CED (Crack Energy Density) in an Arbitrary Direction and Load-Displacement Curves

Abstract

The CED (crack energy density) in an arbitrary direction ε_φ, is expected to describe the fracture behaviors of a mixed mode crack. It was shown previously that ε_φ can be evaluated by a path-independent integral with sufficient accuracy for practical purpose. In this paper, as another evaluation method of ε_φ a method based on the relationship between ε_φ and load- displacement curves is discussed. The contents are as follows. 1) A relationship between initial crack lengths, load-displacement curves and ε_φ, which holds until cracks start to grow, is derived by considering the strain energies of the specimens with different initial crack lengths. A method of evaluating ε_φ from the load-displacement curves is proposed based on this relationship. 2) Based on this method, evaluation of ε_φ is attempted from load-displacement curves obtained by finite element analyses and also from experiments for specimens under tension with a crack inclined to the loading axis, and it is shown that this method is practical for evaluating ε_φ through comparison with the theoretical values and the values found by the path-independent integral.