【摘要】 疲劳断裂是油管失效的一种形式 ,本文针对抽油机井常用油管 (J5 5 ,2 1/ 2″)在循环载荷作用下的疲劳断裂问题进行了理论与实验研究。在实测油管载荷谱与应变谱的基础上应用弹塑性有限元法计算油管螺纹内的应力应变场 ,并进行了有关的疲劳实验 ,以得到油管的疲劳强度。油管内第一啮合齿齿根处应力应变最大 ,应力已经达到屈服阶段 ,油管是在高应力应变水平和低应力应变幅状态下工作。当油管内的应力应变进入强化段εeq >1 0 - 2 ε,塑性应变幅超过 4× 1 0 - 5ε时 ,油管就会发生疲劳断裂更多还原

【Abstract】 Fatigue fracture is one kind of oil tube failure. In t hi s paper, the fractures of oil tube (J55, 212 in) under cyclic loading are investigated by theory and experiment. Such kind of oil tube is wide ly used in the well of suckerrod. The elasto-plastic finite element method is u sed to compute the inner strain and stress field for the oil tube thread on the base of load spectrum and strain spectrum measured on site. Then the fatigue e xperiments concerned are completed to get the fatigue resistance. As the root of the first engaged thread on oil tube bears the maximum stress and strain, the s tress may reach yield limit. The oil tubes often run in a condition of heavily s tress and strain level with low stress and strain amplitude. If the stress is la rge enough to make the material get in to its strengthen phase (the equivalent s train is more than 0.01 ε ), and the plastic strain amplitude surpass 4×10 -5 ε , fatigue fracture will occur.更多还原