Design and experiment of array Rayleigh wave-EMAT for plane stress measurement

The Rayleigh wave excited by the electromagnetic acoustic transducer (EMAT) is an effective selection for surface plane stress measurement. However, the propagation velocity of Rayleigh wave on the metal surface is easily affected by the original rolling process. Besides, the direction of the plane stress state is usually unknown, which means that the propagation velocity cannot be expressed linearly by the stress. As a result, the traditional measurement model of one transmitter and one receiver can only realize the decouple of plane stress components by rotating method, which not only brings position error but also low measurement efficiency. Therefore, this paper focuses on a novel Rayleigh wave-EMAT for plane stress ultrasonic measurement. Firstly, the Rayleigh wave measurement model is established based on the acoustoelastic equation and displacement expression. Furthermore, an array Rayleigh wave-EMATintegrating three transmitters and three receivers is designed. Finally, the typical plane stress state of 5052 aluminum alloy plate after friction stir welding (FSW) is measured. The experimental results show good agreement compared with the hole-drilling method, which verifies the effectiveness of proposed method and designed EMAT.