Formability of sheet metals is influenced by the friction between the sheet and dies, which, in turn, depend upon factors such as lubricant, temperature, pressure, sheet and die surface finish, etc. Pacific Northwest National Laboratory’s sheet metal tribology capability allows users to determine the coefficient of friction between metal sheets and simulated die surface at forming-relevant temperatures. This information then can be used to improve prediction accuracy in sheet forming models.
Specimens typically are 1-in. wide × ~460 mm long. Elevated temperatures usually are ~350°C, and temperature uniformity is maintained via a multi-zone furnace. The effect of surface finish can be evaluated by roughening up the roller surfaces against the pulled test sheet. Sheets can be provided as-lubricated or lubricated by hand prior to testing, and the test atmosphere can be air or inert gas. Materials tested include magnesium (Mg) alloys and aluminum (Al) alloys). Other materials also can be tested, depending on the application.
Quantitative values of elevated temperature coefficient of friction, relevant to high-temperature forming, can be obtained for virtually any sheet metal.
Use typically is coordinated with the capability expert and via collaborative funding proposals or contracts.
Name: Aashish Rohatgi
A. Rohatgi, D. Herling, and E. Nyberg, “Characterization of Continuous-cast AZ31B magnesium Alloy Sheets and Lubricants for Warm-forming – Friction Effects,” Magnesium Technology 2010, Eds. S.R. Agnew, N.R. Neelameggham, E.A. Nyberg and W.J. Sillekens, TMS 2010.
R.W. Davies, M.A. Khaleel, S.G. Pitman, and M.T. Smith, "Experimental Determination of the Coefficient of Friction During Superplastic Forming of AA5083 Aluminum Alloy," Proceedings of the International Symposium on Superplasticity and Superplastic Forming, ASM International, Metals Park, OH, 2002.