On a general concept for the analysis of crack growth and material damage

For finite strain dynamics a variational model of crack evolution is Formulated within the generalized oriented continuum methodology. In this approach position- and direction-dependent deformation and strain measures are used to describe the (macro)motion of the body with defects. which may evolve relative to the moving body. The inelastic behaviour of continua with evolving defects is represented by phenomenological equations including the transversal crack evolution. A strain-induced crack propagation criterion is defined by the difference between the strain energy release rare and the rate of the surface energy of the crack. A possible nucleation of microcracks in terms of the average drag coefficient of the crack configuration is proposed. Based on the crack growth criterion presented in this paper. the kinking of cracks is investigated using variational concepts. A constitutive damage model of Kachanov's type accounting for the crack density is derived in terms of the free energy functional and a dissipation potential. (C) 2001 Elsevier Science Ltd. All rights reserved.