Using DEM method to study graphite migration of copper-based graphite composites during friction

Abstract

The self-lubrication of copper-based graphite composites depends on the formation of a graphite lubricating film on the frictional interface, which results from the graphite migration from the matrix. In fact, the graphite migration process is difficult to observe and record during friction by experimental methods. In our work, a discrete element method (DEM) software “the Particle Flow Code in 2 Dimensions (PFC2D)” was employed to simulate and analyze the graphite migration dynamic process of copper-based graphite composites sliding against 45 steel. The simulation results show that a migrated graphite particle layer was formed on the composite surface during friction, and maintained dynamic equilibrium relied on graphite migration from the matrix. The graphite migration was affected by applied load: the larger the applied load was, the greater the migration depth and number of migration particles were. And the sliding speed has little effect on graphite migration. With increase of graphite content, the migration depth first decreased and then increased, and the number of migration particles increased. With increase of graphite cluster size, the migration depth first decreased and then increased, and the number of migration particles decreased. The simulation results were verified by test analysis on a self-made in-situ observation tribometer, the test results was consistent with simulation results.