Papers by Author: Yasushi Fukuzawa

Abstract: AlN ceramic materials have high thermal conductivity and electrical insulation, prompting consideration of their use as a semiconducting material. Although AlN should be machined with a high accuracy of form and dimension to achieve products and components with requisite precision, mechanical and other machining methods such as the micro blasting technology or laser method cannot be used because of the brittleness and high thermal conductivity of AIN. Recently, we have succeeded in machining many insulating ceramics by EDM with the assisting electrode method. We have already machined many insulating ceramic materials such as Si₃N₄, ZrO₂ and Al₂O₃. However, inferior machining characteristics were obtained with AlN than with other materials. In this study, the effects of several electrical discharge conditions were examined to obtain better machining properties, such as high material removal rate and a low electrode wear ratio. It was found that machining time decreased with an increase in capacitance, while the electrode wear ratio increased. In addition, the machining hole profiles were straight along the depth direction, and the shape of holes was non-tapered

Abstract: This paper describes for verification of bending effect on the performance of the heightwise-asymmetric plunge cutting method, which was composed of an upper-wedge blade and a lower-wedge blade embedded in the lower-counter plate, in order to apply this cutting method for a polycarbonate (PC) thick sheet. By varying the tip angle α_U and the tip thickness w_U of lower blade embedded in the counter plate, and combining a standard steel cutting rule of 42° center bevel blade, the sheared profile of two kinds of PC worksheet (the thickness of which was chosen as t=0.5, 1.0 mm) was experimentally investigated. Through this experiment, it was found that the sheared profile (the necked height η_n, the upper inclination angle β, the lower inclination angle β_U) of PC worksheet was primarily characterized by the normalized lower tip thickness w_U/t. The difference of sheared profile was explained using the Prandtls punching solution for two kinds of PC worksheet. Furthermore, by varying the heightwise position of lower blade tip, the bending effect on sheared profile of worked sheet was experimentally verified.

Abstract: Insulating ceramics were considered as machinable material with the electrical discharge machining method using the assisting electrode method, which was proposed and advanced by the authors. The mechanical properties changed with the experimental parameters, including the physical characteristics of the workpiece and the tool electrode. In this research, sintered ZrO2-Y2O3 insulating ceramics were subjected to EDM. To investigate the effects of the porous tool electrode material on the removal rate, the porous copper cylinder material was fabricated by PECS (pulse electric current sintering) method. The relative density changed from 60 to 95 wt%. The suitable machining characteristics could be obtained with a relative density of 85% at the positive electrode polarity. The shape of electrodes was transcribed on the workpiece surface more precisely than the solid copper electrode.

Abstract: Asymmetric plunge cutting by using grooved knife edge plate was proposed for advanced die cutting of a polycarbonate (PC) sheet. By varying the tip angle U and the tip thickness wU of knife edge in the counter plate, and combining a standard steel cutting rule of 42° center bevel blade, a cutting load response of PC sheet was investigated and also that deformation was observed by a CCD camera. Through this works, the followings were found: 1) there were two deformation modes of sheared profile. 2) The tip thickness wU was a primary factor, compared to the tip angle of U. 3) The equivalent wedge angle effect was revealed with respect to the upper/lower angles  and U, while the PC sheet was bent up by the lower knife indentation.

Abstract: In recent years, to improve the electrical discharge machining properties, several trials have been applied with the ultrasonic vibration system which was combined on the sinking electrical discharge machine. In this paper, the effects of the ultrasonic vibration were investigated with the designed sinking EDM machine. Some experimental parameters of tool electrode polarity, rotational workpiece speed and directions were examined during the sinking EDM process on the cemented carbide material of G5. Material removal rate, electrode wear ratio and surface roughness were estimated as the machining properties under finishing machining conditions. The experiments were carried out on ultrasonic longitudinal frequency 59 kHz and electrode spindle till 1,000 rpm. Two rotational apparatuses were used simultaneously on the opposite rotational direction during discharge machining. The discharge conditions were estimated with the waveforms analysis. As the results, the EDM device system which was combined ultrasonic vibration, improved the material removal rate and surface roughness of the EDMed workpiece.

Abstract: This paper describes for breaking behaviors on the surface layer of a white-coated paperboard during indentation of a center bevel blade. Cutting load response of the paperboard was measured regarding the indentation depth of the blade and the deformation flow in a side view of the paperboard was observed by a CCD camera in order to investigate the effect of blade tip angle on the surface failures of the paperboard. The surface breaking strength of paperboard was analyzed by using Finite Element Method (FEM). Through the experiment and FEM simulation, the followings were revealed. 1) There is a certain critical value of tip angle C at which an inflection load response disappears and also the surface failures are restricted. 2) When the tip angle is less than the C, there is an inflection point as the surface-layer breaking and its surface breaking point was strongly related to the maximum principal stress on the surface. 3) After the surface breaking, the deformation flow and its cutting resistance are strongly affected by the de-laminated and the raised-up of the inner-layer.

Abstract: To make the tungsten and copper joint, several methods has been tried using the diffusion bonding system. When the thin plating Ni layer was used as the interlayer on tungsten surface, it bonded with copper under low bonding temperature and short holding duration by the pulse electric current sintering (PECS) machine. The effects of bonding temperature, bonding duration time, bonding pressure and the difference of specimen shape on the bonding strength were investigated. The tensile strength of joints depended on these factors. Highest strength attained to the copper tensile strength.

Abstract: To develop the new bonding method under low bonding temperature and short holding duration, pulse electric current sintering (PECS) method is applied. The Ni plating layer was used as the interlayer. The following experimental factors were researched:(1) Thickness of Ni plating layer, (2) Bonding temperature, (3) Bonding pressure and (4) Heat treatment after plating. The bonding strength of W-Ni plate-Cu joint could be obtained under low bonding temperature of 773 K and short bonding duration of 10 min.