A fracture mechanics approach for analyzing spiral weld pipes containing crack

Spiral weld pipes are used extensively in the gas and oil industries. Compared to the longitudinal seam pipes, the spiral weld pipes can be manufactured straighter, rounder, longer and with more uniform stress distribution and higher rigidity. However, because of the longer weld line these pipes are more susceptible to damage due to the growth of cracks and defects which exist or are generated in the weldment area. Therefore, it is important to investigate the integrity and the remaining service life for the defected spiral weld pipes. Due to the arbitrary orientation of cracks and application of various external loads in spiral pipes, these pipes experience complex state of stress and deformation. In such cases, crack growth may occur under any combination of shear and tensile loads in the cracked area. In this paper, the application of a fracture criterion called the maximum hoop stress (MHS) criterion is described for predicting the integrity of cracked spiral weld pipes. This criterion can evaluate both the direction of fracture initiation and the final sustainable load of gas and oil pipes containing crack. The failure design curve which is presented in this paper for different loading types and crack orientations can be used for failure assessment of cracked spiral weld pipes or other similar engineering applications.

Keywords:

spiral weld pipes , crack , brittle fracture , engineering analysis