuses on the oxidation behavior of three Nb-based alloys to study the effect of Cr and Si variation and look at the effect of Boron. Boron can form a glassy borosilicate which is viscous at high …

Fabrication And Characterization Of Nanocrystalline Yttrium Oxide Thin Films For Electronic Device Applications, Mudavakkat Vikas Haridas

Open Access Theses & Dissertations

This thesis presents the optimization of growth conditions for fabricating nanocrystalline Yttrium Oxide (Y2O3) thin films on silicon and optical grade, high quality quartz substrates in order to study its structural, optical and electrical properties for electronic device applications.

Commercially Y2O3 has proven to be difficult to fabricate at high quality due to its high temperature growth requirements and the need to alter established fabrication methods for electronic devices. A high temperature requirement for high quality poses a problem for research and analysis. This calls upon for an optimization of the growth conditions to facilitate fabrication of thin films for …

Preparation And Characterization Of Iron Oxide And Hydroxide Based Nanomaterials, Guillermo Carbajal Franco

Open Access Theses & Dissertations

Iron (Fe) oxides and hydroxides are common and abundant materials. They exhibit diverse crystal structures, properties and phenomena by virtue of which they find a wide range of scientific and technological applications. Controlled growth and manipulation of the specific structure and electronic behavior to meet the requirements of a given application is a challenging problem in view of many possible phases and composition of the resulting materials. The preparation method and experimental conditions will, therefore, significantly affect the properties and performance of Fe oxides and hydroxides. The goal of the project is to obtain Fe-based oxide/hydroxide catalytic materials and to …

Fundamental Studies Of Co-Base Superalloy Biomedical Prototypes Fabricated By Electron Beam Melting: Microstructures And Microstructural Architecture, Sara M. Gaytan

Open Access Theses & Dissertations

Rapid prototyping, especially electron beam melting (EBM) technology by ARCAM have proven to provide outstanding microstructural and mechanical properties on different alloys fabricated by this technology. Being a computer designed driven technology, complex components, that are hard or even impossible to fabricate by traditional manufacturing techniques, can be fabricated by layer-by-layer EBM technology.

Microstructural and mechanical properties are compared for an EBM femoral knee component prototype with a traditionally-fabricated and body-removed femoral knee implant. Block and cylindrical shape components fabricated by EBM were also analyzed for this project. The alloy utilized for these components is Co-26Cr-6Mo-0.2C characterized by the standards …

Ballistic Projectile Metallurgical Issues And Fundamentals: Aerosol Production In Rod Penetration Erosion And Erosion Phenomena Associated With Railgun Development, Brenda Ivette Machado

Open Access Theses & Dissertations

The issue is derived from ballistic erosion as it relates to nanoparticle production and respiration of these particles as a health concern ballistic erosion and ballistic erosion as it relates to railgun performance. A common thread between these two issues is dynamic recrystallization (DRX). DRX has been demonstrated to be the dominant mechanism for solid-state flow associated with ballistic projectile/target penetration and interaction, friction-stir welding phenomena, and other high-strain rate deformation phenomena.

Aerosol particulates collected on filters from ballistic penetration and erosion events for W-Ni-Co and W-Ni-Fe kinetic energy rod projectiles penetrating steel target plates were observed to be highly …

Microstructural Architecture Developed In The Fabrication Of Solid And Open-Cellular Copper Components By Additive Manufacturing Using Electron Beam Melting, Diana Alejandra Ramirez

Open Access Theses & Dissertations

The fabrication of Cu components were first built by additive manufacturing using electron beam melting (EBM) from low-purity, atomized Cu powder containing a high density of Cu2O precipitates leading to a novel example of precipitate-dislocation architecture. These microstructures exhibit cell-like arrays (1-3µm) in the horizontal reference plane perpendicular to the build direction with columnar-like arrays extending from ~12 to >60 µm in length and corresponding spatial dimensions of 1-3 µm. These observations were observed by the use of optical metallography, and scanning and transmission electron microscopy. The hardness measurements were taken both on the atomized powder and the Cu components. …

Effect Of Process Parameter On Temperature Distribution, Microstructure, And Mechanical Properties Of Self-Reacting Friction Stir Welded Aluminum Alloy 6061-T651, Monica Adriana Torres

Open Access Theses & Dissertations

Self-reacting friction stir welding is the latest FSW tool configuration developed, it employs two shoulders--one on top and one on the bottom of the workpiece-- this tool configuration offers many advantages over conventional welding techniques. However, the current lack of information and specifications limits its understanding and application. This investigation analyzed the effect of process parameters on temperature distribution, microstructure evolution, and final mechanical properties of 6061-T651 SR-FS welds. A factorial experiment was carried out, in which three-process parameters were analyzed--rotational speed, travel speed, and tool plunge force-- three levels were analyzed for each parameter, except for a tool plunge …

Dispersive Wave Equations For Solids With Microstructure, A. Berezovski, Juri Engelbrecht, Mihhail Berezovski

Publications

The dispersive wave motion in solids with microstructure is considered in the one-dimensional setting in order to understand better the mechanism of dispersion. It is shown that the variety of dispersive wave propagation models derived by homogenization, continualisation, and generalization of continuum mechanics can be unified in the framework of dual internal variables theory.

In Vitro Models For Glaucoma Research: Effects Of Hydrostatic Pressure, Yuan Lei, Shadi Rajabi, Ryan M. Pedrigi, Darryl R. Overby, A. Thomas Read, C. Ross Ethier

Department of Mechanical and Materials Engineering: Faculty Publications

PURPOSE. The response of cells (e.g., optic nerve head [ONH] cells) to mechanical stress is important in glaucoma. Studies have reported the biological effects of hydrostatic pressure on ONH cells cultured on a rigid substrate. An apparatus, designed to independently vary hydrostatic pressure and gas tension (including oxygen tension) in culture medium, was used to evaluate the effects of pressure and tension on cell migration, shape, and α-tubulin architecture in a transformed cell line (DITNC1 rat cortical astrocytes).

METHODS. During the assay period, cells were exposed to one of four experimental configurations: (1) control pressure and control gas tension; (2) …

Nanomechanical Analysis Of Insulinoma Cells After Glucose And Capsaicin Stimulation Using Atomic Force Microscopy, Ruiguo Yang, Ning Xi, King Wai-Chu Lai, Bei-Hua Zhong, Carmen Kar-Man Fung, Chen-Geng Qu, Donna H. Wang

Department of Mechanical and Materials Engineering: Faculty Publications

Aim: Glucose stimulates insulin secretion from pancreatic islet β cells by altering ion channel activity and membrane potential in the β cells. TRPV1 channel is expressed in the β cells and capsaicin induces insulin secretion similarly to glucose. This study aims to investigate the biophysical properties of the β cells upon stimulation of membrane channels using an atomic force microscopic (AFM) nanoindentation system.

Methods: ATCC insulinoma cell line was used. Cell stiffness, a marker of reorganization of cell membrane and cytoskeleton due to ion channel activation, was measured in real time using an integrated AFM nanoindentation system. Cell height that …

Use Of Environmental Scanning Electron Microscopy For In Situ Observation Of Interaction Of Cells With Micro- And Nanoprobes, Alexander Goponenko, B. J. Boyle, K. I. Jahan, Maxim V. Gerashchenko, Dmitri E. Fomenko, Vadim N. Gladyshev, Yuris A. Dzenis

Department of Mechanical and Materials Engineering: Faculty Publications

Precision intracellular sensing, probing and manipulation offer unprecedented opportunities for advances in biological sciences. Next-generation ultra-fine probes will be capable of targeting individual cell organelles. Development of such probes as well as probes capable of penetrating through tough cell walls requires detailed knowledge of cell-probe interaction. This Letter evaluated the applicability of environmental scanning electron microscopy (ESEM) for cell and cell-probe interaction imaging. Several types of cells (plant and yeast cells as well as mouse spermatozoa) were successfully imaged in their natural state, with mouse spermatozoa observed by ESEM for the first time. Computerized stage applied to image was tough …

Achieving High Efficiency Laminated Polymer Solar Cell With Interfacial Modified Metallic Electrode And Pressure Induced Crystallization, Yongbo Yuan, Yu Bi, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

We report efficient laminated organic photovoltaic device with efficiency approach the optimized device by regular method based on Poly(3-hexylthiophene-2,5-diyl) and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM). The high efficiency is mainly attributed to the formation of a concrete polymer/metal interface mechanically and electrically by the use of electronic-glue, and using the highly conductive and flexible silver film as anode to reduce photovoltage loss and modifying its work function for efficiency hole extraction by ultraviolet/ozone treatment, and the pressure induced crystallization of PCBM.

Anomalous Loss Of Toughness Of Work Toughened Polycarbonate, Shawn E. Meagher

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Glassy polymers such as polycarbonate (PC) can be toughened through compressive plastic deformation. The increase in toughness is substantial, showing as much as a fifteen fold increase in the amount of dissipated energy during failure for samples compressed to 50% plastic strain. This toughness increase can be reversed through thermal aging at temperatures below the glass transition temperature (T_g = 147°C).

The combined effect of plastic compression and thermal aging has been studied using Charpy, Single Edge Notch Bending (SENB), and Compact Tension (CT) tests. The tests mapped the response of samples cut along different orientations relative to the …

Processing And Composition Effects On The Fracture Behavior Of Spray-Formed 7xxx Series Al Alloys, Mala M. Sharma, Constance W. Ziemian, Timothy J. Eden

Faculty Journal Articles

The fracture properties of high-strength spray-formed Al alloys were investigated, with consideration of the effects of elemental additions such as zinc,manganese, and chromium and the influence of the addition of SiC particulate. Fracture resistance values between 13.6 and 25.6 MPa (m)^1/2 were obtained for the monolithic alloys in the T6 and T7 conditions, respectively. The alloys with SiC particulate compared well and achieved fracture resistance values between 18.7 and 25.6 MPa (m)^1/2. The spray-formed materials exhibited a loss in fracture resistance (KI) compared to ingot metallurgy 7075 alloys but had an improved
performance compared to high-solute powder …

Deformation Waves In Microstructured Materials: Theory And Numerics, Juri Engelbrecht, Arkadi Berezovski, Mihhail Berezovski

Publications

A linear model of the microstructured continuum based on Mindlin theory is adopted which can be represented in the framework of the internal variable theory. Fully coupled systems of equations for macro-motion and microstructure evolution are represented in the form of conservation laws. A modification of wave propagation algorithm is used for numerical calculations. Results of direct numerical simulations of wave propagation in periodic medium are compared with similar results for the continuous media with the modelled microstructure. It is shown that the proper choice of material constants should be made to match the results obtained by both approaches

Diffuse Ultrasonic Scattering In Advanced Composites, Christer Stenström

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Non destructive testing (NDT) is a noninvasive technique used for characterization and inspection of the integrity of objects. NDT is an important tool for research, manufacturing monitoring and in-service inspections. Ultrasonic testing is the most used NDT technique, which for advanced composites can identify several types of defects, like delamination and interlaminar cracks. Diffuse ultrasonics has shown to be able to extract information at the microscale of metals and therefore it is believed it can be used for advanced composites to extract microstructural information, i.e. at the level of fibers.

In this thesis, diffuse ultrasonic methods, together with spatial variance …

Characterization, Modeling, And Consequences Of The Development During Plastic Flow Of Large Anisotropy In The Wave-Speeds, Quentin Fichot

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

There is a substantial change in the anisotropy of some glassy polymers when they are subjected to large plastic deformations. The most pronounced case probably is seen in polycarbonate (PC), which is a tough thermoplastic used for many structural applications, including as a protective transparent armor for such applications as bulletproof glass. This development of anisotropy in the elastic response can be of the same order as the applied strains, and, therefore, becomes important in problems that show substantial plastic flow. In spite of this, this characteristic of glassy polymers has not been included in the current models. We propose …

Elements Of Study On Dynamic Materials, Marine Rousseau, Gerard A. Maugin, Mihhail Berezovski

Publications

As a preliminary study to more complex situations of interest in small-scale technology, this paper envisages the elementary propagation properties of elastic waves in one-spatial dimension when some of the properties (mass density, elasticity) may vary suddenly in space or in time, the second case being of course more original. Combination of the two may be of even greater interest. Toward this goal, a critical examination of what happens to solutions at the crossing of pure space-like and time-like material discontinuities is given together with simple solutions for smooth transitions and numerical simulations in the discontinuous case. The effects on …

An Experimental Investigation Of Friction Bit Joining In Az31 Magnesium And Advanced High-Strength Automotive Sheet Steel, Rebecca Gardner

Theses and Dissertations

Friction Bit Joining (FBJ) is a recently developed spot joining technology capable of joining dissimilar metals. A consumable bit cuts through the upper layer of metal to be joined, then friction welds to the lower layer. The bit then snaps off, leaving a flange. This research focuses on FBJ using DP980 or DP590 steel as the lower layer, AZ31 magnesium alloy as the top layer, and 4140 or 4130 steel as the bit material. In order to determine optimal settings for the magnesium/steel joints, experimentation was performed using a purpose-built computer controlled welding machine, varying factors such as rotational speeds, …

Design, Fabrication, Structural Testing, And Numerical Analysis Of A Small Scale Composite Wing, Jacob David Gaunt, Juan Carlos Flores, Vincent Andrew Perry

Aerospace Engineering

A small scale composite wing based on a design found on an experimental aircraft was designed, constructed, and tested dynamically and statically. The wing was constructed similarly to an experimental aircraft wing. The performed static test was intended to produce pure bending. Strain gages were used to measure strains on the wing structure. The strains were converted to stresses to aid in analysis. The static test results suggested that the wing was actually under torsion. Four structural modes were found from the static test. A finite element analysis model was made to compare experimental results to numerical analytical results. The …