| An explicit finite element code is developed for solving transient coupled thermo-mechanical elastic-viscoplastic initial-boundary value problems. The finite element formulation is based on a convected Lagrangian approach and is consistent with large deformations and large rotations. The constitutive response of the material is elastic-viscoplastic and includes the effects of material strain hardening, material strain-rate sensitivity at both intermediate and ultra-high plastic strain rates ;The usefulness of this finite element code is demonstrated by studying the edgewise propagation of plastic shear instability from the tip of a pre-existing crack in a high strength structural steel (4340VAR steel hardened to ;In addition, the numerical code is modified to include material failure within the constitutive description of the material. The material failure algorithms allow the creation of a new free surface with the complete loss of stress carrying capacity. Within such a framework, a series of finite element simulations are carried out to obtain qualitative and quantitative descriptions of low temperature dynamic fracture of 4340VAR steel. A number of different dynamic fracture criteria, including crack advance based on elastodynamic modeling of crack growth, and a rate dependent cohesive surface separation model, are critically examined by comparing the computed results with the experimental results obtained during an earlier study by Prakash and Clifton (1992). |
