Material characterization for the forming technology
User report - Research Association Metal Forming mbh
Using the indentation method according to DIN SPEC 4864 the strength of the surface layer and the core of components is obtained, small components can also be examined with regard to their material properties. In addition to the tensile strength RIm, the course of the yield point RIp0.2 and the corresponding flow curves are also determined. These parameters can now be used to optimize the forming process of the component through FEM simulation. This results in more precise simulation results and thus potential savings in tool production or tool training.
The Forschungsgesellschaft Umformtechnik mbh (FGU) is an engineering office in the field of forming technology in Stuttgart. As a spin-off company of the Institute of Forming Technology at the University of Stuttgart, the FGU has been networking current science with industry for more than 30 years. One of the focal points of its services is forming simulation. For this purpose, various FEM programs are used to map the processes from solid to sheet metal forming. An essential part of the forming simulation is the representation of the material used in the material model.
Straight in the area of sheet metal massive and solid forming, very small blanks are often used which cannot be characterized by the usual methods such as upsetting test or tensile test. In some cases, preliminary stages of the blank must then be used to obtain blanks of manageable size. However, this can lead to a deviation in the actual material properties, as forming or other process steps are not included in the image. Another challenge is the characterization of gradients in the component, if these components have a hardened surface layer over a relatively small penetration depth.
The indentation method according to DIN SPEC 4864 can be used to characterize very small components well. In addition, the surface layer can be directly examined for its strength. Thus, the simulation accuracy can be significantly improved. Both the comparative tensile strength RIm as well as the RIp0.2– comparative yield strength are determined and offer an added value to the classic conversion according to EN ISO 18265. The resulting flow curve contains the input parameters necessary for the FEM simulation.