Fatigue Strength of a Bar with a Cotter Hole

Abstract

The author performed rotary bending fatigue tests on a bar of S40C with a rectangular cotter hole. Results of the tests are as follows : 1) The cotter hole had better be made up of a rectangle and two semi-circles, and the notch-factor is about 1.45. 2) If we make a rectangular hole, the fillet radius at the corner must be more than one-tenth of the width of the hole, or else the fatigue crack is liable to occur at the corner of the hole in the bar. 3) If the length of a hole is more than twice its width, the notch-factor is scarcely affected by the size of the hole.