Straightforward comparison of fatigue crack growth under modes II and III

Low-cycle fatigue crack propagation in double circumferentially notched, cylindrical specimens of austenitic steel was studied by means of special testing device in order to identify local fracture micromechanisms under remote shear modes II and III. Remote mode II crack growth rate was found to be approximately two times higher than that of the mode III. Morphological patterns on fracture surfaces revealed that the mode II and the mixed mode I + II were dominating local crack tip fracture modes operating under both remote modes II and III. No evidence of pure mode III mechanisms was detected on any investigated fracture surface.