A Numerical Study on Effective Modulus of Elasticity in Crack Length Evaluation for Single-Edge Bending Specimens

The actual state of stress in the remaining ligament of a single-edge bending (SE(B)) specimen, which is neither plane stress nor plane strain, is critical in accurately predicting the crack length in the specimen involved in the unloading compliance method. Three-dimensional finite element analyses were carried out in this study to evaluate the effective modulus of elasticity that reflects the actual state of stress corresponding to the crack mouth opening displacement (CMOD) compliance of the SE(B) specimen. Both plane-sided and side-grooved specimens with a wide range of geometric configurations and crack lengths were included in the study. A practical approach is further proposed to quickly evaluate the effective modulus from the CMOD compliance determined based on the test data. The proposed approach was verified using experimental data and numerical analysis results. The results of the verification suggest that replacing the elastic modulus corresponding to the plane stress or plane strain condition with the effective modulus in commonly used a/W–CMOD compliance equations can markedly improve the accuracy of the predicted crack length.