TP5: Adjustment of properties for non-rotationally symmetrical sheet components by high-speed blanking

• Applicants: Dr.-Ing. Marlon Hahn, since 10/2024; Professor Dr.-Ing. A. Erman Tekkaya
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins ; Joining and Separation Technology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 460484491

The aim of the project is to describe the influence of the process parameters in high-speed blanking (HSB) on the properties of non-rotationally symmetrical sheet metal components. Methods to influence the component properties systematically by modifying the stress state and simultaneous consideration of the material properties are developed. The properties of the blanked surface are of particular importance. Adiabatic shear bands (ASB) occur with a suitable choice of process parameters and workpiece material. The microstructure in the region of generated ASBs differs from the base material of the workpiece and leads to altered properties in terms of hardness, residual stresses and altered corrosion properties. The research in this project makes it possible to use the blanked surfaces of non-rotationally symmetrical components as functional surfaces. In later project stages, this is extended to general asymmetry. Previous investigations have shown that the quality of the blanked surfaces can be improved by increasing the blanking speed. The improvements concern straightness, roughness and hardness distributions of the blanked surface. Positive properties were particularly evident in the HSB processes with ASB. Shear band occurrence depends on material properties, stress state and thermo-mechanical boundary conditions (strain rate, temperature). In blanking, the imposed thermo-mechanical boundary conditions are largely determined by the process parameters (geometry of workpiece and tool, machine energy, punch speed) and the stress state in HSB. Previous investigations mainly established correlations between blanking clearance and properties of the blanked surface for rotationally symmetrical components (Lode parameter equal to zero). The focus of the project is to influence the stress state in HSB to set the properties of non-rotationally symmetric (Lode parameter differing from zero) components. Components with increasing degree of asymmetry, e.g. with changing radii of curvature, are manufactured by HGSS (blanking speeds up to 10 m/s) for this purpose. The sheared surface properties are determined in cooperation with the other projects and correlated with the stress state. The stress state is determined by finite element simulations, which are validated by strain measurements on the blanked surface. The tools are modified (chamfering of the punch, introduction of an embossing step before the cut, elastomer pad under the part) based on these results to superimpose compressive shear stresses that favor the formation of ASB. The investigated materials are 22MnB5, EN AW-5754, and C60. The relevant properties of the functional surface are hardness, residual stresses, corrosion properties and fatigue properties. The influence of process parameters on the tool life is determined in preparation for a second funding period.

• DFG Programme: Research Units
• Subproject of: FOR 5380: Functional surfaces through adiabatic high-speed processes: Microstructure, mechanisms and model development - FUNDAM³ENT
• Ehemaliger Antragsteller: Professor Dr.-Ing. Till Clausmeyer, until 9/2024