Numerical Simulation And Analysis Of Micro Mechanical Field At The Stress Corrosion Cracking Tip

Stress Corrosion Cracking (SCC) is one of the key factors affecting the long-term safety operation ofnuclear power equipments, which is a hot field in the nuclear safety operation research field. SCC is anelectrochemical behavior which occurred in fracture process zone at the crack tip. Which is interactivelyaffected and acted by the corrosion environment, materials and mechanics at the crack tip and is involvedmultidisciplinary and multi-scale researches. It is almost impossible to reveal the SCC process by usingsingle subject or single scale. Current researches in SCC are based on the macro-scale or directly on thenano-scale, which is skipped micro-scale. Because it is important to understand SCC process in the grainscale, the tasks will focus on the mechanical properties at the SCC tip in micro-scale in this dissertation.By comparing numerical simulation calculation with theoretical analysis of compact tension specimen(1T-CT specimen) the effectiveness of calculating fracture parameters by using ABAQUS software isverified in the dissertation. A global model involved 1T-CT specimen and a sub-model involved SCC tipregion are constructed, and the calculation of the global model provide the boundary condition forsub-model and the calculation of sub-model provide a detailed investigation on the micro-mechanical fieldat the SCC tip. Based on a basic consideration of a narrow grove-type crack existing at the SCC tip, FEmodels with a grove-type crack and FE model with branch cracks in micro scale are constructed by usingthe sub-model technology in ABAQUS. The effects of the grove-type crack length and branch crack on thestress and strain at the SCC tips are analyzed this dissertation.The results of investigation indicate that the grove-type crack and branch crack ahead of SCC tip willinduce a great change on the stress and strain in the oxidation film and base metal at the SCC tips, and thechange is more obvious as the grove-type crack length increase. Comparing with the stress, the plasticstrain is more sensitive to the length at the SCC tip. Therefore, the equivalent plastic strain should be anappropriate mechanical parameter to understand the mechanical properties in the oxide film and base metalat the SCC tip.