金属材料表面残余应力超声测量方法

Surface Residual Stress Measurement of Metal Material Using Ultrasonic

针对金属材料零件制造中的表面残余应力无损检测难题,提出一种平面应力状态超声测量方法。基于线弹性理论,引入晶粒取向表征因子,揭示晶粒取向对超声传播的影响机制。虑及材料力学性质(弹性常数、晶粒取向等)和应力状态对声速的共同影响,建立平面应力分量-声速解耦模型。基于临界折射纵波(LCR波)表面应力测量原理,分析温度与耦合状态对超声信号衰减、畸变以及声时的影响规律,并设计出一种一发双收直接耦合造波探头。以单向拉伸的变截面铝合金板和搅拌摩擦焊后的轧制铝合金板为典型对象,利用自主开发的超声应力测量系统进行表面应力测量试验,分别与有限元法和小孔法进行对比,应力测量结果具有良好的一致性,可为金属材料表面残余应力测量提供可行方案。

To measure the surface residual stress using non-destructive testing method for the metal parts during manufacturing process is still a difficult problem. A plane stress state measurement method using ultrasonic is proposed. The characterization factor of grain orientation is introduced based on linear elasticity theory. And the influence mechanism of grain orientation on ultrasonic propagation is revealed. Considering the joint effect of material mechanical properties(elastic constants, grain orientation, etc.) and stress state on acoustic velocity, a plane stress component-acoustic velocity decoupling model is established. The effect of temperature and coupling state on ultrasonic attenuation, distortion and time-of-flight is analyzed based on longitudinal critically refracted(LCR) wave surface stress measurement principle, and a "one-transmitter-two-receiver" direct coupling wave-generation probe is designed. The variable cross-section aluminum alloy plate under uniaxial tension and the rolled aluminum alloy plate after friction stir welding are taken as typical objects. The surface stress measurement experiment is carried out by using the self-developed ultrasonic stress measurement system. The results of stress measurement are in good agreement compared with finite element method and hole drilling method, which provides a feasible solution for surface stress measurement of metal materials at the manufacturing site.