Ratcheting Analysis Of Nuclear Pipe Under Complex Loading

The piping in nuclear power plant will suffer complex loading condition because of the environment.Long-term loading can cause the accumulation of piping deformation.Finally,fracture may occur.There are many studies on piping test and simulation so far.However,studies are not complete.This study concentrated on ratcheting deformation of straight and elbow pipes.Forecasting performances using different constitutive model for straight pipe deformation were compared.Influence on ratcheting of elbow pipe under different loading path was studied.More studies on elbow pipe deformation were conducted with the method of test.Material and thermal aging were considered.This study makes much sense for comprehensive understanding of nuclear pipe deformation under external loading.Deformation of straight pipe was predicted by ANSYS software with different constitutive models.Constitutive models included Chaboche model,OW-? model and CJK model.Simulation result by CJK model was more accurate by comparing simulation result and test result.Influence of axial load on ratcheting deformation of straight pipe was studied using CJK model.The result showed that tensile load reduced ratcheting strain while compressed load and reversed load increased ratcheting strain.Ratcheting deformation of elbow pipe under different loading paths was studied by ANSYS software.Maximum strain with tensile bending load appeared at crown.Maximum strain compress load and symmetrical load appeared at intrados.Internal pressure had great influence on ratcheting deformation when increasing bending load.Effect of defect on ratcheting deformation of elbow pipe was studied.Defect at crown had greater influence than defect at extrados.Increasing the number of defects did not necessarily increase ratcheting strain.Elbow pipes made of Z2CN18.10 and Z2CND18.12 N were tested using fatigue test machine.Test result showed that deformations of elbow pipe with different material were generally accordant.Strain of Z2CN18.10 elbow pipe was lager.Ratcheting test on elbow pipes after thermal aging treatment was conducted.Ratcheting strain was lager after thermal aging treatment and ratcheting strain increased with treatment time.