应力高阶项对相贯内腔裂尖应力场的影响

摘要

Fracturing pump as a key equipment of fracturing technology used in the oil and gas production,the crack failure at intersecting line has become a main factor that hinder its working life.The theoretical analysis and numerical calculation are applied to research the stress field of crack tip.The results show that the higher order term t11and t33respectively corresponding to the stress σ11and σ33have distinct influences on the stress filed,while the higher order term of opening stress does not.The K-t11-t33theoretical model can describe the stress field better compared with the single parameter model.The higher order term t33of out-plane stress is related to t11and out-plane strain ε33,but it is mainly decided by ε33.The change trend of ε33along the crack front is researched, the results show that ε33is bigger as the place is closer to chamber surface.At the middle place of the crack front, where is far away from the free surface,the ε33is close to zero.In this case,the stress field of crack tip is similar with plane strain state.By studying the stress filed of crack tip,a better description model of crack tip of fracturing pump is built,which is the base of research on fracture criterion and fatigue life prediction.%压裂泵头体作为压裂技术的硬件支撑,相贯线处的开裂失效严重制约了其工作寿命.采用理论分析和数值分析的方法,对泵头体相贯线的裂尖应力场进行了研究.结果表明,裂尖应力分量σ11和σ33的高阶t11、t33项对相贯线处裂尖应力场的影响显著;张开应力σ22的高阶项对裂尖应力场影响不显著,相比于单参数模型,K-t11-t33模型可以更好描述相贯线处的裂尖应力场.离面应力σ33的高阶项t33与t11和离面应变ε33有关,但主要由ε33决定.通过研究裂纹前缘不同位置的应变ε33,结果表明,越靠近两个内腔表面,其应变量越大;越远离两个内腔表面,应变量ε33越小,裂尖应力状越接近平面应变状态.通过研究相贯内腔的裂尖应力场,建立其裂尖应力场的理论模型,可以为相贯内腔结构的临界断裂条件和寿命预估奠定基础.