Analysis of deformation-induced surface morphologies in steel sheet

The surfaces of strained mild steel sheet specimens were examined with scanning laser confocal microscopy. Rigorous assessments were employed to establish the form of the roughness data. The small deviations from the ideal conditions observed in these assessments indicated that the stochastic process responsible for surface roughening does not conform to stationary, Gaussian, Markov statistics. As physical considerations make violations of the stationary and Markov properties unlikely, it was concluded that even small discrepancies in the Gaussian fit have substantial influences on the quality of roughening behavior characterizations. This also confirms that deformation-induced surface roughness occurs by a small number of statistically dominant mechanisms. Analyses of the mean amplitude (Rq) and spatial distributions both exhibited sharp changes in behavior at approximately 4% strain. Since the physical meanings of the two analyses are independent, it was concluded that this common behavior correlated with a change in dominant roughening mechanism.