中文摘要：

利用传统超声检测方法或其他无损检测方法难以实现金属初期塑性变形和疲劳损伤的检测。为了解决这一问题,利用基于二次谐波的非线性超声检测方法,研究2024-T4铝合金的初期塑性变形与疲劳损伤缺陷的测试过程;建立非线性高能穿透法超声检测系统,发现超声非线性系数与铝合金残余塑性变形和疲劳损伤程度具有单调相关关系;通过改进试验方法,利用压电晶片的滤波效应,成功减小试样前端非线性的试验来源,提高了检测的鲁棒性。试验结果表明通过利用晶片的滤波效应,选择合适的激励频率能够减小前端仪器的非线性对试验结果的干扰,使基于二次谐波幅值的超声非线性系数能够作为表征铝合金初期塑性变形和疲劳损伤程度的特征参量应用于实际的检测过程。

英文摘要：

Early stage of plasticity and fatigue damage are difficult to detect by using conventional ultrasonic techniques.Nonlinear ultrasonic technique based on harmonic generation has been shown to have the ability to solve the question.A nonlinear ultrasonic high power transmission testing system is developed to detect early-stage plasticity and fatigue damage of Aluminum 2024-T4 alloy.During the test,the nonlinear parameter of the material based on the amplitude of second harmonic is monotonically correlated with the plasticity and fatigue damage of the samples.The experimental nonlinearities are successfully reduced by using the natural filter effect of piezo-electric discs,which makes the experimental method more robust.The experimental results show that the nonlinear ultrasonic technique based on harmonic generation can be used to detect early-stage plasticity and fatigue damage of aluminum alloy.