Hachiro Tsuchiya

Generation and Propagation of Pressure Wave by Spark Discharge in Liquid

Summary This paper deals with the energy conversion processes as the basic phenomena in underliquid electrical discharge forming. Based on precise observation of electrical and mechanical phenomena, a model is proposed for the process in which the electrical energy released in the electrode gap is converted into the internal energy, the radiation energy of the bubble and the energy of the pressure wave in turn. The validity of the model is discussed with both the pressure wave measured by the device of special design and the electrical energy. It is shown that the pressure level, the size and the possible temperature of the bubble and the form of pressure wave in liquid can be reasonably evaluated by the model in the case of a shorter electrode gap. In the typical electrode gap, the maximum value of the pressure, that of temperature and that of expansion velocity are 2.8×10 2 MPa,8.7×10 4 K and 160 m/s, respectively. The size of the bubble at the end of the first wave of discharge power is 2.2 mm in radius. The results present the basis for the analytical design of the system of underliquid electrical discharge forming.

A Fundamental Study on Electro-Chemical Discharge Machining

This paper deals with relations between the behavior of a needle electrode and machining characteristics in drilling with electro-chimical discharge. The behavior of a needle electrode was observed by using a detector consisting of an optical fiber and a phototransistor. As the machining characteristics, the profile and the volume of pit formed by electro-chemical discharge were measured. The results obtained are as follows:1) The needle electrode rises with the bubbles generated in the electrolytic reaction. The rising speed and the rising distance depend on the voltage across the electrode, but they are independent of the load applied on the needle electrode.2) The pit profiles change from ring- to cone-shape as the discharge time progresses. The pit volume is proportional to the discharge time, but is independent of the load applied on the needle electrode.

A Study on Wire Electro-Chemical Discharge Machin ing (1 st Report)

This paper deals with a new method of wire electro-chemical discharge machining of non-conductive materials such as ceramics.The method is achieved by combining the cutting technique of wire-EDM with electrochemical discharge machining used for drilling non-conductive materials such as glass, diamond and ruby immersed in an electrolyte. In its method a molybdenum wire of 0.1mm in diameter is employed as one electrode and platinum wire of 0.5mm in diameter as the other electrode. The electrolyte of KOH solution is fed to the contact area between the work specimen and the molybdenum wire.Glass and ceramic plates as work specimens can be successfully cut by the electric arcs generated along the contact line between the work specimens and the wire electrode in the electrolyte.The effects of the polarity of the electrodes, the types of the current, the voltage applied to the electrodes, and the conoentration of the electrolyte on the cutting rate and the kerf width are examined.The maximum cutting rate of silica glass (1.0mm in thickness), that of Al2O3 ceramic (1.2mm in thickness), that of Si3N4 ceramic (1.2mm in thickness) and that of ZrO2 ceramic (1.2mm in thickness) are 6.8mm/min, 0.3mm/min, 0.67mm/min and 0.2mm/min, respectively, The kerf width at the maximum cuting rate of silica glass, that of Al2O3 ceramic, that of Si3N4 ceramic and that of ZrO2 ceramic are 0.20mm, 0.31mm, 0.45mm and 0.13mm, respectively.The results obtained show that the method is effective for cutting glass and ceramic materials in two dimensional contour.