YOSHIFUMI AMAMOTO

Scopus Publications

Dry grinding of nano-polycrystalline diamond using thermochemical reaction
Takuya SEMBA, Yoshifumi AMAMOTO, Hirokazu FUJIYAMA, Shinya HASHIMOTO, Hitoshi SUMIYA
Nihon Kikai Gakkai Ronbunshu C Hen Transactions of the Japan Society of Mechanical Engineers Part C, 2013
A polycrystalline diamond (PCD) disk, in which the cobalt (Co) commonly used as a sintering aid is replaced with a transition metal or a high-specific-heat material, was used as a truer, and dry grinding of a laser-preformed rake face of a radius-cutting tool made of nano-polycrystalline diamond (NPD) was conducted to clarify the mechanism by which a chip is removed from the rake face. The grinding test revealed that the surface roughness decreased with decreasing frictional heat of the truer when the damaged layer on the rake face, in which the covalent linking strength was weakened owing to the transfer of electrons from the diamond to the transition metal, was removed by diamond grains on the working surface of the truer. It additionally became clear that the surface roughness decreased with increasing specific heat capacity of the material replacing the Co when the heat-damaged layer, in which the diamond structure was transformed to that of graphite, was removed by diamond grains on the working surface of the truer. A ground surface roughness of 0.5 nm Rz was obtained when the truer with Co replaced by boron carbide (B4C) was employed.
Laser-forming technique of single-point cutting tool made of nano-polycrystalline diamond
Yoshifumi AMAMOTO, Takuya SEMBA
Nihon Kikai Gakkai Ronbunshu C Hen Transactions of the Japan Society of Mechanical Engineers Part C, 2012
A laser forming technique adaptable to producing a single-point cutting tool made of nano-polycrystalline diamond (NPD) with a nose radius of 0.4 mm and a sharp cutting edge was developed. Both the chipping and wear resistance of tools made of NPD and single-crystal diamond (SCD) produced using the laser forming technique were compared by applying both tools to the face turning of cemented carbide with a hardness of 1450 Hv. A forming test was conducted on an NPD chip soldered on a substrate made of cemented carbide. It was verified through the forming test that a sharp cutting edge with a roundness of less than 1.0 μm could be formed by rotating the NPD rake face to the negative Z direction of the machining center and moving the laser beam on the inclined path from the substrate to the NPD rake face when forming the flank face. In addition, a cutting test revealed that the wear volume of the NPD flank face at a total cutting length of 4 km was 23% of the value measured from the SCD flank face.
Electroformed diamond tool adaptable to nanometer grinding of cemented carbide
Naoko Gohya, Wan Fu Sun, Yoshifumi Amamoto, Takuya Semba
Key Engineering Materials, 2012
An electroformed diamond tool with a tool tip radius of 0.2 mm was developed to achieve a surface roughness of less than 10 nm Rz on a mould made of cemented carbide. A polycrystalline diamond disc with a primary grain size of 0.5 µm and a diameter of 15 mm was used as a truer. A concentric guide groove with a reverse profile relative to the hemispherical tool and a surface roughness of 0.5 µm Rz was preformed on the truer by laser machining and wet lapping. It was verified through a truing test that 93 % of the diamond grains on the tool working surface could be flattened when the tool was placed in elastic contact with a guide groove with a depth of 50 µm. A grinding test revealed that the tool had the potential to efficiently fabricate a ground surface with a roughness of less than 10 nm Rz on cemented carbide with a hardness of 2600 Hv.
Development of forming technique for nano-polycrystalline diamond cutting tool using pulsed fiber laser
Proceedings of the 6th International Conference on Leading Edge Manufacturing in 21st Century Lem 2011, 2011
Thermochemical reactions between nano-polycrystalline diamond and grinding tool made of polycrystalline diamond
Takuya SEMBA, Shusuke OHTA, Yoshifumi AMAMOTO, Hirokazu FUJIYAMA, Hitoshi SUMIYA
Nihon Kikai Gakkai Ronbunshu C Hen Transactions of the Japan Society of Mechanical Engineers Part C, 2011
A dry grinding test of a nano-polycrystalline diamond (NPD) using a polycrystalline diamond (PCD) disc as a truer was conducted to clarify the mechanism of thermochemical reactions to remove chips from the NPD. The PCD disc, in which the cobalt used as a second phase was replaced with several transition metals by electrochemical machining and radio frequency sputtering, was used as a truer. It was verified through the grinding test that at least two types of thermochemical reactions generated and affected layers on the ground surface of the NPD were abraded by diamond grains on the PCD truer. One is an affected layer, in which the covalent binding of diamond was weakened by loosing electrons engaged in the binding owing to the transition metal attracting electrons towards itself. Machining efficiency increased and ground surface roughness became rough with an increase in the electronegativity of transition metals when this type of affected layer was generated. The other type of affected layer is a heat-damaged layer, which has the same crystal structure as a laser- machined surface, formed by the friction heat between the NPD and the truer. A generation of this type of affected layer increased and surface roughness became fine by increasing the specific heat capacity of transition metals.
Improvement of wear resistance for carbon steel under unlubricated sliding and variable loading conditions
H. Goto, Y. Amamoto
Wear, 2011
A truing mechanism for flattening diamond grains on the working surface of an electroformed diamond tool
Naoko GOHYA, Wanfu SUN, Yoshifumi AMAMOTO, Takuya SEMBA
Nihon Kikai Gakkai Ronbunshu C Hen Transactions of the Japan Society of Mechanical Engineers Part C, 2011
A truing test was conducted to clarify the truing mechanism for flattening diamond grains on the hemispherical working surface of an electroformed diamond tool with a mesh size of #1 000 and a tip radius of 0.2 mm. A polycrystalline diamond disc of 0.5 μm primary grain size and 15 mm diameter was used as a truer. A concentric groove with a reverse profile relative to the hemispherical tool and a surface roughness of 0.5 μm Rz was preformed on the truer by laser machining and wet lapping. Truing was then performed by placing the tool in elastic contact with the preformed groove on the truer. It was verified through a truing test that primary diamond grains on the guide groove acted as multiple minute cutting edges so that 93% of the diamond grains on the tool working surface could be flattened when the tool was placed in contact with a groove of 50 μm depth and the contact load was set at 5.2 N.
Investigations on the mechanism of quasi-mild wear for carbon steel in dry sliding contact under variable loading, and endurance of the worn surfaces
H. Goto, Y. Amamoto, C.V. Suciu
Wear, 2009
Three-dimensional microfabrication system using focused fiber laser beam
Lem 2007 4th International Conference on Leading Edge Manufacturing in 21st Century Proceedings, 2007
Effects of a stepwise change in load on the subsequent friction and wear characteristics of carbon steel under dry sliding
Hozumi Goto, Yoshifumi Amamoto
Wear, 2007
Friction and wear of carbon steel near T1-transition under dry sliding
Yoshifumi Amamoto, Hozumi Goto
Tribology International, 2006
Effects of contact load on fretting wear of Al-Si alloy impregnated graphite composite
H. Goto, Y. Amamoto
Proceedings of the World Tribology Congress III 2005, 2005
Effect of varying load on wear resistance of carbon steel under unlubricated conditions
Hozumi Goto, Yoshifumi Amamoto
Wear, 2003