Using matrix methods to characterise the evolution of deformation induced surface roughness in aluminium sheet

Abstract

The deformation induced surface roughness of polycrystalline AA6022-T4 aluminium was evaluated with two different analysis protocols. The first determined the rms roughness R_q with linear roughness profiles to be consistent with literature practice. When plotted against strain, the correlation coefficient indicated an excellent linear fit; however, further analysis revealed the roughening behaviour did not support the literature consensus of a linear relationship between plastic strain and R_q. The second determined R_q by matrix methods. This evaluation demonstrates that when R_q data are acquired via linear profiles, they are strongly influenced by correlations. Conversely, matrix based methods sample all of the data and are unaffected by the presence of correlations. Eliminating the correlations in the profile data produced the same R_q behaviour obtained with the matrix methods. An R_q behaviour that exhibits saturation is more representative of the complexities observed in the plastic deformation process of a polycrystal.