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

The 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.

Tensile overload was applied to a compact tension specimen, and fatigue tests were performed at R=0.1 or 0.5.

The value of ΔK_th increased as the tensile overload was increased, and the nominal threshold values were given by the equation Δ^NK_th,R = C+ DK_ov, where C represents ΔK_th, and D is a proportional constant. Experimental results showed that the value of D showed good agreement with theoretical value.

The paper proposes a new model that arrests crack growth or makes cracks harmless by utilizing the overload effect.