Evolution of Deformation-Induced Surface Morphologies Developed on Fe-based Sheet Metal
Mark R. Stoudt, Stephen W. Banovic, T -. Quarrick
The complex strain states that exist within a real metal stamping are likely to generate different surface morphologies when compared to the same level of plastic strain produced via single pass deformation. This results in significant inconsistancies when utilizing finite element codes to numerically predict the final surfaces. However, a better understanding of the roughening behavior that results from a single deformation step is necessary before the more complex condition can be properly examined. This study quantifies the surface morphology that develops when a traditional plain carbon steel sheet is deformed under two different, single-pass stretching operations. The results of roughness measurements performed with contact profilometry on the generated surfaces revealed that the deformation tends to be relatively homogenous on a macroscopic level in both biaxial and uniaxial strain modes. The results also demonstrate that the presence of a pre-existing surface roughness has a noticable influence on the roughening behavior at low levels of plastic strain in both biaxial and uniaxial strain. In contrast to the linear roughening behavior observed on a polished surface, a surface generated under identical straining conditions in the as-received condition exhibits a distinct, non-linear roughening behvaior. This non-linear behavior was confirmed with the surface roughness results obtained with a scanning laser confocal microscope (SLCM) that had a highee measurement sensitivity and resolution than the contact technique. As the plastic strain level increased, the roughening behavior adopted a more linear behavior in both strain modes.