DEVELOPMENT OF BEARING FRICTION MODELS FROM EXPERIMENTAL MEASUREMENTS

For a better understanding of the underlying physics involved in friction phenomena, a carefully controlled experimental study is presented in which the frictional forces and dynamic response of a shaft oscillating within a pair of sleeve bearings were monitored and analyzed in order to gain further insight into the basic phenomenological features of bearing friction forces. Through a qualitative review of the data, it is shown that the trajectory of the bearing force versus slip velocity exhibits an hysteretic-type loop super-imposed on Coulomb and viscous actions. Parametric identification techniques are used to develop a simplified mathematical model incorporating an idealized Coulomb friction element. A comprehensive application of non-linear system identification teniques, to extract more quantitative and less obvious characteristics of the measured frictional behavior, is presented. Processing of the data through the use of a time-domain procedure for the identification of non-linear vibrating structures shows that an optimum (in the least squares sense) non-linear mathematical model can be developed to match, with reasonable accuracy, all of the measured response time histories. Furthermore, the mathematical representation of the model allows convenient separation of the contribution of the equivalent linear and non-linear internal forces developed in the physical system. © 1991.