抽油杆疲劳寿命计算研究

抽油杆是有杆抽油中三抽设备的关键部件之一。其服役寿命直接影响油井的产量、失效概率以及修井作业的成本,准确预测其疲劳寿命具有十分重要的意义。对直井和定向井分别建立了计算抽油杆轴向载荷的数学模型,计算出了抽油杆所受的轴向力。同时,建立了疲劳寿命的预测模型,计算了不同形状裂纹的几何形状因子和应力强度因子。并根据以上理论,编写了计算机程序,能计算有初始裂纹和无初始裂纹抽油杆柱的疲劳寿命。采用Forman模型预测抽油杆疲劳寿命,其特点是在Paris模型的基础上考虑了应力比R,计算结果更加准确。同时,分析比较计算结果可得:裂纹初始长度对抽油杆柱的使用寿命影响较大。文中给出的方法简单,精度较高,便于工程应用。

RESEARCH ON FATIGUE LIFE CALCULATION METHOD OF SUCKER ROD

Sucker rod is the key component of the rod pumping system. Its service life has something to do with the quantity of the production,failure rate and work over,and it is very important to predict the fatigue life of sucker rod.The mathematic models to calculate the forces of vertical and deviated well were established.At the same time,the model to calculate the fatigue life was also established.The stress intensity factor of different cracks was calculated in this paper,and developed correspond software,which can succeed in predicting of service life of sucker rod with initial crack or without initial crack.The Forman model is used to predict the fatigue life,compared to the Paris model,the stress ratio is taken into account,so the result is more exact than Paris model,and can get following result,the initial length of the crack has a great affectation on the life of the rod,and it is easy to calculate the fatigue life of rod exactly.