Size effects on material behavior in microforming

The development in a significant way of cold metal forming processes for very small mechanical components is limited by the understanding of geometric and material effects due to size reduction. Cylinder upsetting tests have been used to observe the so-called size effects in microforming. In this study, a set of experiments is performed where the diameter of the cylinder is scaling down from 5 mm to 1 mm. Cylinder upsetting tests were conducted by using a specific tool system for cold forging of micro parts, which have been developed in our laboratory. Compression tests were carried out by reducing the height of the cylinder by 70% at a constant rate of 0.03 mm/s and without lubricant. During the tests, the loading force is measured and the load-displacement curve can be plotted. The material parameters were identified by an inverse method.