金属构件疲劳微裂纹非线性超声检测

通过对固体非线性超声传播模型的研究,分析了裂纹静态压力与超声波作用力对裂纹超声非线性响应的影响,建立了反映裂纹区应力-应变非线性关系的弹性接触机制超声非线性响应模型以及反映裂纹闭合状态转换的碰撞接触机制超声非线性响应模型。通过实验研究发现,裂纹尖端区的二次谐波激发效率与裂纹的开口区和闭合区及裂纹最终扩展的极限长度有关。因此,可使用二次谐波激发效率作为定量表征金属试件疲劳微裂纹缺陷的特征参数,实验中使用了自主研制倍频双晶复合换能器,这种倍频双晶复合换能器在工程实际应用中更为方便、实用。

Nonlinear ultrasonic test for fatigue crack in metal component

The effects of static pressure of crack,acting force of ultrasonic wave on ultrasonic nonlinear response of crack were analyzed by means of ultrasonic nonlinear transmission model.Two kinds of models were established,such as ultrasonic nonlinear response model based on elastic contact mechanism,which can respond nonlinear relationship of stress and strain,and ultrasonic nonlinear response model based on collision contact mechanism,which can respond crack closed state transition.Experimental results show that secondary harmonic exciting efficiency is associated with the open zone and the close zone of crack as well as the limit length of crack propagation.Therefore secondary harmonic exciting efficiency can serve as characteristic parameter to quantitatively characterize fatigue microcrack of metal specimen.A self-made multi-frequency macle compound transducer was applied in the experiment.The results show that the transducer is more convenient and practical for engineering application.