Ductile tearing of pipeline-steel wide plates II. Modeling of in-plane crack propagation

The purpose of this work is to develop a finite element simulation of stati c ductile tearing tests carried out on pipeline-steel wide plates. Experime nts have been presented in a companion paper (Part I [1]). The simulation is based on an extension of the Gurson-Tvergaard-Needleman m odel which includes plastic anisotropy and viscoplasticity effects. The par ameters of the model are fitted using tensile specimens (smooth and notched bars). Simulated tests are used to evaluate macroscopic fracture parameter s which were experimentally measured: the energy dissipation rate R and the thickness reduction Z. The simulation tool is then used to numerically investigate the effect of p late thickness, plastic anisotropy and through-thickness hardness gradients on the crack growth resistance. It is shown that with increasing thickness , the energy dissipation rate first increases and then decreases. A through -thickness hardness gradient is beneficial when the surface is harder than the bulk. Plastic anisotropy can be either detrimental or beneficial depend ing on the loading direction. These effects are explained in terms of plast ic localization inducing necking along the crack path and in terms of stres s distribution. (C) 2001 Elsevier Science Ltd. All rights reserved.