Mechanical synergistic interaction between adjacent corrosion defects and its effect on pipeline failure

Abstract

This work provides a new comprehensive assessment method to determine the complex mechanical interaction of adjacent corrosion defects. Firstly, a three-dimensional (3D) finite element model of pipelines containing adjacent defects (involving longitudinally aligned, circumferentially aligned, and diagonally aligned defects) was developed and validated by full-scale burst tests. Then, the synergistic stress interaction between adjacent defects was analyzed, and the relationship between the burst position of the pipeline and defect spacing was determined. At last, the applicability of several commonly used critical spacing rules for identifying the interaction between adjacent defects was compared and discussed in detail. The results show that the failure position of the pipeline containing adjacent defects is related to the relative position of defects. For longitudinally aligned corrosion defects, the stronger the interaction between defects (i.e., the shorter the distance between two defects), the closer the failure position of the pipeline to the center of the defect spacing. For circumferentially aligned corrosion defects, the failure position of the pipe tends to move from the defect edge to the geometric center of the defect with increasing defect spacing. For diagonally aligned defects, the failure position is generally located on the path connecting the defect and the spacing. The currently available evaluation criteria for identifying circumferentially interacting defects display the most accuracy, and the identification effect of diagonally aligned defects is the poorest. In addition, the critical spacing rule proposed by Li presents the highest precision in identifying the interacting defects. The results are expected to provide a stress synergistic failure assessment method for pipelines containing cluster corrosion defects in engineering.