A self-excited vibration model based on special elastic vibration modes of friction systems and time delays between the normal and friction forces: A new mechanism for squealing noise

Depending on the configuration of a friction system, one direction of a special elastic vibration of the friction system may be arranged to be identical to the sliding direction while another direction perpendicular to this direction may be arranged to be consistent with the normal direction. This arrangement of the elastic vibration of a friction system plays the same role as the modal coupling of a friction system. In this paper, a model based on a special elastic vibration mode of a friction system was proposed. A new concept of the time delay between the normal force fluctuation and its causing friction fluctuation was introduced to the model. Several simulations were carried out using the model. The simulation result shows that instability vibration can be excited by the time delay. Moreover, a series of tests on the time delay between the normal force fluctuation and its causing friction were performed. The normal excitation frequency was set to 200–500 Hz. The test result shows that the time delay increases with increasing normal excitation frequency. Generally, the time delay in the down stroke of reciprocating sliding is larger than that in the up stroke.