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Ōsaka, Japan

Arimoto K.,Arimotech Ltd. | Ikuta F.,NETUREN Co. | Yamanaka S.,Maruemu Works Co.
International Journal of Microstructure and Materials Properties | Year: 2012

Gas nitriding is well established as a suitable process for realisinglow distortion in precision parts under optimal conditions. However, efforts for optimising the distortions by trial and error, which are not avoidable, have been repeated over many years. A software tool based on the finite element method is developed by use of the latest models of nitriding for resolving the problems, which was applied to the nitrided austenitic stainless steels specimens. In this study, distortions in nitrided steel cylinders, which were measured systematically in 1930s, were investigated using the tool for understanding their tendencies derived from different conditions. The fruits will be used for enhancing the tool by additional verifications, and applying finally to distortion problems in practical parts. Copyright © 2012 Inderscience Enterprises Ltd. Source


Arimoto K.,Arimotech Ltd. | Yamanaka S.,Maruemu Works Co. | Funatani K.,IMST Institute
ASTM Special Technical Publication | Year: 2010

Case carburizing is recognized as a suitable process for realizing low distortion and high compressive stresses near the surfaces under optimal conditions. Patterns of distortion and residual stresses in carburized cylinders and rings under different conditions have been identified from measurements performed for many years. Some pioneers of the heat treatment simulation compared their simulated results of carburized and quenched parts with experimental data for verifying their programs. However, these early researchers did not sufficiently explain their distortion and stress generation mechanism using their simulated results. Although one of the authors tried to illuminate their mechanism of a carburized and quenched ring, the work has not been finished because the purpose was limited in examining the role of transformation plasticity in the process. In this paper, the same simulated results were analyzed more comprehensively for explaining the origin of distortion and residual stress in the ring based on a concrete strategy newly developed. Copyright © 2008 by ASTM International. Source


Yamanaka S.,Maruemu Works Co. | Yamanaka S.,Tohoku University | Amiya K.,Tohoku University | Saotome Y.,Tohoku University | Inoue A.,Tohoku University
Materials Transactions | Year: 2011

Bolts are commonly employed machine elements used for joining and fastening, and their performance and reliability influence the overall performance of machines. In this study, we have plastically worked and formed bolts using metallic glass (MG) that exhibits unique mechanical properties such as high tensile strength, low Young's modulus, and large elastic limit. The large elastic limit increases the permissible elongation range of the bolt and helps avoid bolt loosening, while the low Young's modulus effectively resists screwed-in bolt loosening by increasing the frictional forces on both bolt-nut contact area and bearing surface. We employed a zirconium-based MG Zr 55Al10Cu30Ni5 for our experimental investigations. A pre-form of a hexagon socket head cap screw (bolt) was fabricated by squeeze casting. Cold and warm thread rolling were performed to form a metric screw thread M3×0.5 (class 6g (ISO)) below the glass transition temperature (7'g) using a flat rolling machine. Despite the extremely poor ductility of MG at room temperature, thread rolling was successfully performed. Straining behavior analysis by a three-dimensional finite element method demonstrated that these remarkable results are due to the compressive stress distribution induced during the thread rolling process. In addition, thread rolling is fundamentally an incremental process, and it enhances the deformability of MG by gradually improving ductility in the deformed region. The tensile strength of the thread-rolled bolt was approximately 1600MPa, which is considerably higher than that of conventional heat-treated high strength steel bolts. MG was thus successfully employed to manufacture improved bolts. © 2011 The Japan Institute of Metals. Source


Narita K.,Tohoku University | Narita K.,Maruemu Works Co. | Niinomi M.,Tohoku University | Nakai M.,Tohoku University
Materials Science and Engineering A | Year: 2015

This study investigates the effect of heterogeneous precipitation induced by the segregation of substitutional and interstitial elements in Ti-29Nb-13Ta-4.6Zr alloy (TNTZ) on its mechanical properties. For this, samples both with and without segregation of substitutional elements were prepared, with only the latter being subjected to long-term homogenization. It was found that micro-scale segregation of substitutional elements such as Nb, Ta, and Zr does not significantly affect mechanical properties such as fatigue strength, not even if heterogeneous precipitation occurs as a result of this segregation. On the other hand, segregation of interstitial elements was achieved by controlling the aging time. The segregation of interstitial elements creates precipitate-free zones (PFZs), grain boundary (GB) plates, and Widmanstätten α phases with migrating O atoms that all significantly affect the mechanical properties. Specifically, the PFZs have the potential to improve fatigue life, while the Widmanstätten α phase increases the tensile strength and reduces the fatigue ratio, the GB-plates reduce elongation, These results indicate that the formation of a Widmanstätten α phase by the migration of interstitial elements has a varying influence on the tensile and fatigue properties. © 2015 Elsevier B.V. Source


Yamanaka S.,Maruemu Works Co. | Amiya K.,Tohoku University | Saotome Y.,Tohoku University
Journal of Materials Processing Technology | Year: 2014

Metallic glass (MG) has unique mechanical properties, combining high strength and low Young's modulus. By using MG to fabricate fasteningbolts, high resistance against bolt loosening is expected. However, MG components are considered brittle because MG exhibits poor ductility when subjected to uniaxial loading at room temperature. We have developed hexagonal cap bolts made of zirconium-based MG by cold thread rolling. The MG bolts showed a 1.6% plastic strain with a tensile strength of more than 1550 MPa. In addition, the load-strain curve was similar to that of a strain hardening material, although MG itself is free of strain hardening. In this study, we attempted to clarify the reasons for these characteristics, which are advantageous for bolts in terms of toughness and reliability. Various experiments and numerical analysis indicated that residual stress plays an important role in the behavior. © 2014 Elsevier B.V. Source

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