The role of lubricating fluid pressurization and entrapment on the path of inclined edge cracks originated under rolling-sliding contact fatigue: Numerical analyses vs. experimental evidences

A 2D Finite Element model of an edge crack has been developed, in which the combined effects of the travelling Hertzian load and the lubricant are accounted for. As the Hertzian load moves over the crack mouth, a transition from fluid “pressurization” to fluid “entrapment” is observed. Pressurization is implemented by applying the external contact pressure acting on the crack mouth to the crack faces. As soon as the external load, despite the internal pressure, is able to close the crack mouth, fluid “entrapment” occurs and the new fluid pressure inside the crack is found by an iterative procedure based on the condition of constant volume. The contribution of fluid entrapment to the SIFs is investigated through an extensive parametric analysis. The FE model was then used to simulate the sub-superficial path of cracks produced in disk-on-disk rolling-sliding lubricated wear tests. The numerical results and the experimental evidences were the base for a discussion on the effect of the lubricant on the crack propagation.