Experimental Determination of Material Boundary Conditions for Computer Simulation of Sheet Metal Deep Drawing Processes

Abstract

In solving technological problems related to sheet metal deep drawing with the use of computer tools, the key issue is still the correct determination and entering of boundary conditions to FEM-based software. The procedure for preparing input data for modelling such processes includes geometric data (drawing of tools and material), technological parameters along with the contact conditions between the workpiece and the tools (friction model and type of lubricant) and material properties, in which work-hardening curves are of particular importance. In typical material databases of FEM-based software and designed for computer modelling of deep drawing processes, the properties of only a small number of material grades are available, and commercial software producers charge additional fees for each additional quantity. Those properties that are already in the database are usually devoid of basic information, e.g. related to the state of the material (material after recrystallization, annealing, cold working has different properties). In paper, experimental tests were carried out to determine flow curves based on cold tensile curves for flat samples made of EN-AW 1050A aluminium, Cu-ETP copper, CuZn37 brass and S235JRG2 steel. The investigation used a universal testing machine with a 20 kN pressing force, equipped with specialized Test & Motion software for measuring forces and displacements. It was calibrated and satisfies the metrological requirements for class 0.5. A comparative analysis of the curves determined by the analytical method was carried out. The material models obtained in the experimental tests were used in the computer simulation of the deep drawing processes of cylindrical drawpieces in the ABAQUS software. The results were experimentally verified in terms of comparing the changes in the pressing forces as a function of the displacement of the punch. The re-sults obtained in the research can be used in industrial practice for computer-aided design of cold-deep drawing processes for drawpieces of various shapes from the discussed materials.