Detection of a second harmonic ultrasonic component generated from a fastened bolt using a double-layered piezoelectric transducer

Abstract

This paper investigates the use of ultrasonic second harmonic components in the quality control of bolt fastened structures. The second harmonic components from a fastened bolt were detected using a double-layered piezoelectric ultrasonic transducer (DLPT). The fundamental ultrasonic pulse waves (1MHz) are transmitted when the DLPT is electrically connected in parallel, while the second harmonic ultrasonic components (2MHz) are detected when the DLPT is connected in series. A hexagon head bolt (the diameter and length of the screw are 12mm and 100mm) was used in the experiments. The bolt was fastened by a torque of 40N-m. The second harmonic component increased by approximately 10dB before and after the bolt was fastened.