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

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 mode I and mode II stress distributions ¿_yy, ¿_xy 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 K_II were evaluated by ¿_yy, ¿_xy. 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, K_I and K_II 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 mixed-mode conditions even though stress distributions are unknown.