Thickness measurement using ultrasonic scanning method for large aerospace thin-walled parts

Wall thickness is one of the most important quality index for those large aerospace thin-walled parts. In industrial site, the ultrasonic has been widely employed for wall thickness inspection, but the measurement process is generally hand-held and point-by-point. Thus, it is time-consuming and large amount of labor for large parts. One problem may arise, how to increase the thickness measurement efficiency. In this research, a wall thickness measurement using ultrasonic scanning of large thin-walled parts is proposed. The isoplanar-based ultrasonic scanning process is modelled to extract thickness and coordinates of the measuring points. To meet the requirements of the normal incidence and the stable control of contacting during measurement, an ultrasonic scanning device is designed. Then, an impedance control strategy is established based on real-time feedback of contact force. During the scanning process, the incident angle was identified based on first-echo energy attenuation, and angleinduced error could further compensated. Finally, on the developed thickness ultrasonic scanning equipment, a large aerospace Aluminium alloy grid panel has been employed to verify the validity of the proposed method.