FRICTION IN METAL FORMING PROCESSES - A STUDY USING EXPERIMENTS AND SIMULATION

Surface texture of the die plays an important role on friction during metal forming. In the present study, unidirectional and random surface finishes were produced on hardened steel plate surfaces. To understand the influence of surface texture on the friction, experiments were conducted using Al-Mg alloy pins that slid against steel plates of different surface texture. In the sliding experiments, a high value of coefficient of friction was observed when the pins slid perpendicular to the sliding direction and a low value of friction occurred when the pins slid on the random surfaces. FE simulations were performed using the measured friction values to understand the stress and strain evolutions of various surface textures. The numerical results showed that the states of stress and strain rates are strongly influenced by friction at the interface, and hence would influence the final material microstructure. To substantiate the numerical results, laboratory compression tests were conducted. Surface textures on the die were attained so as to experience different friction values at different locations. A large variation in the microstructure at these locations was observed during experiments, verifying the hypothesis that surface texture and friction influence fundamental material behavior.