Papers by Author: Tsuyoshi Furushima

Abstract: Tooling feature size to minimum thickness becomes small in micro scale products and its ratio affects the deformation behavior in micro sheet forming significantly. In this study, the effect of this relative tooling feature size on drawing characteristics and effects to improve the drawability, such as friction holding effect, hydrodynamic lubrication effect and compression effect by blank edge radial pressure, in micro hydromechanical deep drawing (MHDD) are investigated using plasticity theory and numerical simulation. The results show that the micro drawing characteristics in MHDD can be improved by applying counter pressure. However, the required fluid pressures for friction holding and hydrodynamic lubrication effects increase as the relative punch diameter and/or die shoulder radius to thickness decrease, although the compression effect by radial pressure on the blank edge is independent of the relative tooling feature size.

Abstract: Micro hydro deep drawing is a promising technology to fabricate micro metal products with complex 3D shapes. However, the size effects in the micro hydro deep drawing become considerable and significantly influence shape accuracy of drawn cups. In this study, a Voronoi micro scale simulation model was developed to consider the size effects of SUS304 foils. A surface layer model was additionally applied in the simulation to further explain the size effects. The micro hydro deep drawing experiments were conducted with annealed SUS304 foils and the drawn cups were examined. The wrinkling phenomenon was generally aggravated with the hydraulic pressure. Simulation results also show that the high hydraulic pressure does not improve the shape accuracy of the drawn cups as that in the normal scale hydro deep dawning process does. The simulation results are in accordance with the experimental results.

Abstract: A novel superplastic dieless drawing technique with local heating and tensile deformation has been focused on for fabrication of zirconia ceramic tube. In this study, 3Y-TZP zirconia ceramic tube with outer diameter of 6mm and inner diameter of 4mm as a superplastic material is used experimentally. An apparatus of superplastic dieless drawing with rotary stage for circumferential uniform heating and acetylene burner for high temperature of 1700°C is developed. The superplastiac dieless drawing experiment is carried out to investigate the effect of the ratio of drawing speed to feeding speed on the flexible controllability of diameter after drawing process. As a result, the reduction in area after drawing process can be controlled by the ratio of drawing speed to feeding speed. In addition, a maximum reduction in area of 79.2% can be realized in this process. Consequently, the validity of developed apparatus of superplastic dieless drawing for Zirconia ceramic tube can be demonstrated.

Abstract: A heat assisted superplastic dieless drawing process that requires no dies or tools is applied to the drawing of a Zn-22Al and β titanium superplastic alloy for not only circular but also noncircular microtubes such as square, rectangular and noncircular multi core tubes having square inner and rectangular outer cross sections. As a result, the tendency has been to increase the limiting reduction in area with increasing strain rate sensitivity index m value. We successfully fabricate Zn-22Al alloy, AZ31 magnesium, β titanium circular microtubes with outer diameter of 191μm, 890μm and 180μm, respectively. Furthermore, a noncircular micro tube, which has inner square tubes with a 335μm side, and an outer rectangular tube of 533×923μm were fabricated successfully. During the dieless drawing process, the geometrical similarity law in cross section which the tube is drawn while maintaining its initial shape can be satisfied. The smooth surface can be obtained in case of superplastic dieless drawing process without contact situation with dies and tools. Consequently, it is found that the superplastic dieless drawing is effective for the fabrication of circular and noncircular multicore microtubes.

Abstract: We develop new drawing technologies of rotary laser dieless drawing for the fabrication of micro-tubes without the need for tools such as dies, plugs and mandrels. A rotary laser dieless drawing apparatus with local heating using a laser irradiated from one direction as the heating source has been focused on for the fabrication of micro-tubes. In this study, a dieless drawing with a semiconductor laser setup with power of 30W is designed and developed. A workpieces was rotated about a tensile axis by rotary stage with chucks for circumferential uniform temperature distribution. A tube of stainless steel SUS304, with an outer diameter of 0.5mm and thickness of 0.13mm is used in the experiments. In this experiment, we verify the effectiveness of the developed rotary laser dieless drawing apparatus.

Abstract: The metal bellows are used in a large number of industrial applications for their flexile and elastic properties. For the traditional manufacturing methods for metal bellows, the dies and (or) tools are required. It is inconvenient to change the shape of metal bellows and also leads to the high cost. To reduce the manufacturing cost and produce the metal bellows with various shapes, the semi-dieless metal bellows forming process was proposed. The deformation behavior of aluminum alloy tube in semi-dieless bellows forming process was investigated in the study. The effects of compression ratio, heating length on the convolution height, pitch of bellows during the semi-dieless bellows forming process were studied. The results showed that the deformation conditions of semi-dieless forming process have significant influences on the shape of aluminum alloy bellows and deformation behavior of aluminum alloy tube in the forming process. The increase of compression ratio, heating temperature and heating length resulted in the increase of pitch and decrease convolution height of aluminum alloy metal bellows.

Abstract: The newly proposed rotating bending process of metal tubes is a novel kind of Severe Plastic Deformation (SPD) process, which is expected to refine and control the microstructure of metallic tubular materials. The stress distribution and accumulated equivalent plastic strain of deformation part have a significant influence on the microstructure refinement and control of metal tubes during the rotating bending process. The present study focused on the analysis of stress and strain of deformation part during rotating bending process of metal tubes. The model of the deforming metal tubes was proposed. The formulas for determining the stress and accumulated equivalent plastic strain were successfully achieved by analyzing the deformation of metal tubes during rotating bending process.

Abstract: In this study a cyclic rotating bending process for microstructure control of metal tubes was newly proposed. The AZ31 magnesium alloy tube was conducted to investigate the effect of the rotating bending process on the microstructure and mechanical properties of metal tubes. The rotating bending process was carried out with rotation speed of 20r/min for 10min at the temperature of 150, 200, 250, 300 and 350°C. The rotating bending processes carried out with various conditions show that the grains in cross-section and longitudinal section of magnesium alloy tube were refined for all samples by the rotating bending process with rotation speed of 20r/min for different rotation numbers and temperatures. The rotating bending temperature shows a various effects on the mechanical properties. When the temperature was 200°C, the highest strength as well as ductility was obtained.

Abstract: Grain refinement processing by severe deformation, combined equal-channel angular extrusion (ECAE) processing and conventional tube extrusion, is applied to AZ31 magnesium alloy. By a combination of ECAE processing and tube extrusion, a fabricated tube, with outer and inner diameters of 2 mm and 1 mm, respectively, has fine, homogeneous, and equiaxed grain structure with an average grain size of 1.5m. Tensile test results indicate that the fine-grained tubes exhibited a superplasticity potential m value of 0.55.The maximum elongation (688%) is obtained at a temperature of 673K. Furthermore, the tubes fabricated by combined ECAE/extrusion process is applied to dieless drawing process without using any tool and die.As a result, dieless drawing limit is enhanced due to high m value achieved by combined ECAE/Extrusion process. From these results, the effectiveness of new grain refinement processing for fabricating fine-grained tubes and its application for dieless drawing process to fabricate the fine tubes was demonstrated experimentally.

Abstract: A drawing process using tools such as dies, plugs and mandrels has been conventionally applied as a means of miniaturizing tubes. However, it is not easy to scale down the conventional process to micro sizes for many reasons related to the tools used in the process. It is difficult to fabricate micro tools with high accuracy, and to insert a plug or a mandrel into a fine tube. Thus, the development of new drawing technologies for the fabrication of micro-tubes without the need for tools such as dies, plugs and mandrels is necessary. A laser dieless drawing technique with local heating using a laser as the heating source has been focused on for the fabrication of micro-tubes. In this study, a dieless drawing with a semiconductor laser setup is designed and developed. A tube of stainless steel, SUS304, with an outer diameter of 0.52mm and thickness of 0.1mm is used in the experiments. A laser dieless drawing experiment is carried out to investigate the effect of the laser power and drawing speed on the drawing limit. Finally, the effectiveness of laser dieless drawing process is discussed.