Solving linear and nonlinear three-dimensional problems of fracture mechanics by a semi-analytic finite element method. Part 2. A procedure for computing the invariant J-integral in fem discrete models

A new procedure for computing the J-integral for FEM discrete models, which is based on the use of magnitudes of nodal reactions and displacements, has been implemented. The paper presents theoretical substantiation and practical evidence that confirm the invariance of the J-integral values found by this procedure for the case of cracks of Mode I and mixed fracture mode. A three-dimensional elastic-plastic deformation problem for a compact specimen has been solved.