Volume 35, Issue 1 (January 2007)
A Test Method to Determine Low-Cycle-Fatigue Behavior of Wrinkled Pipe
Field observations of buried pipelines used by energy industries for transporting natural gas and oil indicate that it is not uncommon for geotechnical movements to impose large displacements on buried pipelines resulting in localized curvature, deformations, and strain in the pipe wall. Often these local deformation results in local buckling in the pipe wall (wrinkling) and, in its post-buckling range of response, wrinkles develop rapidly. Subsequent cyclic load histories may produce cyclic plastic strain reversals in the wrinkle region leading to formation of fractures in the wrinkle region. This paper presents an innovative and simple material test method, called a strip test, which was designed and carried out at the University of Alberta in order to simulate the complicated behavior of pipe wrinkles subject to such low-cycle-fatigue loading. It is found that the strip test is capable of replicating the complicated behavior of wrinkled pipe subject to plastic strain reversals at the wrinkle location due to low-cycle-fatigue loading and provides necessary information that can be used for further studies. For the current project, a total of 16 such strip tests were carried out, and the test data from these strip tests have been used successfully to develop a fracture life assessment (FLA) model for the wrinkled energy pipe subject to strain reversal due to low-cycle-fatigue loading. The development of the FLA model will be presented in a future publication.