ピーニング用ショットについて(III)

Abstract

Results of an investigation into the effect of shot hardness on residual stress induced in the sub-surface layer of specimen are reported in this paper. Analyses of residual stress were made by the dissection method.Some of the conclusion reached are;(1) Residual stress distributions show the tendency to take max. value on the surface when the soft specimen is peened with hard shots, while the rest of combination cause max. point at the inner part of specimen.(2) The magnitude of max. residual stress is concerned to the hardness of specimen, and the min. shot hardness to take the full gain of this value is equal to that of specimen.(3) Size or velocity of shot has minor effect on the magnitude of residual stress in specimen.(4) Depth of cold-worked layer increase as the hardness of specimen decrease or using harder shot.(5) In the industrial viewpoint, hardness of shot is desirable to be same with that of work.(6) Almen test strip is useful to measure the residual stress as it is or tempering at low temperature to the same hardness of the work.