Bolted joints are widely applied in engineering structures. Significant advantages of bolted joints are that they can be easily disassembled and the possibility to design for bearing large working load. However, in practical applications, preload loss in pre-tensioned bolts is inevitable. Reliable detection of bolt loosening is significant to ensure structural reliability and safety. In the past decades, the guided wave-based structural health monitoring (SHM) methods have been developed for the detection of bolt loosening, and considerable advancements have been made in this area. This chapter presents a review of the existing studies on bolt preload monitoring method based on guided wave. The basic principle and characteristics of the typical methods are discussed, which involve wave energy dissipation, time reversal guided wave, contact acoustic nonlinearity, and active chaotic ultrasonic excitation-based methods. In addition, this chapter presents an experimental comparison of the detection sensitivity of wave energy dissipation and time reversal method. The results show that the TR method is more sensitive to bolt loosening.
Part of the book: Structural Health Monitoring from Sensing to Processing