A Hydrodynamic Lubrication Theory for Strip Rolling Including Thermal Effects

Abstract

A model of hydrodynamically lubricated cold rolling including thermal and pressure effects on the lubricant is developed in this paper. The hydrodynamic film thickness is calculated as well as the work zone pressure and shear stress distribution for several conditions assuming that the lubricant behaves as a Newtonian fluid. Pressure measurements made with vapor-deposited thin-film transducers on the roll surface are used for experimental comparison.

Numerical and experimental analysis of lubrication in strip cold rolling

“…Therefore the friction coefficient is significantly reduced and the pressure shows a small increase (around 4%) with a less pronounced profile. Dow et al (1975) analyzed the pressure variation in the rolling of steel and aluminum strips and obtained profiles similar to those obtained in this work. …”

“…This is a suspicious assumption since the heat generation by viscous shearing in that zone could not be negligible (Dow et al, 1975), as will be shown in this work.…”

“…Dow et al (1975) stated that it is not necessarily true that films thick enough would be established with low viscosity lubricants if adequate rolling speeds are chosen.…”

“…Wilson and Walowit (1971) combined Reynolds equations and the plasticity theory to define a hydrodynamic theory, but they assumed that the process was isothermal. Dow et al (1975) extended that theory by including the effects of viscous shearing and lubricant heating, but they did not consider the influence of the temperature increase in the work region on the film thickness. Wilson and Murch (1976) presented a thermo-plastohydrodynamic model based on the slab method that included the thermal effects on the film formation in the inlet zone, on the friction and on the variation of the film thickness in the work region.…”

Film Formation Analysis with Starvation in the Inlet Zone of Cold Rolling Interface at High Roll Speeds

“…The findings of these studies are mainly applicable for the low operating speeds (less than 5 m/s). Dow et al 16 22) , Tieu et al 23) and Singh et al [24][25] have investigated analysis of lubricated interface in metal forming by incorporating thermal effects. But no relation/formula has been established by the investigators for the prediction of minimum film thickness (thermal) at high roll speeds (20 , and Louaisil et al 30) have carried out experimentations on cold strip rolling process.…”