Fundamental study on mixed mode fracture criterion in terms of CED (Crack Energy Density)

A fundamental study on the mixed mode fracture criterion of an elastic-plastic crack was performed based on the concept of CED (Crack Energy Density). The CED, ε_φ, in arbitrary direction, which is defined and has a consistent meaning without any restriction on constitutive equation, can be divided into the contributions of each mode generally and the CED, ε_φ^I, for mode I is expected to play the most important role in the mixed mode fracture criterion. In this paper, ε_φ and ε_φ^I for elastic specimens under tension with a crack inclined to the loading axis are evaluated by two methods, that is, by path-independent integrals and the relationship between ε_φ and load-displacement curves through finite element analyses, and a practical method to evaluate ε_φmax^I, which is ε_φ^I in the direction where ε_φ^I takes the maximum value, through finite element analyses with a sufficient accuracy is proposed through the comparison of the results with theoretical ones.