Fatigue Strength and Size Effect of Shrink-fitted Specimens

Abstract

This paper deals with the summary of the results of rotating-bending fatigue tests on shafts 10 to 100 mm in diameter of medium carbon steel of 0.39% carbon content. Shafts were tested under a concentrated stress, as represented by both shrink-fitted member and fillet. Shrink-fitted specimen hardened by induction-hardening exhibited large size effect as well as untreated shrink-fitted specimen ; the reudction ratio 1.8 was obtained by comparing the endurance limit for shrink-fitted specimen 10 mm in diameter with that of the 100 mm in diameter and the value 1.6 was obtained for induction-hardened shrink-fitted specimens. The enduramce limit of large shrink-fitted specimen as well as small one was increased by 1.8∼2.1 times by induction-hardening. The stress distribution of shrink-fitted specimens with fillet was studied by the photo-elastic method and was investigated the critical ratio between the diameters of fillet specimen, in which the stress at the end of shrink-fitted part is equal to that of fillet part. By using this critical ratio between the diameters was given a practical expedience for increasing the fatigue strength of shrink-fitted specimen with fillet.