Analysis Of The Stick-Slip Motion Characteristic Induced By Rotary Friction

In this paper, the engineering structure formed by the contact of the rotary body and non-rotary body is regarded as research object, the stick-slip vibration laws of the non- rotary body induced by rotary friction are analyzed when the rotary body rotates at low speed. And the main factors influencing the amplitude and period of the stick-slip vibration are discussed. This paper aims to provide theoretical evidence to utilize the friction and to seek for the effective means of reducing the friction. The main contents are as follows:(1) The non-rotary body is simplified as the cantilever beam with an concentrated mass at the free end, in the case of the small deformation of the cantilever beam, its vibration laws in the y direction are studied. Then by the calculation and simulation, the conclusion was drawn that the motion of the mass is the periodic stick-slip vibration, the cantilever beam's certain bending deformation position is the equilibrium position of this periodic vibration. At first, the mass sticks to the rotary body, then it slips in the direction of the stick motion, at last it slips in the opposite direction. The mass repeats the motion mentioned above, until the rotary body stops rotating or the mass breaks away from the rotary body. Decreasing the static friction coefficient, increasing the rigidity of the non-rotary body, slowing down the speed of rotary body, shortening the distance between the rotary body's axis center and the initial contact point of the non-rotary body and rotary body ,all can reduce thevibration induced by rotary friction.(2) The theoretical analysis and simulation of two-dimensional unconventional stick-slip vibration of the non-rotary body induced by the rotary friction show that this stick-slip vibration is different from the vibration induced by friction between the normal contact surface, the non-rotary body vibrates in x and y direction during the sticking and slipping. The motion finally become steady as the periodic stick-slip vibration in which the non-rotary body vibrates along certain invariable curve and the vibration's equilibrium position is the non-rotary body's certain bending deformation position .Increasing the rigidity of the elastic pole, the amplitude of the vibration decrease, decreasing the static friction force and the kinetic friction force can shorten the time of the mass's periodic motion along certain invariable curve.(3) The two-dimensional stick-slip vibration law of the system with viscous damping is similar to the undamping system, because of the damping, the amplitude of the stick-slip vibration increase obviously, but the non-rotary body get into the stabile stage of vibrating along certain invariable path quickly.(4) The rotary body and the stepped cantilever beam with an concentrated mass at the free end are considered as research object, the stick-slip vibration law of the stepped cantilever beam in y direction is analyzed, the analysis and simulation results indicate that while the total length of the cantilever beam is constant, increasing the length of the beam near the fixed end can suppress the vibration effectively, in the case of the cross-section moment of inertia of the beam near the fixed end is greater than that of the beam near the free end, it is helpful to reduce the amplitude and period of stick-slip vibration to increase the cross-section moment of inertia of the beam near the free end.