Thermomechanical material behavior

In the field of thermomechanical and mechanical material characterisation, flow properties of metallic materials are characterised at different temperatures, degrees of deformation and strain rates. These are determined by means of compression or tensile tests. Various testing machines like the GLEEBLE 3800-GTC are available at the Institute for Forming Technology and Machines (IFUM) and can be used to determine temperature- and strain-rate-dependent characteristic values of metallic materials. Using the experimental data flow curves are calculated and used to parameterise various material models. Hence, realistic calculations of workpiece and die behaviour in forming processes are possible.

In addition, hydraulic cupping test (bulge test) can be used with an optical measuring system (GOM Aramis). The tests are carried out according to EN ISO 16808 and used to determine biaxial stress-strain curves and flow curves at high plastic deformation. By means of this characterisation procedure, an extension of the flow curve recorded in the tensile test up to the uniform strain can be realised by means of conversion to the uniaxial stress state. This proven procedure allows a more accurate extrapolation of the flow curves. The improvement of the material characteristics ensures an improved simulation and design of sheet metal forming processes.


The automotive industry is striving to reduce weight in order to lower fuel consumption. This leads to the development of high-strength steel grades and lightweight materials such as aluminium. In addition to reducing density, this means that the properties of conventional steels must at least be replaced or ideally even exceeded. Within a processed project the forming behaviour of a novel ultra-high carbon (UHC) lightweight steel was investigated. In addition to extrusion tests, a comprehensive material characterisation was carried out. The temperature-, strain- and strain-rate-dependent flow behaviour was determined. Furthermore, ring compression tests were performed to identify the temperature- and tooling-dependent friction factors. The results were used as for a material model to perform numerical simulations to develop the tool system for piston pin extrusion. Furthermore, this work provides a basis for forming high strength and ultra-high-strength steels that are difficult to process and can be applied to metals with similar properties.

„Fabrication of piston pins made of a novel aluminium-alloyed UHC steel”

Bernd-Arno Behrens, Alexander Chugreev, Mohammad Kazhai, D. Yarcu, Chistoph Büdenbender, Roman Relge (2019); International Journal of Advanced Manufacturing Technology, Volume: 102, Issue: 9-12, Pages: 3781-3789