压裂泵泵头体内腔相贯线裂尖J积分研究
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摘要
对于三维形式的裂纹问题,尤其是结构相对复杂,以角裂纹形式存在于十字形内腔相贯线处的裂纹问题尚没有适用的方法描述。鉴于此,针对压裂泵泵头体主要的失效形式,建立了含有不同尺寸角裂纹的有限元模型,计算了裂纹前缘J积分及裂尖塑性区尺寸。综合有限元分析和理论结果发现:随着裂纹长度的增加,裂纹前缘J积分逐渐增大但增幅逐渐减小,且吸入腔表面裂纹尖端J积分大于柱塞腔,内腔几何特征影响J积分分布;裂纹尖端塑性区形态为鱼尾形,断裂模式仍由I型断裂模式主导;沿裂纹面方向裂纹前缘塑性区尺寸与J积分分布规律一致,裂纹端部由于存在压力约束,实际计算塑性区尺寸较平面应力条件下差异较大,J积分最小处的塑性区尺寸与平面应变条件下的理论公式计算值非常接近。所得结论可为研究塑性区尺寸对压裂泵泵头体内腔相贯线裂纹扩展影响奠定基础。
To address the primary failure modes of the fracturing pump head,a finite element model with different angular crack size is established. The J integral of the crack front and the plastic zone size of the crack tip are calculated. The finite element analysis and theoretical results show that with the increase of crack length,the J integral of the crack front gradually increases with reduced increase rate. The J integral of the crack tip in suction chamber is larger than that of the plunger chamber. The geometric shape of the chamber affects the J integral distribution. The plastic zone of the crack tip is fishtail shaped. The fracture mode is still dominated by the I-type fracture mode. The plastic zone size of the crack front is consistent with the J integral distribution along the crack face. The calculated plastic zone has a big difference with the plastic zone under the plane stress owing to the pressure constraint at the crack tip. The plastic zone size at the minimum J integral point is very close to the calculated result under the plane strain condition. The study can lay a foundation for analyzing the influence of the plastic zone size on the propagation of intersecting line crack on the chamber of the fracturing pump head.
To address the primary failure modes of the fracturing pump head,a finite element model with different angular crack size is established. The J integral of the crack front and the plastic zone size of the crack tip are calculated. The finite element analysis and theoretical results show that with the increase of crack length,the J integral of the crack front gradually increases with reduced increase rate. The J integral of the crack tip in suction chamber is larger than that of the plunger chamber. The geometric shape of the chamber affects the J integral distribution. The plastic zone of the crack tip is fishtail shaped. The fracture mode is still dominated by the I-type fracture mode. The plastic zone size of the crack front is consistent with the J integral distribution along the crack face. The calculated plastic zone has a big difference with the plastic zone under the plane stress owing to the pressure constraint at the crack tip. The plastic zone size at the minimum J integral point is very close to the calculated result under the plane strain condition. The study can lay a foundation for analyzing the influence of the plastic zone size on the propagation of intersecting line crack on the chamber of the fracturing pump head.
引文
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[2]方惠军,杜道军,周海军,等.基于局部网格细化的泵头体强度有限元分析[J].石油机械,2013,41(7):98-101.FANG H J,DU D J,ZHOU H J,et al.Local mesh refinement-based finite element analysis of pump head strength[J].China Petroleum Machinery,2013,41(7):98-101.
[3]CHIKH B O,IMAD A,BENGUEDIAB M.Influence of the cyclic plastic zone size on the propa-gation of the fatigue crack in case of 12NC6 steel[J].Computational Materials Science,2008,43:1010-1017.
[4]SHI K K,CAI L X,QI S,et al.A prediction modelfor fatigue crack growth using effective cyclic plastic zone and low cycle fatigue properties[J].Engineering Fracture Mechanics,2016,158:209-219.
[5]TIEYING W,DANILE W,DANIEL K.Analysis of the plastic zone of a circle crack under very high c-ycle fatigue[J].International Journal of Fatigue,2016,93:415-412.
[6]WAHIDOUDAD,DJAMAL E B,HAMIDA F,et al.A-nalysis of the plastic zone under mixed mode fract-ure in bonded composite repair of aircraft structures[J].Aerospace Science and Technology,2017,69:404-411.
[7]CHEN J J,HUANG Y,DONG L L,et al.A new method for cyclic crack-tip plastic zone size determination under cyclic tensile load[J].Engineering Fracture Mechanics,2014,126:141-154.
[8]ALIREZA H,REZA T F.Dugdale’s modelfor plastic zone size of interacting cracks under anti-plane deformation[J].Procedia Structural Integrity,2017(2):2424-2431.
[9]CAMAS D,LOPEZ-CRESPO P,GONZALEZ-HER-RERA A,et al.Numerical and experimental study of the plastic zone in cracked specimens[J].Engineering Fracture Mechanics,2017,185:20-32.
[10]PAUL S K.Numerical models of plastic zones and associated deformations for a stationary crack in a C(T)specimen loaded at different R-ratios[J].Theoretical and Applied Fracture Mechanics,2016,84:1-9.
[11]RICE J R.A path independent integral and approximate analysis of strain concentration by notches and cracks[J].Journal of Applied Mechanics,1968,35(2):379-386.
[12]陈国栋,吕运冰,汪冬生.空间体J积分表达式及其守恒性[J].武汉理工大学学报(交通科学与工程版),2007,31(1):130-132.CHEN G D,LY B,WANG D S.Definition of J integral and the prove of it’s integral conservation in three dimensions[J].Journal of Wuhan University of Technology(Transportation Science&Engineering),2007,31(1):130-132.
[13]黄天成,吕伦,袁新梅.柱塞泵泵头体应力集中及疲劳寿命分析[J].机械设计与制造,2008,12:193-194.HUANG T C,LL,YUAN X M,Stress concentrateon and fatigue life analysis for plunger pump end[J].Machinery Design&Manufacture,2008,12:193-194.
[14]SHAFIQUE M A K,MARWAN K K.A new criteri-on for mixed mode fracture initiation based on the c-rack tip plastic core region[J].International Journal of Plasticity,2004,20:55-84.