THE COLLAPSE LOAD OF CIRCULAR ARCH PIPE WITH 3D DEFECTS

The volume defects, especially the pitting defects, are very common when the pipeline is corroded. The burst test is performed on the straight and circular arch pipes, which have pitting defects and are subjected to internal pressure. The shape of defects is spherical and long spherical in axial and circular directions. The collapse pressure is calculated by large displacement nonlinear elastic-plastic finite element method and GB/T19624-2004 (in straight pipe). The numerical results and failure modes of finite element method are in good agreement with burst tests. The finite element method and the burst test result both show that the defects in axial direction have larger influence on the collapse load. The calculation formulas of plastic limit load for bent and straight pressured pipeline with 3D defects are put forward.