Improvement in Fatigue Strength of Notched Plate-Specimen by Local Plastic Deformation.

Abstract

In this paper a plane bending fatigue tests have been performed to investigate the effect of die pressing on fatigue strength of the plate specimens with a central circular hole. The main results are as follows : (1) The fatigue limit of notched specimen by die pressing is increased by 60% as compared to that of the same notched specimen without die pressing and is equal to that of plain specimen. (2) The reason of increase in the fatigue limit is attributed to the work hardening and compressive residual stress, which are generated by die pressing to the edge of the hole, which increase the resistance against crack initiation and suppress its initial growth. (3) In the case of die pressing, the lifetime summations of the period of the fatigue crack initiation and short crack propagation within 1mm is about 80% of the total number of cycle to failure.