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Wang W.,Shanghai JiaoTong University | Zhang Y.,Shanghai JiaoTong University | Yang J.,Shanghai JiaoTong University | Zhang Y.,Shanghai Aerospace Equipments Manufacturer | Yuan F.,Shanghai Aerospace Equipments Manufacturer
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science | Year: 2013

The fast and accurate modeling for machine errors is an important step for the implementation of error compensation. In this article, a new approach for real-time compensation of geometric and thermal errors is presented, including an accurate error model and a real-time error compensation system. An experiment is carried out on a three-axis milling center to obtain machine positioning errors under different temperatures. A serial of error data collected under normal temperature is regarded as the basic error and modeled with the machine position coordinates based on Newton interpolation method which is also used for modeling the other error curves under different working temperatures in order to get their coefficients of fitting formulas. According to the relationship among these formulas, all the coefficients and the corresponding temperature variations are modeled using the Newton interpolation method again. The final compensation model can be obtained by substituting the coefficients of basic error formula. In addition, an external realtime error compensation system is developed based on the function of external machine zero point shift in Fanuc CNC systems. Experimental results show that the proposed geometric and thermal error compensation system can be utilized as an effective manner to improve the accuracy of CNC milling machines. © IMechE 2012.

Jiang H.,Shanghai JiaoTong University | Yang J.,Shanghai JiaoTong University | Yao X.,Shanghai JiaoTong University | Zhang Y.,Shanghai Aerospace Equipments Manufacturer | Yuan F.,Shanghai Aerospace Equipments Manufacturer
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2013

A new least squares support vector machine (LS-SVM) modeling method based on Bayesian inference is presented to predict the spindle thermal distortion of computer numerical control (CNC) machine tool. With laser displacement sensors and thermal resistor sensors, a series of measurements on a 5-axis CNC machining center with double rotate tables are carried out to acquire spindle thermal distortions of different directions and temperature values for modeling. During the modeling process, the parameters of LS-SVM are chosen by Bayesian inference method, which can obtain the optimized parameters of maximum posterior probability. With these optimized parameters, the established model can predict the spindle thermal distortion accurately. The LS-SVM model based on Bayesian inference, the conventional LS-SVM model and the Back propagation artificial neural networks (BP-ANN) model are respectively used to predict the spindle thermal distortion under variable working conditions. With the prediction results comparison, the LS-SVM model based on Bayesian inference has the best prediction accurate, and is more effective and robust especially when the spindle runs under variable working conditions, it can smoothlg over some shortages of the traditional modeling methods. ©2013 Journal of Mechanical Engineering.

Chen D.,Shanghai JiaoTong University | Chu X.,Shanghai JiaoTong University | Sun X.,Shanghai Aerospace Equipments Manufacturer | Li Y.,China University of Mining and Technology | Su Y.,Shanghai JiaoTong University
Information Sciences | Year: 2015

This paper aims to develop a decision making approach based on the Information Axiom under hybrid uncertain environments. In these environments fuzziness and randomness co-exist. To model the hybrid uncertainties, the design range and system range of an evaluation criterion are expressed as a fuzzy variable and a random variable respectively. Calculating the Information Contents for these criteria would involve integrals whose bounds are fuzzy variables. To calculate these integrals, an expected Information Content Model (eICM) is proposed based upon the credibility theory. To reflect the designer's risk appetite accurately, the confidence levels are introduced and a credibility Information Content Model (cICM) based on the chance constrains programming model is constructed. Two algorithms based on fuzzy simulation methods and Genetic Algorithm are developed for these two models. Finally, a case study is illustrated to highlight the effectiveness and accuracy of the proposed approach. © 2015 Elsevier Inc. All rights reserved.

Zhang Z.H.,Harbin Institute of Technology | Zhang Z.H.,Xiamen University | Li M.Y.,Harbin Institute of Technology | Liu Z.Q.,Harbin Institute of Technology | And 2 more authors.
Acta Materialia | Year: 2016

This work investigated the growth characteristics and formation mechanisms of the Cu6Sn5 phase at the liquid-Sn0.7Cu/(111)Cu and liquid-Sn0.7Cu/(001)Cu joint interfaces. As a result of contributions from the interfacial environments, regular arrays of the roof-type Cu6Sn5 grains with fixed intersecting angles were generated on both types of the Cu single crystals after soldering at 250 °C for 1 s-1 h. At the liquid-Sn0.7Cu/Cu6Sn5 interface, a hexagonal-rod-type growth mechanism for Cu6Sn5 phase was proposed on the basis of its anisotropy in surface energy and roughness. According to this mechanism, the Cu6Sn5 roofs formed on the (111) and (001) Cu pads would consistently elongate in the [0001] direction of Cu6Sn5 phase, regardless of whether they belonged to the minimum mismatch direction of Cu6Sn5 and Cu phases; and they would maintain the {112¯0} and {101¯0} planes as the side faces respectively, despite the reaction time being prolonged to 1 h. At the Cu6Sn5/Cu interface, two types of the three-dimensional placement rules for Cu6Sn5 roofs on the Cu single crystals were determined on the basis of the suitable Cu matches of these two phases. Specifically, the junction interfaces between Cu6Sn5 roofs and Cu single crystals were confirmed to be ∥{101¯0} ∥ {111} and {112¯0} ∥ {001}; and the parallel orientation relationships of {0001} ∥ {011} were always present on both types of interfaces. Our study can help to clarify the growth mechanism of Cu6Sn5 phase and to provide a scientific basis of Cu6Sn5 orientation design for three-dimensional integrated circuit interconnect applications. © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Zhao H.,Harbin Institute of Technology | Zhang G.,Shanghai Aerospace Equipments Manufacturer | Yin Z.,Shanghai Aerospace Equipments Manufacturer | Wu L.,Shanghai Aerospace Equipments Manufacturer
Journal of Manufacturing Science and Engineering, Transactions of the ASME | Year: 2013

Interpass idle time is an important parameter affecting the thermal stress distribution in weld-based rapid prototyping. In this paper, the effects of interpass idle time on thermal stresses in multipass multilayer weld-based rapid prototyping are investigated using numerical simulation. Meanwhile the single-layer weld-based rapid prototyping experiment is carried out, and the residual stresses are measured in the blind-hole method. The variation trend of calculated residual stresses agrees with that of experimental measurements. The research results indicate that there exist stress release effects of rear pass on fore passes and that of rear layer on fore layers. The interpass and interlayer stresses and residual stresses are significantly dependent on interpass idle time. The residual stresses of deposition workpiece decrease with the increase of interpass idle time, whereas the interpass and interlayer stresses on the central line of substrate increase with the increase of interpass idle time. © 2013 American Society of Mechanical Engineers.

Mai C.,Harbin Institute of Technology | Li M.,Harbin Institute of Technology | Yang S.,Shanghai Aerospace Equipments Manufacturer
RSC Advances | Year: 2015

Silica glass pairs were directly bonded by wet chemical surface activation at a low temperature. A smooth joint interface with no voids and micro cracks was obtained with the assistance of a 250 °C heat treatment and a pressure of ∼30 MPa, and the excellent transmittance of the bonded pair was demonstrated by UV-Vis absorptions. This new method can tolerate a silica glass surface roughness as high as 6 nm. A demo chip with a microfluidic channel was also prepared by this method. A modified model for the glass-to-glass bonding mechanism is proposed based on the surface and interface characterization. Raman scattering analysis showed that Si-O-Si linkages at the silica glass surface were broken, and colloid-like hydrolyzed layers formed on the glass surface after the activation treatment. TEM and EELS results revealed that the 3D glass structure of the Si-O-Si linkages formed again at the interface of the directly bonded silica glass pairs after lowerature annealing. © The Royal Society of Chemistry 2015.

Dong H.,Dalian University of Technology | Yang Z.,Dalian University of Technology | Yang G.,Shanghai Aerospace Equipments manufacturer | Dong C.,Dalian University of Technology
Materials Science and Engineering A | Year: 2013

Dissimilar metal vacuum brazing between TiAl alloy and 40Cr steel at 900. °C for 5. min, 10. min and 15. min was conducted with Ti-based alloy foil as the filler. Five distinct regions were detected in the brazed seam from each joint during microstructure examination. The hardness in the brazed seam was measured much higher than those in the two substrates, and the hardness in the filler metal layer was higher than that in the reaction layer. However, brazing for longer time can reduce the hardness of the brazed seam. The average shear strength of the joint was 26. MPa when the joint was brazed for 5. min, and it increased to 32. MPa when brazed for 10. min and 15. min. The specimen brazed for 5. min fractured through the interface between 40Cr steel base metal and filler metal layer, but the specimen brazed for 10. min and 15. min fractured through the filler metal layer in the brazed seam. It was found that the compositions of the filler material and sufficient interdiffusion between the filler and substrates are important to improve the joint strength, and the mechanical properties of the filler metal also control the strength of the resultant joint. © 2012 Elsevier B.V.

Liu C.,Jiangsu University of Science and Technology | Yi X.,Shanghai Aerospace Equipments Manufacturer
Materials and Design | Year: 2013

Residual stress is a crucial factor when assessing the integrity of engineering components and welded assemblies. The internal longitudinal stresses in 4. mm and 8. mm thick AA6061-T6 aluminum alloy friction stir welding (FSW) specimens are measured with contour method. The measuring procedure of the contour method including specimen cutting under clamps with a wire electric discharge machine, precise contour measurement with a coordinate measuring machine, careful data processing and elastic finite element analysis are introduced in detail. Finally, the longitudinal residual stresses throughout the cut plane for the two joints are mapped, and the through-thickness longitudinal stresses of the two FSW joints are also analyzed. Investigated results show that the contour method can be applied to measure the internal residual stress in thin plates with a thickness of 4. mm; the longitudinal stress distribution in the present study is not an apparent M-shaped distribution in the transverse direction; within the weld region, the tensile longitudinal stress in the advancing side is larger than that in the retreating side; the longitudinal stresses are not uniform across the thickness of specimens; the peak tensile longitudinal stresses for both joints reach 168. MPa (amount to 61% of the yield strength of AA6061-T6 alloy at room temperature), and appear at a depth of 62.5% thickness at the edge of the tool shoulder in the advancing side of the weld. © 2012 Elsevier Ltd.

Xu W.F.,Northwestern Polytechnical University | Liu J.H.,Northwestern Polytechnical University | Chen D.L.,Ryerson University | Luan G.H.,China Center Beijing Technology Ltd Company | Yao J.S.,Shanghai Aerospace Equipments Manufacturer
Scripta Materialia | Year: 2012

The microstructure and cyclic deformation behavior of three slices of a thick plate of friction-stir-welded Al-Cu alloy were investigated. Friction stir welding resulted in a composite-like nugget zone consisting of fine particles uniformly dispersed in the recrystallized fine-grained matrix. The top slice had larger grains, smaller particles, higher hardness, stronger cyclic hardening, higher hysteresis energy and lower fatigue life than the bottom slice. Fatigue cracks initiated from near-surface particles in the low-hardness zone, and propagated via striation formation mechanisms along with particle cracking. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Li S.,Beijing University of Chemical Technology | Zuo Y.,Beijing University of Chemical Technology | Ju P.,Shanghai Aerospace Equipments Manufacturer
Applied Surface Science | Year: 2015

Abstract A Co-Pd film was deposited on 316L stainless steel by electroplating. The erosion-corrosion behavior of the Co-Pd plated samples in hot sulfuric acid solution with SiO2 particles was investigated. The results showed that there was a significant synergistic effect between erosion and corrosion. At higher stirring speed, even in such strong corrosive environment the erosion-corrosion rate of Co-Pd plated samples was controlled mainly by the erosion resistance. The erosion-corrosion resistance of pure Pd plated sample decreased rapidly with increasing stirring speed, whereas that of Co-Pd plated sample kept almost stable under the tested conditions due to the high micro-hardness and good corrosion resistance of the film. © 2015 Elsevier B.V. All rights reserved.

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