Research On Rebound And Residual Stress About The Cold Bending Process Of Large-Diameter Cooling Tubeused For Nuclear Power Plant

High-strength,large-diameter and thick-walled cold bend steel tube is an importantpart in industrial equipment, which has a wide range of applications in the chemical andnuclear power fields Some defects such as springback Angle bigger, wall thicknessreduction thin and curved areas ovality changes will appear because that the deformationof the above tube is more complex, which affects the usage. This paper is to study the coldroll forming technology of the high-strength, large-diameter main pipeat AP1000nuclearpowerplant. The purpose is to explore the distribution law of springback Angle and theresidual stress in the cold bending process.The paper is divided into the following three parts:First, the springback Angle is derived through the use of classical mechanics theory，in which process pipe bending of the parts of the mechanics equation is established. Thespringback Angle expressions are derived through the unloading theorem. Then thespringback Angle was obtained by combining the equations and pipe basic performanceparameters.Second,thespringback Angle size and the distribution of residual stress were obtainedby using numerical simulation method, in which the pipe pressure bending of the basicmodel was established and the reasonable boundary condition set up.Finally, the physical model of Large-diameter and thick-walled tube cold bendingprocess was designed according to similarity theory. The methods of theoretical derivationand numerical simulation were validated through the experiments. Theexperiments showthat the results of numerical simulation are closer to the realistic。Reasons for thedifferences between The theoretical derivation and numerical simulation were analyzedand explained based on the experimental results.The results of the study showed that：In cold bending deformation process the bendrebound Angle is3.71°, tube body residual stress mainly exists in the curved convexplatform root and curved parts and the overall residual stress do not appear stressconcentration, themain line of cold section used in the AP1000nuclear power because of the technical requirements. In addition, the experimental data and experience inproduction in the production of high-strength, large-diameter and thick-walled cold bendsteel tube could be Accumulated through the study.