Measurement of Deformation Behaviour near Discharge Point by using Optical Fiber Sensor

Abstract

Recently, electrical discharge machining (EDM) is widely used for manufacturing various kinds of die and molds. However, the mechanism of material removal in EDM has not been sufficiently clarified. In order to clarify the mechanism of material removal, the transitions in the melted and vaporized regions should be precisely examined as well as the transitions in the impulsive forces acting on a work. We attempted to examine the mechanism by measuring the generation and propagation of elastic wave in a work by single pulse discharge. The elastic wave by the single pulse discharge was measured by using an optical fiber sensor and a piezoelectric sensor on the work. Simultaneously, the discharge current and voltage were measured. The measured results of the optical fiber sensor were compared with those of the piezoelectric sensor. It was found that optical fiber sensor was not affected the electromagnetic noise unlike the piezoelectric sensor. Moreover, the optical fiber sensor was useful in the measurement of the elastic wave, including high frequency of several MHz. As the results, the elastic wave detected by optical fiber sensor was Lamb wave. It is expected that the mechanism of material removal by discharge will be clarified using the optical fiber sensor.