The Propagation Behaviour of Mode I Surface Cracks under Biaxial Stresses by the Combination of Plane Bending and Cyclic Torsion

Abstract

The crack propagation rate of a mode I surface crack in a plate, the crack tip opening stresses or displacements under various biaxial stress ratios by the simultaneous action of plane bending and cyclic torsion are examined. The aspect ratio of a crack is not affected by the biaxial stress ratio, but the relationship between the propagation rate da/dN and the stress intensity factor range ΔK or the effective stress intensity factor range ΔK_eff depends on the biaxial stress ratio. This is mainly due to the differences of both CTOD and the scale of the slipped region at the crack tip caused by the difference of the biaxial stress ratio.