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Theoretical analysis and experimental investigation of valveless piezoelectric pump with unsymmetrical ridges
ZHANG Jianhui, LU Jizhuang, XIA Qixiao, LI Hong
Front. Mech. Eng.. 2007, 2 (1): 13-19.
https://doi.org/10.1007/s11465-007-0002-1
A novel valveless piezoelectric pump with unsymmetrical ridges is presented at first. It ingeniously utilizes the inner space of its chamber by developing its chamber bottom into unsymmetrical ridges along the direction of the inlet and outlet of the pump. Hence, a series of cuneiform channels are asymmetrically and alternately formed between the unsymmetrical ridges and the piezoelectric vibrator, which enables the pump to form a one-way flow instead of the function of the traditional diffuse or nozzle elements fitted outside the chamber. Then, by analyzing the vibration of the piezoelectric vibrator, the vibration deformation function and the equation of volume change are established. Meanwhile, the theoretical equation of the pump flow rate is established. Finally, a real valveless piezoelectric pump with unsymmetrical ridges is manufactured, and the flow rate of the pump is measured through experiments. It is proved that the theory is rational and correct by comparing the experimental flow rate and the theoretical flow rate. In addition, for calculating the theoretical flow rate, the positive and converse flow resistance coefficients of unsymmetrical ridges are measured through experiments, when one slope angle of the unsymmetrical ridges is 90º and another is changing from 20º to 60º, respectively.
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Dilution rate and microstructure of TIG arc Ni-Al powder surfacing layer
SHAN Jiguo, DONG Wei, TAN Wenda, ZHANG Di, REN Jialie
Front. Mech. Eng.. 2007, 2 (1): 20-24.
https://doi.org/10.1007/s11465-007-0003-0
Surfacing beads are prepared by a direct current tungsten inert gas arc nickel-aluminum (Ni-Al) powder surfacing process. With the aim of controlling the dilution rate and obtaining surfacing beads rich in intermetallic compounds, the effects of surfacing parameters on geometric parameters, dilution rate, composition, and microstructure of the bead are investigated. An assistant cooler, which can potentially reduce the temperature of the base metal, is used in the surfacing process and its effect on dilution rate and microstructure is studied. The result indicates that with the surfacing parameter combination of low current and speed, the width and penetration of the bead decrease, reinforcement increases, and dilution rate drops markedly. With the reduction of the parameter combination, the intergranular phase ?-(Fe, Ni) is formed in the grain boundaries of Ni-Al intermetallic matrix instead of the intergranular phase ?-Fe, and large amount of intermetallics are obtained. With the use of an assistant cooler on a selected operation condition during the surfacing process, the reinforcement of the bead increases, penetration decreases, and dilution rate declines. The use of an assistant cooler helps obtain a surfacing bead composed of only intermetallics.
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Feature extraction from slice data for reverse engineering
ZHANG Yingjie, LU Shangning
Front. Mech. Eng.. 2007, 2 (1): 25-31.
https://doi.org/10.1007/s11465-007-0004-z
A new approach to feature extraction for slice data points is presented. The reconstruction of objects is performed as follows. First, all contours in each slice are extracted by contour tracing algorithms. Then the data points on the contours are analyzed, and the curve segments of the contours are divided into three categories: straight lines, conic curves and B-spline curves. The curve fitting methods are applied for each curve segment to remove the unwanted points with pre-determined tolerance. Finally, the features, which consist of the object and connection relations among them, are founded by matching the corresponding contours in adjacent slices, and 3D models are reconstructed based on the features. The proposed approach has been implemented in OpenGL, and the feasibility of the proposed method has been verified by several cases.
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Analysis of stability and nonlinear response of rotor system with elliptical sliding bearing supports
LU Yanjun, LIU Heng, YU Lie, LI Qi, JIANG Ming, ZHANG Zhiyu
Front. Mech. Eng.. 2007, 2 (1): 37-45.
https://doi.org/10.1007/s11465-007-0006-x
Based on the variational constraint approach, the variational form of Reynolds equation in hydrodynamic lubrication is revised continuously to satisfy certain constraints in the cavitation zone of oil film field. According to the physical characteristic of oil film, an eight-node isoparametric finite element method is used to convert the revised variational form of Reynolds equation to a discrete form of finite dimensional algebraic variational equation. By this approach, a perturbance equation can be obtained directly on the finite element equation. Consequently, nonlinear oil film forces and their Jacobian matrices are calculated simultaneously, and compatible accuracy is obtained without increasing the computational costs. A method, which is a combination of predictor corrector mechanism and Newton Raphson method, is presented to calculate equilibrium position and critical speed corresponding to Hopf bifurcation point of bearing-rotor system, as by-product dynamic coefficients of bearing are obtained. The timescale, i.e., the unknown whirling period of Hopf bifurcation solution of bearing-rotor system is drawn into the iterative process using Poincar?Newton Floquet method. The stability of the Hopf bifurcation solution can be detected when estimating Hopf bifurcation solution and its periods. The nonlinear unbalanced T periodic responses of the system are obtained by using PNF method and path-following technique. The local stability and bifurcation behaviors of T periodic motions are analyzed by Floquet theory. Chaotic motions are analyzed by Lyapunov exponents. The numerical results revealed the rich and complex nonlinear behavior of the system, such as periodic, quasiperiodic, jumped solution, chaos, and coexistence of multisolution, and so on.
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Test investigation on hydraulic losses in the discharge passage of an axial-flow pump
QIU Baoyun, CAO Haihong, JIANG Wei, GAO Zhaohui, WANG Fei
Front. Mech. Eng.. 2007, 2 (1): 50-56.
https://doi.org/10.1007/s11465-007-0008-8
In a discharge passage with a guide blade discharge circulation and secondary flow because of bend pipe, the flow in a 1-channel discharge passage of an axial flow pump is a complicated spiral flow. For a 2-channel passage, the discharge in the left channel is bigger than that in the right, and the passage hydraulic losses are abnormal. In this study, the section current energy of the passage is accurately measured and determined with a 5-hole probe. The hydraulic loss characteristics are determined and analyzed. The methods deducing the hydraulic losses are investigated. The results indicate that the passage hydraulic losses are not proportional to the flow discharge. Compared with a circular pipe, the hydraulic losses of a divergent discharge passage are smaller and the pump assembly efficiency is 10% 30% higher. As for the 1-channel passage, the axial-flow pump outlet circulation is usually too big; the passage hydraulic losses are also big, but a small circulation can slightly reduce hydraulic losses. As for the 2-channel passage, discharges in the two channels are not equal and the hydraulic losses increase. The outlet guide blade with a small discharge circulation or without circulation could reduce discharge passage hydraulic losses and increase pump assembly efficiency by 6% 11%.
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Variable identification and automatic tuning of the main module of a servo system of parallel mechanism
YANG Zhiyong, XU Meng, HUANG Tian, NI Yanbing
Front. Mech. Eng.. 2007, 2 (1): 82-88.
https://doi.org/10.1007/s11465-007-0014-x
The variables of the main module of a servo system for miniature reconfigurable parallel mechanism were identified and automatically tuned. With the reverse solution module of the translation, the module with the exerted translation joint was obtained, which included the location, velocity and acceleration of the parallelogram carriage-branch. The rigid dynamic reverse model was set as the virtual work principle. To identify the variables of the servo system, the triangle-shaped input signal with variable frequency was adopted to overcome the disadvantages of the pseudo-random number sequence, i.e., making the change of the vibration amplitude of the motor dramatically, easily impact the servo motor and make the velocity loop open and so on. Moreover, all the variables including the rotary inertia of the servo system were identified by the additive mass. The overshoot and rise time were the optimum goals, the limited changing load with the attitude was considered, and the range of the controller variables in the servo system was identified. The results of the experiments prove that the method is accurate.
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Research on integrating customization design for mechanical product
TAI Ligang, LI Dianqi, ZHONG Tingxiu, LI Zhi
Front. Mech. Eng.. 2007, 2 (1): 89-93.
https://doi.org/10.1007/s11465-007-0015-9
This paper proposes an integrating rapid customization design system which combines various technologies such as Web, knowledge based engineering (KBE), engineering database and Computer Aided Design (CAD) and has been used in elevator design. The whole system is set up on the base of engineering database technology, integrating Product Data Management (PDM), Enterprise Resource Planning (ERP) etc. It adopts Web technology to enable customers to individually customize products remo tely through the internet. The system also adopts KBE to manage and reuse product design knowledge, while combining the technology of product family modeling and technologies of feature modeling and parametric design, based on the assembly of the CAD system of Unigraphics Solutions Inc., to create a product family case library that achieves intelligent, rapid design customization.
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Process Planning Support System for Green Manufacturing and its application
HE Yan, LIU Fei, CAO Huajun, ZHANG Hua
Front. Mech. Eng.. 2007, 2 (1): 104-109.
https://doi.org/10.1007/s11465-007-0018-6
Owing to a lack of practical methods and software tools in the existing researches on green manufacturing (GM), process planning support system for green manufacturing (GMPPSS) was developed to deal with the problems in optimization of environment-benign process planning. The GMPPSS consisted mainly of three function modules and related model repositories including: selection of process elements, optimization of process courses, and evaluation of process projects for GM. The database of the GMPPSS was used to provide plentiful information on resources consumption and environmental impact in manufacturing processes, which consisted of process attribute database, inventory database, machine database, tool database, and the cutting fluid database. Raw materials, secondary material consumption, energy consumption, and environment impacts of process planning were optimized to improve the green attribute of process planning of parts with the supports of the databases and model repositories. The gear processing in the machining tool factory was presented to verify the system s applicability.
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Modular structure of a self-reconfigurable robot
FEI Yanqiong, DONG Qinglei, ZHAO Xifang
Front. Mech. Eng.. 2007, 2 (1): 116-119.
https://doi.org/10.1007/s11465-007-0020-z
This paper proposes a novel, hermaphroditic, and lattice self-reconfigurable modular robot. Each module is composed of a center body a cubic part and six sides that can rotate independently. There are two holes and two extensible pegs on each side. The rotary motion of each side and the extensible motion of the pegs are generated by a motor connected to a reducer, using a cone-shaped gear, belt, clutch, etc. The structure of the module is compact, and has space to extend further.
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21 articles
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