Mechanical behavior investigation on the formation of the plain dent of an API 5L L245 pipeline subjected to concentrated lateral load

Abstract

As the main geometric defect in pipeline maintenance, dent has been paid more attention by pipeline managers because of its strong stress concentration. To investigate the formation mechanism of a pipeline dent, an indentation test of a pipe subjected to concentrated lateral load was carried out in the laboratory to simulate the formation process of the dent, and a 3D numerical model corresponding to the test was established to verify the results between the experiment and simulation. Subsequently, the stress and strain response of the dented pipeline was analyzed in detail in various stages of dent formation process. Deformation analysis revealed that the residual stresses state formed in the dented area after unloading is related to the depth of the dent, which may be in tension or in compression. During the formation of the dent, the pipeline presents “∽”-type wave-like bending state in the axial direction. These dent formation mechanisms may provide a guidance for dent assessment studies.