A unified model for the fatigue crack growth rate in variable stress ratio

Abstract

ABSTRACT The paper presents four equations for Fatigue Crack Growth Rate (FCGR) description taking into account Δ J , ΔCTOD, ΔCMOD and Δ K . CT specimens made of steel were tested for different values of stress ratio ( R ) by Δ P = constant method. The influence of R ‐ratio has been studied on crack propagation and crack initiation region. The experimental results show that Δ J and ΔCTOD, contrary to Δ K and ΔCMOD which are constant in R ‐ratio variations, vary with the variations of R ‐ratio in the range R = 0.3–0.6. Therefore, there is no need to enter R parameter directly in the well‐known Paris equation if Δ J or ΔCTOD parameter is used instead of Δ K in this equation. The constants of these equations are independent of loading unlike the constants of Paris equation.