Evaluating Stress Distributions and Stress Intensity Factors of a Crack under Mixed-Mode conditions in Aluminum Alloy

摘要

England has examined the two-dimensional problem of a mode Ⅰ crack opened under constant pressure between two dissimilar materials. But in many cases, it has to be considered that a crack under mixed-mode conditions is lying in a similar material such as aluminum alloy. In this paper, therefore, equations of modeⅠ and mode Ⅱ stress distributions σyy, σxy were derived according to opening/sliding discontinuous displacements for cracks under mixed-mode conditions, considering effect of finite plate, using England's basic formulas. Then mode Ⅰ stress intensity factor K Ⅰ and mode Ⅱ stress intensity factor KⅡ were evaluated by σyy, σxy. On the other hand, for an ideal mixed-mode crack lying in an aluminum alloy specimen (finite plate), this method was verified by measuring the opening and sliding discontinuous displacements along the crack. As a result, KⅠ and KⅡ are almost the same with the results calculated by empirical equations. That is to say, it provides an effective method to evaluate the deformation behavior of a crack under mixedmode conditions even though stress distributions are unknown.