Papers by Author: Dong Ying Ju

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Authors: Dong Ying Ju, J.G. Wang, Minoru Abe
Abstract: The purpose of this investigation is to detect damage from stress distribution in the surface of near pre-crack tip by using X-ray diffraction technique during biaxial tension test. An measurements apparatus to measure stress distribution along pre-crack direction was fabrication by use of a biaxial tensile test device and a stress analyzer based on single exposure technique with one position sensitive proportional counter. Stress distribution with different tensile applied stress ratios were measured during biaxial tension test. As results, the shape of actual stress was keeping increase with increasing tensile applied stress. At maximum applied stress, the residual stress increases with the increasing distance from the crack tip; after reaching a maximum it gradually diminish.
Authors: Dong Ying Ju, Ryuji Mukai, Nobuaki Minakawa, Yukio Morii, Atsushi Moriai
Authors: B. Han, Dong Ying Ju, Xiao Guang Yu
Abstract: Water cavitation peening (WCP) with aeration, namely, a new ventilation nozzle with aeration is adopted to improve the process capability of WCP by increasing the impact pressure induced by the bubble collapse on the surface of components. In this study, in order to investigate the process capability of the WCP with aeration a standard N-type almen strips of spring steel SAE 1070 was treated byWCP with various process conditions, and the arc height value and the residual stress in the superficial layers were measured by means of the Almen-scale and X-ray diffraction method, respectively. The optimal fluxes of aeration and the optimal standoff distances were achieved. The maximum of arc height value reach around 150μm. The depth of plastic layer observed from the results of residual stresses is up to 150μm. The results verify the existence of macro-plastic strain in WCP processing. The distributions of residual stress in near-surface under different peening intensity can provide a reference for engineers to decide the optimal process conditions of WCP processing.
Authors: B. Han, Dong Ying Ju
Abstract: As a novel surface strengthening technique, Water-jet cavitation peening has been applied to improve the fatigue life by inducing the compressive residual stress in the near surface layer of mechanical components. Compared with conventional shot peening, one advantage of WCP is that the complicated and tiny surface can be peened more easily. In this study, the small holes with various diameters and depths in the SUS304 stainless steel specimens were treated by WCP. In order to estimate its strengthening capability to the small holes, the surface residual stress and the depth distributions in the near surface layer of the small holes were measured by X-ray diffraction method. The experimental results show that WCP can successfully improve the near surface compressive residual stress of small holes. The maximum of surface compressive residual stress of WCP state is up to around –450 MPa. The dept of compressive residual stress zone is up to around 125 μm.
Authors: Pei Bian, Dong Ying Ju
Abstract: Low temperature sintering NiCuZn ferrite was employed at most cases due to its co-firability with Ag (below 960°C). The purpose of this study is to fabricate NiCuZn ferrite sintered body with high-strength and high-frequency magnetic properties. Following is the procedure: firstly, NiCuZn ferrite powder was synthesized under CO2 atmosphere at 500°C from the mixed doxalate synthesized by liquid phase deposition method; then a small amount of boric acid [H3BO3] was added to the powder, and the NiCuZn ferrite powder compact was prepared with Newton press and CIP methods; finally, NiCuZn ferrite sintered body was fabricated by sintering at 900°C under CO2 atmosphere. By this method, NiCuZn ferrite sintered body with 0.5 mass% boric acid was obtained, which was additive with strength 340 MPa, high frequency applied scope below 20MHz and initial permeability 38.
Authors: Y. Chen, Dong Ying Ju
Abstract: Because of the raw material elements and its purity and so on, the Nd-Fe-B permanent magnet, the strongest magnetic material, which needs artificial synthesis, can hardly be used directly. The performance of the permanent magnet has not yet been greatly developed owing to the limitation of the artificial synthesizing technology, of the powder sintering technology and that of the application. In this paper, the magnetic abrasive machining method as a new application is put forward, and from this viewpoint, are discussed the performance and the processing technology of the permanent magnet and the magnetic abrasive machining method. A sintering route combining the direction heat treatment technique to increase the magnetic energy is suggested.
Authors: Yu Hong Zhao, Dong Ying Ju, Hua Hou
Abstract: With the microscopic phase-field model, the early precipitation mechanisms of the ternary Ni75AlxV25-x alloys with middle Al composition were explored by computer simulation in this paper. Through the simulated atomic pictures and composition order parameters of precipitates, we can explain the complex precipitation mechanisms of θ (Ni3V) and γ′ (Ni3Al) ordered phases. Simulated results also show that the precipitation characteristic of γ′ phase transforms from non-classical nucleation and growth to congruent ordering + Spinodal decomposition gradually, otherwise, the precipitation characteristic of θ phase transforms from congruent ordering + Spinodal decomposition to non-classical nucleation and growth mechanism gradually.
Authors: G. An, Dong Ying Ju, Pei Bian, T. Kumazawa, M. Okasabe
Abstract: The composite magnetic nanoparticles of coated SiO nano film with about 8 nm size can be dispersed in various liquid media, widely known as magnetic fluids or ferrofluids with both magnetic and liquid properties. In this paper, a bio-medicine coating technology on surface of magnetic nanoparticles and the optimum fabrication condition and the magnetism of composed bio-nanoparticles are investigated. Through observation of micro-structure of the bio-nanopaticles on coating surface, and evaluation of magnetic property and safety to apply to biomaterials, we know the bio-medicine coated on surface of magnetic nanoparticles is suitable of bio-solutions into surface of biomaterials.
Authors: Dong Ying Ju, S. Koga, Pei Bian, T. Mitamura
Abstract: In order to improve the durability of Pt coated Ti electrodes as an anode of the sulfuric acid system electrolysis, tantalum oxide (Ta2O5) additions have been used widely. However that is not enough for uses under severe conditions. In this study,boric acid (H3BO3) was added into the Pt coating during manufacturing process of Ti/Pt-coated electrodes, and the (Pt + B2O3)/Ti electrodes were obtained. The effect of H3BO3 addition on the microstructure, surface area, and lifetime of (Pt + B2O3)/Ti electrodes was also investigated in detail. Commercially available titanium plates (10 100.5mm) were employed for prepare Ti/ (Pt + B2O3) electrodes, where it was confirmed by XRD that B2O3 formed by heating the boric acid was amorphous in the temperature range of 250 to 550. The coating solution of 2 μl of H2PtCl66H2O (Pt:50 g/l) dissolved in butanol and 5~20 mass% H3BO3 mixture was spread over the etched Ti plates. After drying at 70 for 30 min, the substances were heated at 250 to 550 for 10 min. The lifetime of the electrodes was examined by a direct current of 1 A using Pt plate as the counter electrode in 1 M H2SO4 solution at 40. The end of life was determined as the time when the cell voltage changed 2 times of the beginning.
Authors: Xiu Juan Zhao, Jun Wen Wang, Chun Huan Chen, Yuan Sun, Rui Ming Ren, Dong Ying Ju
Abstract: Comparing with conventional mechanical shot peening (SP) technique, water cavitation peening (WCP) experiments of Almen strips were carried out on a self-manufactured equipment. The results show that WCP demonstrates a wide range of standoff distance (SD) that from the nozzle to the surface of the object. By measuring the colour changes of the Fuji pressure sensing film, over 110 MPa impacting pressure was detected, which is resulted from the bubbles blasting on the sample surface when the SD is from 65 to 100 mm under 40 MPa of operating pressure. 600 MPa compressive residual stress achieved on the suface of the Almen strips after WCPed for 32 min. The depth of the zone affected by the compressive residual stress is about 100 µm. The highest residual stress appears in the top surface layer, while in case of SP it appears in the subsurface. Compared to SP, WCP is capable to get rather smoother surface and cause less deformation of the testing sheet, simultaneously.
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