Mixed mode fracture in epicycloid specimens iii. Dislocations

Complex stress potentials are derived to obtain an analytical solution for the stresses in epicycloidal specimens which contain a dislocation. The solution is used to obtain an analytical expression for the stress intensity factors of cusp-like cracks in such specimens which can be considered as a generalization of the well established concept of Griffith cracks. It is shown that by suitable positioning of the dislocation, both positive and negative mode I stress intensity factors will result. This illustrates the potential of epicycloid specimens for determination of fracture properties under compressive loading where frictional contact of the crack surfaces is a priori avoided.