Relations between numerical simulation and experiment in closed die forging of a gear

The improvement of specific metal forming technologies, nowadays includes the use of numerical program packages. One such technology is the radial extrusion of gears and gear-like components in the cold state. This technology is known for its high productivity, achievable high specific strength and low cost per part produced. Improvements of such high technology products can be only achieved by the detailed numerical analysis. Since there is a large number of programs available, it is necessary to carry out the comparisons between the experiment and simulation. One of the commonly used methods is the comparison of experimentally and numerically obtained load–displacement diagrams. Although significant, good accordance of such load–displacement diagrams is insufficient proof of having a good numerical model. In this paper an additional, non-conventional method is used to assess the strain distribution within the workpiece. Though the experimentally obtained strain field was used as a reference, the numerically obtained strain distribution pointed to the highly stressed points, giving a direction to the further experimental examination of strain distribution in greater detail. The result is an improvement of both experiment and numerical model. In the simulation there are inherent non-linearities coming from geometry, strain hardening and friction. In the determination of the strain distribution, a very complex phenomenon of restoration was used. The combination resulted in a model of the radial extrusion that can be used in numerical simulations of similar metal forming processes.