Identification of Friction Coefficient in Forging Processes by Means T-Shape Tests in High Temperature

Abstract

In hot metal bulk forming and forging, the interface heat transfer and the friction between the tooling and the billet are of particular importance since they have a significant effect on material flow, deformation, forming forces, component surface finish and die wear. Several authors have used different characterization methods to measure the friction coefficient using cylindrical upsetting tests, ring compression tests, Spike tests and T-Shape tests among others.In the present paper, The T-Shape test has been used in order to measure the friction between aluminium billets and tool steel. In order to obtain the sensitivity of the test, a Finite Element (FE) parametric study has been performed which indicates that shape of specimen could be chosen to measure the friction. For this, compression tests for three specimens in dry conditions have been carried out and shape of specimen has been measured. These measurements and the use of adequate inverse modelling techniques enabled a precise characterization of the forging friction coefficient. Heat transfer coefficient (HTC) has been precisely characterised from the columnar upsetting thermal tests and later used in simulating the T-Shape tests to estimate the friction factor (m). Friction factor has been determined by comparing the experimental results with the numerical simulation results of T-Shape compression test. An encouragingly good agreement has been found between the experimental and numerical results.