In this paper, a stress integration algorithm is presented for a generalized elasto-plastic material model governed by the three stress invariants I1, J2 and J3. The methodology is successfully applied to the Mohr–Coulomb material model with a non-associated flow rule and implemented in ADINA.

The dependence of the Weibull stress is investigated on the parameters of the elasticplastic crack tip field. The general form of the Weibull stress is given for a three-parameter approximation of the elasto-plastic crack tip field. This is the basis to define a constraint correction of the critical value of the J-integral for cleavage fracture.