基于超声高阶兰姆波的薄板应力测量技术研究

金属薄板结构在加工制造和服役的过程中，通常会伴随着残余应力和外部应力，过大的应力会使薄板产生变形，严重影响整体结构的正常工作。应力状态的评价是判断工程构件是否安全和可靠的一项重要指标，超声应力检测法是一种有效的应力无损测量方法。针对超声应力测量技术对薄板结构应力灵敏度不高且研究较少的问题，提出了一种基于超声高阶兰姆波的薄板应力测量技术。首先，基于Bloch-Floquet边界和域约束的有限元特征频率法，研究了兰姆波各高阶模态的声弹性效应，选取应力敏感的兰姆波模态。然后，搭建超声兰姆波应力测量系统，在特定频率激励A₁模态，并在均匀薄板中进行应力标定。最后，在非均匀薄板中进行应力检测，成功检测出薄板中不同位置的应力，且最大应力误差为15 MPa。结果表明，该文从理论和实验方面验证了超声高阶兰姆波的薄板应力测量技术，可以实现金属板材中的应力准确测量。

Research on Thin Plate Stress Measurement Technology Based onUltrasonic High-Order Lamb Wave

In the process of manufacturing and service of the thin metal plate structure, it is usually accompanied by the residual stress and external stress. Excessive stress will cause the thin plate to deform and seriously affect the normal operation of the overall structure. The evaluation of the stress state is an important index for judging whether the engineering component is safe and reliable, and the ultrasonic method is an effective non-destructive measurement method for stress. However, the current ultrasonic stress measurement technology has low sensitivity and there is little study on it. A thin plate stress measurement technology based on ultrasonic high-order Lamb waves is proposed in this paper. First, based on the finite element characteristic frequency method with Bloch-Floquet boundary and domain constraints, the acoustoelastic effect of each high-order mode of the Lamb wave is studied, and the mode sensitive to stress is selected. Then, an ultrasonic Lamb wave measurement system is built. The A₁ mode at a specific frequency is excited and the stress calibration is carried out in a uniform thin plate. Finally, the stress detection was carried out in the non-uniform thin plate, the stress at different positions in the thin plate is successfully detected, and the maximum stress error was 15 MPa. The results show that this work verifies the proposed thin plate stress measurement technology based on ultrasonic high-order Lamb wave from the theoretical and experimental aspects, and the stress in metal plate can be measured accurately.