套管的残余应力对抗挤毁强度的影响

运用弹性力学理论,建立石油套管的力学模型,通过理论和有限元计算,得到残余应力与石油套管抗挤毁强度之间的关系.研究表明残余应力在很大程度上影响着石油套管的抗挤毁强度,当切向残余应力存在时,适当的压应力明显有利于提高石油套管的抗挤毁强度,而拉应力的存在会显著降低石油套管的抗挤毁强度;当石油套管上存在轴向残余应力时,拉应力使石油套管的抗挤毁强度降低,而压应力使石油套管的抗挤毁强度有所提高;非均匀分布挤压载荷对石油套管抗挤毁强度的影响同均匀分布载荷相似.因此,为了提高石油套管的抗挤毁强度,应根据管体的受力状态,使石油套管的管体上产生最佳的残余应力,提高石油套管的抗挤毁强度,延长使用寿命.

Study on collapsing strength of casing pipe on the residual stress

Based upon the principle of the elasticity,a mechanical model of the casing pipe is built and the relationship between residual stress and collapsing strength is developed through the theory and calculation ofFEM.The results show that the residual stress in the process of making casing pipe mainly influences the collapsing strength.The advisable crushing stress can enhance the collapsing strength of the casing pipe when the tangential residual stress existing whereas the existence of stretching stress can remarkably degrade the collapsing strength.When the axial residual stress exists,the stretching stress degrades the collapsing strength of the casing pipe whereas the crushing stress enhances that of the casing pipe.The influence of non-uniform extrusion stress imposes the same extent to the casing pipe as the uniform extrusion stress.Thus,to elevate the collapsing strength and the life span of the casing pipe the residual stress should be kept in the casing pipe based upon the situation of the stress.