2014 Volume 55 Issue 636 Pages 28-33
A nonlinear friction coefficient model considering contact pressure, sliding velocity, and sliding length has been developed to improve prediction accuracy of the formability of steel sheets. The effects of contact pressure and sliding velocity under the condition of mixed lubrication were estimated using a friction test, in which a long steel sheet was sandwiched between dies and then drawn. The effects of sliding length under the condition of lack of lubricants were estimated using another friction test, in which a long tool bar was sandwiched between steel sheets and then drawn. The results of the cup drawing experiments and FE forming analysis using the friction model developed showed that the model improves the prediction accuracy of the formability of steel sheets determined by monitoring the change inpress load with press stroke and the thickness distribution on the cup wall. Finally, the formability in press motion control with a servo press was predicted with the model developed, and the effects of press motion control on the improvement of the formability of steel sheets were estimated.
