Thermo-Elastic-Plastic Behaviors of Vibro-Acoustically Modulated Interfacial Waves in Bolted Joint and Its Application in Monitoring of Early Bolt Loosening

Abstract

The non-monotonic variation of nonlinear intensity of vibro-acoustic modulation (VAM) during the evolution of contact-type damage has been well observed. To enhance the detectability of modulated waves for bolt loosening, a method, which ingeniously makes use of the thermo-elastic-plastic susceptibility of the modulated waves under varying temperatures, is developed, referred to as thermally interfered vibro-acoustic modulation (TI-VAM). The level of the acoustic nonlinearity in the fully tightened joint can be enhanced under higher temperatures and that in low-stress preload can be enhanced under lower temperatures. The nonlinear response from bolt loosening dominates over material nonlinearity, ensuring the sensitivity of TI-VAM in practical applications. With such merit, this method can improve the monitoring of early bolt loosening or detecting other contact-type damage.