Analytical investigation of effect of stress ratio on threshold stress intensity factor range improved by overload

Abstract

PurposeThe purpose of this paper is to describe the effects of stress ratio (R) on the threshold stress intensity factor range (ΔKth) by applied overload and to conduct an analytical investigation of the effect of the stress ratio.Design/methodology/approachTensile overload was applied to a compact tension specimen, and fatigue tests were performed at R=0.1 or 0.5.FindingsThe value of ΔKth increased as the tensile overload was increased, and the nominal threshold values were given by the equation ΔNKth,R = C+ DKov, where C represents ΔKth, and D is a proportional constant. Experimental results showed that the value of D showed good agreement with theoretical value.Originality/valueThe paper proposes a new model that arrests crack growth or makes cracks harmless by utilizing the overload effect.

Improvement of fatigue limit by overload for high-tensile strength steel containing a crack in the stress concentration zone

“…The size of the yield zone v r is calculated using equation (4). When a crack propagates in this yield zone v r , a negative stress intensity factor is generated and prevents crack propagation (Mizukami et al, 2010;Houjou and Ando, 2012). The width of the non-propagating crack, indicated by B in Figure 14(b) and (c), is less than v r which is calculated by substituting K ov into equation (4).…”