CED (crack energy density) in an arbitrary direction and load-displacement curves

The CED (crack energy density) in an arbitrary direction, E_φ, is expected to describe the fracture behaviors of a mixed mode crack. It was shown previously that E_φ can be evaluated by a path-independent integral with sufficient accuracy for practical purposes. In this paper, another evaluation method of E_φ, based on the relationship between E_φ and load- displacement curves, is discussed. A relationship between initial crack lengths, load-displacement curves and E_φ, which holds until cracks start to grow, is derived and a method of evaluating E_φ from the load-displacement curves is proposed. Based on this method, evaluation of E_φ is attempted from load-displacement curves obtained by finite element analyses and experiments. It is shown that this method is practical for evaluating E_φ through comparison with the theoretical values and the values found by the path-independent integral.