Nondestructive Evaluation of Stress in Bent Pipe by Magnetic Anisotropy Sensor — In−Plane Bending —

Abstract

A method is developed to nondestructively estimate stresses in bent pipes by magnetic anisotropy sensor. The values measured by the magnetic method contain both stresses generated during manufacture and generated by external forces. In-plane-bending tests of a welded elbow and an induction pipe bend were performed. The stresses obtained by the magnetic method were regressed to Karman's theoretical equation for a bent pipe. From the regression curve obtained, it was possible to obtain the external moment that was purely applied to the bent pipe. The stress range where measurement is possible is lower than that in a straight pipe, because the residual stress is even larger than that of a straight pipe.