ULTRASONIC INVESTIGATION OF FRICTION MECHANISM IN METAL-FORMING

A newly developed friction and lubrication test is used to examine the quantitative relation between real contact area (rca.) and coefficien t of friction in metal forming processes. The first part of the paper will give a description of the experimental set-up. It enables the in- situ ultrasound measuring of the r.c.a. simultaneously to the measurin g of the friction coefficient In the second part the relation between r.c.a. and the coefficient of friction is analysed, using a ring and a closed-die upsetting lest to determine the coefficient of friction, e ach combined with the ultrasound method for measuring the r.c.a..