薄板残余应力电磁超声高阶Lamb波的检测方法研究

航空航天装备蒙皮类薄板中的残余应力直接影响材料的成型和性能。在役薄板构件因残余应力而导致变形失效的案例屡见不鲜。基于体波声弹性效应的临界折射纵波法是广泛应用的超声残余应力检测方法，然而薄板结构中激发体波较为困难。利用超声Lamb波对薄板构件进行残余应力测量，高阶模态的Lamb波应力检测灵敏度相比体波更高，但针对残余应力的高阶模态Lamb波检测理论与技术研究鲜有报道。本项目提出利用高阶模态Lamb波表征残余应力的新方法，主要研究内容包括：（1）多参量高阶Lamb波频散理论。建立包含应力、织构和温度参量的Lamb波频散方程，揭示不同Lamb波模态的传播规律，提出应力的Lamb波检测与表征方法；（2）单一高阶模态Lamb波EMAT的研制；（3）声时测量中多参量的分离方法；（4）残余应力的Lamb波检测技术。项目的研究可实现薄板结构残余应力的精确测量，为薄板构件残余应力的无损检测提供可靠技术支持。

Residual stresses in thin plates for aerospace equipment’s skin directly affect the forming and properties of materials. Many cases of deformation and failure existing thin plate members are due to the existence of residual stress. The critically refracted longitudinal (Lcr) wave method based on the acoustic-elastic effect is a widely used method for detecting the residual stress, but it is difficult to generate in the thin plate structure. Measuring residual stresses in thin plates by ultrasonic Lamb waves, the stress detection sensitivity for high-order Lamb wave is higher than that for bulk wave, but there are few reports on the theory and technology about high-order Lamb wave residual stress detection. In this project, a new method by using high-order Lamb wave to characterize residual stress is proposed. The main research contents include: (1) Multi-parameter high-order Lamb wave dispersion theory. Establishing the dispersion equations of Lamb wave including stress, texture and temperature parameters; discussing the propagation characters for different Lamb wave modes, and proposing the method for characterization residual stress by using Lamb waves. (2) Development of single mode high-order Lamb wave EMAT. (3) The separation method of multi-parameters for time of flight (TOF) measurement; (4) The residual stress detection technology by using Lamb waves. The research results of this project can realize the accurate measurement of the residual stress for the thin plate structure, and provide reliable technical support for the nondestructive testing of the residual stress for the thin plate components.