Nagoya-shi, Japan
Nagoya-shi, Japan

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Seki M.,Okayama University | Fujii M.,Okayama University | Kobayashi Y.,Shintokogio Ltd. | Sato M.,Kobe Steel | Yoshida A.,Hiroshima International University
Journal of Mechanical Science and Technology | Year: 2010

To investigate the influence of shot peening on the surface durability of powder-forged rollers, the case-hardened powder-forged rollers with a forging density of 7.5 g/cm3 treated by the single shot peening and the double shot peening were fatigue-tested under a sliding-rolling contact condition. The surface roughness, the surface hardness and the surface compressive residual stress of the rollers were increased by the shot peening. In addition, the pores near the roller surface were deformed by the shot peening. The failure mode of all the test rollers was spalling due to subsurface cracking. The fatigue lives of all the test rollers were improved by the shot peening, and that of the test roller S08, which was shot-peened with the hardest steel shots in this experimental range, was especially improved. The surface durability of the test roller S08 was also most improved by the shot peening. Cracks became difficult to occur and propagate under the roller surface since the pores near the roller surface were deformed by the stronger shot peening. In this study, double shot peening, which generally restrains the increase in surface roughness, was not particularly effective for the improvement in the surface durability of the powder-forged rollers, because the influence of tangential force on fatigue was not always great in a case of subsurface cracking. © KSME & Springer 2010.


Fujiwara Y.,Osaka Municipal Technical Research Institute | Fujiwara Y.,Nara Institute of Science and Technology | Koishikawa A.,Kansai University | Koishikawa A.,UACJ Corporation | And 6 more authors.
Journal of the Electrochemical Society | Year: 2014

Ag nanoparticle catalysts having a Ag@SnO2 core/shell structure were adsorbed from their colloidal solution on the smooth epoxy substrates conditioned with poly(diallyldimethylammonium chloride). The amounts and morphology of the adsorbed catalysts suggest the uniform monolayer adsorption and the formation of the agglomerated two-dimensional domains comprising several nanoparticles. Citrate acceleration of the adsorbed catalysts dissolved the SnO2 shell of the catalysts, and somewhat increased the size of the agglomerated domains and the surface roughness of the substrate with adsorbed nanoparticles. Electroless Cu deposition rate on the substrates with adsorbed catalysts went through a maximum at the initial stage, and then decreased to its constant value. Isolated Cu particles were deposited at the initial stage, and they coalesced to form the continuous films after the deposition rates reached the constant value. On the substrates without the citrate acceleration, Cu particles were deposited only at the beginning, due to the desorption of catalysts into the plating bath. The citrate acceleration prevented the desorption, and hence increased the catalyst availability. This led to the higher deposition rate and the faster morphology development at the initial stage because of the rapid and progressive deposition of Cu particles. © 2014 The Electrochemical Society. All rights reserved.


Takata T.,University of Tokyo | Enoki M.,University of Tokyo | Chivavibul P.,University of Tokyo | Matsui A.,SHINTOKOGIO LTD | Kobayashi Y.,SHINTOKOGIO LTD
Materials Transactions | Year: 2016

Laser shock peening (LSP) is one of surface treatments to induce residual compressive stresses near metal surface to improve the resistance of materials to surface-related failures, such as fatigue and stress corrosion cracking. In LSP process, short pulsed laser is focused and irradiated to the material covered by transparent overlay such as glass or water. This transparent overlay is also known as a confinement layer and has an important role to increase impact pressure during LSP process. When confinement layer is liquid, the characteristics of the layer such as temperature, viscosity, etc. affect the phenomena occurring during the peening process and undoubtedly influence the induced residual stress. In the present study, Acoustic Emission (AE) technique coupling with high speed camera was applied to study the effect of confinement layer on LSP process. The results were discussed using the impact force calculated by inverse analysis of detected AE waveforms and bubble parameters observed by high speed camera. The results showed that temperature, thickness and viscosity of confinement layer had strong influence on the generation and collapse of cavitation bubble. The optimization of process parameters could be obtained by AE technique. © 2016 The Japan Institute of Metals and Materials.


Takata T.,University of Tokyo | Enoki M.,University of Tokyo | Matsui A.,Shintokogio Ltd. | Kobayashi Y.,Shintokogio Ltd.
13th International Conference on Fracture 2013, ICF 2013 | Year: 2013

Laser shock peening (LSP) is now recognized as an efficient surface treatment to improve the fatigue life of metal components. To evaluate the process conditions, Almen strip is used as well as shot peening. As this is limited to specific material and size, we cannot apply to a wide variety of substrates. Acoustic emission (AE) method is expected to be useful for understanding LSP process because an elastic wave generates when laser is radiated on a target. The water layer on a target confines the shock wave due to laser irradiations during LSP process. In this study, laser irradiations during LSP process were monitored by AE method with varying the temperature and the thickness of the water layer on a target, respectively. Impact forces during LSP process were obtained from detected AE waveforms by deconvolution technique. In addition, laser irradiations were observed by high speed camera, and the image was compared with the detected AE signal. This result shows that shock wave was emitted by not only laser ablation but also collapse of a bubble which was generated after laser irradiation and a bubble was affected by the water layer.


Masaki K.,Okinawa National College of Technology | Yamashiro K.,Kobe University | Kobayashi Y.,ShintoKogio Ltd. | Tuji T.,ShintoKogio Ltd.
Zairyo/Journal of the Society of Materials Science, Japan | Year: 2014

Fatigue tests of friction stir welded (FSWed) joints of A6061-T6 aluminum alloy have been conducted with fully reversed plane bending conditions (R= -1) to investigate the effect of shot peening on the high cycle fatigue property. Shot peening was performed with two types of fine zirconia shot grid. The results showed that the fatigue strength at 107 cycles of unwelded specimens (base material) was 130 MPa and fine zirconia shot peening enhanced the strength by 10 MPa with B120 shot grid type. The fatigue lives were dramatically improved in all stress levels by the peening. On the other hand, the fatigue strength at 107 cycles of the SP treated FSWed specimens was nearly the same as that of the base material, and the fatigue lives were improved at only lower stress levels. To discuss these fatigue properties, fracture surfaces were observed and peening effects such as surface roughness, hardness and residual stress distributions were examined. ©2014 The Society of Materials Science.


Takata T.,University of Tokyo | Enoki M.,University of Tokyo | Chivavibul P.,University of Tokyo | Matsui A.,SHINTOKOGIO LTD. | Kobayashi Y.,SHINTOKOGIO LTD.
Materials Transactions | Year: 2016

Acoustic Emission (AE) technique is one of the nondestructive methods to evaluate the size, location and generation time of deformation or damage of material in real times. Generally AE sensors are directly attached on the surface of the component to detect AE wave, however this method brings about inconvenient setting to many industrial processes. In the present study, an arrangement of AE sensors was investigated to monitor laser shock peening (LSP). Instead of direct attachment of the sensors on the target, several AE sensors were located in the water layer to detect acoustic wave propagating through the water. The results showed that the sensor arrangement has a good performance to monitor LSP. Impact pressures during LSP process were obtained from detected AE waveforms by deconvolution technique. In addition, with AE measurement, sample surface was observed by high speed camera and investigated phenomena during LSP process. © 2016 The Japan Institute of Metals and Materials.


Patent
Shintokogio Ltd. | Date: 2014-01-22

A sand-mold molding method for producing a molded article obtained by packing foamed sand may include stirring a binder with an aggregate to form foamed sand; forming a cavity via clamping a metallic mold closed; packing the foamed sand into the cavity of the metallic mold and then heating and solidifying the foamed sand; and opening the metallic mold partially to provide a gap in the metallic mold while maintaining the cavity.


A mold and die metallic material, an air-permeable member for mold and die use, and a method for making the same are provided. The mold and die metallic material is made by forming a mixed material containing stainless steel fibers with an equivalent diameter of 30-300 m and a length of 0.4-5.0 mm, and stainless steel powder, heat sintering a green body of the mixed material, and heating the sintered body thus obtained in a nitrogen atmosphere and nitrided; wherein average open pore diameter thereof is 3-50 m.

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