Coupled multi-physics simulation methods for control of PECM processes with Magnetic-Field-Assistance (MPECM)

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As part of this research project, pulsed electrochemical machining (PECM) with superimposed directed magnetic fields is being researched for the purpose to increase the efficiency of the production process and achieve better local functionalization of the workpiece surface. In the first funding phase of the SPP 2231, the development, evaluation and validation of coupled fluid-dynamics simulation models of the magnetic field assisted ECM and the implementation of measurement strategies to determine the influence of the magnetic fields on the ECM-process were focus of the working program. Based on derived dimensionless numbers and fluid dynamics simulations of the electrolyte flow, an optical measurement system (stereo Particle Image Velocimetry - PIV) was developed and then calibrated. With this PIV-system, an electrolyte flow, which was transferred to the millimeter-scale by utilizing a mesoscale-analysis cell, was measured successfully. In addition to that, numerous ECM experiments with a superimposed magnetic field were conducted. The results of those experiments showed, that a superimposed magnetic field has an influence on the machining process as well as the machining results. Based on the setup of the machining experiments, a transient simulation model of the magnetic field assisted ECM was developed. By calculating the ion species transport influenced by the interactions between the fluid-dynamic, thermodynamic and electromagnetic fields in the working gap, the material dissolution process was simulated successfully and results showed good agreement in comparison with the experiments. The project´s aim during the second funding phase of the SPP 2231 is the consideration of integral measurement quantities to characterize the process under the influence of transient conditions and to compare the process with simulation models. One essential focus of work is the development and validation of the simulation methods describing the MPECM under the influence of relevant physical mechanisms occurring in different time scales. Mainly, this is the mass- and charge transfer in the working gap and the workpiece formation under pulsed conditions. To evaluate the MPECM-process metrological, a geometric multiscale, optical analysis of the electrolytes properties and resulting process gases will be applied by combining in-situ measurements in a mesoscale-analysis cell and ex-situ measurements in an area downstream of the microscale-analysis cell. Additional experiments will be conducted to characterize the influence of different superimposed magnetic field parameters on the resulting surface properties and localization of the anodic dissolution. At least results from the surface properties measurements, machining parameters and simulation results will be merged and used to prove the MPEC-technology based on a three dimensional EC-sinking process.