Mechanism of creation of compressive residual stress by shot peening

In order to clarify the mechanism of the creation of compressive residual stress by shot peening, a static compression test and a dynamic impact test using a single steel ball against a flat steel plate were carried out. In the static compression test, compression residual stress was created near the center of the ball indentation mark. However, in the dynamic impact test, tensile residual stress was created near the center of the ball indentation mark and compression residual stress was created outside of the indentation. Furthermore, the tensile residual stress in the center of the first ball indentation mark changed to compressive stress as the density of the ball indentations surrounding the first ball indentation mark increased. Therefore, the compressive residual stress created by shot peening is considered to be the result of the superposition of residual stress produced by surrounding shots. (C) 1998 Published by Elsevier Science Ltd.