Buried gas and oil pipelines can be subjected to unexpected bending loads causedby such earth movements as earthquakes, wash-outs, road building, mining subsidence, etc.as well as by denting from unintentional digging. In order to make a fitness-for-serviceassessment, it is necessary to measure any residual stresses that are left in the pipe wall aswell as the degree of plastic flow within regions of severe damage. A portable instrumentthat uses EMATs to rapidly measure ultrasonic shear wave birefringence in the wall of a pipehas been developed and applied to a 5 m (15 ft) long section of 0.56 m (22 in ) diameterlinepipe loaded in three point bending by a 22 MN (five million pound) load frame. Theresults showed that: (1) a large correction for shear wave anisotropy caused by texture in thesteel had to be introduced and (2) the degree of plastic flow could be deduced from changesin the texture contribution alone. An attempt to separate the stress and texture effects byusing SH wave modes in the pipe wall proved unreliable because of magnetostrictiveEMATs used for these experiments.
Review of Progress in Quantitative Nondestructive Evaluation, Annual Review | 14th | | AIP
and McColskey, J.
Measurement of Residual Stress in Bent Pipelines, Review of Progress in Quantitative Nondestructive Evaluation, Annual Review | 14th | | AIP
(Accessed February 27, 2024)