Multi-scale Analysis Of Mechanical Properties On Fracture Process Zone

Environmentally assisted cracking (EAC), especially stress corrosion cracking (SCC), is a core issue in the long-term safety operation of the nuclear power equipments, and the mechanical state in crack tip is one of the important factors affecting the EAC growth rate. With multi-scale method, the mechanical properties in the fracture process zone were analyzed and researched in this study.The main research tasks and results are as follows:(1) Through comparing the stress intensity factor (KI) of compact tension specimen calculated by finite element software with the theoretical value, the feasibility of calculating fracture parameters of crack tip in ABAQUS software was verified.(2) The relationship between the elastic modulus (E) of the material and research scale was studied based on deriving the cohesive stress theory and other relevant theories. And the elastic modulus of the material on meso-scale was determined.(3) Global model and sub-model of the finite element were built in the macro-scale, and stress-strain field nearby the crack tip was analyzed, and the results show that the detailed stress-strain in the crack tip could be obtained by using the sub-model technique.(4) In meso-scale, the crack growth model was also established by assuming the crack propagating along the grain boundary, and the detailed stress-strain field in the crack tip was obtained.(5) The effect of crack length on Von Mises stress, and maximum principal stress and strain was analyzed in meso-scale when equivalent KI equals 30MPa.m^1/2. And the results show that except for crack tip area, the stress-strain distribution in whole specimen is not affected.(6) The stress-strain in the crack tip was analyzed when the elastic modulus is 210GPa and 420GPa in meso-scale, respectively, and the results show that the elastic modulus has great influence on stress but little on strain.The conclusions provide a theoretical foundation for further analyzing the stress-strain in the fracture process zone and researching the stress corrosion cracking along the grain boundary.