Fracture failure analysis and research on solid expandable tubular with joint thread

Abstract

Fracture failure occurred in solid expandable tubular with thread joint during bulging experiment. The mechanical properties and microstructure of fracture shell were investigated by scanning electron microscopy and tensile test. Tensile tests show that the plastic deformation capacity and strength of box thread joint material (AISI 316L) are better than that of pin thread joint material (SAE 1020). Dimples and cleavage facets can be observed in the fracture surface. The finite element analysis shows that the threaded joints carry great compressive stress in the axial and annular directions during the solid expandable tubular bulging. The irregular deformation of the threaded joints during bulging leads to stress concentration at the thread root. There is a great risk of cracking in the case of insufficient strength thread material, and finally leads to the fracture of the joint thread.