Alit-Kinked, forked and twisted paths of a mode I crack cause a "local mixed" mode loading at the crack tip. The best known single parameter description of this problem is the local crack driving force &,, based on the maximum strain energy release rate. For fatigue crack propagation near the threshold, the shear stress distribution may be more important than the strain energy release rate. Hence, for kinked and doubly kinked cracks the dependence of 'ffi,, is compared to the dependence of the shear stress distribution as a function of the angles of the kmks. It will be shown that Ktip is more atTected by the geometry than the shear stress field. length of the main crack length of the first kink length of the second kink mode I stress intensity factor for a linear crack or applied mode I stress intensity local mode I stress intensity at the tip of a kinked or doubly kinked crack local mode II stress intensity at the tip of a kinked or doubly kinked crack local crack tip stress intensity based on the maximum strain energy release rate threshold of effective stress intensity range angle of the first deflection angle of the second kink shear stress polar coordinates