Detection of the rail bolt loosening based on nonlinear ultrasonic

The rail bolt joint is an important component of railway tracks, which ensure operational safety and vehicle comfort. However, existing non-destructive testing methods fail to accurately assess the severity of the rail bolt joint looseness. A detection method based on Vibration-acoustic modulation was proposed to detect early loosening of the rail bolt joint. First, A single degree of freedom model was established based on the relationship between bolt torque and equivalent stiffness. Then, the looseness index was constructed using the fundamental wave and sideband amplitude. Finally, a rail bolt loosening detection experiment was carried out. Experimental studies showed that the degree of bolt loosening had a significant effect on the frequency amplitude characteristics of the modulating signal. Moreover, the bolt loosening index exhibited staged changed corresponding to increases in bolt prestress, which can be used to identify early loosening of the rail bolt joint.