Quantification of roping in aluminium sheet alloys for car body applications by combining 3D surface measurements with Fourier analysis

Abstract The present study introduces a new method to characterise and evaluate the roping behaviour of aluminium sheet alloys of the AA 6xxx series for car body applications. The new approach combines two known methods into a novel powerful tool, (i) the measurement of a 3D surface topography with a white-light interferometer and (ii) the subsequent data analysis by means of Fourier analysis. Use of the white-light interferometer allows analysing roping of deformed samples without the need of additional surface preparation steps, e.g. inking, stoning, etc., which may falsify the surface appearance. The use of data analysis by means of fast Fourier transform allows differentiating between different surface phenomena, e.g. unidirectional component versus isotropic components. It was found that the new approach is capable of giving reliable and reproducible data, which qualifies this method to study roping in aluminium car body sheets in an objective manner.

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