Ultrasonic non-destructive evaluation for spot welding in the automotive industry

The pulse echo non-destructive evaluation (NDE) technique has been used within the automotive industry for many years, but this is an offline approach, where tests are carried out after welding. Recent research has been carried out to monitor spot welding online. This paper proposes a portable online, real time, through-transmission, continuous wave ultrasonic non-destructive evaluation system for the monitoring of spot weld quality. The ultrasonic transducers are mounted on the top and bottom electrode arms of the spot welding machine. Results have been achieved that show an increase in received signal amplitude upon formation of the spot weld, but a reduction with the occurrence of splash, indicating a poor weld, when compared to results taken from destructive tests.