Measurements of surface roughness in cold metal rolling in the mixed lubrication regime

This paper describes measurements of the change in surface roughness of alu minium strip due to cold rolling. Rolling is in the mixed lubrication regim e, where there is both asperity contact and hydrodynamic action, The strip is in the as-received condition before rolling, with a continuous spectrum of roughness wavelengths, The spectra of roughness for both the initial and rolled surfaces are used to extract amplitudes for long and short waveleng th components, with an arbitrary division at a wavelength of 14 mu m betwee n these components. It is found that the short wavelength components persis t more than the long wavelength components, and that flattening of the stri p increases with reduction in strip thickness. The qualitative effect of wa velength on flattening is similar to that observed with unlubricated rollin g (Sutcliffe, 1999), and is in line with theoretical models of mixed lubric ation. The effect of reduction is not predicted by existing theories, but i s in agreement with measured variations of friction with reduction.