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 per cent carbon content. Shafts were tested under a concentrated stress, as represented by both a shrink-fitted member and a fillet. The shrink-fitted specimen hardened by induction-hardening exhibited the same size effect as an untreated shrink-fitted specimen ; the reduction ratio 1.8 was obtained by comparing the endurance limit for a shrink-fitted specimen 10 mm in diameter with that of a specimen 100 mm in diameter and the value 1.6 was obtained for induction-hardened specimens with a shrink-fitted hub. The endurance limit of a large shrink-fitted specimen as well as a small one was increased 1.8 to 2.1 times by induction-hardening. By the photoelastic tests and the fatigue tests was obtained the critical ratio between the diameter of fillet specimen, in which the stress and the fatigue strength at the end of shrink-fitted portion is equal to that of fillet portion. Using this critical diameter has practically effective for increasing the fatigue strength of the fillet specimen with a shrink-fitted member.