Theoretical and experimental investigations on control parameters of piezo-based vibro-acoustic modulation health monitoring of contact acoustic nonlinearity in a sandwich beam

Detection of the rail bolt loosening based on nonlinear ultrasonic

“…where C and m are related to the surface roughness of the material. They can be set to 6 6 10 C   and 0.42 m  for linear elastic steel. Since only the torque of the bolt can be controlled during the actual inspection, it is necessary to obtain the relationship between torque T and pressure p as follows:…”

“…For example, Janette J. Meyer et al [5] evaluated the feasibility of extending impact modulation to bolt joint detection, and proved that the impact modulation method is sensitive to the torque change of bolts joints. Ehsani et al [6] performed sensitivity analysis of various test parameters of VAM to improve the detection capability of the method. Furui Wang et al [7] used a swept frequency method to determine the best signal frequency, and improved the sensitivity of the traditional VAM by replacing the vibration table with a piezoelectric plate.…”