Modeling fatigue crack growth for a through thickness crack: An out-of-plane constraint-based approach considering thickness effect

Though several studies have tried to explain and model the effect of thickness on crack growth behavior, this remains a controversial topic. The present paper proposes an approach to model the fatigue crack growth with different thicknesses, which requires crack growth experimental data with different specimen thicknesses and out-of-plane constraint distribution relations for CT specimens. Empirical formula, for the distributions of two types of constraint factors T_z and T₃₃, were fitted according to the FEA results. The stress state variation induced by the thickness was quantified using the formulas; then, the crack driving force was modified to establish the novel crack growth model. The predictions using this model largely agree with the experimental data. So, the newly developed model was verified. This paper proposes a new perspective on quantifying the effect of crack thickness, and provides an alternative to the traditional method of modeling the crack growth behavior.