KIII-DEFORMATION MODES IN INTERNAL OBLIQUE CRACKS UNDER PLANE-STRESS CONDITIONS

The exact shape of the deformed internal oblique crack in an infinite elastic plate under conditions of plane stress was studied. The Muskhelishvili potential function yielded the exact stress and displacement field around the crack. The out-of-plane component of displacements is determined and its influence on the exact shape of the deformed crack in space is presented. As soon as shear displacements appear in the cracked plate under plane stress, out-of-plane shear displacements are a compulsory consequence for plane-stress conditions of the plate. The compulsory co-existence of mode II and mode III deformations makes the internal crack present a complicated pattern of determination at its deformed crack tips. All results are supported by experimental evidence with caustics, which always show either a simple mode I pattern or a complex mode II and III pattern as soon as shear interferes in the mode of deformation.