Effects of fastener load on wave propagation through lap joint

Experimental results on the propagation of guided waves through a bolted joint under various bolt load values are presented. Piezoelectric wafer active sensor (PWAS) transducers are used for the generation and reception of the guided waves. Two specimen types are used, a strip lap joint and a plate lap joint. The signals measured under various bolt load values and frequency values are studied in order to identify relevant features that change drastically with bolt load. We found that some of the signals, especially those at S0 tuning frequency of 320 kHz, were very much simplified by the change from strip to plate conditions. The main contribution of this paper to the advancement of the state of the art consists in highlighting the need for removing the confounding effects of the strip side reflections on the correct interpretation of guided wave changes as they travel through a lap joint with various fastener loads.