Determination of coefficient of friction on a drawing process based on the load required to pass a wire through the straight section of the die

The force required for a forming process has three major components: uniform deformation, friction and redundant work; can be estimated through analytical techniques or by numerical approximation such as the Finite Element methods, but in any case it is necessary to know the coefficient of friction between the working material and the matrix. In this work, the friction coefficient was determined by drawing wire of electrolytic copper, using Upper Bound Method, measuring the force required to move the drawn wire again through the die, in which case there is no plastic deformation and strength applied is needed to overcome friction in the straight section of the die. Two output diameters and two angles of attack were used for each outlet diameter, for a total of four dies. The load was measured both for the drawing and to pass the wire back through the die. Different friction coefficients were obtained on each die, between 0,069 and 0,117, with which it was possible to estimate the burden of drawing with a maximum difference of 8% compared to the experimentally measured load in 75% of the dies.