关键词: 钻杆, 环向表面裂纹, 静扭试验, 有限元数值模拟

Abstract: In order to investigate the influence of surface circumferential crack on the performance of mine drilling rods, the problem was analyzed using linear elastic fracture mechanics. Static torsion tests were carried out for 9 mine drilling rods, and the cracks under different levels of lengths and depths were put on the surface of drilling rods in advance. The torque values of crack propagation and crack growth angle were obtained. The test results indicate that the crack is difficult to propagate when the size of crack is too small (length 10 mm, depth 2.5 mm); the values of the crack growth angle are about 10°, it increases with the increase of the crack depth; when the length (depth) of the crack is relatively large, the torque values of crack propagation decrease sharply with increase of the crack depth (length). Finally, the stress distribution before the crack propagation was obtained using finite element modelling method. The values of the stress decrease almost linearly on both sides of the crack from outside to inside. The stress curves of inside and outside round edges of the crack are all similar to parabola shape, but they are in the opposite direction. When the length of the crack is small (10 mm, 20 mm), the maximum stress is in the surface tip of the crack. The maximum stress of the inside round edge is in the middle of the edge, and the value is smaller than it in the surface tip of the crack. When the length of the crack is relatively large (30 mm), the value of the maximum stress of inside round edge is larger than it in the surface tip of the crack, which suggests that the crack will propagate from inside round edge possibly. The results obtained in this study have an important guiding significance for drilling rods design and the accident treatment in the drill site.