Mechanical Engineering Commons^™

Photoreflectance Spectroscopy Of Strained (In)Gaasn/Gaas Multiple Quantum Wells, J. B. Heroux, Xiaodong Yang, W. I. Wang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The effect of a variation of the indium and nitrogen concentrations in Inᵪ Ga_1-x As_1-y N_y /GaAs multiquantum wells grown by molecular beam epitaxy is studied systematically by room temperature photoreflectance spectroscopy. The band gap redshift caused by a nitrogen fraction of 1.5% decreases by as much as 30% as the indium fraction increases from 0% to 20%. A moderate increase of electron effective mass (Δmₑ ~ 0.03m₀) is found in all samples containing nitrogen (y ≳ 1%). In compressively strained quantum wells, the energy separation between the first confined heavy and light hole energy levels decreases …

Screw Dislocation Interacting With An Interfacial Edge Crack Between Two Bonded Dissimilar Piezoelectric Wedges, Xiangfa Wu, Yuris A. Dzenis, Wen-Sheng Zou

Department of Engineering Mechanics: Faculty Publications

This letter is concerned with an interface edge crack interacting with a screw dislocation under antiplane mechanical and in-plane electric loading in a piezoelectric bimaterial wedge. In addition with a discontinuous electric potential across the slip plane, the dislocation is subjected to a line-force and a line-charge at the core. The out-of-plane displacement and electric potentials are obtained in closed-form on the basis of the conformal mapping technique and the solution for a screw dislocation in an infinite piezoelectric bimaterial with a semi-infinite interface crack. The intensity factors (IFs) and energy release rate (ERR) are obtained explicitly.

Virtual Surfaces, Director Domains And The Freedericksz Transition In Polymer Stabilized Nematic Liquid Crystals, Pavel A. Kossyrev, Jun Qi, Nikolai V. Priezjev, Robert A. Pelcovits, Gregory P. Crawford

Mechanical and Materials Engineering Faculty Publications

The critical field of the Freedericksz transition and switching dynamics are investigated for polymer stabilized nematic liquid crystals as a function of polymer concentration. A simple phenomenological model is proposed to describe the observed critical field and dynamic response time behaviors as a function of concentration. In this model the polymer fibrils form director domains, which are bounded by virtual surfaces with a finite anchoring energy. The Freedericksz transition occurs independently within each of these domains.

Educating Engineering Students In Entrepreneurship, William W. Durgin, Donald N. Zwiep

Office of the Provost Scholarship

Since it’s founding in 1865, the faculty, students, and alumni of Worcester Polytechnic Institute have been responsible for the establishment of nearly all the manufacturing industry in the region. Beginning with the Norton Company, a world-wide abrasives manufacturer now owned by Saint Gobain, to recent biotechnology companies, they have combined confidence, innovation, and resourcefulness to continuously accomplish what is now referred to as technology transfer to form start-up companies. By following the historical development of these firms, we seek to determine some of the traits and environmental factors that have fostered the continual entrepreneurial success of the founders.

Worcester Polytechnic …

Ole Miss Engineer 2002

Ole Miss Engineer

No abstract provided.

Rectangular Bursting Energy Absorber, John D. Reid, John R. Rohde, Dean L. Sicking

Department of Mechanical and Materials Engineering: Faculty Publications

A bursting energy absorber System having an impact head, and energy absorption mechanism. The energy absorbing mechanism has a generally rectangular mandrel for rupturing cooperating thin-walled generally rectangular tubes in a controlled rupture to absorb impact forces for a colliding vehicle. A frame may be used to mount the System to a truck, trailer, guardrail, median barrier end treatment, or a crash cushion. Stress concetrators such as saw cuts or scoring may be incorporated into the absorption tubes to selectively control rupturing and energy dissipation. The mandrels may be tapered, rectangulary shaped with beveled edges to reduce frictional forces along …

Evaluation Of Distributed Effects In Field Effect Transistors For High Frequency Applications, Srinivas Rowjee Cuddapah

Electrical & Computer Engineering Theses & Dissertations

Metal Semiconductor Field Effect Transistors are at the heart of currently used microwave and millimeter-wave devices. CAD (Computer Aided Design) models for MESFET are used in the development and optimization of high-speed microwave devices. The increase in the chip density demands more accurate models. A distributed small signal model was developed for a GaAs MESFET account of the high frequency effects.

The lumped model of the MESFET is inadequate at frequencies where the wavelength of operation approaches device dimensions. This is because different regions in the device can experience different amplitudes and phases of the biasing signal. In this thesis, …

2002 (Fall) Ensi Informer Magazine, Morehead State University. Engineering Sciences Department

ENSI Informer Magazine Archive

The ENSI Informer Magazine published in the fall of 2002.

An Under-Hand Steering Wheel Grasp Produces Significant Risk To The Upper Extremity During Airbag Deployment, Patrick J. Atkinson, Prem Hariharan, Shresta Mari-Gowda, Paul Telehowski, Sidney Martin, Jack Van Hoof, Cynthia Bir, Theresa Atkinson

Mechanical Engineering Presentations And Conference Materials

Recent laboratory investigations suggest that a deploying airbag may fracture the forearm. These studies positioned the arm in an overhand grasp placing the forearm over the airbag module. However, there is little published data on how drivers grip the steering wheel and the general proximity of the upper extremity to the airbag module. The objective of the current study was to identify 'real world' upper extremity positions and to correlate these with accident and experimental data. A survey of the National Automotive Sampling System (NASS) for the years 1995-99 revealed an increase in the number of forearm fractures due to …

Field Testing And Computer Modeling To Characterize The Energy Impacts Of Air Handler Leakage, Florida Solar Energy Center, James Cummings

FSEC Energy Research Center®

In order to determine the impact of air handler location upon heating and cooling energy use, the amount of air leakage which occurs in the air handler cabinet needs to be known. Also, the leakage which occurs at the connections between the air handler cabinet and the return and supply plenums needs to be known as well because these connection leaks would also be located in the attic or any other location.

In order to assess this leakage, testing was performed on a total of 69 air conditioning systems. Thirty systems were tested in the year 2001 under funding from …

A Mechanical System For Soil Reconstruction, John Patrick Fulton, Larry G. Wells, Timothy D. Smith

Biosystems and Agricultural Engineering Faculty Publications

One of the most perplexing problems associated with reclaiming surface–mined lands is excessive compaction of soil due to the heavy earthmoving equipment used during the reclamation process. Over the years, some innovative material handling schemes have been devised to limit vehicle traffic during reclamation on reconstructed soil. However, final grading operations can often create root–limiting bulk densities, which affect plant growth and yield. The purpose of this article is to describe a mechanism designed at the University of Kentucky whereby mine soil can be reconstructed without introducing compaction caused by surface traffic in order for the soil to sustain desirable …

Comment On "Quadriceps Protects The Anterior Cruciate Ligament", Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

No abstract provided.

Closed-Form Solution For A Mode-Iii Interfacial Edge Crack Between Two Bonded Dissimilar Elastic Strips, Xiangfa Wu, Yuris A. Dzenis

Department of Engineering Mechanics: Faculty Publications

A closed-form solution is obtained for the problem of a mode-III interfacial edge crack between two bonded semi-infinite dissimilar elastic strips. A general out-of-plane displacement potential for the crack interacting with a screw dislocation or a line force is constructed using conformal mapping technique and existing dislocation solutions. Based on this displacement potential, the stress intensity factor (SIF, K_III) and the energy release rate (ERR, G_III) for the interfacial edge crack are obtained explicitly. It is shown that, in the limiting special cases, the obtained results coincide with the results available in the literature. The present …

Closed-Form Solution For The Size Of Plastic Zone In An Edge-Cracked Strip, Xiang-Fa Wu, Yuris A. Dzenis

Department of Engineering Mechanics: Faculty Publications

This paper is concerned with the problem of plastic zone at the tip of an edge crack in an isotropic elastoplastic strip under anti-plane deformations. By means of complex potential and Dugdale model, the stress intensity factor and the size of plastic zone are obtained in closed-form. Furthermore, the analytic solutions for an edge crack at the free boundary of a half-space and a semi-infinite crack heading towards a free surface are determined as the limiting cases of the strip geometries.

Composite Structures Using Asphalt Based Roofing Scrap Materials: Eiera -- Final Report, V. J. Flanigan, K. Chandrashekhara, Susan L. Murray

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The uses of recycled materials in composites provide the potential for large cost savings and a solution to the ever-growing disposal problem. Shingles contain petroleum based binders and fillers, which used as a valuable resource in composite production. Composites offer inherent advantages over traditional materials in regard to corrosion resistance, design flexibility and extended service life. Use of scrap-roofing shingles as a core material in glass fiber reinforced composite materials offer potential low cost composite products such as sound barrier system, railroad ties and other building materials including blocks. In the present work, processes have been developed for shredding scrap …

The Evolution Of The Long Term Performance Of Fiber Reinforced Composites Materials Based On Vinyl Easter Resin, Nasser Abdullah Ali-Al Ghailani

Theses

Fiber reinforced polymer (plastic) FRP composites are different from traditional

structural materials such as steel or aluminum since the an-isotropic nature of a Fiber _ reinforced composite material creates a unique opportunity of tailoring its properties according to the design requirements. With the accelerated change in the technological sphere, FRP composite materials

have taken a paramount importance in various structural applications, where they successfully replaced conventional materials such as steel. Such success is based on the advantages offered by composite materials such as a high strength to weight ratio. However one aspect that is still delaying full acceptance of these …

In Situ Corrosion Studies On The Battleship Uss Arizona, John D. Makinson, James D. Carr, Matthew A. Russell, David L. Conlin, Larry E. Murphy

Department of Mechanical and Materials Engineering: Faculty Publications

U.S. National Park Service Submerged Resources Center archaeologists and University of Nebraska-Lincoln metallurgists are assessing hull corrosion by drilling through accumulated concretions and measuring pH and corrosion potentials. Concretion samples are being analyzed to determine the role of microbes in the corrosion process, identify chemical species, and measure electrical and physical properties. The lowest values of pH and E corr occur at the metal/concretion interface. Analysis suggests a variable corrosion rate supported by hydrogen discharge and/or oxygen reduction inside the concretion.

Modeling, Fabrication, And Optimization Of Niobium Cavities: Phase Ii Quarterly Report, Robert A. Schill Jr., Mohamed Trabia

Transmutation Sciences Materials (TRP)

Multipacting is one of the major loss mechanisms in rf superconductivity cavities for accelerators. This loss mechanism limits the maximum amount of energy/power supported by the cavities. Optimal designs have been identified in others’ studies. In practice, these designs are not easily manufactured. Chemical etching processes used to polish the cavity walls result in a nonuniform surface etch. A nonuniform surface etch will leave some unclean areas with contaminants and micron size particles. These significantly affect mutipacting. Further, a nonuniform etch will leave areas with damaged grain structure, which is not good for superconducting properties. Typically, the depth of chemical …

Modeling The Thermal Behavior Of A Surface-Micromachined Linear-Displacement Thermomechanical Microactuator, Christian D. Lott, Timothy W. Mclain, John N. Harb, Larry L. Howell

Faculty Publications

Thermomechanical microactuators possess a number of desirable attributes including ease of fabrication and large force and displacement capabilities relative to other types of microactuators. These advantages provide motivation for improving thermomechanical microactuator designs that are more energy efficient and thus better suited for low-power applications. To this end, this paper describes the development and experimental validation of a finite-difference thermal model of a thermomechanical in-plane microactuator (TIM). Comparisons between the model and experimental results demonstrate the importance of including the temperature dependence of several parameters in the model. Strategies for reducing the power and energy requirements of the TIM were …

Use Of Positron Annihilation Spectroscopy For Stress-Strain Measurements: Quarterly Progress Report (June 1 – August 31, 2002), Ajit K. Roy

Transmutation Sciences Materials (TRP)

The purpose of this collaborative research project involving the University of Nevada Las Vegas (UNLV), the Idaho State University (ISU), and the Los Alamos National Laboratory (LANL) is to evaluate the feasibility of determining residual stresses in cold-worked, plastically-deformed, and welded materials using a nondestructive method based on positron annihilation spectroscopy. This technique uses γ-rays from a small MeV electron Linac to generate positrons inside the sample via pair production. This method is known to have capabilities of characterizing defects in thick specimens, that could not be accomplished by conventional positron technique or other nondestructive methods. The generated data will …

Atomic Force Microscopy Used To Determine The Young's Modulus Of Vascular Smooth Muscle Cells, Samuel C. Lieber

Theses

The Young's modulus of cultured mouse and rat vascular smooth muscle cells (VSMC) was measured with an atomic force microscope (AFM). The AFM can image the three-dimensional structure of biological cells in a physiological environment enabling real-time biochemical and physiological processes to be monitored at a resolution similar to that obtained for the electron microscope (EM). Cellular mechanical properties were determined by indenting the cell's body, and analyzing the indentation data with classical infinitesimal strain theory. This calculation was accomplished by modeling the AFM probe as a cone. as well as a blunted cone. The blunted cone geometry fits the …

Stability And Heat Transfer Characteristics Of Condensing Films, James C. Hermanson, Peder C. Pedersen, Jeffrey S. Allen, M. A. Shear, Z. Q. Chen, Andreas N. Alexandrou, William W. Durgin

Office of the Provost Scholarship

No abstract provided.

Laser Aided Part Repair -- A Review, Jinglei Wang, Sashikanth Prakash, Yashodhan Joshi, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Laser aided part-repair is an emerging trend that has great potential for future industrial applications. Part-repair technologies are currently used in repairing military and civilian equipment. The focus of this paper is to review the current repair processes, which use the laser-aided metal deposition technology. Many metal parts, which are worn by continual use, can be restored to working condition by the deposition of metal with a laser and machining. This not only extends the life of the part, but also, saves on cost. A comparison between various processes, their parameters, efficiency, cost, and etc. are also presented. The process …

Object-Oriented Modeling And Fauly Detection Of A Powder Feeder For A Laser Metal Deposition System, Robert G. Landers, Michael Gene Hilgers, Frank W. Liou, Bruce M. Mcmillin

Mechanical and Aerospace Engineering Faculty Research & Creative Works

One of the most critical components of a laser metal deposition system is the powder feeder unit. Techniques are required to efficiently design and analyze these systems and to ensure fault tolerance during the operation. In this paper, a model of the powder feeder unit, based on object- oriented abstractions of it components, is developed. This model is modular in that specific components can be efficiently updated or replaced with components that perform a similar function. In addition, the model can be used for simulation allowing for efficient design and analysis. Assurance of the correctness of the powder feeder system …

Investigation Of Part Accuracy And Surface Roughness In Rapid Freeze Prototyping Based Investment Casting, Qingbin Liu, Ming-Chuan Leu, Stephen M. Schmitt

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The study as described in this paper is aimed at investigating the dimensional accuracy and surface finish of metal parts made by investment casting with ice patterns generated by rapid freeze prototyping. The process of investment casting with ice patterns is described and contrast with conventional investment casting with wax patterns is made. The selection of binder material for ceramic slurries and the need for an interface agent to separate the ice pattern from the ceramic slurry in the mold making process are discussed. The accuracy and surface finish of ice patterns and of the metal castings are presented and …

System Integration And Real-Time Control Architecture Of A Laser Aided Manufacturing Process, Mallikharjuna R. Boddu, Robert G. Landers, Srinivas Musti, Sanjeev Agarwal, Jianzhong Ruan, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper discusses a hybrid deposition–removal manufacturing system being developed at the University of Missouri--Rolla. The system consists of a laser system, five-axis CNC machining center, and powder feeder system. A description of the control software, real-time control architecture, and integration of various subsystems to build the hybrid system is given. The interaction of the real-time controller with various sensors and subsystems to monitor and regulate the process is presented. The communication between integrated process planning for the system and real–time control is also discussed in this paper.

A Study On Effects Of Process Parameters In Rapid Freeze Prototyping, Frances D. Bryant, Guanghua Sui, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Rapid Freeze Prototyping (RFP) is a relatively new solid freeform fabrication process, which builds a three-dimensional part according to a CAD model by depositing and freezing water droplets layer by layer. A study on the effects of RFP process parameters including the nozzle scanning speed, droplet size, and droplet frequency in building ice parts with a single-nozzle work head is made. Presented in this paper are the results of this study which indicate that these process parameters determine the ice layer thickness and ice line width, which in turn determine the surface roughness and the waiting time required after depositing …

Object-Oriented Modeling And Fault Detection Of A Powder Feeder For A Laser Metal Deposition System, Robert G. Landers, Michael Gene Hilgers, Frank W. Liou, Bruce M. Mcmillin

Mechanical and Aerospace Engineering Faculty Research & Creative Works

One of the most critical components of a laser metal deposition system is the powder feeder unit. Techniques are required to efficiently design and analyze these systems and to ensure fault tolerance during the operation. In this paper, a model of the powder feeder unit, based on object-oriented abstractions of it components, is developed. This model is modular in that specific components can be efficiently updated or replaced with components that perform a similar function. In addition, the model can be used for simulation allowing for efficient design and analysis. Assurance of the correctness of the powder feeder system is …

The Effects Of Corrosive Chemicals On Corrosion Rate Of Steel Reinforcement Bars: I. Swamp Water, Sulistyoweni Widanarko, Henki W. Ashadi, Andri Krisnadi Wicaksono

Makara Journal of Technology

Most of infrastructures using steel concrete to reinforce the strength of concrete. Steel concrete is so vulnerable to chemical compounds that can cause corrosion. It can happen due to the presence of chemical compounds in acid environment in low pH level. These chemical compounds are SO4 2-, Cl-, NO3 -. There are many swamp area in Indonesia. The acid contents and the concentration of ion sulphate, chlorides, and nitrate are higher in the swamp water than in the ground water .The objective of this research was to find out the influence of corrosive chemicals in the swamp water to the …

The Effects Of Corrosive Chemicals On Corrosion Rate Of Steel Reinforcement Bars: Ii. Swamp Sludges, Henki W. Ashadi, Sulistyoweni Widanarko, Irma Gusniani

Makara Journal of Technology

A polluted environment will influence the building age. The objective of this research was to find out the influence of corrosive chemicals within the sludge swamp area with the corrosion rate of steel concrete. Corrosion in steel concrete usually occur in acid area which contain of SO4 2-, Cl- and NO3 -. The research treatment used by emerging ST 37 and ST 60 within 60 days in ‘polluted’ sludge swamp area. Three variation of ‘polluted’ swamp sludge were made by increasing the concentration a corrosive unsure up to 1X, 5X and 10X. The corrosion rate measured by using an Immersion …