The Influence of Bulk Plastic Flow on Lubricant Permeation from Micro Oil Pits in Metal Forming

An analysis of the oil permeation from micro oil pits under the influence of bulk plastic flow has been developed. A series of rolling experiments was conducted and the experimental results were analyzed. It is found that the bulk strain rate can reduce the resistance of asperity to permeation and change the surface finish significantly. The influence of strain rate on the nondimensional specific permeation flux, which is defined as the permeation flux per unit relative sliding velocity and width of oil pit, is also studied. The average nondimensional specific permeation flux increases rapidly with increasing strain rate. For small reduction where the interfacial pressure is small, it is easy for the lubricant to seep into the contact area. The nondimensional specific permeation flux is therefore higher for smaller reduction and is saturated when the strain rate becomes sufficiently high.