Dynamics and lubrication analyses of a planar multibody system with multiple lubricated joints

In order to ensure the mechanical systems a better performance, most of their joints are designed to operate with lubricant. The differently located lubricated joints interact with each other, influencingthe total performances of the system. This study proposes a numerical approach for the multibody system modeling with the consideration of the interactions among the multiple lubricated joints to investigate the dynamics and tribological performances of the mechanism. This approach couples the lubrication model of both translational and revolute joints with the dynamics model of the multibody system, and is performed on a four-stroke gasoline engine with the lubricated piston skirt-liner subsystem and lubricated big-end bearing of the connecting rod. The multibody dynamics model is built with Lagrange's method. The lubrication models are built based on the average Reynolds equation, and solved with finite element method to derive the hydrodynamic forces according to the motion of the system. The piston skirt profile, pin offset and the effects of surface roughness on the lubrication performances are taken into account. The simulation results reveal that there are obvious interactions between the differently located lubricated joints, and the larger clearance can pronounce the interactions.