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Multiphysical Problems

Development of an efficient methodology for predicting the dissolution during electrochemical machining of metals

Gepulste elektrochemische Bearbeitung

Electrochemical machining (ECM) uses chemical reactions to dissolve material from the surface layer of a structural component. This particular type of non-conventional machining avoids unwanted microstructural changes in the surface, such as the formation of dislocations. This makes ECM a promising processing technique for high-strength materials. In order to model the complex chemical reactions in a computationally efficient way, an inner variable is introduced that describes the degree of dissolution of the material. The evolution of the internal variable is formulated based on Faraday's law of electrolysis. Furthermore, the use of an effective formulation of the necessary material parameters allows the homogenized description of the dissolution process to be considered within an electrical finite element framework. Each effective material parameter is a result of classical mixture rules.

In cooperation with:

  • Stefanie Reese (RWTH Aachen University / University of Siegen)
  • Andreas Klink (RWTH Aachen University)
  • Daniela Zander (RWTH Aachen University)
  • Christian F. Niordson (Technical University of Denmark)

References:

  • van der Velden, T., Ritzert, S., Reese, S., & Waimann, J. (2023). A novel numerical strategy for modeling the moving boundary value problem of electrochemical machining. International Journal for Numerical Methods in Engineering, 124(8), 1856-1882.
  • van der Velden, T., Rommes, B., Klink, A., Reese, S., & Waimann, J. (2021). A novel approach for the efficient modeling of material dissolution in electrochemical machining. International Journal of Solids and Structures, 229, 111106.

Mechanical and thermo‐mechanically coupled process simulation

In order to enable a mechanism-oriented analysis of the relations between manufacturing processes and the resulting material modifications at the surface of a workpiece in classical metalworking processes such as deep rolling, we have been working within the SFB/TRR 136 on the highly resolved simulation of mechanically and thermo-mechanically coupled processes. The basic assumption is that the loads present in the material during the process are responsible for its response in the form of a modification. This mechanism-oriented approach to the interaction of manufacturing processes with the material is scientifically new. In the future, it should enable manufacturing processes and process chains to be selected and adjusted in a targeted and knowledge-based manner with regard to the desired surface properties of the workpiece in order to enable a sustainable and resource-conserving production.

In cooperation with:

  • Bob Svendsen (RWTH Aachen University / Max-Planck Institut für Eisenforschung, Düsseldorf)
  • Stefanie Reese (RWTH Aachen University / University of Siegen)
  • Jens Sölter (University of Bremen)
  • Rainer Fechte-Heinen (University of Bremen)

References:

  • Schmidt, A., Gierden, C., Fechte-Heinen, R., Reese, S. & Waimann, J., (2025). Efficient thermo-mechanically coupled and geometrically nonlinear two-scale FE-FFT-based modeling of elasto-viscoplastic polycrystalline materials. Computer Methods in Applied Mechanics and Engineering, 435, 117648.
  • Gierden, C., Kochmann, J., Waimann, J., Svendsen, B., & Reese, S. (2022). A review of FE-FFT-based two-scale methods for computational modeling of microstructure evolution and macroscopic material behavior. Archives of Computational Methods in Engineering, 29(6), 4115-4135.
  • Gierden, C., Kochmann, J., Waimann, J., Kinner-Becker, T., Sölter, J., Svendsen, B., & Reese, S. (2021). Efficient two-scale FE-FFT-based mechanical process simulation of elasto-viscoplastic polycrystals at finite strains. Computer Methods in Applied Mechanics and Engineering, 374, 113566.

A coupled model for the evolution of size and chemical composition of volcanic crystals

volcano

In the lower magma reservoirs of volcanoes olivine crystals are formed. These crystals grow as they rise into the higher magma reservoirs until the volcano erupts. Diffusion chronometry is used to understand the diffusion history of the olivine crystals in volcanic eruptive products. However, the timescales which can be accessed by diffusion chronometry are restricted by recrystallization. While it has been shown in both experimental and field observations, the coupling of mechanical and chemical processes has not been explored in a quantitative framework yet. A new material model is developed, which takes the coupling of mechanical and chemical processes into account to describe the evolution of magnesium-based forsterite crystals exchanging iron as a fayalite component from the initial growth phase until the point of recrystallization.

In cooperation with:

  • Sumit Chakraborty (Ruhr-Universität Bochum)

References:

  • Haddenhorst, H. H., Chakraborty, S., & Hackl, K. (2023), A model for the evolution size and composition of olivine crystals. PAMM, 23(4), e202300081.