Software framework for two-dimensional mixed mode I/II elastic-plastic fracture

Abstract

We present a new two-dimensional software framework for predicting curvilinear elastic-plastic crack growth and residual strength. The framework is an extension of the existing FRANC2D/L software. The crack tip opening displacement (CTOD) is used as the fracture criterion, and the near-tip maximum tensile stress is used as the direction criterion. In some cases, crack tip constraint is modeled using a mixed state of stress, with elements near the crack tip kept in a state of plane strain and elements away from the crack tip in a state of plane stress. A mapping algorithm transfers state variables during remeshing as the crack propagates. Comparisons are made with numerical and experimental results for straight cracks in compact tension and middle crack tension specimens. Further comparisons are made with experimental results for curved cracks in ARCAN Mode I/II specimens. The analyses predict residual strength within 10% of experimental data. For tensile dominated fracture behavior, predicted crack paths are generally in agreement with experimental results; as expected, the maximum tensile stress criterion does not predict the appropriate crack propagation direction for materials that exhibit shear dominated cracking under Mode II loading.