A PARAMETRIC STUDY OF THE SHOT PEENING PROCESS

Abstract

Summary: Shot peening is a cold working process widely used to extend the fatigue life of metallic components that undergo cyclic loading conditions such as in aerospace and automobile industries. Shot peening is one of the most interesting surface treatments as this treatment is controlled by variables that lay under a stochastic and probabilistic nature, attempts are made increasingly to control these variables to represent a controlled environment for the shot peening process. The repeatability and effectiveness of this treatment depends greatly on the process parameters, such as almen intensity and surface coverage. Although great attention is directed to the shot peening finite element modeling (FEM) existing FEM studies are invested in a single shot impact with limited investigation on a collective multiple shot results. In addition, a systematic study to support the selection of the process parameters for general purpose is lacking. This thesis will provide a detailed study based on experimental setup and finite element models on how different process parameters affect the peening results and this leads to define the limits of beneficial shot peening through the following objectives. The First objective is to analyze the coverage progression of peening indentation through a novel approach using image processing. The second objective is to develop parametric studies to examine the effects of the variation in the process parameters such as shot size, velocity and impact angle. The third objective is to use a novel interpretation algorithm based on the super position principle in assessing the overall induced residual stresses. The fourth objective is a selection procedure designed to decrease the number of experiments required to select the shot peening parameters, the proposed procedure is used to present a novel peening diagram that relates the almen intensity directly to the residual stress.