A STUDY OF THE MECHANICS OF WIRE DRAWING WITH A SUPERIMPOSED ULTRASONIC STRESS

SUMMARY Experiments are described which were designed to study the mechanics of load reduction during ultrasonic wire drawing, and to establish under what conditions greater reductions of area may be achieved. The first section describes single-die wire-drawing experiments performed on mild steel, brass and aluminium, with the die oscillating parallel to the direction of drawing at a frequency of 18·7 kHz. Results show that, with the amplitudes of die oscillation used in these experiments, the reduction in mean drawing force can be explained entirely by a mechanism of force superposition, i.e. the reduction in drawing force equals the amplitude of the acoustic force induced in the wire. The second section discusses experiments designed to take advantage of this superposition effect. Mild steel wire was drawn through a three-die arrangement, the centre die being oscillated in the direction of drawing at a frequency of 18·7 kHz. Data obtained shows that, as a result of die vibration, an oscillatory force is induced in the lengths of wire between the dies, and between the last die and the coiler drum. This, together with a back tension effect, produces a genuine reduction in the total drawing force at the coiler drum, and hence shows that, with a multi-die arrangement, greater reductions in area may be achieved without an increase in plasticity or a decrease in interface friction.