Evaluation of Friction Coefficient of Stamping

Abstract

Long term, his scientific and research activities are oriented to the field of technological prediction of formability of steel sheets with higher strength properties, testing of material properties of steel sheets, simulation of stamping processes, the evaluation of the technical-economic level of production and engineering products. Prof. Evin was the principal investigator of 4 VEGA and 1 APVV projects, co-partner of several national VEGA, APVV and international scientific research projects and dozens of projects for practice. B.Sc. and M.Sc. degree in the field of Mechanical Technologies at the same university in 2010 and 2012. His current field of interest is focused on the area of sheet metal forming, such as measurement and evaluation of deformation, simulation of sheet metal forming processes.Abstract: This In order to define the friction coefficient the simulator of strip drawn test between flat dies and cup test were applied. To evaluate the coefficient between flat dies the modified Coulumb law was used and for defining the friction at drawing edge of die the modified Ouehler formula was applied. Due to these both evaluation processes it was enabled to point out the difference of friction coefficient values in various contact areas of rolling product and the tool. In his paper there are presented the measurement and evaluation processes of friction coefficient by applying the cup test. For experimental research the following types of materials are suitable: DC 05-extra deep drawable steel sheet, DX 54D -extra deep drawable Zn coated steel sheet, austenitic steel sheet DIN 1.4301.

Verification the Numerical Simulation of the Strip Drawing Test by its Physical Model

“…2B the strip is bent and slides on the drawing die radius. coefficient under the specific combination of blank, die surface, die coating and a lubricant [9][10][11][12]. The tests usually model the material stressing at stamping processes.…”

“…3) -is expressed by b0.rd.a, where b0 is initial blank width). Under the same conditions of stamping -material, lubricant, contact surfaces roughness, normal pressure -the friction coefficients on a flat and rounded surfaces are equal [5,11,12].…”

“…where: b0 -initial blank width, s0 -initial blank thickness, kf -blank flow stress. Since a reacting force at point A is a result of both forces FN and FbA with the same value respectively, the friction force Ff2N between the blank and the die is calculated as follows [5,12]:…”

“…where: Ff1N, Ff2N are friction forces and f1, f2 are friction coefficients between flat dies. When the friction coefficients f1 (blank-holder to blank) and f2 (blank to die) are assumed equal, then the friction coefficient is calculated as follows [5,12]:…”

“…Including the belt friction equation into the calculations, the longitudinal drawing force FL at point A is as follows [11,12]:…”