An optimal forward extrusion device proposed for numerical and experimental analysis of materials tribological properties corresponding to bulk forming processes

This paper concerns the design and the analysis of an optimal forward extrusion die used in order to characterize and to identify the tribological properties corresponding to real contact conditions, which occur during bulk plastic forming processes. The main idea is to find the friction parameters by a two-step inverse analysis method applied to a finite element model of the extrusion process. A compression test, using a special dumbbell specimen, is also performed in order to describe correctly the real rheological behaviour of the material. Experimental upsetting and extrusion tests are carried out for an AA5083 aluminium alloy and the corresponding rheological and friction coefficients are identified using only the recorded load–stroke curves. Experimental analysis of the contact surfaces, validation of the obtained results and influence of the friction on the local mechanical and microstructural properties of the material are performed via tribometer tests, micro-hardness measurements and EBSD characterisation.