Engineering Commons^™

Prediction Of Crack Growth Rate And Load Interaction Effects Using Damage Accumulation Model, Virender Goswami

Masters Theses

In damage tolerant designs, it is important to know the crack growth behavior of a material, so that sudden failure of a component can be avoided by determining a safe life. There are numerous models available to predict the crack growth rate. Among them the "crack closure model" is most often used for predicting the crack growth rate for different R-ratios and load interaction effects. However recently, the crack closure model has come under criticism by many authors to be flawed and overrated owing to its inherent drawbacks.

Therefore, a mathematical model for the fatigue crack propagation based on damage …

Pre-Impact Lower Extremity Posture And Brake Pedal Force Predict Foot And Ankle Forces During An Automobile Collision, Elizabeth C. Hardin, Anne Su, Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

Background: The purpose of this study was to determine how a driver’s foot and ankle forces during a frontal vehicle collision depend on initial lower extremity posture and brake pedal force. Method of Approach: A 2D musculoskeletal model with seven segments and six right-side muscle groups was used. A simulation of a three-second braking task found 3647 sets of muscle activation levels that resulted in stable braking postures with realistic pedal force. These activation patterns were then used in impact simulations where vehicle deceleration was applied and driver movements and foot and ankle forces were simulated. Peak rearfoot ground reaction …

Environment Assisted Cracking Of Target Structural Materials Under Different Loading Conditions, Venkataramakrishnan Selvaraj

UNLV Theses, Dissertations, Professional Papers, and Capstones

Martensitic Alloy HT-9 has been tested for its evaluation of stress corrosion cracking resistance in neutral and acidic solutions at ambient and elevated temperatures incorporating smooth and notched cylindrical specimens under constant load and slow strain rate (SSR) conditions. C-ring and U-bend specimens have also been tested for stress corrosion cracking evaluation in the acidic solution. The role of hydrogen on the cracking tendency has been evaluated by cathodic applied potential.

The results of constant load testing enabled the determination of the threshold stress for stress corrosion cracking in susceptible environments. The magnitudes of ductility parameters were reduced with increasing …

Stress Corrosion Cracking Resistance Of Martensitic Stainless Steels For Transmutation Applications, Phani P. Gudipati

UNLV Theses, Dissertations, Professional Papers, and Capstones

The susceptibility of Alloy EP-823 to stress corrosion cracking has been evaluated using smooth and notched cylindrical specimens in neutral and acidic solutions at ambient and elevated temperatures using constant load and slow strain rate testing (SSR) techniques. C-ring and U-bend specimens have also been tested in the acidic solution. The effect of hydrogen on the cracking susceptibility has been evaluated under controlled cathodic potential. While no failures were observed with smooth specimens at constant load, the notched specimens showed failure. The SSR test results indicate that the true failure stress (o'_f), time to failure and ductility parameters …

Cfd Analysis Of 3-D Thermalhydraulics Flow Effects On Wall Concentration Gradient Profiles For Lbe Loop Fittings, Narain Armbya

UNLV Theses, Dissertations, Professional Papers, and Capstones

The objective of the thesis is to study the effects of thermalhydraulics flows on the wall concentration gradient profiles in LBE loop fittings. To that end detailed models of the fittings have been constructed to study these effects. These fittings include sudden expansion, sudden contraction, t-joint and elbow. The typical flow rates chosen for these simulations are typical of design criteria chosen for the loop with Reynolds numbers expected around 200,000 and the usual axial temperature profiles which are being characterized in the DELTA loop at LANL. STAR-CD is the simulation package used to make these predictions, which include detailed …

Stress Corrosion Cracking And Hydrogen Embrittlement Of Martensitic Alloy Ep-823, Mohammad K. Hossain

UNLV Theses, Dissertations, Professional Papers, and Capstones

This investigation is focused on the evaluation of stress corrosion cracking (SCC), localized corrosion, and hydrogen embrittlement (HE) susceptibility of martensitic Alloy EP-823 in neutral and acidic solutions at ambient and elevated temperatures. While no failures were observed in smooth specimens in the neutral solution, failures were noticed in the 90°C acidic solution at constant-load (CL) leading to a threshold stress (O'_th) of 102 ksi. The presence of a notch reduced the O'_th value to 91 ksi in a similar environment. The ductility (%El and %RA), time-to-failure (TTF), and true failure stress (O'_r) were gradually …

Thermodynamic Analysis Of Separation Systems, Yaşar Demirel

Papers in Thermal Mechanics

Separation systems mainly involve interfacial mass and heat transfer as well as mixing. Distillation is a major separation system by means of heat supplied from a higher temperature level at the reboiler and rejected in the condenser at a lower temperature level. Therefore, it resembles a heat engine producing a separation work with a rather low efficiency. Lost work (energy) in separation systems is due to irreversible processes of heat, mass transfer, and mixing, and is directly related to entropy production according to the Gouy-Stodola principle. In many separation systems of absorption, desorption, extraction, and membrane separation, the major irreversibility …

Measurement Of Handle Forces For Crimping Connectors And Cutting Cable In The Electric Power Industry, Richard W. Marklin, Lia Lazuardi, Jeremy R. Wilzbacher

Mechanical Engineering Faculty Research and Publications

Overhead and underground line work in the electric power industry is physically very strenuous and can expose workers to musculoskeletal disorders (MSDs), particularly in the upper extremity. Crimping compression connectors—such as sleeve connectors and lugs—and cutting cables are two of the most frequent tasks that line workers perform. Line workers at many utilities in the US crimp connectors and cut cable with long-handled manual tools. However, the actual magnitude of the forces applied to the handles of these tools is not known. The objectives of this laboratory study were to measure the forces applied to the handles of a manual …

Indentation Of A Square Elastomeric Thin Film By A Flat-Ended Cylindrical Punch In The Presence Of Long-Range Intersurface Forces, Bing Feng Ju, Kai-Tak Wan, Kuo Kang Liu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper reports an experimental study of the elastic deformation of a 200 μm thick microfabricated square membrane with sides ranging from 8.5 mm to 15 mm as indented by a fine cylindrical, flat-ended punch with diameter 500 μm in the presence of long-range intersurface forces. an apparatus was constructed to allow simultaneously measurements of the indenter displacement and the applied force. a number of interesting phenomena such as the "jump-into-contact" and the "pull-off" between the membrane and the moving cylinder were observed. a simple theoretical analysis using linear elasticity was adopted to fit the load-displacement curve (compliance) and thus …

Introduction To Mechanical Engineering, Lorik Abdullai, Joseph R. Dunn

Honors Theses

I can still remember back in high school when I was faced with a decision thousands of students experience every year: What college was I going to choose, and what major was I going to study? It seemed like every time I saw friends and relatives they asked me that question. Meanwhile, I knew that going to a major university would give me more choices in case I changed majors. As it turned out, Western Michigan University was the best package for me when I considered the financial aid, the program ofmy major, location of the university, and its friendly …

Cooling Load Reduction And Air Conditioner Design In A 19th Century Florida House Museum, Florida Solar Energy Center, Dave Chasar

FSEC Energy Research Center®

Restoration plans at the H.S. Williams house included the installation of a space conditioning system. This contract report details how building envelope construction and air conditioner design were optimized as a system. Many aspects of the effort lent themselves to maintaining important "character-defining" features of the building including the resurrection of passive cooling attributes like light colored exterior paint and operable storm shutters. In addition, outside air infiltration was measured on the Williams house and six other balloon-frame homes to document this often significant cooling load component.

Development Of Pole Impact Testing At Multiple Vehicle Side Locations As Applied To The Ford Taurus Structural Platform, Mark Halford Warner

Theses and Dissertations

A test method was developed whereby repeated pole impacts could be performed at multiple locations per test vehicle, allowing a comparison of energy and crush relationships. Testing was performed on vehicles moving laterally into a 12.75 inch diameter rigid pole barrier. Crush energy absorption characteristics at the different locations were analyzed, and the results compared to test data from broad moving barrier crashes and available crash tests with similar pole impacts. The research documents the crush stiffness characteristics for narrow impacts at various points on the side of the Taurus vehicle platform. Factors encountered during the research include the importance …

The Effectiveness Of Computer-Based Tutorials In Learning Computer-Aided Design Methods For Tool Design Procedures, Andrew Moroni Hall

Theses and Dissertations

Throughout the past twenty-five years the process of designing and manufacturing a product has been revolutionized by the integration of Computer Aided Design (CAD). Although three-dimensional solid modeling, or 3-D CAD offers a better representation of the product in a virtual environment, it can be complicated and difficult to learn. Tutorials have been developed to assist manufacturing tool design student in the learning of 3-D CAD principles as they apply to tool design. This study seeks to test the effectiveness of those tutorials. A BYU tool design class was divided into two groups according to their assigned laboratory time. The …

Compliant Mechanisms To Perform Bearing And Spring Function In High Precision Applications, Jesse R. Cannon

Theses and Dissertations

An increasing number of mechanical systems are being designed on the micro and meso scales. Assembly and maintenance become increasingly difficult as the size of mechanisms decrease, and the minimum size of traditional elements such as bearings and springs is limited. The backlash of bearings also limits their usefulness in applications where high precision and repeatability are needed. At small scales and for high precision applications, alternative, non-traditional elements are needed.

The objective of this thesis is to develop reliable and scalable compliant components to replace bearings and helical springs. Components replacing springs must be able to produce specified torque/motion …

Lead-Free Solder Joint Reliability – State Of The Art And Perspectives, Jianbiao Pan, Jyhwen Wang, David M. Shaddock

Industrial and Manufacturing Engineering

There is an increasing demand in replacing tin-lead (Sn/Pb) solders with lead-free solders in the electronics industry due to health and environmental concern. The European Union recently passed a law to ban the use of lead in electronic products. The ban will go into effect in July of 2006. The Japanese electronics industry has worked to eliminate lead from consumer electronic products for several years. Although currently there are no specific regulations banning lead in electronics devices in the United States, many companies and consortiums are working on lead-free solder initiatives including Intel, Motorola, Agilent Technologies, General Electric, Boeing, NEMI …

Coordination Variables And Consensus Building In Multiple Vehicle Systems, Tim Mclain

Faculty Publications

Much of the research focus in the cooperative control community has been on formation control problems. This focus may be due to the fact that the group control problem can be reduced to well-established single-agent control problems by employing a leader-follower type control strategy. For example, single-agent path planning and trajectory generation techniques can be employed for the leader, and conventional trajectory tracking strategies can be employed for the followers. Indeed, formation control problems are much like linear systems theory: we search where the light is the brightest. It can be argued that formation control problems are the simplest type …

Thermally Developing Electro-Osmotic Convection In Circular Microchannels, Spencer L. Broderick

Theses and Dissertations

Thermally developing, electro-osmotically generated flow has been analyzed for a circular microtube under imposed constant wall temperature (CWT) and constant wall heat flux (CHF) boundary conditions. Established by a voltage potential gradient along the length of the microtube, the hydrodynamics of such a flow dictate either a slug flow velocity profile (under conditions of large tube radius-to-Debye length ratio, a/lambda_d) or a family of electro-osmotic flow (EOF) velocity profiles that depend on a/lambda_d. The imposed voltage gradient results in Joule heating in the fluid with an associated volumetric source of energy. For this scenario coupled with a slug flow velocity …

Analysis Of Power Takeoff Shafts To Prevent Injuries/Fatalities, Naomi Bronson

Morehead State Theses and Dissertations

A thesis presented to the faculty of the College of Science and Technology at Morehead State University in partial fulfillment of the requirement for the Degree of Master of Science by Naomi Bronson on November 1, 2004.

Screw Dislocation Interacting With Interfacial Edge-Cracks In Piezoelectric Bimaterial Strips, Xiangfa Wu, Yuris A. Dzenis, Bradley D. Rinschen

Department of Engineering Mechanics: Faculty Publications

This paper is concerned with the interaction between an interfacial edge-crack and a screw dislocation under out-of-plane mechanical and in-plane electric loading in a piezoelectric bimaterial strip. In addition to a discontinuous electric potential across the slip plane, the dislocation is subjected to a line-force and a line-charge at the core. Under the framework of linear piezoelectricity, the out-of-plane displacement and in-plane electric potentials are constructed in closed-form by means of conformal mapping technique and the known solution for screw dislocation in cracked piezoelectric bimaterial. The intensity factors (IFs) and energy release rate (ERR) are derived explicitly.

Edge-Cracked Orthotropic Bimaterial Butt Joint Under Antiplane Singularity, Xiangfa Wu, Yuris A. Dzenis, Emrah Gokdag

Department of Engineering Mechanics: Faculty Publications

Explicit elastic solutions are given for an edge-cracked orthotropic bimaterial butt joint under antiplane singularity of a screw dislocation and a line-force. During the procedure, conformal mapping and known dislocation solution are utilized for constructing the fundamental solution to the present problem. Stress intensity factor (SIF) and energy release rate (ERR) of the edge-cracked butt joint are given in closed-form. In limiting cases, results provided in this work cover those in literature.

Exergy Use In Bioenergetics, Yaşar Demirel

Papers in Analytical Chemistry

Every developed and adapted biological system extracts useful energy from outside, converts, stores it, and uses for muscular contraction, substrate transport, protein synthesis, and other energy utilizing processes. This energy management in a living cell is called the bioenergetics, and the useful energy is the exergy, which is destroyed in every irreversible process because of the entropy production. The converted exergy is the adenosine triphosphate (ATP) produced through the oxidative phosphorylation coupled to respiration in which the exergy originates from oxidation of reducing equivalents of nutrients. A living cell uses the ATP for all the energy demanding activities; it has …

Quantifying The Effects Of Aging On The Mechanical Properties Of Medical Grade Polycarbonate And Uv Cured Adhesives, Christopher James Lewis

Theses and Dissertations

Advances in engineering polymer technology have created a generation of high strength-to-weight materials for medical applications, with virtually no adverse interactions with body fluids. Polycarbonate is a widely used engineering polymer, and is often used in connection with ultra-violet light (UV) cured adhesives. Because of the chemical complexity of polymers, little is known about their actual aging characteristics. By characterizing the effects of aging, storage environment, and sterilization on medical grade polycarbonate/adhesive system properties, more accurate failure predictions can be made. In this thesis, efforts to better understand the effects of accelerated aging on a medical grade polycarbonate and UV …

A Cad-Centric Approach To Cfd Analysis With Discrete Features, Matthew Lee King

Theses and Dissertations

During the conceptual design stage several concepts are generated, and a few are selected for detailed analyses. CAD models from conceptual design often follow the "over-the-wall" approach for downstream analyses such as FEA, CFD, heat transfer, and vibrations. A CAD-centric approach will be applied to the CAD-to-CFD process to help industry in an ongoing quest to shorten the design cycle time. The CAD-centric approach consists of using the CAD model as a source of data for downstream applications such as mesh generation, and CFD setup. The CAD model used in the CAD-centric approach contains the geometry to be analyzed and …

Work In Progress: Combining Concept Inventories With Rapid Feedback To Enhance Learning, John Chen, Jennifer Kadlowec, Dexter Whittinghill

Mechanical Engineering

In this project our goal is to adapt the Concept Inventory for frequent classroom use, and to implement it in a system to provide rapid feedback to students of their understanding of key concepts being presented. The feedback system acts as the focal point and catalyst to encourage students, working in pairs, to assist each other in correcting misconceptions or deepening each other’s understanding of the topic at hand. Furthermore, the system allows the professor to assess the students’ level of comprehension (or misconception) in a just-in-time fashion, and thus guides his or her pacing and coverage of the material. …

Oct 2004, Tractor Museum

Lester F. Larsen Tractor Museum: Planning and Development Documents

Old Trusty Show New Paint Scheme History of Ag Engineering Department

Development Of A Virtually Calibrated Projection Moire Interferometry Technique Capable Of Inaccessible Surface Measurements, Mark Lee Kimber

Theses and Dissertations

Optical-based techniques have found merit in measuring displacement and strain for decades. These techniques are commonly used in numerous applications ranging from large displacements in wind tunnel experiments to displacement measurements on the submicron scale. Projection Moiré Interferometry (PMI) is an out-of-plane displacement measurement technique, and consists of capturing reference and deformed images of a grid pattern projected on the test object. By differencing the reference and deformed images of the projected grid pattern, a fringe pattern is generated from which the displacement field can be extracted. This computation requires calibration procedures that analyze a number of fringe patterns from …

Variation Simulation Of Fixtured Assembly Processes For Compliant Structures Using Piecewise-Linear Analysis, Michael L. Stewart

Theses and Dissertations

While variation analysis methods for compliant assemblies are not new, little has been done to include the effects of multi-step, fixtured assembly processes. This thesis introduces a new method to statistically analyze compliant part assembly processes using fixtures. This method, consistent with the FASTA method developed at BYU, yields both a mean and a variant solution. The method, called Piecewise-Linear Elastic Analysis, or PLEA, is developed for predicting the residual stress, deformation and springback variation in compliant assemblies. A comprehensive, step-by-step analysis map is provided. PLEA is validated on a simple, laboratory assembly and a more complex, production assembly. Significant …

Almost Global Asymptotic Formation Stabilization Using Navigation Functions, Amit Kumar, Herbert G. Tanner

Mechanical Engineering Faculty Publications

We present a navigation function through which a group of mobile agents can be coordinated to achieve a particular formation, both in terms of shape and orientation, while avoiding collisions between themselves and with obstacles in the environment. Convergence is global and complete, subject to the constraints of the navigation function methodology. Algebraic graph theoretic properties associated with the interconnection graph are shown to affect the shape of the navigation function. The approach is centralized but the potential function is constructed in a way that facilitates complete decentralization. The strategy presented will also serve as a point of reference and …

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

Transmutation Sciences Materials (TRP)

This quarterly report provides an update to the last phase of the Modeling, Fabrication, and Optimization of Niobium Cavities. Designing the experimental setup of secondary electron emission was well underway in early summer of 2003 when funding was made available for this portion the study. By March 2004, many of the components of the experimental study reached UNLV with some assembly accomplished. The first secondary electron emission (SEE) measurement was made from the surface of a Faraday cup in September 2004. At a particular beam energy, the current measured with the Faraday cup and electrometer changed sign over a range …

Solvent And Method For Extraction Of Triglyceride Rich Oil, Shubhender Kapila, Paul Ki-Souk Nam, V. J. Flanigan

Chemistry Faculty Research & Creative Works

The present invention relates to a solvent for use in extracting oil from an oil bearing material, such as soybeans, with the solvent resulting in the selective extraction of a triglyceride rich oil, which contains 95% or greater triglycerides and non-polar constituents, with the solvent comprised of a hydrocarbon, preferably hexane, and a fluorocarbon, so that the solvent has a viscosity less than 2.6 centipoise and a polarity of less than 0.1. The present invention also relates to a method of using the solvent to extract the triglyceride rich oil, with the method including preferably extracting the oil at a …