Grease film variation in reciprocating sliding motion

In this study, optical interferometry experiments were carried out to investigate the grease film distribution over long working periods in sliding reciprocating motion. In the experiments, the ball was stationary while the glass disk was sliding in a triangular wave or a rectangular wave. Due to the existence of the thickener fiber, in the first several working periods, the variations of the film shape in the first and second stokes are different. With the increase of the period, the starvation effect gradually emerges, together with the occurrence of the grease replenishment. Thus the variations of the grease film in both strokes are similar. For the same sliding speed vmax, the replenishment is more drastic for a rectangular wave and the minimum film thickness is a little thicker.