非线性声学在材料无损检测及成像中已经获得越来越多的应用。前期的研究结果表明，非线性弹性波谱（NEWS）技术和时间反转（TR）技术的结合可以有效提高缺陷检测的灵敏度和精度，但这两者的结合在Lamb波的检测应用中鲜有介绍。本课题就Lamb波与TR及NEWS技术在缺陷检测及成像中的结合应用展开研究。课题组拟采用实验研究和数值仿真计算相结合的研究方法，对Lamb波的模态转换、时间反转特性、非线性谐波特性等做深入研究；通过对时间反转（TR）技术与非线性弹性波谱（NEWS）技术的两种不同结合方式TR-NEWS及NEWS-TR做对比分析，并对不同的时间反转声学技术：经典时间反转（TR）、反向滤波（IF）及1位（1B）处理技术进行应用，以探讨不同的时间反转技术在Lamb波的非线性裂纹检测及成像中的应用问题，进而完善和发展Lamb波非线性检测及成像理论。

Now, nonlinear acoustic technique has been obtained more and more applications in material nondestructive testing and imaging. Recent researches prove that the combination of Nonlinear Elastic Wave Spectroscopy (NEWS) and Time Reversal Acoustic (TRA) methods can effectively improve the sensitivity and precision of damage detection, however, scarcely researches of Lamb waves application in this combination have been done and presented. The research of Lamb waves in the combination of NEWS and TRA for material defect detection and imaging will be done in this project. The mode transmission, time reversal technique and nonlinear properties of Lamb waves will be investigated by means of numerical simulations and experiments research at the same time. In order to profoundly understand the interaction between the nonlinearity of material and Time Reversal Acoustic (TRA), the research of invariance influence of the TRA introduced by material attenuation will be carried out. In our experiments of Lamb waves, two different kinds of combination applications of NEWS and TR (TR-NEWS and NEWS-TR) will be expanded in material crack detection and imaging. Moreover, the other time reversal techniques, e.g., Inverse Filter (IF) and 1 Bit proceeding (1B) methods, will replace the TR and make some different kinds of combinations with NEWS technique for improving the quality of Lamb waves imaging. Finally, the aim of our research project is to realize the nonlinear time reversal detection and imaging based on Lamb waves application and to enrich and develop nonlinear theory of Lamb waves.