Fractal Characteristics of Free Surface Profiles of Metal Sheets under Equi-biaxial Tension

Free surface profiles of aluminum sheets under equi-biaxial tension are examined by employing three kinds of fractal analyses, i.e., the zeroset, power spectrum and box-counting methods. With an increase in plastic strain. long-wavelength components of the surface profiles become dominant, and their fractal structure tends to be constant beyond a certain strain. It is found that the surface roughness and fractal dimensions depend on the equivalent strain, independent of the stress ratio. A method for simulating the surface roughening behavior is presented by utilizing the power spectrum method