Punch friction tests for sheet metal forming

Abstract

A previously described tensile strip test which simulates the stretching of sheet over a punch corner radius in a typical draw die was used to compare frictional effects in different sheet materials. Various grades of steel including galvanized samples were tested as well as soft and age-hardening aluminum alloy sheets. The measured friction coefficients varied over a wide range and the experiments illustrate how the straining process over the punch is influenced by both the stress-strain curve of the sheet and its friction characteristics.