Numerical investigations on fracture behavior of ductile materials
Abstract
The objective of the present work was to establish a criterion to characterize the fracture behavior of crack extension in ductile materials. The first part of this dissertation explored some useful techniques dealing with the fracture behavior of nonlinear elastic solid as the ideal model for ductile material. Five different methods of calculation of nonlinear strain energy release rates were investigated. Their efficiencies and accuracies were compared and discussed. The present work identified the cause of deviations between the numerical result and the HRR solution. The present result showed that all field components near the crack tip converged to the HRR solutions in all directions if FEM meshes were sufficiently refined, and that the HRR fields exist not only for small scale yielding, but also for general yielding. Moreover, the near tip field solutions for incremental plasticity are almost identical to those for deformation plasticity. For incremental plasticity, however, the crack tip fields progressively deviate from the HRR solutions as elastic unloading occurs. The present work also investigated the plastic crack tip fields in the presence of residual stresses. To establish a ductile fracture criterion, several potential fracture parameters were investigated in simulations of crack extensions by combining numerical techniques with existing experimental results. Based on the present observations, a fracture criterion, the Global-Local Fracture Criterion (GLFC) was proposed. The feasibility of the proposed fracture criterion in predicting the ductile fracture behavior was extensively verified. It was shown that the GLFC is highly accurate and is satisfactory for ductile fracture analyses.
Degree
Ph.D.
Advisors
Sun, Purdue University.
Subject Area
Aerospace materials
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