再制造抽油杆疲劳寿命评估的磁记忆检测实验研究

Experimental Research on Predicting Fatigue Life of Remanufacturing Sucker Rod by Magnetic Memory Testing

废旧零部件寿命评估一直是再制造工程的技术难点之一。通过对预制沟槽抽油杆试件的拉-拉疲劳实验,利用磁记忆检测仪在线测量试件表面在不同循环次数下的磁记忆信号,研究抽油杆疲劳损伤演化的切向幅值和法向峰峰值变化规律。通过引入李萨如图,表明随着循环的进行所围成的面积由变大到最大后又逐步减小,而非闭合图形面积达到最大时正好对应着宏观裂纹即将发生失稳扩展的临界状态。在此基础上,提出切向法向合成磁场梯度最大值作为预测疲劳寿命的指标,结果表明该特征参数与疲劳循环发展的不同阶段相对应,基于高斯函数拟合建立了其与归一化寿命之间的定量关系模型,可用于抽油杆的疲劳寿命预测。

Fatigue life evaluation of retired parts is always one of the most difficult problems in remanufacturing engineering.Tension-tension fatigue experiments of precut groove sucker rod specimens were conducted,and on-line magnetic memory signals on the surfaces of specimens under different cyclic numbers were measured by magnetic memory testing instrument,and the variation regularities of the tangential amplitude and normal peak-peak value with different fatigue damage were exploited simultaneously.The Lissajous figure introduced shows that the surrounded area becomes larger,the largest and smaller finally,whilst the maximum closure area corresponds to the critical state of macroscopic crack about to unstable propagation.Furthermore,the maximum value of synthetic magnetic field gradient is proposed as an index to predict fatigue life.The results demonstrate that the characteristic parameter can reflect different development stages of fatigue cycles,and the quantitative relationship between the characteristic parameter and the normalized life is established by virtue of Gauss function,which can be used to predict the fatigue life of sucker rods.