Numerical And Experimental Research On Residual Stress In Hydraulic Expanded Tube-to-Tubesheet Joints Of Steam Generator

Steam generator is very important for the safe operation of nuclear power station,for it isthe hinge for the primary loop and the second loop.Leakage accidents of steam generatoroften occur with serious consequances on the safety and reaiability of the nuclear facility.Thestress corrosion cracking of tube to tubesheet joints is the main cause of leakage accients dueto the residual stress produced during manufacturing process.Therefore it has very ipmortantsignificance to study the residual stress level in the tube to tubesheet after manufacturingprocess to improve manufacturing process and prevent accidents．By establishing the finite element model of the tube to tubesheet joints for the steamgenerator,the overall numerical simulation course of hydraulic expansion for tube to tubesheetjoints was conducted with ANSYS software.The simulation result of different hydraulicexpansion pressure，such as240MPa、250MPa、260MPa、270MPa、280MPa、290MPa，300MPa has been obtained.The result includes the residual contact pressure between the tubeand tubesheet contacting boundary,the residual stress and the tube wall thickness reductionrate. The results of simulation indicate that residual contact pressure between the tube and thetubesheet increases with the increasement of expansion pressure，but the increment presentsreverse trend, the stress on the inner surface of the tube and the tube wall reduction increasewith the increase of the expansion pressure.By means of blind-hole method,the residual stress in expansion trasnsition zone wasmeasured,and the stress corrosion resistance of the tube to tubesheet expanded joints wasstudied by stress corrosion test. The experimental results coincide with the numericalsimulation result, the residual stress on the inner surface of the tube of280MPa expansionpress is92.6MPa.Therefore the expanded joints have a good ability of stress corrosionresistance.The research result not only verify the accuracy of numerical simulation but also provideprovided academic basis for the confirming of the optimal expansion pressure．...