Influences of upsetting on the propagation characteristic of the elastic wave in the countersunk head riveted joints

Abstract

The countersunk head riveted joints (CHRJ) have extensive use in the aerospace and marine industry. When testing the CHRJ with ultrasonic technology, the signal near the initial pulse cannot be used to detect near-surface defects due to the blind zone of the ultrasonic testing (UT). Moreover, the presence of clutters between the first and second bottom echoes can significantly affect the effectiveness of the UT. Therefore, it is crucial to investigate the propagation characteristic of ultrasonic waves in the CHRJ. The relationship between the interface stiffness and the upsetting length was obtained because of the multi-interface feature of the CHRJ. The propagation characteristic of ultrasonic waves in the CHRJ was investigated using the finite element simulation based on the spring model of the imperfect interface. The simulation results showed that shank echoes would generate at the surface of the rivet shank when the elastic wave propagates in the shank of the CHRJ. The shank echoes would propagate obliquely downward and reflect repeatedly on the surface of the rivet shank. Furthermore, the amplitude of the first shank echo would decrease with the increase of the upsetting length due to the increase of contact stress and deformation. To verify the simulation results, the experiments were carried out using the piezoelectric ultrasonic transducer, and the experimental results matched well with the simulation results. This paper can provide a reference for the ultrasonic testing of defects in the CHRJ.