Multiple Shot Analysis In Shot-peeningUsing Finite Elements

Abstract

A computer program OB AID has been used to analyze complex target plate and allows for dynamic loading due to impinging single and multiple shot. Theoretical model using three dimensional isoparametric finite element has been presented, in which a provision is made for the surface hardening and cyclic impact loading caused by multiple shots. Theoretical model agrees reasonably well with other models. INTRODUCTION Shot peening is viewed as a process involving multiple and progressively repeated impact. The object is to include compressive residual stresses in the surface of the target. A general form of residual stress in a typical shot-peening operation is shown in Figure 1. The impact of spherical shots, which usually takes place at a high velocity 100 m/sec, also causes plastic deformation which results in changes in the mechanical properties in the surface material. An extensive work has been carried out by several authors [1-12] to model the process. An attempt to modelize the process, in viewing as process involving multiple repeated impact. When shots impinge upon a target of elastic/plastic material and the impact velocity is sufficiently high, the target material below each impact undergoes local plastic deformation and, upon rebound, the rest of the elastic material tends to push the plastically deformed zone resulting in compressively applying numerous impacts over the whole surface, the target acquires a shallow layer of superficial compressive residual stress below which it develops smaller equilibrating tensile stresses. This paper attempts to present theoretical model using three dimensional isoparametric finite element, as will be seen, it surprisingly agrees reasonably well with other model. [1,2] THREE-DIMENSIONAL FINITE ELEMENT MESH GENERATION The finite element mesh for the target plate is shown in Fig. 2. In order to produce accurate residual stresses, it has been decided to divide the thickness of the target steel plate into nine layers (in the Y-direction). The plate thickness below the Transactions on Engineering Sciences vol 2, © 1993 WIT Press, www.witpress.com, ISSN 1743-3533