Engineering Commons^™

Use Of Positron Annihilation Spectroscopy For Stress-Strain Measurements: Quarterly Progress Report (June 01 – August 31, 2003), 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 (bent), and welded materials using a nondestructive method based on positron annihilation spectroscopy (PAS). 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 …

External And Intrinsic Anchoring In Nematic Liquid Crystals: A Monte Carlo Study, Nikolai V. Priezjev, G. Skacej, R. A. Pelcovits, S. Zumer

Mechanical and Materials Engineering Faculty Publications

We present a Monte Carlo study of external surface anchoring in nematic cells with partially disordered solid substrates, as well as of intrinsic anchoring at free nematic interfaces. The simulations are based on the simple hexagonal lattice model with a spatially anisotropic intermolecular potential. We estimate the corresponding extrapolation length b by imposing an elastic deformation in a hybrid cell-like nematic sample. Our estimates for b increase with increasing surface disorder and are essentially temperature independent. Experimental values of b are approached only when both the coupling of nematic molecules with the substrate and the anisotropy of nematic-nematic interactions are …

Oct 2003, Tractor Museum

Lester F. Larsen Tractor Museum: Planning and Development Documents

Farmall Donation Storage Space Funding Opportunities

Exotendons For Assistance Of Human Locomotion, Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

Background: Powered robotic exoskeletons for assistance of human locomotion are currently
under development for military and medical applications. The energy requirements for such devices are excessive, and this has become a major obstacle for practical applications. Legged locomotion in many animals, however, is very energy efficient. We propose that poly-articular elastic mechanisms are a major contributor to the economy of locomotion in such specialized animals. Consequently, it should be possible to design unpowered assistive devices that make effective use of similar mechanisms.

Methods: A passive assistive technology is presented, based on long elastic cords attached to an
exoskeleton and guided …

Large Eddy Simulation Based Turbulent Flow-Induced Vibration Of Fully Developed Pipe Flow, Matthew Thurlow Pittard

Theses and Dissertations

Flow-induced vibration caused by fully developed pipe flow has been recognized, but not fully investigated under turbulent conditions. This thesis focuses on the development of a numerical Fluid-Structure Interaction (FSI) model that will help define the relationship between pipe wall vibration and the physical characteristics of turbulent flow. Commercial FSI software packages are based on Reynolds Averaged Navier-Stokes (RANS) fluid models, which do not compute the instantaneous fluctuations in turbulent flow. This thesis presents an FSI approach based on Large Eddy Simulation (LES) flow models, which do compute the instantaneous fluctuations in turbulent flow. The results based on the LES …

Predictive Joint Motion Limiting In Robotic Applications, Edward Red, Brian Fielding

Faculty Publications

Three joint space algorithms slow the Cartesian path motion when it appears that joint motion is approaching a joint, speed, or acceleration limit. All three algorithms use quadratic curve fitting to predict where the joint motion is heading, followed by a prediction as to how much time would elapse until a limit is reached.

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

Transmutation Sciences Materials (TRP)

Niobium cavities are important parts of the integrated NC/SC high-power linacs. Over the years, researchers in several countries have tested various cavity shapes. They concluded that elliptically shaped cells are the most appropriate shape for superconducting cavities. The need for very clean surfaces lead to the use of a buffered chemical polishing produce for surface cleaning to get good performance of the cavities. The third phase concludes the experimental a fluid flow study and optimization study. The first quarter and second quarter of phase three also begins the experimental set-up of secondary emission studies from niobium in superconducting mode. This …

Ole Miss Engineer 2003

Ole Miss Engineer

No abstract provided.

2003 (Fall) Ensi Informer Magazine, Morehead State University. Engineering Sciences Department

ENSI Informer Magazine Archive

The ENSI Informer Magazine published in the fall of 2003.

On The Mechanical Response In A Thermal Barrier System Due To Martensitic Phase Transformation In The Bond Coat, Anette M. Karlsson

Mechanical Engineering Faculty Publications

Recentstudies have shown that Pt-aluminide—a common bond coat material inthermal barrier coatings—undergoes martensitic transformations during thermal cycling. The transformationsare associated with both large transformation strain and a strainhysteresis, leading to accumulation of a mismatch strain. Thermal barriersystems based on Pt-aluminide bond coats are susceptible to interfacialmorphological instabilities. In this study, we investigate how the cyclicmartensitic transformation influences the morphology. Two key results are: (i)the morphological instabilities are highly sensitive to the thermo-mechanical propertiesof the substrate due to the martensitic transformation; (ii) thehysteresis associated with cyclic martensitic transformation cannot drive the morphologicalinstabilities; the strains associated with the formation of the thermallygrown …

Method For Performing Accelerated Characterization Of Viscoelastic Constitutive Behavior Of Asphaltic Concrete, Curtis Berthelot, D. H. Allen, Chad Searcy

Department of Engineering Mechanics: Faculty Publications

Constitutive models based in continuum mechanics are formulated for modeling the time dependent mechanical re¬sponse of asphaltic concrete. The model chosen for the initial phase of study is linear viscoelastic, resulting in stress-strain re¬lations that are of the single integral Boltzmann type in time. Experimental equipment and testing protocols are described for obtaining material properties within the viscoelastic framework selected for characterization. A frequency sweep experimental technique is described for obtaining composite properties from short-term tests that can be used to predict long-term, time-depen¬dent material behavior. Mathematical techniques are described for converting experimentally obtained complex compliances to creep compliances and …

Wind-Induced Exchange In Semi-Enclosed Basins, Rosario Sanay

OES Theses and Dissertations

The wind-induced circulation over laterally varying bathymetry was investigated in homogeneous and in stratified systems using the three-dimensional Regional Ocean Model (ROMS). For homogeneous systems, the focus was to describe the influence of the earth's rotation on the lateral distribution of the flow with particular emphasis on the transverse circulation. Along-basin wind-stress with no rotation caused a circulation dominated by an axially symmetric transverse structure consisting of downwind flow over the shoals and upwind flow in the channel along the whole domain. Transverse circulation was important only at the head of the system where the water sank and reversed direction …

Compliant Centrifugal Clutches: Design, Analysis, And Testing, Nathan B. Crane

Theses and Dissertations

Existing classes of centrifugal clutch concepts were reviewed. The pseudo-rigid-body model (PRBM), rigid-body replacement synthesis, force-deflection analysis, compliance potential evaluation, and compliant concept evaluation were used to develop effective new centrifugal clutch concepts. These methods helped develop and model four novel compliant centrifugal clutch designs, model two existing designs, and identify a concept with excellent potential for low-cost centrifugal clutch applications. This concept, the floating opposing arm (FOA) clutch, doubles the torque capacity metric relative to existing compliant designs. Torque and engagement speed models for this clutch were developed and verified against four prototype clutches. Additional novel designs devel-oped through …

A Texture Evolution Model In Cubic-Orthotropic Polycrystalline System, Brent L. Adams, H. Garmestani, D. S. Li

Faculty Publications

This work has been funded under the AFOSR Grant # F49620-03-1-0011 and Army Research Lab Contract # DAAD17-02-P-0398 and DAAD 19-01-1-0742. B.L. Adams acknowledges support of Army Research Office, Proposal No. 42566-MS. The authors express their sincere gratitude to Professor Surya Kalidindi, for helpful suggestions and correspondence for the derivation of the processing path functions. A new methodology based on a conservation principle in the orientation space is developed to simulate the texture evolution in a cubic-orthotropic polycrystalline system. A least squares error method was used to improve the accuracy of the simulation results obtained from the texture evolution function. …

Thermal Transport Eveluations Related To Waste Package Design -- Model Evaluations -- Task 19, Roald Akberov

Publications (YM)

The purpose of the “Thermal Transport Evaluations Related to Waste Package Design” Task # 19 of Cooperative Agreement Number DE-FC28-98NV12081 was to develop a new CFDHT model for heat transfer and fluid flow in the potential rsepository at the Yucca Mountain, Nevada and to study the effects of forced convection during the pre-closure period and natural convection during the postclosure period. The analysis was performed for the drift dimensions shown in Figure 4-1 below. The intended use of the model is to estimate the velocity and temperature distribution as well as the highest temperature in the drift during the pre-closure …

A Five-Zone Model For Direct Injection Diesel Combustion, Rich Asay

Theses and Dissertations

Recent imaging studies have provided a new conceptual model of the internal structure of direct injection diesel fuel jets as well as empirical correlations predicting jet development and structure. This information was used to create a diesel cycle simulation model using C language including compression, fuel injection and combustion, and expansion processes. Empirical relationships were used to create a new mixing-limited zero-dimensional model of the diesel combustion process. During fuel injection five zones were created to model the reacting fuel jet: 1) liquid phase fuel 2) vapor phase fuel 3) rich premixed products 4) diffusion flame sheath 5) surrounding bulk …

A Descriptive Performance Model Of Small, Low Cost, Diskless Beowulf Clusters, Curtis R. Nielson

Theses and Dissertations

Commodity supercomputing clusters known as Beowulf clusters, have become a low cost alternative to traditional supercomputers. Beowulf clusters combine inexpensive computers and specialized software to achieve supercomputing power. The processing nodes in a diskless Beowulf cluster do not have a local hard disk unlike the nodes in most commodity clusters. Research has provided performance information for diskless clusters built with expensive, high performance equipment. Beowulf clusters use commodity off-the-shell hardware, and little information is available about their performance. This research includes the construction of several diskless Beowulf clusters. Using the NAS Parallel Benchmarks, the performance of these clusters was measured. …

Magneto-Hydrodynamic Squeeze Film Characteristics Between A Sphere And A Plane Surface, Tsu-Liang Chou, Jen-Wen Lai, Jaw-Ren Lin

Journal of Marine Science and Technology–Taiwan

Based upon the thin-film magneto-hydrodynamic (MHD) theory, this paper analyzes the squeeze-film characteristics between a sphere and plane surface lubricated with an electrically conducting fluid in the presence of a transverse magnetic field. The MHD Reynolds-type equation governing the squeeze-film pressure is derived using the continuity equation and the magneto-hydrodynamic motion equations. A closed-form solution for the squeezing film pressure is obtained, and applied to predict the MHD squeeze-film characteristics. According to the results obtained, the presence of externally applied magnetic fields signifies an enhancement in the squeeze-film pressure. On the whole, the magnetic-field effects characterized by the Hartmann number …

Sufficient Conditions For Admittance To Ensure Planar Force-Assembly In Multi-Point Frictionless Contact, Shuguang Huang, Joseph M. Schimmels

Mechanical Engineering Faculty Research and Publications

An important issue in the development of force guidance assembly strategies is the specification of an appropriate admittance control law. This paper identifies procedures for selecting the appropriate admittance to achieve reliable planar force-guided assembly for multi-point contact cases. Conditions that restrict the admittance behavior for each of the various types of two-point contact are presented. These conditions ensure that the motion that results from contact reduces part misalignment for each case. We show that, for bounded misalignments, if the conditions are satisfied for a finite number of contact configurations, the conditions ensure that force guidance is achieved for all …

Admittance Selection For Planar Force-Guided Assembly For Single-Point Contact With Friction, Shuguang Huang, Joseph M. Schimmels

Mechanical Engineering Faculty Research and Publications

This paper identifies procedures for selecting the appropriate admittance to achieve reliable planar force-guided assembly for single-point frictional contact cases. A set of conditions that are imposed on the admittance matrix is presented. These conditions ensure that the motion that results from contact reduces part misalignment. We show that, for bounded misalignments, if an admittance satisfies the misalignment-reduction conditions at a finite number of contact configurations and a given coefficient of friction /spl mu//sub M/) then the admittance will also ensure that the conditions are satisfied at all intermediate configurations for all coefficients less than /spl mu//sub M/.

Efficient Contact State Graph Generation For Assembly Applications, Feng Pan, Joseph M. Schimmels

Mechanical Engineering Faculty Research and Publications

An important aspect in the design of many automated assembly strategies is the ability to automatically generate the set of contact states that may occur during an assembly task. In this paper, we present an efficient means of constructing the set of all geometrically feasible contact states that may occur within a bounded set of misalignments (bounds determined by robot inaccuracy). This set is stored as a graph, referred to as an Assembly Contact State Graph (ACSG), which indicates neighbor relationships between feasible states. An ACSG is constructed without user intervention in two stages. In the first stage, all hypothetical …

Study Guide For Photovoltaic System Installers And Sample Examination Questions, Florida Solar Energy Center, James Dunlop

FSEC Energy Research Center®

This Study Guide presents some of the basic cognitive material that individuals who install and maintain photovoltaic (PV) power systems should know and understand. This information is intended primarily as a Study Guide to help individuals better prepare for the NABCEP PV installer examination but does not provide all of the materials needed for completing the certification examination. Knowledge of the information presented, knowledge of pertinent sections of the National Electrical Code and appropriate experience and qualifications, are generally required of those applying for and completing the NABCEP certification process. Applicants and certificants are also reminded that local installation codes …

Achieving Airtight Ducts In Manufactured Housing, Florida Solar Energy Center, Janet Mcilvaine

FSEC Energy Research Center®

Data and findings presented here were gathered between 1996 and 2003 during 39 factory visits at 24 factories of six HUD Code home manufacturers interested in improving the energy efficiency their homes. Factory observations typically showed that building a tighter duct system was the most cost effective way to improve the product's energy efficiency.

Utilization Of A Piezoelectric Polymer To Sense Harmonics Of Electromagnetic Torque, Jason Neely, Steven Pekarek, Daniel S. Stutts, Philip Beccue

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, the use of a piezoelectric polymer material to measure the harmonics of electromagnetic torque produced by a permanent magnet synchronous machine is described. The advantages of the polymer include low cost, durability, and flexibility. In addition, wide-bandwidth sensors are relatively easy to design and couple to drive system hardware for harmonic evaluation or to use in feedback-based control. To illustrate the use of the polymer, the electrical and mechanical properties of three sensors are described. The results of time-domain simulation and hardware experiments are used to validate that the voltage obtained from the sensors is linearly related …

Vibration Based Crack Detection In A Rotating Disk: Part 1—An Analytical Study, Andrew L. Gyekenyesi, Jerzy T. Sawicki, George Y. Baaklini

Mechanical Engineering Faculty Publications

This paper describes the analytical results concerning the detection of a crack in a rotating disk. The concept of the approach is based on the fact that the development of a disk crack results in a distorted strain field within the component. As a result, a minute deformation in the disk’s geometry as well as a change in the system’s center of mass occurs. Finite element analyses were conducted concerning a notched disk in order to define the sensitivity of the method. The notch was used to simulate an actual crack and will be the method utilized for upcoming experiments. …

Two Semi-Infinite Interfacial Cracks Between Two Bonded Dissimilar Elastic Strips, Xiangfa Wu, Yuris A. Dzenis, Tian-You Fan

Department of Engineering Mechanics: Faculty Publications

The complex stress intensity factor and energy release rate are obtained for two semi-infinite interfacial cracks between two bonded dissimilar elastic strips with equal thickness under inplane deformations. During the procedure, by means of conformal mapping technique, the mixed boundary-value problem is reduced to a standard Riemann–Hilbert problem, which is further solved in closed-form. In some limiting cases, the present explicit solutions can cover the well-known results in the literature.

Business Case For Implementing Two Ergonomic Interventions At An Electric Power Utility, Patricia Seeley, Richard W. Marklin

Mechanical Engineering Faculty Research and Publications

Ergonomics analysis of line workers in the electric power industry who work overhead on utility poles revealed some tasks for which less than 1% of the general population had sufficient strength to perform. During a 2-year study, a large Midwestern US electric utility provided a university with a team of represented workers and management. They evaluated, recommended, and monitored interventions for 32 common line worker tasks that were rated at medium to high magnitude of risk factors for musculoskeletal disorders (MSDs). Two of the recommended ergonomic interventions—the battery-operated press and cutter—were selected by the team as having the greatest potential …

Autonomous Vehicle Technologies For Small Fixed Wing Uavs, Derek B. Kingston, Randal Beard, Timothy Mclain, Michael Larsen, Wei Ren

Faculty Publications

Autonomous unmanned air vehicle flight control systems require robust path generation to account for terrain obstructions, weather, and moving threats such as radar, jammers, and unfriendly aircraft. In this paper, we outline a feasible, hierarchal approach for real-time motion planning of small autonomous fixed-wing UAVs. The approach divides the trajectory generation into four tasks: waypoint path planning, dynamic trajectory smoothing, trajectory tracking, and low-level autopilot compensation. The waypoint path planner determines the vehicle's route without regard for the dynamic constraints of the vehicle. This results in a significant reduction in the path search space, enabling the generation of complicated paths …

Development Of A New Apparatus To Measure Flame Spread Through A Free Stratified Fuel/Air Mixture: Numerical Modeling And Experimental Results, Fred Hovermann

Theses and Dissertations

While flame spread through uniform fuel-air mixtures has been widely studied in combustion science, there has been relatively little attention given to the study of non-homogenous, or layered, fuel-air mixtures. However, these systems are common occurrences in such cases as terrestrial fuel spills and fuel leaks in both normal and microgravity. Conducting research on layered fuel-air mixtures and understanding the properties of flame propagation has potential implications for fire safety (both on earth and in space), as well as being of fundamental interest. The main objective behind this study is to determine flame speed, flammability regions, stability limits, and the …

Finite Element Modeling Of A Commuter Category Aircraft Seat Under Crash Loading, David William Bowen

Theses and Dissertations

This thesis describes the development and validation of a finite element model of a commuter aircraft seat under crash loading. In particular, this effort has developed an LS-DYNA model of a Beechcraft 1900C low back passenger seat.

Although air travel is one of the safest forms of transportation, crash-related fatalities do occur even in relatively low severity crashes. Many of these fatalities can be traced to the inability of production seats to absorb crash energy. The goal of this research effort is to develop a computational model of a production aircraft seat as a first step towards the development of …