Measurement of friction in a cold extrusion operation: Study by numerical simulation of four friction tests

摘要

The measurement of friction in the industrial metal working operations is a complex problem because the friction test must impose at the tool/metal interface conditions similar to those in the industrial operations. So in the European Network VIF (Virtual Intelligent Forging), a workshop (WP3) was held to evaluate friction condition in cold forging by using numerical simulation and experimental methods. It was chosen an industrial cold extrusion operation, in which a low carbon steel bar, covered with phosphate layer and soap, was drawn, cropped and then formed by extrusion. In order to know the friction condition in this industrial extrusion operation, four kinds of friction tests, forward extrusion, double-cup extrusion, upsetting-sliding test and T-shape compression were carried out in four labs, IPU, DIMEG, LAMIH and CEMEF, respectively. In a first preliminary step we simulate the drawing and extrusion operations in order to estimate the contact conditions in extrusion along the container and the die surfaces. Then by numerical simulation we estimate the contact conditions in the friction tests and define the parameters of the tests which insure the better similarity with the industrial operation. In the next step experiments will be performed in order to compare the results of these various friction tests.