ABSTRACT
Lubricant film breakdown often leads to galling in sheet metal forming. Adopting a strip-reduction test between flat dies emulates ironing of sheet metals; textured tool design is studied as a method to prevent galling by creating pockets for lubricant entrapment, pressurization and subsequent escapes. A flat table-mountain-like topography was manufactured on tool surfaces with shallow oblong pocket geometries-oriented perpendicular to sliding direction. The textured tool surfaces are therefore studied in a severe tribological condition, the Strip Reduction Test (SRT). The pockets have small angles to the workpiece surface, and flat plateau distance is varied in order to evaluate optimum plateau distance as well as optimum contact area ratio α existing at varying speeds. A theoretical formulation supports the experimental findings, the contribution to friction by mechanical interlocking of the strip in the pockets is limited and lubrication of the plateaus is enhanced by micro-hydrodynamic lubrication.
