Effect Of Inner-pressurized Bending Process On Working Stress Of Thin-walled Pipe

The pipe in nuclear power steam generator is a typical thin-walled pipe structure. The thin-walled pipe would have an elliptical deformation in cross-section, wall thinning, and inner surface defects in cold bending process. And the cold bending residual stress in the thin-walled pipe is an important factor influencing the stress corrosion cracking of the nuclear primary piping materials. Studies have shown that inner-pressurized could solve many technical problems in the cold bending process of the thin-walled pipe. An inner-pressurized cold bending model of thin-walled pipe is established, and the inner-pressurized bending process of the thin-walled pipe and the effect of the cold bending residual stress on the mechanical field at the crack tip are researched combined by the theoretical analysis and the numerical simulation in this thesis. The main researches are performed in this thesis are as follows:(1) A bending model of the inner-pressurized pipe is constructed by using ABAQUS, and the effect of oval degrees and wall thickness changes of the thin-walled pipe are obtained through imposing different pressure to the pipe;(2) The characteristic of stress-strain variation of the steam generator pipe bending by the inner-pressurized is analyzed, and the effect of bending angle on the bending mechanical properties and the changes in the bending process of neutral layer are researched;(3) The characteristics of the inner-pressurized bending process of the thin-walled pipe are analyzed, and the cold bending residual stress feature and distribution low of the steam generator pipe are researched;(4) The effect of residual stress at the crack tip is analyzed under different crack depth and bending angle based on the cold bending process of thin-walled pipe with a surface half-ellipse crack.