DEM Simulation on the Startup Dynamic Process of a Plain Journal Bearing Lubricated by Granular Media
Granular lubrication is a promising extreme environment lubrication candidate. Lubricated by granular media, the startup dynamic process of a plain journal is significant to the mechanical performance, which is not well investigated yet. A research model focusing on the startup process of a granular flow lubrication bearing is constructed by the discrete element method. The granules filled in slim gaps extrude and collide with each other, which transfers the force to the shaft and causes instability to the shaft movement. During the movement from rest to stable running position, repeated position mutations of the shaft were found to occur. The variations in axis resistance torque and average unbalanced force are indistinctive, whereas those in average contact force, coordination number, and slip ratio are apparent. In this process, the force interacts within the inner granular assembly, which results in the formation of a force chain network. The breakage and reconstruction of this network can be used to analyze the movement and force variation characteristics. The movement and load tend to stabilize after a certain running period. The results provide a deeper understanding of the unique behavior of the granular-lubricated bearing induced by granular media.
Keywords: Plain Journal Bearing, Granular Lubrication, Discrete Element Method, Startup