The propagation threshold of a through crack in a plate under the combination of plane bending and cyclic torsion. The effect of plate thickness and crack shape.

Abstract

In order to investigate the effects of plate thickness and crack shape in cross section on the threshold condition for crack propagation under the mixed mode, a through or a surface precrack was made in a carbon steel plate with various thickness by a plane bending or a pulsating tension test. It was concluded that the magnitude of the frictional stress acting on the crack surface at the propagation threshold under cyclic torsion was remarkably affected by the plate thickness, so the accurate estimation of the threshold stress of crack propagation under the mixed mode with an optional plate thickness must be based on the strain energy density criterion with use of the plane bending and cyclic torsion tests of identical plate thickness.