Effect of Mean Stress on Fatigue Srength, Crack Strength and Notch Radius at Branch Point in Axial Fatigue of 7:3 Brass

Abstract

The rotating bending and axial fatigue tests of plain and notched 7 : 3 brass specimens were carried out.The main results obtained are as follows.(1) The characteristic in fatigue of notched specimens under rotating bending stress is similar to the one under completely reversed axial stress, and the root radii of notches at the branch point ρ₀ (branch point means the critical point for a non-propagating crack to develop) are about 0.6 mm for both cases.(2) The relations of σ_w1/σ_w0 and σ_w2/σ_w0 (σ_w1 : limit stress for crack initiation, σ_w2 : limit stress for complete fracture in the range of non-propagating crack existing, σ_w0 : σ_w1 of plain specimens) to stress concentraiton factors α are almost the same in rotating bending fatigue of 7 : 3 brass and 0.13 % C steel.(3) In axial fatigue, the maximum stress repeated at a notch root at the crack initiation limit ασ_w1 becomes almost constant irrespective of mean stress, if the stress gradient χ is constant.(4) In axial fatigue, ρ₀ increases as mean stress decreases. This means that σ_w2 increases as mean stress decreases.