Low Speed Mixed Lubrication of Bulk Metal Forming Processes

Abstract

A simple analysis for the lubrication of saw-tooth surfaces with longitudinal lay under conditions of high fractional contact area is developed. This is then coupled with Wilson and Sheu’s asperity flattening model to treat the mixed lubrication of a bulk metal forming process (rolling). It is shown that, even under low speed conditions where the inlet zone does not generate significant hydrodynamic pressures, relatively high hydrodynamic pressures can be generated in the work zone. This explains the persistence of hydrodynamic effects noted in low speed experiments.

A novel multi-scale statistical characterization of interface pressure and friction in metal strip rolling

“…They combined the Wilson-Sheu model [3] of asperity deformation with an average Reynolds equation to take the surface roughness effect on lubricant flow. Chang et al [1,8] used a similar method to study the lubrication of low-speed strip rolling in the mixed lubrication regime, and used a modified Reynolds equation to calculate the normal pressure, hydrodynamic pressure, lubricant film thickness, real contact area and frictional stress. However, most of the analytical models based on the planestrain deformation of a strip require many assumptions.…”

Development of a mixed film lubrication model in cold rolling

“…5, x c is the point at which the plastic deformation is occurred and x b is the point at which the asperities are start flattening. The lubricant thickness in the elastic inlet zone and before the deformation of asperities is given by the following relation [13]:…”

Multi-factor coupling system characteristic of the dynamic roll gap in the high-speed rolling mill during the unsteady lubrication process

“…where H is the nondimensional work zone film thickness, and 00 h is the film thickness in steady state inlet zone [7]. In the mixed lubrication state, the average film thickness t H can be calculated by the full-film lubrication theory…”

“…Due to the vibration of the rolling mill structure, a non-steady-state lubrication and friction will be caused during rolling [4][5][6]. Since the rolling process is one of the most important metal forming processes with large deformations [7,8], it is of great significance to understand the unsteady lubrication [9][10][11][12] phenomenon, and then to build up a more realistic tribological model under a unsteady state process, producing a desirable strategy for vibration avoidance [13,14]. An accurate dynamic model for the rolling process had been developed based on the understanding of the unsteady lubrication mechanism.…”