Mixed-mode stress intensity factors for partially opened cracks

Failure considerations under mixed-mode loading require knowledge about the influence of friction between partially closed crack faces in the case of a negative mode-I stress intensity factor. A simple relation is derived, which allowes to compute friction contributions to the mode-II stress intensity factor K-II for the case of negative mode-I stress intensity factors K-I. The relation is exact for the limit case of an edge crack in a half-space. It can be shown that small cracks in finite bodies can also be described with sufficient accuracy.