A New Method of Evaluating Metal-Working Lubricants

When two identical penny shaped disks mounted one above the other are upset simultaneously in uniaxial compression, they deform differently if friction on the upper die surface may be covered by a thin film of teflon which results in essentially zero friction there while the lower die surface corresponds to a lubricant-die material-work material combination to be evaluated. After deformation, the thickness of the upper disk at its center (h₁) will be less than the central thickness of the lower disk (h₂) if friction on the lower die surface is greater than on the upper die surface. The ratio h₁/h₂ provides a sensitive measure of the difference in frictional resistance on the upper and lower die surfaces and may be used to evaluate different lubricant-die material-work material-die finish combinations for different degrees of reduction. Representative experimental results are presented and discussed.