Investigation of the frictional damping in friction induced vibration

Abstract

Some phenomena of friction induced vibration can be illustrated using negative damping theory, basing on the assumption that the frictional damping of friction induced vibration is constant. The frictional damping of friction induced vibration, however, has not been investigated in details yet. In order to address this problem, a test rig is developed in this research to provide a constant sliding velocity underneath the block. In order to acquire the frictional damping of friction induced vibration, force and vibration should be measured simultaneously. As Fibre Bragg Grating sensing technology can measure distributed systems simultaneously, it is applied to develop the force sensor and acceleration sensor. The natural frequencies of these two sensors designed by finite element method are much higher than the vibration frequency of the test rig acquired with analytical method, ensuring the accuracy of measurement. The force and vibration are measured by the force sensor and acceleration sensor that connected together via one fibre, and the results show that measured dominant frequencies of force and vibration are consistent at various sliding velocities when the block vibrates steadily. In comparison, the dominant vibration frequencies of the test rig acquired by experimental method are slightly lower than the vibration frequency acquired by analytical method due to the existence of frictional damping at the contact interface. A mathematical method for the frictional damping at various sliding velocities is developed, and the results show that the frictional damping is constant when sliding velocity is beyond a certain value, which can verify the assumption that the frictional damping of friction induced vibration is constant, thus complementing negative damping theory.