Effect Of Strain Hardening On Driving Force Of SCC Propagation In 304 Stainless Steel

During the service period,the nuclear power structural materials represented by austenitic stainless steel are subjected to complex amplitude-changing loads,which will inevitably lead to the strain strengthening phenomenon of the crack tip local the crack tip,which makes the propagation behavior of stress corrosion cracking(SCC)cracks more complicated,thus bringing great safety risks to the long-term service of nuclear power structure.Due to the difficulty of obtaining the mechanical properties of the local micro-region of the crack tip after strain strengthening,it has a great influence on the driving force and rate of SCC crack propagation.In this paper,the mechanical properties of local micro-materials were obtained by combining theory,experiment(physical test and numerical simulation)and macro-micro-view.The influence of mechanical properties of local micro-materials on the micro-driving force and crack growth rate of SCC crack tip was studied.The main studies completed are as follows:(1)Based on the strain calibration method of DC potential drop(DCPD)software measurement system,strain gauge and finite element,the law of strain change in tensile process was analyzed,the strain of tensile sample section was accurately obtained,and the engineering stress and strain curve of 304 austenitic stainless steel was modified.(2)The mechanical properties of 304 austenitic stainless steel were measured and obtained by indentation theory and its test method,and the corresponding indentation numerical simulation test was established to verify.at the same time,the reliability of the indentation method to characterize the mechanical properties of the material was evaluated compared with the tensile test.(3)With the help of pre-reinforced samples with different notch widths,the local material properties at the notch were measured by indentation test,and the local material mechanical properties at different notch widths were obtained.The variation law between the notch and the material mechanical properties parameters was analyzed and established.The mechanical properties of the local micro region material at the crack tip were obtained by theoretical derivation.(4)By using ABAQUS finite element software and combining theoretical research and finite element analysis,the macroscopic model and submodel of SCC crack tip were established to analyze and study the driving force and rate of SCC crack growth of typical nuclear power materials before and after strain strengthening of local crack tip materials.