New Proposal to Calculate the Friction in Sheet Metal Forming Through Bending Under Tension Test

There are 6 different types of equations that have been formulated to measure friction through the bending under tension test, however, there is no work to show whether these calculations actually represent what is happening in a sheet metal stamping process. This paper aims to make a direct comparison between the bending under tension test and the sheet metal forming of a test piece to see if the friction coefficient reported by the test is able to predict friction in a real part. Several sources of information were used such as computer simulations, bending under tension test with different sensors and sheet metal forming tests of a cylindrical geometry to evaluate the friction. The results indicate that the equations already developed are not able to accurately predict the friction at the sheet interface and, therefore, a new equation was developed for this that is simpler to measure and presented satisfactory results.