Fatigue Crack Growth Behavior Of SA508 Gr.3 Cl.2 Under Different Stress Ratios And Effect Of Fatigue Damage On Fracture Toughness

During the "Thirteenth Five-Year Plan" period,China's nuclear power development faces a rare historical opportunity,and nuclear power safety is the primary promblem.The safe development of nuclear power depends on the safety of the process and equipment,and the key to the safe operation of the equipment is to ensure its structural integrity.Fatigue and fracture assessment are the two most important aspects of the research on the structural integrity of nuclear power equipment.The two are interdependent and mutually influential.With the advancement of localization of nuclear power equipment,nuclear power materials are also being implemented on a large scale.The domestic SA508 Gr.3 Cl.2 is the main material of steam generator,stabilizer,passive waste heat exhaust heat exchanger and safety injection container in the CAP1400 nuclear power plant,and its fatigue fracture performance will penetrate life extension process including designing,manufacturing,in-service inspection of the nuclear power equipment.Therefore,this paper mainly studies the fatigue crack propagation behavior of domestic SA508 Gr.3 Cl.2 and the fracture toughness of the material after crack propagation.The main contents are as follows:(1)For the standard compact tensile CT specimens of domestic SA508 Gr.3 Cl.2materials,the fatigue crack propagation test under different stress ratios under normal amplitude loading was carried out.The test results show that the domestic SA508 Gr.3 Cl.2 material has a significant stress ratio effect.(2)The fatigue test data was analyzed by the crack closure model and Kujwaski two-parameter model.The results show that the Kujwaski two-parameter model has good applicability to the domestic SA508 Gr.3 Cl.2 material under different stress ratios.When the crack closure model is made to the domestic SA508 Gr.3 Cl.2.,the applicability of the model at different stress ratios has certain limitations.(3)The fracture toughness test was carried out on CT specimens with different degrees of fatigue damage at room temperature using the unloading compliance method in the single specimen method.The test results show that the local fatigue damage will affect the fracture toughness value of the sample,and the correspondingfracture toughness will decrease to some extent.(4)Based on the in-service equipment defect assessment process in the ASME XI volume standard,the fatigue crack growth behavior of the domestic SA508 Gr.3 Cl.2material is compared with the formula data given in the standard,and the evaluation method of fracture toughness is discussed.