Research and Development
Ductile Fracture Simulation of Structural Steel

Ductile fracture of structural steel using constitutive models was investigated, by using finite element simulation, supported by scanning electronic microscope (SEM). The ductile fracture of structural steel, which is a process of void nucleation, growth and coalescence, has been confirmed from the metallurgical observations.
Based on the metallurgical observations and laboratory tests of tensile specimens, predictions of ductile fracture, using J resistance curve, for compact tension specimens have been accomplished using an uncoupled Rice and Tracey and coupled Gurson-Tvergaard-Needleman models applied in both explicit and standard finite element elastic-plastic stress analyses. These two models of ductile fracture aim at predicting crack initiation and propagation by modelling the successive process of nucleation, growth and coalescence of voids during the application of load to a component. The material parameters in the micro-mechanical models were calibrated by simulating the test of the tensile specimens. The test data and the predicted results have been compared and the effects of some important parameters have been examined.
A local approach methodology to predict the ductile fracture of steel structures was developed, based on the application of the micro-mechanical models of failure in which the stress, strain and local 'damage' at the crack tip area is related to the critical conditions required for fracture. This procedure was used to predict fracture in service components.