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Harbin, China

Li F.-C.,Harbin Institute of Technology | Chen W.-L.,Harbin Institute of Technology | Li H.,Harbin Institute of Technology | Zhang R.,Harbin Welding Institute
Sensors and Actuators, A: Physical | Year: 2010

Water rivulets will appear on the inclined cables of cable-stayed bridges and oscillate around the cable surface when rain-wind-induced vibration (RWIV) occurs. This paper develops an ultrasonic transmission thickness measurement system (UTTMS) capable of measuring time-dependent spatial distribution of water rivulets around the surface of the stayed cable suffering from the RWIV. Consequently, the geometry and oscillation of water rivulets around the cable can be obtained, providing valuable information for investigating the dynamics of RWIV phenomenon. The mechanism, layout, and measurement accuracy of UTTMS are first illustrated in detail. A wind tunnel test of the RWIV of an inclined cable model incorporated with the UTTMS is then carried out. The measurement results indicate that a lower rivulet and upper rivulet form on the surface of the test cable. The lower rivulet is more or less fixed, while the upper rivulet oscillates along the circumferential direction of the test cable. The thickness and width of rivulet are statistically analyzed. The amplitude, dominant frequency and equilibrium position of upper rivulets along the circumferential direction of the cable are also presented in this paper. © 2010 Elsevier B.V. All rights reserved. Source

Lu H.,CSR Qingdao Sifang Co. | Xing L.,CSR Qingdao Sifang Co. | Chen D.,Harbin Welding Institute
Hanjie Xuebao/Transactions of the China Welding Institution | Year: 2013

A-MAG welding was proposed to obtain the welded joints with high quality. The experiment results show that A-MAG weld appearance, internal quality of welded joint and the welding operation performance are very well. Experiments also show that the A-MAG welding can improve weld penetration, which is compared with MAG welding under the same heat input. The tensile strength and bending strength of A-MAG welded joint are not reduced, while impact strength is improved, especially in the HAZ. Dimples size in fracture appearance of A-MAG welded joint is finer. It is showed that the active MAG welding can improve the welding quality and weld penetration of weathering resistant steel, which is applicable in engineering application. Source

Xu F.,Harbin Welding Institute | Lv Y.,Academy of Armored force Engineering | Liu Y.,Academy of Armored force Engineering | Xu B.,Harbin Institute of Technology | And 2 more authors.
Physics Procedia | Year: 2013

Pulsed plasma arc deposition (PPAD) was successfully used to fabricate the Ni-based superalloy Inconel 625 samples. The effects of three heat treatment technologies on microstructure and mechanical properties of the as-deposited material were investigated. It was found that the as-deposited structure exhibited homogenous cellular dendrite structure, which grew epitaxially along the deposition direction. Moreover, some intermetallic phases including Laves phase and MC carbides were precipitated in the interdendritic region as a result of Nb segregation. Compared with the as-deposited microstructure, the direct aged (DA) microstructure changed little except the precipitation of hardening phases γ' and γ'' (Ni3Nb), which enhanced the hardness and tensile strength. But the plastic property was inferior due to the existence of brittle Laves phase. After solution and aging heat treatment (STA), a large amount of Laves particles in the interdendritic regions were dissolved, resulting in the reduction of Nb segregation and the precipitation of needle-like δ (Ni3Nb) in the interdendritic regions and grain boundaries. The hardness and tensile strength were improved without sacrificing the ductility. By homogenization and STA heat treatment (HSTA), Laves particles were dissolved into the matrix completely and resulted in recrystallized large grains with bands of annealing twins. The primary MC particles and remaining phase still appeared in the matrix and grain boundaries. Compared with the as-deposited sample, the mechanical properties decreased severely as a result of the grain growth coarsening. The failure modes of all the tensile specimens were analyzed with fractography. © 2013 The Authors. Published by Elsevier B.V. Source

Li Z.,North University of China | Wang W.,Harbin Welding Institute | Wang X.,Harbin Welding Institute | Li H.,Tianjin University
Optics and Laser Technology | Year: 2010

To study the coupling of a Nd:YAG laser beam and a MIG arc with the spectrum of the plasma, a new hollow probe method is used to collect radiation from specific points within the arc plasma. With the probe, the spatial distributions of the MIG arc radiation with and without the Nd:YAG laser hybrid plasma are collected and analyzed by a fiber spectrometer. Through analysis of the spectrum, radiation in the ultraviolet (Fe II dominated), visible (Fe I dominated) and infra (Ar I dominated) spectral zones are acquired for comparison of the difference between the MIG and Laser-MIG hybrid welding processes. The electronic temperature is calculated using the Boltzmann plot method and the electronic density is calculated using the Stark broadening method. The results show that the Laser-MIG hybrid welding processes cause the plasma energy to focus on the center of the welding arc and approach the welding pool. An ionizing duct abundant with Fe ions will be formed near the position of the impinging laser beam, which makes the welding arc stable. The electronic temperature of the Laser-MIG hybrid welding arc is a little higher than that of the MIG. The electronic density of Laser-MIG hybrid welding is higher than that of the MIG. © 2009 Elsevier Ltd. All rights reserved. Source

Qin G.,Shandong University | Lin S.,Harbin Welding Institute
Zhongguo Jiguang/Chinese Journal of Lasers | Year: 2010

The effect of laser on the frequency of metal transfer and welding current in Nd: YAG laser+P-GMA (pulsed gas metal arc) hybrid welding was studied. The results show that the addition of laser energy into P-GMAW (pulsed gas metal arc welding) process can help to increase the frequency of metal transfer at the lower welding current and decrease its frequency at higher welding current. The addition of laser energy can reduce the welding current of P-GMAW, but its effect is very weak. The analyses indicate that the laser exerts the influence on metal transfer by the vaporization of material and the interaction between laser induced plasma and arc plasma, and its effects on welding current are exerted by the interaction between laser induced plasma and arc plasma. Source

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