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The drilling environment and drill string assembly in deep and ultra-deep wells are complex, leading to increased vibration loads that can cause fatigue and crack propagation in drill pipe joints, resulting in premature scrapping. This paper addresses these issues through several research steps. First, a dynamic calculation model for drill pipe joints is developed to analyze the axial force, torque, and bending moment on the joints beneath the well. Next, a finite element analysis model is constructed to assess whether the forces on the joints meet material strength requirements. Additionally, a crack propagation model is established to evaluate the remaining service life of the joints. The findings are as follows: The dynamic calculation model is validated against laboratory experiments. In the target environment, drill pipe joints are subjected to an axial force of 13.11 kN, a torque of 35 kN·m (including make-up torque), and a bending moment of 0.75 kN·m. The analysis of composite loads reveals maximum von Mises stresses of 551.2 MPa for internal thread joints and 323.2 MPa for external thread joints, both of which satisfy material strength requirements. Furthermore, cracks in the threads of drill pipe joints are primarily opening cracks, with depth significantly influencing crack propagation more than length. Under current operating conditions, a minimum crack propagation size of 3×2 mm corresponds to a remaining service life of 126,820 cycles.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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