Publication Date
2011
Document Type
Dissertation
Committee Members
Robert Brockman (Committee Member), Ramana Grandhi (Advisor), Nathan Klingbeil (Committee Member), Kristina Langer (Committee Member), Ravi Penmetsa (Committee Member)
Degree Name
Doctor of Philosophy (PhD)
Abstract
Mechanical surface enhancement techniques have been used to successfully increase the fatigue life of metallic components. These techniques impart compressive surface residual stresses that reduce the tensile stresses experienced during service loading. Laser Peening (LP) is a surface enhancement technique that uses high intensity, short duration laser pulses to create plastic shockwaves in metallic components. Experimental investigations and limited simulation studies have been conducted to determine the effects on the fatigue life of simple coupons when key LP parameters are varied. Used primarily in the aerospace and biomedical engineering fields, LP has been limited to industries that can afford its currently high development and processing costs. Reducing these costs requires that LP simulations, which currently require tremendous amounts of computational power and time due to their complexity, become more time effective and user accessible. This work seeks to address these needs by reducing the overall simulation time of large surface LP processing. The first objective of this work is to reduce the simulation time of an individual LP shot by furthering the development of an extended duration explicit Finite Element Analysis method. Error between the new method and the accepted analysis method is calculated to demonstrate the viability of the new approach. The second objective is to reduce the simulation time of large LP patterns. A symmetry cell approach is developed and used to create a base unit of an LP shot pattern, which is used to reproduce the pattern over a large surface. The last objective is to investigate the effects that the sequencing of LP shots within a pattern can have upon the fatigue life of the component. Due to interactions between adjacent LP shots, the most recent shot in an LP pattern will have the largest compressive stresses. By sequencing the shots in a particular order, the fatigue life of a component can be increased over that of a generic pattern.
Page Count
142
Department or Program
Ph.D. in Engineering
Year Degree Awarded
2011
Copyright
Copyright 2011, all rights reserved. This open access ETD is published by Wright State University and OhioLINK.
