A MODEL OF FRACTURE SHOWING THE INFLUENCE OF THE MICROSTRUCTURE ON THE CRACK PATH

We consider the fracture of materials having a microstructure (crystal s, grains, etc.) such that the crack propagates by discrete elements. We consider a model of such a material where the ''grains'' are associ ated with the finite elements of numerical discretization. In certain cases, depending on the microstructure the following phenomenon is obs erved; if one of two equally solicited elements (by symmetry) breaks i n advance of the other (as a consequence of a small heterogeneity for instance), subsequent propagation of the crack starts from this elemen t, whereas the element which was behind is not broken. This amounts to an instability of the shape of the crack.