SURFACE ROUGHENING MECHANISM OF POLYCRYSTALLINE METAL SHEET DURING PLASTIC DEFORMATION. (EFFECT OF STRAIN PATH ON SURFACE TOPOGRAPHY).

Abstract

A surface roughening phenomenon was investigated using commercially pure aluminum sheets deformed plastically along various proportional strain paths. Surface profiles were measured in three directions of a major principal strain epsilon //1, a minor principal strain epsilon //2 and 45 degrees to epsilon //1 direction. The mean value of R//a in the three directions could be expressed by the equation: R OVER BAR //a equals 3. 14 epsilon //d, where epsilon //d is an absolute value of principal strain vector in-plane, independently of the strain path. Both R//a and the wavelength lambda //m at spectrum maximum showed a relatively large difference between epsilon //1 and epsilon //2 direction in the case of the plane strain path, but no significant difference in every direction in the balanced bi-axial tensile path. The anisotropic geometry of surface topography correspond with the direction of the maximum shear stress plane in the bulk metal.