A novel analysis model for friction-induced vibration coupling microscopic contact characteristics and system structural parameters

The microscopic topography of friction surfaces and system structural parameters are both critical factors influencing the characteristics of friction-induced vibration (FIV). However, no existing analytical model for FIV has incorporated these factors. To address this issue, we developed a novel coupled model to explore the combined effects of surface microscopic topography and structural parameters on the FIV characteristics. Furthermore, we conducted two friction-induced vibration and noise (FIVN) simulation experiments to validate the conclusions derived from the numerical simulations. The results showed a strong correlation between the microscopic surface morphological parameters and the friction surface's contact properties. A higher fractal dimension increases contact stiffness, whereas a larger fractal scale factor reduces contact stiffness. The contact damping initially increases and then decreases with changes in the fractal dimension. The surface microscopic parameters significantly affect the modal coupling characteristics and FIV. In a certain range of fractal dimension, modal coupling takes place in the friction system, and with an increase in the fractal scale factor, the region of system instability also grows. FIVN simulation experiments showed that smoother friction surfaces tend to result in high-intensity FIVN. Regarding the structural parameters, when the contact interface has a large fractal dimension and scale factor, structural changes do not significantly affect the system's modal coupling. However, when these parameters decrease, structural parameters exert a more substantial influence on modal coupling. In particular, when both the fractal dimension and scale factor are small, a reduced block thickness does not affect system stability, and FIV also minimal. As the thickness increases, modal coupling and unstable vibrations emerge in the system. Thus, for new brake pads with large block thicknesses, such as those used in high-speed trains, increasing the fractal dimension and scale factor of the friction surface is recommended to reduce high-intensity FIVN in the saturation stage.