Ph.D. Thesis Defense by H. Lewis Zion
Monday, April 7, 2003

(Dr. Steven Johnson, advisor)

"A Dynamic Finite Element Simulation of the Shot-Peening Process"

Abstract

The process of shot peening has been widely used for more than 70 years to improve fatigue life as well as corrosion and wear resistance in metallic components. The basic mechanism involves repetitive stretching and unloading of the surface by bombarding it with small spherical shot media so that a uniform residual compressive stress is eventually created. Historically the implementation of shot peening has relied on empiricism for its control and only recently have there been attempts to develop a better analytical understanding of the mechanics of the process. High strength steel is often the material of choice for certain aircraft components, such aircraft landing gear, that must be able to withstand infrequent occurrences of very high limit loads in addition to more frequent applications of fatigue loads of much lower amplitude. In order to obtain reasonable fatigue life it is essential that these components be shot peened with the utmost quality assurance. In addressing the mechanics of shot peened high strength steel analytically, the significance of nonlinear contact and plasticity to the solution make the problem well suited to a finite element modeling (FEM) approach. In addition to the need to understand the mechanics of the process deterministically, there is also a need to understand how material and process variation affect the residual stress state produced. Both of these objectives have been addressed in this research.