Mechanics of surface roughening in metal forming processes

Inspection of 1100-H14 and 5052-0 aluminum alloy surfaces deformed in tension, sheet forming, and rolling with a thick lubricant film indicated that similar mechanisms were involved in the roughening process. The predominant mechanism was associated with the orientation of slip systems in adjacent grains leading to mismatch strains at the grain boundaries. The emergence of slip planes played a lesser role in the roughening process. A roughening model that assumed a spatial hardness variation was developed. Theoretical predictions of the dependence of the R-a surface roughness with bulk strain, based on micro-hardness measurements, show excellent agreement with experiment.