中文摘要：

通过对固体中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,在此基础上,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。基于上述理论,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作在线检测更为方便、实用。

英文摘要：

On the basis of researching nonlinear ultrasonic transmitting model and analyzing the effect of crack ambient hydrostatic pressure and the driving force of incident elastic waves, Two nonlinear ultrasonic response models are establised. 1） elastic contact mechanism reflecting the relation of stress-strain nonlinear in crack area; 2）clapping contact mechanism induced change of the open/closure part of the crack. The second harmonic generation efficiency from the crack tip area is associated with the open crack and the closed and the limit length of crack propagation by the experiment research based on the theories above listed. Therefore, The second harmonic generation efficiency can be used as the characteristic parameter of tokening quantificationally fatigue micro-crack defect for metal specimen. In the experiment, Multi-frequency macle compound sensor are manufractured, and this sensor is more convenient and applied in practical engineering application.