Effect Of Plastic Hardening Of 316 Stainless Steel On Stress Corrosion

316 stainless steel pipes and pressure vessels will inevitably produce plastic hardening caused by plastic deformation during the manufacturing,welding and assembly processes.Plastic hardening not only affects the mechanical properties of the material,but also affects the stress-strain field at the tip of the stress corrosion crack and the law of the driving force of crack propagation during the service process of the material.In order to study the effect of plastic hardening of 316 stainless steel on the stress corrosion law,the influence of plastic hardening on the driving force of stress corrosion crack growth of 316 stainless steel was analyzed by a combination of experiment,theory and finite element method.The main research contents are as follows:(1)Use experiments to obtain the stress-strain curve of 316 stainless steel,and analyze the distribution law of yield strength and hardening index of 316 stainless steel with different degrees of plastic hardening.Study the change law of plastic hardening and Vickers hardness of 316 stainless steel,and establish the relationship between material yield strength and Vickers hardness based on the analysis of material mechanical properties.Scanning electron microscope was used to observe the fracture morphology of 316 stainless steel with different pre-stretching amount,and the fracture was compared and analyzed.(2)Establish a finite element model,and analyze the influence of different mechanical parameters of 316 stainless steel and the plastic hardening of the material on the stress and strain field at the crack tip based on the experimental data.Analyze the influence of material yield strength and hardening index on the stress corrosion crack tip Mises stress field,tensile stress field,equivalent plastic strain field and tensile strain field,and further study the influence of material plastic hardening on the stress corrosion crack tip mechanical field.(3)Study the mechanical parameters of stress corrosion crack growth driving force,analyze the influence of the yield strength and hardening index of 316 stainless steel on the stress triaxiality of the stress corrosion crack tip,the strain rate of the crack tip,and the creep rate of the crack tip.The sensitivity of crack tip stress triaxiality,strain rate and creep rate to material mechanical parameters is analyzed.It also compares and analyzes the reasonable mechanical parameters of the crack propagation driving force.(4)Combining experiments to study the law of plastic hardening in the heat-affected zone of pipe welded joints,and analyze the influence of the plastic hardening of the heat-affected zone on the stress-strain field at the tip of the stress corrosion crack on the fusion line.The effect of plastic hardening of the heat-affected zone on the driving force of stress corrosion crack tip crack propagation on the fusion line is studied.