Samenvatting
This thesis discusses the development and evaluation of reliable and generally applicable electrode shape change models and methods for Electroforming (EF) and Electro Chemical Machining (ECM) applications. The development and evaluation of such models requires the normal current density distribution at the electrode surface to be known at each moment. At the same time techniques to change the electrode surface proportional with this current density are required. The current density distribution is the outcome of a set of partial differential equations which represent the electrochemical model. A general class of electrochemical models is described by the Multi-Ion Transport and Reaction Model (MITReM) that can be simplified to the Potential Model (PM) for many practical applications. Methods and techniques for solving the general and simplified classes of electrochemical models are well-known in literature and an important part of these have been developed within the Computational Electrochemistry Group (CEG) of the Electrotechnics Department of the Vrije Universiteit Brussel. This work adds new techniques and algorithms to the existing codes of CEG that account for electrode shape changes in both two-dimensional (2D) and three-dimensional (3D) applications. Within this work two methods have been implemented to simulate these electrode shape changes: the Level Set Method (LSM) and the String Method (SM). While for both methods, the electrode shape change rate is provided by Faraday’s law, they differ both conceptually and through the electrode shape change rate definition. The first method has recently been introduced as a changing boundary technique, but has not yet been used in combination with an electrochemical model to account for electrode shape changes. The LSM naturally allows to deal with topology changes such as electrodes that break apart and/or merge. Within this work the LSM is used for the simulation of 2D electrode shape changes. Despite its poor performance with respect to topology changes, the SM has been used within this work for computing 3D electrode shape changes due to its simplicity and low computation time. To the author’s knowledge, a three-dimensional (3D) electrode shape change algorithm based on the SM has so far not been published in literature. The validity and performance of both the 2D and 3D electrode shape change algorithms are demonstrated with examples found in literature for the copper EF in the vicinity of a singularity (incident angle between the electrode and insulator surface = 180o). 3D electroforming in the vicinity of a singularity, being a square plate electrode contained in an insulating plane, is further presented. An example that deals with 2D copper EF on two parallel conductors of different radii is analysed using both the PM and the MITReM to compute the current density distribution and the LSM to account for the electrode shape changes. Finally the PM is used for the calculation of the electrode shape change rate on the equivalent configuration with finite wires of unequal length.The numerical methods and algorithms developed for the ECM applications are demonstrated for a slot machining of a stainless steel plate, up to the perforation for different kinds of cathode tools using both 2D and 3D electrode shape change algorithms. The 2D and 3D results are compared in a transversal cross-section for different time steps and showed very good agreement.Both the 2D and 3D simulations demonstrate that the developed electrode shape change methods and algorithms can easily be used to analyse and improve EF and ECM processes.
Originele taal-2 | English |
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Plaats van publicatie | Brussels |
Status | Unpublished - 2005 |