Geometric imperfections of large diameter and thick-walled pipe fabricated by push bending with induction heating

Abstract

Push bending with local induction heating is a kind of advanced method fabricating large diameter and thick-walled pipe. However, geometric imperfections of the bent pipe (section flattening, excessive wall thinning at the extrados, and wall thinning even wrinkling at the intrados) have done severe damage to the safe operation of the pipeline system. In this article, a finite element model of the push bending for large diameter and thick-walled pipe with local induction heating is built and validated via experimental results first, and then the characteristics of temperature distribution and the geometric imperfections mentioned above are investigated based on the finite element model built. It is found that (1) the wall thickness fluctuates a little bit along the bending direction, and the section flattening is severest if the section position angle is between 50 and 60°; (2) the section flattening become more serious with smaller relative bending radius or narrower induction coil or lower heating temperature or faster push velocity because greater bending moment acts on the pipe under these situations; (3) relative bending radius affects the extrados wall thinning and intrados wall thickening much more than other three parameters; and (4) the intrados is probably to wrinkle if the heat temperature is too low or the induction coil is too wide or the push velocity is too fast.