Abstract
This paper focuses on the roughness evolution and surface topography variation of constrained surface, which is restricted by the mold or tool in the forming process. A crystal plasticity finite element model, which couples the microstructure of polycrystalline, the crystal plasticity constitutive model and the real surface topography of the material, is developed. How to use the real surface of the workpiece as the surface topography of the finite element model is proposed, in which number and location of peaks and valleys on the surface, are accurately captured in the constructed real surface model. The comparison shows that simulation predictions of both the deformed surface topography and the surface roughness agree reasonably well with experimental measurements at various press down ratio of mold. The influences from workpiece and mold on the roughness evolution of constrained surface are comprehensively analyzed. It can be seen clearly that roughness evolution of constrained surface is the combination result of both the surface flattening due to the mold restriction and the surface roughening due to the material inhomogeneity of the workpiece. The lubricant existing in the contact surface of the workpiece and mold should been paid much more attention in the roughness evolution analysis. The influence of the lubrication condition on the roughness evolution of constrained surface is analyzed by combining the CEL finite element method and compression experiments. In deformation stage II of the roughness evolution, the closed cavities begin to form on the surface. Lubricant in the closed cavities plays an important role in limiting the flattening behavior of the surface topography. This paper provides a deeper insight into the comprehensive understanding of the roughness evolution of constrained surface, which contributes to the surface roughness control of plastic deformation products considering the effects of the workpiece, mold and lubrication condition.
NSTL
Elsevier