Engineering Science and Materials Commons^™

Residual Stress Effects On Fatigue Life Via The Stress Intensity Parameter, K, Jeffrey Lynn Roberts

Doctoral Dissertations

Residual stresses are known to have a significant effect on fatigue crack propagation and thus fatigue life. These effects have generally been quantified through an empirical approach, lending little help in the quantitative prediction of such effects. The weight function method has been used as a quantitative predictor, but its use neglects residual stress redistribution, treating the residual stress as a constant during crack growth. At least three different behaviors contribute to the redistribution of residual stress. First, the residual stress behind the crack tip is reduced to a negligible level as soon as the crack tip passes. Second, the …

Intelligent Fault Tolerant Control For Telerobotic System In Operational Space, Sewoong Kim

Doctoral Dissertations

Telerobotic systems combine conventional teleoperation with industrial automation techniques, such as control, vision, planning, etc, to improve work efficiency, and have been expanding their applications from hazardous and remote areas to unstructured industrial uses. Unstructured environments and uncertainties in task space require human-in-the loop control to ensure and supervise safe operation since present autonomous capabilities cannot handle the vast range of tasks and uncertainties. The inherent characteristics of telerobotic systems make operational faults more likely, and require autonomous fault detection, isolation (FDI) and recovery abilities since the nature of task space makes it difficult for human operators to detect and …

A Taxonomy Of The Adoption Of Lean Production Tools And Techniques, Bradley Mullins Greene

Doctoral Dissertations

The purpose of this study is to discover if the pattern of lean tool adoption for mature lean enterprises varies by type of value stream. The study empirically tests the effect of types of production processes, production volume, and order fulfillment strategies on lean production tool adoption in mature lean enterprises. The results of the study show that each of these factors does affect the pattern of tool adoption among mature lean enterprises.

Eleven different value stream profiles are identified in the study (ex. Discrete, Low Volume, Build-to-Order, value stream such as a commercial satellite producer). A binary logistical regression …

Design And Analysis For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides, Xiaolong Wu

UNLV Theses, Dissertations, Professional Papers, and Capstones

Fundamental issues related to the selection of a metallic fuel casting furnace design are presented and discussed including heating mechanisms, casting issues, crucible design, and issues related to the mass transport of americium. The process of evaluating all of these different criteria is undertaken to select a concept that would have the greatest chance of success for casting americium in a metallic fuel rod. Based on this evaluation process, a concept for the casting of metallic fuel pins containing high vapor pressure materials is selected and discussed. The important physics of this concept include mass transport of americium from the …

Classification Of Risks For International Construction Joint Ventures Projects, Yasser Abd El Ghany Azmy Elshabassy

Archived Theses and Dissertations

No abstract provided.

Effects Of Shot-Peening On High Cycle Fretting Fatigue Behavior Of Ti-6al-4v, Halil I. Yuksel

Theses and Dissertations

Effects of Shot-peening on High Cycle Fretting Fatigue behavior of Ti-6Al-4V were investigated. Experiments were performed with 6.35 mm thick specimens which provided S/N curves. After the tests, it was observed that the specimens failed near the trailing edge of contact. Scanning Electron Microscopy showed that cracks initiated on the contact surface for 6.35 mm, and at the depth of specimen ranging from 200 to 300 microns for 3.81 mm thick specimens. Initial crack orientation was around 37 and 42 degrees respectively for 6.35 and 3.81 mm thicknesses. Finite Element Analysis (FEA) was conducted, and using FEA results, Smith-Watson-Topper, Findley, …

Examination Of Contact Width On Fretting Fatigue, Russell S. Magaziner

Theses and Dissertations

The primary goal of this study was to find the effects on the fretting fatigue life when systematically holding the fretting fatigue variables, peak contact pressure, maximum/minimum nominal bulk stress, and the ratio of shear traction to pressure force constant while varying the contact semi-width through changes in pad radius and normal load. Experimental tests were performed on a test setup capable of independent pad displacement. Analytical and finite element simulations of the different experimental tests were performed. The local mechanistic parameters were inspected. Five different critical plane based fatigue predictive parameters lacked effectiveness in predicting changes in life with …

Impact Of Subject Related Factors And Position Of Flight Control Stick On Acquisition Of Simulated Flying Skills Using A Flight Simulator, Bo-Keun Cho

LSU Doctoral Dissertations

Increasing demand on aviation industry calls for more pilots. Thus, pilot training systems and pilot-candidate screening systems are essential for civil and military flying training institutes. Before actual flight training, it is not easy to determine whether a flight trainee will be successful in the training. Due to the high cost of actual flight training, it would be better if there were low cost methods for screening and training candidates prior to the actual flight training. This study intended to determine if subject related factors and flight control stick position have an impact on acquisition of simulated flying skills using …

Data Mining And Knowledge Discovery: A Guided Approach Base On Monotone Boolean Functions, Vetle Ingvald Torvik

LSU Doctoral Dissertations

This dissertation deals with an important problem in Data Mining and Knowledge Discovery (DM & KD), and Information Technology (IT) in general. It addresses the problem of efficiently learning monotone Boolean functions via membership queries to oracles. The monotone Boolean function can be thought of as a phenomenon, such as breast cancer or a computer crash, together with a set of predictor variables. The oracle can be thought of as an entity that knows the underlying monotone Boolean function, and provides a Boolean response to each query. In practice, it may take the shape of a human expert, or it …

The Effect Of Periodic Operation On Biofilters For Removal Of Methyl Ethyl Ketone From Contaminated Air, Charles William Norman

LSU Master's Theses

In recent years, biofiltration technology has been used at numerous locations worldwide as an air pollution control technology for treating gases contaminated with low concentrations of biodegradable volatile organic compounds (VOCs). At the same time, there have been many reports in the literature of contaminant emissions from biofilters during transient loading conditions. There is currently a need to develop methods for controlling such emissions. Periodically operated bioreactors have been used successfully in treatment of wastewater and soils for several decades to mitigate the effects of uncontrolled unsteady-state loading on waste treatment systems. Such operating strategies have only recently been applied …