Abstract
At present, the researches on the factors affecting the fatigue life of type III hydrogen storage cylinder mainly focus on the structure and technological parameters of the cylinder, and there are few studies on the type III cylinder with initial liner cracks. In this paper, a finite element model of fatigue analysis for 70MPa Type III cylinder based on fracture mechanics method was established. The influences of the depth, length, and position of the axial semi-elliptical initial liner crack on the fatigue life of the cylinder were discussed, and the tolerance size of inner surface crack was calculated. The results show that the cylinder fatigue life increased significantly with the decrease of the crack size. The fatigue life of the cylinder is more sensitive to the change of crack depth than the change of crack length. According to GB/T 35544, the fatigue life requirement of the cylinder studied in this paper is 7500 cycles of filling and releasing hydrogen. For the inner surface axial crack, when the crack depth-length ratio is 1/3, the maximum allowable crack depth is 0.167 mm; when the crack depth is 0.2 mm, the maximum allowable crack length is 0.443 mm. Furthermore, under the same initial crack size, the fatigue life of the cylinder with a crack on the outer surface is longer than that on the inner surface.
