Okazaki, Japan
Okazaki, Japan

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Asao M.,Gifu University | Mano H.,Gifu University | Yoshida Y.,Gifu University | Wang Z.,Gifu University | And 2 more authors.
aEngineering Plasticity and Its Applications - Proceedings of the 10th Asia-Pacific Conference, AEPA 2010 | Year: 2011

Shaving is a process to shave off an edge face obtained in shearing. However, in the shaving process, it is generally difficult to obtain the burnished surface over all aspects on the processing surface, because a little fractured surface often remains. Until now, there are a lot of experimental reports for this process, but analytical researches using finite element method etc. are still few. In this study, analytical investigation of an effect of punch tip shape (edge radius and clearance angle of shaving punch) on stress state and strain distribution on processing surface was performed. Furthermore processing conditions of shaving to make burnished surface all over the shaved surface were examined. As the results, it is observed the fracture morphology of shaving is ductile fracture. The shaving load decreases and the burnished surface area increases with increase of tool tip radius.

Hayakawa M.,Japan National Institute of Materials Science | Mizuno H.,Aichi Steel | Suzuki T.,NHK Spring Co. | Sugimoto A.,Aichi Steel | And 5 more authors.
Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan | Year: 2015

The susceptibility to hydrogen embrittlement for vanadium added spring steel (9254 V) with a tensile strength of 2 GPa class was evaluated by conventional strain rate tensile tests (CSRT) and torsion tests, using smooth specimens respectively. In the CSRT evaluation, the maximum tensile stress decreased with an increment in the diffusible hydrogen content, especially over 5.5 massppm the maximum tensile stress tended to fall off to the lower limit of 1.1 GPa and the fracture appearance changed to fully intergranular. On the other hand, in the torsion tests, the maximum shear stress hardly exhibited any decrease until the hydrogen content reached 6 massppm, where the cracking trace changed from shear plane (transverse direction of the specimen) to a resolved tensile stress plane (45° against the shear plane); fractgraphically, from micro-void coalescence (MVC) to intergranular fracture, and the torsional strength began to decrease. The resistance to hydrogen embrittlement as regards the CSRT properties of 9254 V was superior to that of vanadium-free SAE9254 but with the same tensile strength. Although the superior performance for 9254 V is partially attributable to the reduction of phosphorous and sulfur contents, it should be noted that the addition of vanadium causes refining the prior austenite grains followed by an effective reduction of the intergranular segregation in phosphorus and sulfur, and probably hydrogen trapping at the vanadium carbide interface. However, there was no difference between 9254 V and SAE9254 as regards the torsion properties insusceptible to hydrogen compared with CSRT.

Miura T.,Ritsumeikan University | Sakai T.,Ritsumeikan University | Sakakibara T.,Chuo Spring Co. | Mimura S.,Chuo Spring Co. | And 3 more authors.
13th International Conference on Fracture 2013, ICF 2013 | Year: 2013

In order to investigate the effects of hardness, residual stress and loading type on the fatigue property for spring steel(SUP7), two kinds of tempering temperature, three kinds of surface finishing (grinding, electrolytic polishing and shot-peening) and two kinds of fatigue test (rotating bending and axial loading) were accepted. Specimens in harder (lower tempering temperature) series showed higher fatigue limit; however, those in shot-peened series showed approximately same fatigue limit as grinding finished series, although the former has compressive residual stress higher than that in the latter. In the case of same tempering temperature and surface finishing, specimens in rotating bending series showed higher fatigue limit comparing with the axial loading. This fact can be attributed to the difference of critical volume participating in the crack initiation. Fracture surfaces of all the failed specimens were carefully observed by a scanning electron microscope(SEM) in order to examine the fracture mode. Two types of interior initiated fracture, with and without inclusion, were found. The latter was found only in axial loading and had granular structure whose angle of slope to the loading direction was 60 degree. In the case of specimens with residual stress (grinding and shot-peening), the depth of interior fracture origin in rotating bending was shallower than that in axial loading. In both grinding and shot-peening series, the crack has initiated beneath the surface layer with compressive residual stress, and, the fatigue limits of these series were thus almost same to each other. Copyright © (2013) by International Conference on Fracture.

Li W.,Beijing Institute of Technology | Sakai T.,Ritsumeikan University | Wakita M.,Chuo Spring Co. | Mimura S.,Chuo Spring Co.
Materials Science and Engineering A | Year: 2012

The effect of surface finishing and loading condition on competing failure mode of a newly developed spring steel, SUP7-T386, in very high cycle fatigue (VHCF) regime was experimentally studied. As a result, this steel for ground specimen represents the duplex S-N characteristics under rotating bending and the continuously descending S-N characteristics under axial loading, respectively, and all corresponding to surface and interior failure, whereas that for electro-polished specimen represents traditional S-N characteristics with a clear fatigue limit, only corresponding to surface failure. Owing to the combined effect of stress gradient and surface residual compressive stress, as well as the larger size of inhomogeneous microstructure (IM), the interior inclusion-induced failure with fine granular area (FGA) and the interior IM-induced failure without FGA become the predominant failure mode of this steel for ground specimen under rotating bending and under axial loading in VHCF regime, respectively. The threshold stress intensity factor for controlling surface and interior small defect-induced crack propagation of this steel is evaluated to be 2.86MPam 1/2 and 2.04MPam 1/2, respectively, the short crack effect plays a key role in causing the small defect-induced failure of this steel in VHCF regime. Considering the effect of surface residual stress, the surface fatigue limit of this steel can be well evaluated by the size of inclusion or IM. For the evaluation of interior fatigue limit of this steel, it is suitable by the size of IM under axial loading but it is all conservative by the size of inclusion, or IM and or FGA under rotating bending. © 2012 Elsevier B.V.

Miura T.,Ritsumeikan University | Sakakibara T.,Chuo Spring Co. | Mimura S.,Chuo Spring Co. | Kuno T.,Chuo Spring Co. | And 3 more authors.
Zairyo/Journal of the Society of Materials Science, Japan | Year: 2015

In order to investigate the interior-induced fatigue crack propagation behavior of spring steel (SUP7), fatigue tests in axial loading were performed for 4 kinds of specimen with different hardness (tempered at 450 °C or 386°C) or residual stress (finished by grinding, electrochemical polishing or shot peening). Harder specimen has indicated longer fatigue life resulting from its mechanical properties of matrix. Ground specimen and shot-peened specimen also provided longer fatigue life than electrochemical-polished specimen, and the fatigue life of shot-peened specimen was almost same as one of ground specimen. After fatigue tests, fracture surfaces were observed using a scanning electron microscope (SEM). In some cases, non-metallic inclusion was not observed at interior fracture origin, but granular microstructure was observed. Profile analysis and crack-path analysis with FRASTA (Fracture surface topography analysis) method were performed to investigate the fatigue fracture mechanism induced by the granular microstructure. As results of these analyses, it was clarified that a facet of the granular microstructure was inclined from 33 to 42 degrees to the fracture surface. It was another finding that small countless cracks emanated discretely inside the granular microstructure during fatigue process. © 2015 The Society of Materials Science, Japan.

Miura T.,Ritsumeikan University | Sakakibara T.,Chuo Spring Co. | Kuno T.,Chuo Spring Co. | Ueno A.,Ritsumeikan University | And 2 more authors.
Key Engineering Materials | Year: 2016

In order to investigate the interior-induced fatigue crack propagation behavior of high cleanliness valve spring steel (JIS SWOSC-V), rotating bending fatigue tests were performed for various kinds of specimens with different hardness or surface finishings. The harder specimen with higher compressive residual stress showed longer fatigue life. The electrochemical polished specimen pre-Treated with shot peening showed almost same fatigue life as the shot-peened specimen in spite of the difference in surface roughness. After fatigue tests, fracture surfaces were observed using a scanning electron microscope (SEM) to evaluate the fatigue fracture mechanism. Most specimens failed in surface-induced fracture mode due to high cleanliness; however, some specimens failed in interior-induced fracture mode in the very high cycle regime. Although non-metallic inclusions were not observed at interior fatigue crack initiation sites, 2 types of significant microstructures (with smooth surface or granular surface) were observed. EBSD analysis, profile analysis and computational simulation using a fracture surface topographic analysis (FRASTA) method were performed to investigate the mechanism of the interior-induced fatigue fracture caused by the microstructure at defect without any inclusion. © (2016) Trans Tech Publications, Switzerland.

Takeuchi H.,Chuo Spring Co. | Hoguro M.,Prime Inc | Umezaki T.,Nagoya Institute of Technology
IEEJ Transactions on Electronics, Information and Systems | Year: 2010

KARAOKE is a popular amusement for old and young. Many KARAOKE machines have singing evaluation function. However, it is often said that the scores given by KARAOKE machines do not match human evaluation. In this paper a KARAOKE scoring method strongly correlated with human evaluation is proposed. This paper proposes a way to evaluate songs based on the distance between singing pitch and musical scale, employing a vibrato extraction method based on template matching of spectrum. The results show that correlation coefficients between scores given by the proposed system and human evaluation are -0.76 ∼ -0.89. © 2010 The Institute of Electrical Engineers of Japan.

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