Residual Stresses under Radial Deformation of Steel Pipes

A new numerical method is considered for studying the formation of the residual strain–stress state in pipes under plastic change of the diameters (expansion or contraction) followed by the elastic recoil. A tube section is nominally divided into 20 cylindrical layers of similar thickness. A finite increase in the inner diameter is forcibly given. Geometric changes have been found for each layer with calculation of the circumferential stress by an experimental stress diagram; then, the radial and axial stresses are calculated. Further, the expanded pipe is forcibly compressed in diameter by a predetermined value followed by calculation of the geometrical changes and stresses. The numerical experiment results converge with those obtained in real experiments.