Effect of Stress Ratio on Short Fatigue Crack Growth

Abstract

A model of short fatigue crack growth is proposed, which is based on the blocked slip concept and the shear decohesion mechanism. The analysis is extended to the case of mean stress loading. A theoretical proof is presented for the transfer of slip bands across grain boundaries. The rate of growth is proportional to the shear strain range and the maximum plastic zone size. There are no adjustable parameters in the theory for the case of high strain level, when the plastic strain dominates the decohesion process. Otherwise only one constant is needed, which may be derived from long crack growth data. The model is shown to provide satisfactory predictions of experimental results under uniaxial loading with various stress amplitudes and mean stresses.