Acoustic emission investigations into electrical discharge machining

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Electrical discharge machining (EDM) is a precision material removal process that utilizes the heat generated from rapid (~20-100 kHz) spark discharges between the tool and the workpiece that are separated by a small gap filled with a dielectric fluid. A single discharge entails 4 distinct stages: (1) application of a voltage between the tool and the workpiece, (2) dielectric breakdown leading to plasma formation, (3) discharge between the tool and the workpiece leading to the flow of a current resulting in melting and vaporization of both the tool and the workpiece, and (4) implosion of the plasma channel that ejects material off the molten pool, followed by flushing and solidification of the molten particles. The physics involved in the gap phenomena above are rather complex and currently not well understood. In this context, the proposed research program seeks to develop a simple but novel approach to investigate acoustic emission (AE) in EDM.