Drill pipe joints on stress distribution analysis, is used to improve the performance of key drill

Drill pipe is used for power transmission, conveying the main tool for drilling, oilfield drill pipe failure accidents often to bring huge economic losses. Statistical analysis showed that 65% of the drill string failure drill pipe joints in the accident. Drill pipe joints in use will determine the stress distribution pipe  High pressure needle valve  and sealing performance. Therefore, the tool joint distribution of stress analysis is used to improve the performance of key drill. Tool joint drill by the elastic-plastic finite element model of the threaded joints  Instrument valve manifolds  with female buckle buckle male contact surface is a space helical surface and drill pipe joint force is more complex, in addition to passing the turntable torque, but also by tension (mainly caused by the weight drill pipe), the pressure (mainly caused by the drilling fluid) and so the load effect. Stress Analysis of drill pipe joints involving material  Valve manifolds , geometric nonlinearity and complexity of the contact friction conditions and other nonlinear problems, the establishment of a complete and accurate mathematical model, seeking analytical solution is very difficult.

Stress intensity factor and the crack shape changes in turn affect the crack propagation life

Since the position of welded structures there is a high weld toe nonlinear stress distribution, the weld toe surface near the crack tip stress field will inevitably be affected. Meanwhile, due to the nonlinear stress crack surface makes the existence of the peak stress at the end increases, the speed surface cracks extended along the longitudinal  Valve manifolds  of the crack, changing the shape of the crack propagation. Near the crack tip stress field variations and changes will affect the shape of the crack surface crack stress intensity factor of size. Stress  Instrument valve manifolds  and the crack shape changes in turn affect the crack propagation life. Therefore, the discussion of non-linear distribution of stress on the surface crack stress  High pressure needle valve , crack shape and crack propagation life of welded structures for an accurate calculation of fatigue life is important. In this paper, butt weld toe surface crack crack propagation behavior of a large number of finite element analysis. Analysis assumes that there is no residual stress, porosity, incomplete penetration, dislocation, undercut other welding defects, the study focused on non-linear distribution of stress at the weld toe surface crack extension.