Complex stress potentials were constructed in order to obtain an analytical solution for the stresses in epicycloidal specimens which contained a dislocation. The solution was used to obtain an analytical expression for the stress intensity factors of cusp-like cracks in such specimens. It was shown that, by suitably positioning the dislocation, both positive and negative mode-I stress intensity factors could result. This demonstrated the potential value of epicycloidal specimens for the determination of fracture properties under compressive loading, where frictional contact of the crack surfaces was avoided.

Mixed Mode Fracture in Epicycloid Specimens - III. Dislocations. W.H.Müller, W.Littmann, H.Gao: International Journal of Solids and Structures, 1999, 36, 3339-48