Functional surfaces through adiabatic high-speed processes: Microstructure, mechanisms, and model development FUNDAM³ENT

Project description

High-speed shear cutting (HGSS) is an economically and ecologically interesting alternative to conventional cutting methods such as normal, fine, or laser cutting. HGSS offers great potential, particularly for high-strength and ultra-high-strength steels, but also for light metals, in terms of producing cut surfaces that can be used directly as functional surfaces without further mechanical, thermal, or thermochemical post-processing steps. This is due to the fact that, depending on the materials and the process parameters, adiabatic shear bands (ASB) can form during HGSS, in which the material separation then takes place.

The resulting cut surfaces are characterized by high hardness, low edge indentation, and low roughness, and have virtually no burrs. However, there is still a lack of fundamental understanding of the mechanisms that lead to the formation of ASB in HGSS. This, in turn, is essential in order to be able to make targeted use of the exceptional cutting surface properties described above. The FUNDAM³ENT research group is dedicated to researching the materials and process-related factors that influence the formation of ASB in HGSS in an interdisciplinary consortium.

The overarching goal of the research group is to develop a model based on materials science and process technology that describes shear band formation in HGSS as comprehensively as possible, i.e., for different materials and across a wide range of process parameters.

Important research questions that are being examined in more detail by the research group include, for example, the influence of different microstructural components and the deformation history on the tendency to form shear bands, or the question of whether ASB can also be generated in materials with good thermal conductivity, such as aluminum. Furthermore, research is being conducted into the extent to which the strain rate in the HGSS process determines the microstructure, geometry, and properties of the shear bands, and whether the melting or recrystallization temperature of materials influences ASB formation and the resulting microstructure. Extensive experiments in different strain rate ranges of HGSS (10²–10⁵ s⁻¹) generate comprehensive process knowledge on the one hand and form the basis for a sound understanding of the microstructural effects occurring in the shear band on the other. This is supported by multiscale simulation methods at the microstructural and process level. Systematic investigations of the materials behavior of HGSS cut surfaces under tribological, corrosive, and cyclic mechanical stress enable an examination of the relationships between the shear cutting process, the microstructure, and the resulting cut surface properties.

Fraunhofer IWM subproject:

The Fraunhofer IWM subproject focuses on the development of numerical modeling approaches to describe the formation and propagation of ASB during HGSS and the microstructure development within the ASB. Taking experimental data into account, a fundamental understanding of the mechanisms relevant to ASB formation is to be developed by linking thermo-mechanical and microstructural simulation approaches. From this, a model of ASB formation during HGSS for the materials under consideration is to be developed, implemented, and applied to real processes. This will enable the HGSS process to be better analyzed, evaluated, and understood, and will support process optimization. In addition, it will be possible to make statements about the ASB that forms and the expected properties of the cut edge.