Application of the (lanteigne) plastic zone correction in elastic-plastic fracture

Abstract

where K, is the stress intensity factor, a is a coefficient which depend on plane stress or plane strain conditions, a, is the yield strength and A,, Al.. . are given in terms of the coefficients ol, 02. . . of Westergaard[2] for a crack in an infinite elastic plate. A method for evaluation of yy for compact tensile specimens has been described and its use to obtain a value of the J-integral, namely JrC, under controlled loading conditions using a single specimen has been reported[3]. In Ref. [3], ‘yy was obtained experimentally for a tool steel, 06, in the as-received condition. This material exhibited an elastic-plastic fracture behavior as evident from the load against load point displacement curves obtained. In this investigation, the plastic zone correction yy was obtained for four steels which also exhibit an elastic-plastic fracture behavior in the conditions under which they were tested. The results confirm that the plastic zone correction yy produces an improved reproduction of the experimental data. Because three point bending specimens were used in this investigation, a modification of the procedure described in Ref. [3] is necessary. If the total load point displacement is expressed as,