Analysis For The Formational Stresses Of The Large Diameter Straight-weld Pipe

This article carries on the finite element numerical simulation to end squaring and tack welding in JCOE forming. Obtained the remaining stress distribution on the straight seam welded pipe by using this model, the computed result is according to the actual result. The unfinished welded-pipe width and the ellipticity data carry on the statistical analysis and acted according to 3σrules to determine the computation characteristic value used in the finite element model. The unfinished piping geometry shape possibly has made the comprehensive consideration in the actual production. The computed result indicated, however the unfinished piping geometry shape changed, the remaining stress peak value which on the circumference outside surface is away from nearby the welded joint 180°position by JCOE. It is reasonable takes shape the unfinished piping to the flat ellipse for reduce the remaining stress peak value and ellipticity. The unfinished piping aperture width is essential craft parameter to the control the remaining stress peak value. The specification of unfinished piping should be as far as possible the flat ellipse and the aperture width is smaller than 100mm in the actual production process.By means of analyzing the deformation mechanism of diameter expanding of a straight-weld pipe, this paper educes a formula for calculating the hoop residual stress on outside surface of welded pipe after expanding by the ring splitting method. Actual measurements show that theσBform the formula can represent correctly the distribution and peak value of hoop residual stress on outside surface of a straight-weld pipe after expanding. However, for the straight-weld pipe before expanding, theσBform the formula can only reflect approximately the mean value of hoop residual stress distribution on outside surface of a welded pipe.