Effect of fractal parameters on optical properties of cold rolled aluminum alloy strips with induced surface deflection: Simulations and experimental correlations

Cold rollings for Al5182 aluminum alloy strips are carried out to evaluate the optical parameters with the applications of two lubricants and various operating conditions. In order to obtain these optical parameters, the fractal parameters which includes periodic lengths (L-x, L-y) and fractal dimensions (D-x, D-y) in the modified three-dimensional formula for the fractal surface morphology have been solved first for the rolled surfaces. This three-dimensional formula can provide an effective way to correlate these fractal parameters with the optical parameters using TracePro software, which can help to define rolling conditions efficiently for the specific demand of optical properties. The deterministic results for fractal surface simulations using MATLAB in series and 20 incident angle simulation in TracePro software explain that an increase in D-x and D-y will yield dense profiles which elevates the maximum illuminance and lower down the minimum illuminance. While an increment in L-x and L-y would increase the characteristic distance between two predominant asperities and increase minimum illuminance and decrease maximum illuminance. Finite element analyses prove that different friction coefficients in the upper and lower rolls potentially induce surface deflection and thus affect the optical properties. A high illuminance uniformity can be achieved by making a compromise among the fractal parameters (D-x, D-y, L-x and L-y) such that a small difference in the maximum and minimum illuminances is available.