Time filter

Source Type

Liu F.,University of Chinese Academy of Sciences | Zhang Z.,University of Chinese Academy of Sciences | Wei Y.,Shanghai Aircraft Manufacturing Co | Zhang Q.,University of Chinese Academy of Sciences | And 2 more authors.
Optics Express | Year: 2014

We demonstrate the photophoretic trapping of more than several hundreds of absorbing particles by tapered-ring optical traps diffracted from a circular aperture. The experiments with different laser powers show the influence of air flow acting on particles. Three kinds of particles with different densities (about 1-7 g/cm3) and different shapes (spherical, nonspherical) can be trapped. The non-spherical particles (toner particles) disperse in optical field, while the spherical particles (ink droplets and iron particles) arrange as a straight line. More importantly, in the experiments of two counter-propagating tapered-ring beams, the agglomeration of particles is achieved and can help research the dynamics of aerosols. ©2014 Optical Society of America.

Liu Z.Q.,Shanghai JiaoTong University | Liu Z.Q.,Jiangsu University of Science and Technology | Xu J.,Shanghai JiaoTong University | Han S.,Shanghai Aircraft Manufacturing Co | Chen M.,Shanghai JiaoTong University
International Journal of Precision Engineering and Manufacturing | Year: 2013

This paper presents a new flexible method referring to coupling response surface methodology (CRSM) to acquire optimum cutting parameters in machining of difficult-to-cut titanium alloy under minimum quantity lubrication (MQL) condition. Cutting speed, feed rate and depth of cut are designed as three factors by using the Taguchi method, which are also subject to several constraints including processing efficiency, cutting force and surface quality. In addition, turning experiments of titanium alloy were performed in order to set up the model based on Taguchi experimental design and multiple regression method. ANOVA was carried out to prove the adequacy of the developed mathematical model and the influences of cutting parameters on constraints were also observed. The results indicated that the feed rate was the dominant factor affecting surface roughness and cutting forces, which were minimized when the feed rate and depth of cut were set to the lowest level, while cutting speed was set to the highest level. Moreover, the predicted values obtained by CRSM were in good agreement with the experimental values, which indicated that CRSM was an effective method to determine optimum cutting conditions for machining process under MQL condition. © 2013 Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg.

Zhu J.,Beihang University | Duan Y.,Beihang University | Chen J.,Shanghai Aircraft Manufacturing Co | Zhao Y.,Beihang University
Fuhe Cailiao Xuebao/Acta Materiae Compositae Sinica | Year: 2012

In order to choose the best parameters of tackifier in vacuum assisted resin infusion (VARI) processing, the effects of tackifier on perform permeability, fiber compression and mechanical performance were addressed. The component of tackifier and its melting characteristics were ananlyzed by DSC and IR. The perform permeability, fiber compression characteristics and mechanical performance at different temperatures were examined. It is shown that the tackfier is a kind of polymer with epoxide group and low melting point. For the same tackifier concentration, the perform permeability and compressed thickness decrease as the temperature increasing below 100°C, but between 100°C and 140°C, the compressed thickness keeps constant and the permeability increases as the temperature increasing. The temperature has no significant effect on the mechanical properties.

Liu Z.,Shanghai JiaoTong University | Liu Z.,Jiangsu University of Science and Technology | An Q.,Shanghai JiaoTong University | Xu J.,Shanghai JiaoTong University | And 2 more authors.
Wear | Year: 2013

Dry machining and minimum quantity lubrication (MQL) machining which are two types of green manufacturing processes have vast potentials for machining of titanium alloys. Tool coating is one key factor to realize high speed machining and green manufacturing. However, the tool coatings used presently in machining of titanium alloys cannot meet with the requirement of high speed machining and green manufacturing processes. The nanocomposite coatings can be alternativly applied in high-speed machining of α+β phase titanium alloy Ti-6Al-4V. In this research, the wear rate, wear pattern and wear mechanism of two kinds of nanocomposite coatings, (nc-AlTiN)/(a-Si3N4) and (nc-AlCrN)/(a-Si3N4), in dry and MQL conditions were investigated. Results showed that (1) MQL condition, which has cooling and lubricating effects, was found to have more significant influence in improving the tool life as compared to dry condition. Furthermore, the (nc-AlTiN)/(a-Si3N4) coated tool was confirmed to be more suitable for machining of titanium alloy than (nc-AlCrN)/(a-Si3N4) coated tool under MQL condition, which emphasizes the significance of matching between cutting fluids and coating materials. (2) The slower wear rate of (nc-AlTiN)/(a-Si3N4) coated tool in MQL condition was obtained than that of the (nc-AlCrN)/(a-Si3N4) coated tool. As a result, MQL condition can greatly prolong the tool life of (nc-AlTiN)/(a-Si3N4) coated tool while has minor influence on improving the tool life of (nc-AlCrN)/(a-Si3N4) coated tool. (3) Adhesive wear was observed to be the main wear type. The MQL technique not only has cooling and lubricating effects on nanocomposite coated tool, but also helps to form powerful protective layer. In addition, in MQL condition, the (nc-AlTiN)/(a-Si3N4) coated tool only suffered adhesive wear while the (nc-AlCrN)/(a-Si3N4) coated tool suffered adhesive, diffusion and oxidation wear. In contrast, when turning tests were performed under dry cutting condition, adhesive wear and oxidation wear might be the main wear types for the two coated carbide tools. © 2013 Elsevier B.V.

Chu G.N.,Harbin Institute of Technology | Chen G.,Harbin Institute of Technology | Chen B.G.,Shanghai Aircraft Manufacturing Co | Yang S.,Tianjin Aerospace Electromechanical Equipment Research Institute
International Journal of Advanced Manufacturing Technology | Year: 2014

In order to overcome difficulties in non-uniform thickness distribution and cracking failure during rectangular tube quasi-static hydroforming, a new forming technology, named as electromagnetically assisted hydroforming, is put forward. Both experiment and finite element method were conducted to investigate corner deformability and deformation pattern and its effect mechanisms. Results indicate that both corner deformability and thickness distribution are improved greatly under electromagnetic-assisted hydroforming. The reason is that deformation behavior changed after electromagnetic force application. As electromagnetic force is applied, tine petal cross sections are periodically produced and flattened. Thus, petal-like preform continues to generate and play a useful role in corner filling. Such deformation pattern overcomes friction holding back defect and results in stress state going over from tensile stress to compressive stress, which helps to avoid cracking failure and greatly improve thickness uniformity. At the same time, it also contributes to improve surface quality and decrease forming pressure simultaneously. © 2014 Springer-Verlag London.

Discover hidden collaborations