Combined physical and numerical simulation in metalforming

Abstract

The plastic deformation of metals in bulk metalforming can be simulated physically (using the model-material technique) and numerically (using large computer-programmes). The advantage of the computer is that calculations regarding strain, stress, forces and temperature gradients, etc., can be done quickly and inexpensively. The required input for the computer concerning the process can be, for instance, filling of the tool, direction of the friction forces and knowledge of the normal pressure between the workpiece and the tool. The disadvantage of the computer is that the above-mentioned data can only be generated in relative simple plane- and axisymmetrical-deformation processes. On the other hand, the advantage of the model-material technique is that it illustrates how the process develops and provides basic parameters: in this way it is relatively easy to obtain the required input for the computer. The objective in this project has been to combine these two completely different methods into a common method of analysis, illustrated here by an example of cold forging. For the cold forging process of extrusion of can and rod the model-material experiment gives information on the filling of the tool, dead-zone formations, ram forces, etc, whilst the computer programme — consisting of a combination of the coefficient and visioplasticity methods — calculates the distribution of strain and stress in the plane of the diameter. To illustrate the accuracy of the method a plane-strain experiment employing a pressure transducer for measuring the pressure at the tool/workpiece interface has been performed: the agreement between the pressure measurements and the calculated pressures is quite good.