Studies on Crack Mechanics

: Theoretical studies have been done on crack tip stress and deformation fields based on continuum plasticity for single crystals. Asymptotic analysis has been carried out for ideally plastic single crystals for both stationary and moving cracks under anti-plane shear and mode I plane strain conditions. They show that in the near tip region the plastic flow is confined primarily to planes along which both the stresses and the displacements are discontinuous for stationary cracks, or the velocity is discontinuous for quasi- statically growing cracks. These planes may be parallel or perpendicular to the traces of the slip planes which are locally stressed to yield levels and provide the plastic straining. The inclusion of strain hardening, as studied so far based on power hardening with resultant HRR fields, removes these discontinuities in the case of the stationary crack, although small angular ranges of very rapid stress variation result instead when there is only moderate strain hardening. In the ideally plastic limit however, these HRR fields yield a continuous displacement field, while resulting in the correct stress discontinuities. Thus, it is conjectured that the domain of validity of the HRR field must shrink as the ideally plastic limit is approached. Furthermore, this domain is expected to be confined to only part of the plastic zone immediately adjacent to the crack tip. Studies are now underway to check these conjectures. Keywords: Crack mechanics, Abstracts, Mechanical properties, Shear strain, Elasticity, Fracture(Mechanics), Weight functions, Dislocations, Tensile cracks, Crack tips.