| Summary: | 碩士 === 國立成功大學 === 機械工程學系 === 107 === Cold rollings for the Al5182 aluminum alloy and CQ steel strips are carried out for the purpose of improving the reflected illuminance parameters and the reflection uniformity due to the uses of lubricants and the changes in operating conditions. A three-dimensional (3D) fractal model is developed through the extension of the two-dimensional (2D) Weierstrass-Mandelbrot (W-M) model for the morphologies of rolled and roller surfaces. A numerical scheme is developed in this in this study for the morphologies of roller and rolled surfaces in order to determine the solutions of the periodic lengths, Lx and Ly, and fractal dimensions, Dx and Dy, in the x and y directions, which are the parameters existing in the 3D W-M fractal model. This 3D fractal model in combination with the “TracePro” software is able to have the reflection light tracking simulations for the rolled surfaces with different deflection angles (θ) after rolling. The simulational reflection distribution fraction (RDF) for an incident angle of 20⁰ is obtained for Al 5182 to compare with that shown in the experimental one in order to prove the trustworthiness of this 3D fractal model. For Al 51825, an increase in θ of rolled specimen can reduce Dx and Dy slightly but increase Lx and Ly significantly; an increase in either Dx and Dy can elevate the maximum illuminance ((IL)max), but lower the minimum illuminance ((IL)min); the illuminance uniformity is reduced by increasing either Dx and Dy to be sufficiently large; Lx and Ly created in the specimens with a relatively smaller θ are shorter than those formed in the specimens with a relatively large θ; (IL)max is a value determined to be dependent on the θ value; however, (IL)min is always lowered by increasing either Lx or Ly, irrespective of the θ value; Increasing Dx, Dy, Lx and Ly can result in a reduction of the illuminance uniformity (Un); a specimen with a relatively larger θ can result in a higher uniformity; increasing the ((IL)max–(IL)min) value in the specimens with a small θ may result in a reduction of illuminance uniformity; increment in either of Lx, Ly or decline in either of Dx, Dy can increase the glossiness. For CQ steel, an increase in reduction ratio or fractal parameters, Dx, Dy Lx, and Ly of roller surface can result in higher Dx, Dy, Lx, and Ly values of rolled surfaces; decrease in Hersey number causes a minor decrease in Lx and Ly, but increases the Dx and Dy values of specimens; an increase in the Dx, Dy or a decrease in Lx, Ly can raise the (IL)max and lower the (IL)min of specimens; Un can be elevated by either decreasing Dx, Dy or increasing Lx, Ly of specimens; Un can be reduced by increasing the (IL)max or decreasing (IL)min; an increase in the reduction ratio of specimen causes a decrease in ferrite intensity and increase the austenite and cementite intensity which causes an increase in hardness (HRB) of rolled specimens. However, no significant correlation was found between reduction ratio and Young's modulus.
|
|---|
