Crack tip fields in a material with three independent slip systems: NiAl single crystal

The crack tip stress and deformation field is analyzed for an ideally plastic ordered NiAl single crystal of B2 (BCC type) structure which has only three independent slip systems at room temperature, the (100)(100) systems. For the crack on the (010) plane growing in the (101) direction, only one of these systems is capable of sustaining considerable plane plastic flow. It involves slip planes lying parallel to the crack tip, making an angle of 90 degrees with the crack plane, and has the yield condition sigma 12=+or- tau 0 (1 is the cracking direction, 2 the crack plane normal, and tau 0 the critical resolved shear stress). An elastic-ideally plastic asymptotic solution is derived in which the stress field has a In r type singularity, with a shearing discontinuity at 90 degrees . These features are verified and more fully quantified by a finite element solution.