Experimental Investigation and Simulation of Lead Extrusion Process for Complex Shape

This is an analytical and experimental research study of cold extrusion of lead billets through complex E and X-shaped dies based on the upper bound theorem method, relying on predictive analysis. The purpose of the research is to assess the potential of the upper bound analysis of the determination of critical extrusion parameters, i.e. forming load, pressure, effective strain, and strain rate. A theory of energy dissipation based on theoretically determined kinematically admissible velocity fields was worked out, including the contribution of the internal deformation work, the losses through friction and interface shear. To examine how interfacial friction affects the performance of extrusion, four types of lubrication conditions were taken: no lubricant, red oil, brake oil, and mustard oil. A hydraulic press and precision-machined steel dies were used in the conduct of experimental trials, and data on the forming loads and displacements were measured by hand. The finite element modelling was also used to carry out the extrusion simulation and verification of theoretical assumptions. The results were such that prognostic predictions made using the analysis, the experiment, and the FEM were well matched, and the extrusion load difference was 3.7-6.7 % in reversion. Brake oil, being of the highest viscosity, reduced forming loads consistently in support of the model as regards the lubricant effect on forming loads. The findings substantiate the idea that hybrid analytical-numerical tools are of enormous value in terms of developing concepts of imagination of deformation processes and manufacturing strategy on the industrial level.