Simulation of crack opening through a corner node, using rigid-plastic interface elements

Recently, the authors of this paper have proposed a new technique based on a double minimization with respect to a Mohr circle, for the computation of stresses and forces transmitted across mesh lines at the corner nodes of FE mesh in 2D (Ciancio et al. 2006). That procedure establishes the basis for the general modeling of crack development along mesh lines without the need of the onerous systematic pre-insertion of zero thickness interface elements with elastic compliance and duplicated nodes from the beginning of the analysis. In this context, the present paper goes one step further, focusing on the crack opening conditions for a set of mesh lines (also interpreted as rigid plastic interfaces) which concur on an inner node of the FE mesh. The cracking condition is assumed in the form of rigid plasticity in terms of the stress traction components. With those assumptions, the state of cracking at the node undergoes in general three different stages of evolution. For each of them, the appropriate procedure for the calculation of the corresponding forces and stresses is presented, and the overall scheme is illustrated with some examples of application.