Determination of Frictional Resistances of Deep Drawing Quality Steel Sheets in Bending Under Tension Test

Among many friction tests, the bending under tension (BUT) test simulates the frictional conditions on rounded edge of punch in deep drawing operations. The experimental evaluation of coefficient of friction value has been carried out using a special tribological simulator. Two friction conditions i.e. dry friction and lubrication were analysed. As a test material the deep drawing quality (DDQ) steel sheet commonly used in automotive industry was selected. The mechanical properties of the sheets were selected in the uniaxial tensile test. The experimental results show that the friction coefficient value is very stable after reaching a certain value of sheet deformation. It was found that an increase of rolls surface led to an increase of the sample elongation value at which exists the maximum effectiveness of lubricant. It was also observed that an increase of the amount of sample elongation decreases the sheet surface roughness and friction behaviour changes as a result of high contact pressure and plastic deformation of surface asperities.