The phenomenon of crack propagation in a heterogeneous material is a central research topic in fracture mechanics. Over the last two decades, several studies, both experimental and theoretical, were conducted to determine the conditions of stabilities and roughness properties of the crack front and the surfaces thus created. One of the central difficulties in this type of problem is to obtain the theoretical tools for describing the behavior of the stress field near the crack front. This behavior is characterized by the quantities called stress intensity factors which are the basic prior for any theoretical characterization of the dynamics of crack propagation. In this context, we have performed work both theoretical and experimental, to determine these quantities for different modes of deformation and crack geometries.
