Ductile Material Damage Numerical Simulation Of The Fracture Process

To study the change of microcosmic material structure in the crack tip and its effect on cracks propagation from microcosmic view is one of the develop directions and advance tasks of today's Fracture Mechanics. Meanwhile, it is a worthy field to develop that research failure of materials by means of combining Damage Mechanics and Fracture Mechanics.In the present thesis, the finite element method is applied to study the process of ductile material's crack, and main work is as follows:1. The numeric simulation and macrocosmic analysis is carried out based on the CTOA Fracture Criterion, meanwhile the limitation of traditional Fracture Mechanics in analyzing and discovering the mechanism of crack's emergence and propagation is clarified.2. Applying of Cohesive Zone Model to the crack problem is tried primarily, and the numeric result indicates that the damage evolution reaches the largest at the front of the crack tip, not at the crack tip.3. Some research is carried out on the applying of Gurson Model to the crack problem. Using elastic-plastic large deformation FEM based on the Gurson Model, the relation between the size of voided element at the crack propagation path and the velocity of crack propagation is numeric simulated and analyzed, furthermore, recurring to the general rule of ductile material's cracking process and some experimentation data, the reasonable size of Voided element is obtained.4. On the base of above work, an opinion that the fracture judgment of critical void fraction depends on the size of voided element is brought forward here, so that the large engineering structure can be analyzed by using FEM with relative large voided elements. In this case, less difficulty is met in design the model and so more efficiency is obtained.