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Jiang Y.,National Key Laboratory for Remanufacturing | Jiang Y.,Naval Flying Academy of China | Xu B.S.,National Key Laboratory for Remanufacturing | Wang H.D.,National Key Laboratory for Remanufacturing | Lu Y.H.,National Key Laboratory for Remanufacturing
Computational Materials Science | Year: 2010

The distribution of residual stresses in the sprayed coating is discussed by finite element method (FEM). With the increasing of coating thickness, residual stresses in the coating tend to change from compressive to tensile, the stress distribution along the radius of the specimen is smoother, but the concentration near the edge of coating, especially near the edge of hole, is sharper, which lead to failure of the coating. The hole radius of specimens took great effect on the distribution of residual stress near the inner radius, however, little effect on the distribution near the outer radius. © 2010 Elsevier B.V. All rights reserved. Source


Jiang Y.,Academy of Armored force Engineering | Jiang Y.,Naval Flying Academy of China | Xu B.,Academy of Armored force Engineering | Lu Y.,Academy of Armored force Engineering | And 2 more authors.
Chinese Journal of Mechanical Engineering (English Edition) | Year: 2011

Arc pressure is one of the key factors for variable polarity plasma arc(VPPA) and welding pool formation. In this paper, VPPA pressure is measured by pressure transducer and U-tube barometer methods, and advantages and disadvantages of the two methods are compared. The effects of welding parameters, including with straight polarity(SP) current, reverse polarity(RP) current, time ratio of SP to RP, plasma gas flow rate, on VPPA pressure are investigated by using an orthogonal design. The experimental results indicate that the influencing degree of the welding parameters are in the order of plasma gas flow rate, SP current, time ratio of SP to RP, RP current. These results are important to researches of VPPA welding process and its mechanism. The physics behavior of VPPA is taken into account when the above influence mechanisms are analyzed. Firstly, according to the mechanism of the cooling compression to the arc, the compression to VPPA is enhanced with the increase of plasma gas flow, so the VPPA pressure would increase obviously. Secondly, although the temperature of VPPA is as a function of the welding current, the radius of VPPA is also enhanced. So the effects of SP current on VPPA pressure are inferior to the effects of plasma gas flow. Thirdly, VPPA pressure increases as a function of time ratio of SP to RP because the frequency of welding current influences the arc pressure to the some degree; Finally, the RP intervals are farther less than the SP intervals, so the influence to the pressure is minimal. ©2011 Chinese Journal of Mechanical Engineering. Source


Jiang Y.,Academy of Armored force Engineering | Jiang Y.,Naval Flying Academy of China | Xu B.,Academy of Armored force Engineering | Lu Y.,Academy of Armored force Engineering | Liu C.,Academy of Armored force Engineering
Hanjie Xuebao/Transactions of the China Welding Institution | Year: 2010

Molten pool and weld formation of variable polarity plasma arc (VPPA) welding are influenced greatly by VPPA pressure. Therefore, researches on VPPA pressure are meaningful. Furthermore, discussions about radial distributions of VPPA pressure can actually guide mechanical analysis and numerical simulation of VPPA and its molten pool. In this paper, the distribution of VPPA pressure along the radial distance at different welding currents was measured and discussed by U-tube barometer. It was concluded that the radial distribution of VPPA pressure still belonged to Gaussian distribution rather than exponential distribution. Furthermore, the analyzed results show that the VPPA pressure increases with the increase of welding current, but its increasing rate tends to slow. Source


Yi J.,Academy of Armored force Engineering | Yi J.,Naval Flying Academy of China | Yi J.,National Key Laboratory for Remanufacturing | Bin-Shi X.,Academy of Armored force Engineering | And 3 more authors.
Applied Surface Science | Year: 2011

In this paper, residual stresses of the Ni-Cr-B-Si coatings prepared by supersonic plasma spray processing were measured by moiré interferometry and X-ray diffraction method. Moiré interferometry method was used in measuring the distribution of residual stresses of the Ni-Cr-B-Si coatings alongside the specimen thickness direction, then the distribution of residual stresses both in the substrate and the coating was also analyzed. Experimental results showed that residual stresses in the coating and the substrate are tensile and compressive separately; residual stresses of the coating are diminished with the increase of the distance from the coating surface and almost zero at the coating-substrate interface; the maximum of compressive residual stresses of the substrate are present to the vicinity of the coating-substrate interface. It could be concluded that residual stresses in the specimen would result from the dismatch of thermophysical properties between the coating and substrate during the spray process, and the distribution of residual stresses of the substrate would be influenced by the sandblasting prior to spraying. © 2010 Elsevier B.V. All rights reserved. Source


Wang H.,Academy of Armored force Engineering | Xu B.,Academy of Armored force Engineering | Jiang Y.,Academy of Armored force Engineering | Jiang Y.,Naval Flying Academy of China | And 2 more authors.
Hanjie Xuebao/Transactions of the China Welding Institution | Year: 2011

NiCrBSi coating was sprayed by supersonic plasma spraying technology, and microstructure and mechanical properties of NiCrBSi coating were analyzed. Microstructure of coating was investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), hardness and elastic modulus were measured by nano-indention method. Bonding strength between coating and substrate was investigated by tensile test. The distribution of residual stress alongside the coating thickness was measured by X-ray diffraction method. The results showed that the coating structures were uniform and had a low porosity and oxide. Nano-hardness was near to 15 GPa, nano elastic modulus was 200 GPa and boding strength was close to 50 MPa. It is concluded that the coating has good wear-resistance and excellent mechanical properties. Residual stress in the coating is tensile, and decreases with the incrense of the distance from the coating surface. Source

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