Error analysis and practice of extrusion force formulas on backward extrusion

At present, the extrusion force formulas used in calculating backward extrusion are all based on the according direct extrusion's, and the friction between the metals and inside of the container is assumed to become zero. In practice, the calculated extrusion force according to these formulas has much difference with the real figure frequently, which can not guide production. The main reason is to neglect the difference of the temperature rice and strain hardening between the direct extrusion and the backward extrusion. Through the experiment, the backward extrusion force formulas were found. The error of backward extrusion force calculated by the formulas is not more than 5%, so it can be applied in engineering calculation.