考虑包辛格效应的特殊螺纹连接循环加载变形仿真分析

Simulation of the Premium Threaded Connections Deformation under Cyclic Loading by Considering the Bauschinger Effect

用于高温高压深井的油管特殊螺纹连接受到包括轴向拉伸-压缩和径向内-外压的复杂循环载荷作用。复杂循环载荷会造成油管特殊螺纹在连接处出现局部的弹塑性变形,加剧了油气泄漏问题导致的安全事故、资源浪费与环境污染等风险。因此,揭示复杂循环载荷条件对油管特殊螺纹连接变形的影响规律,已成为油气井工程领域亟须解决的热点问题。油管特殊螺纹连接马氏体型不锈钢在循环加载条件下表现出明显的拉压不对称屈服和包辛格效应,为此,建立考虑拉压不对称各向异性的Reduced Cazacu-Barlat J2-J3(J2-J3)屈服准则和考虑包辛格效应的Armstrong-Frederick(A-F)随动强化模型,对特殊螺纹连接在循环加载下的变形情况进行仿真分析。结果表明,内部压力是造成特殊螺纹接头出现高接触应力峰值和塑性形变积累的主要原因,油管内部循环压强造成的包辛格效应对于油管特殊螺纹连接变形产生较大影响;轴向的拉伸压缩循环载荷仅驱动螺纹处局部出现塑性变形,包辛格效应的影响不明显;前几周次循环加载中包辛格效应显著影响油管特殊螺纹连接的变形,但并未造成的密封接触强度显著下降,能够满足接头密封完整性要求。

The premium threaded connections(PTCs)of tubing used in high temperature and high-pressure deep wells are subjected to complex cyclic loads including axial tension-compression cyclic load and radial internal-external cyclic pressure.Under the co-action of complex loads,local elasto-plastic deformation is easy to occur in the connection part,resulting in the increasing risks of leakage,accident,waste and environmental pollution.Therefore,it is crucial to reveal the influence of complex cyclic loads on the deformation of PTCs in the field of oil and gas well engineering.However,the material,martensitic stainless steel,exhibits obvious tension-compression asymmetry and Bauschinger effect under the complex cyclic loads.To account for this,a new model containing the Reduced Cazacu-Barlat J2-J3 yield criterion considering tension-compression asymmetry and the Armstrong-Frederick(A-F)kinematic hardening model considering Bauschinger effect was established.The deformation of PTCs under complex cyclic loads was analyzed,and the results show that the radial internal pressure is the main factor that causes the high contact stress peaks and the accumulation of plastic deformation in the PTCs.The Bauschinger effect caused by the cyclic internal pressure has a large impact on the deformation of the PTCs.Under the axial tension-compression cyclic loads,the plastic deformation only occurs in local threaded connections,so that the Bauschinger effect has no obvious effect on the deformation of the PTCs.The Bauschinger effect affects the deformation of the PTCs much only in early few cycles,but the decrease of the seal contact strength caused by the Bauschinger effect does not significantly,which meets the requirements of sealing integrity of PTCs.