The effect of friction reduction in the presence of in-plane vibrations

Abstract

A reduction of friction by vibrations has been observed in various experiments. This effect can be applied to actively control frictional forces by modulating vibrations. Moreover, common methods of controlling friction rely on lubricants and suitable material combinations. The superimposition of vibrations can further reduce the friction force. This study presents a theoretical approach based on the Dahl friction model that describes the friction reduction observed in the presence of the tangential vibrations at an arbitrary angle. Analysis results indicated that the tangential compliance should be considered in modeling the effect of vibrations in reducing friction. At any vibration angle, the tangential compliance of the contacts reduces the friction reduction effect. The vibrations parallel to the macroscopic velocity are most effective for friction reduction.

Modeling Friction Performance of Drill String Torsional Oscillation Using Dynamic Friction Model

“…The scale of artificial elements was the micron level; the curvature of the wellbore surface can be ignored. It was determined by the coordinates of points and M [10], where M is the projection of point on the wellbore surface and can be expressed as follows:…”

“…At consecutive instants, the point M changes its relative position and the elastic deformation also underwent a magnitude and directional change. The deformation of the elastic bristle was separated into two phases at any interval Δ [10,12].…”

“…Pohlman and Lehfeldt [6] found that longitudinal tangential vibrations exert a significantly greater influence on the friction force than the normal ones. Papers argued that [7][8][9][10] changes of the friction force vector under the influence of vibrations cyclic are the cause of the reduction of friction resistance. A variable vector of the relative sliding velocity resulted in the force being two components, one of which is parallel and the other of which is perpendicular to the direction of motion.…”

“…Unlike Tsai and Tseng [10], Storck et al [8], or Gutowski and Leus [12], the discretized LuGre model was utilized for the friction model between the drill string and wellbore rock in a well-hole surface. The computational model establishing process took into account difference in the hardness of the friction pair material in the downhole.…”

Kinetic Friction Coefficient Measured in Tribotesting: Influence of Frictional Vibration

“…However, if they are caused by mechanical vibrations induced by friction, i.e., frictional vibration [3][4][5][6], the time-averaged spring force may not give the true value of the kinetic frictional force, except in the case of stick-slip in an undamped single-degree-of-freedom (SDOF) system with the Coulomb friction [3]. Many researchers have reported on the effect of externally applied oscillating forces on the friction coefficient [7][8][9][10][11][12][13][14][15][16][17][18][19], which indicates that even when the instrument-related uncertainty [1,2] is negligible, frictional vibrations generate some other errors in tribotesting, although the mechanisms of forced vibration and self-excited vibration are completely different.…”