Rigid-plastic interface for an embedded crack

Discrete cracks have traditionally been modelled by zero-thickness interface elements. Such models usually assume that the relative displacements across the interface have both elastic and inelastic components. In such a case, the elastic stiffness assigned to the interface acts as a penalty parameter that must be high enough to ensure that the elastic deformations will be minimal. In recent years, solid finite-elements with embedded displacement discontinuities have emerged as an alternative way to model discrete cracks. A method that allows for an embedded crack element to use any plasticity-based constitutive model for the internal interface, but without penalty parameters, is presented in this paper. In this method, the elastic properties of the solid portion of the element are used to perform the function that the penalty parameters previously have been used to perform. The resulting interface model is perfectly rigid-plastic. Numerical comparisons show significant improvements in accuracy and efficiency over the penalty method.