Review and comparison of empirical friction coefficient formulation for multibody dynamics of lubricated slotted joints

In recent times, many industrial applications have demanded innovative energy-efficient solutions. One of the main causes of energy loss is due to friction between body surfaces in contact. A great amount of research has been aimed at understanding the friction mechanisms to allow for its reliable prediction during multibody simulation. In the 1950s and 1960s, many experimental studies were carried out, leading to the coefficient of friction formulas for lubricated surfaces under a combination of sliding and rolling relative motion. The formulas have been mainly derived by the mathematical fitting of results obtained from experimental measurements on rolling disks and different load, lubricating and kinematic conditions. The purpose of this paper is twofold: on the one hand, it reviews semi-empirical formulas for computing the friction coefficient in lubricated contact under various operating conditions; on the other hand, it implements and compares contact force models coupled with the metal-metal lubricated empirical friction formulas in a multibody dynamics simulation environment. Implementing empirical formulas is straightforward and computationally efficient, but one can evaluate the performance of these models in characterizing the dynamics of the lubricated joint. For this purpose, a multibody simulation of a Scotch yoke and a Whitworth quick return mechanisms with a nonideal prismatic joint are conducted. The existence of clearance causes the dynamic behavior of the system to be different from the ideal joint. The difference between each friction coefficient model is emphasized by simulation output and computation time.