Dec 2010, Volume 5 Issue 4
    

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  • Wojciech SZYNKIEWICZ, Teresa ZIELIŃSKA, Włodzimierz KASPRZAK

    A planner for a self adaptable and reconfigurable fixture system is proposed. The system is composed of mobile support agents that support thin sheet metal parts to minimize part dimensional deformation during drilling and milling operations. Compliant sheet metal parts are widely used in various manufacturing processes including automotive and aerospace industries. The main role of the planner is to generate an admissible plan of relocation of the mobile agents. It has to find the admissible locations for the supporting heads that provide continuous support in close proximity to the tool and trajectories of the mobile bases characterized by very high speeds during the relocation phases.

  • RESEARCH ARTICLE
    Kirsten BOBZIN, Nazlim BAGCIVAN, Lidong ZHAO, Stefania FERRARA, Jan PERNE

    In the last decade, microsystems evolved to decisive technology in many technical applications. With increasing requirements on the performance of microsystems, more and more dissimilar materials are used in the same assembly. Correspondingly, suitable joining methods are required to fulfil the requirements on good properties of joints. In this study, a new transient liquid phase (TLP) system Au-Sn-Au was developed for potential medical applications in hybrid microsystems. The high and low melting phases Au and Sn were deposited onto diverse substrates by magnetron-sputter-ion plating. The coated substrates were soldered in a microsoldering station under different conditions. The influence of soldering conditions on the microstructure and properties of the joints was investigated. Results show that the developed solder led to high-quality joints that can be used in microsystems for medical applications.

  • RESEARCH ARTICLE
    Nathan HOWELL, Weihua LI

    This paper discusses methods of microfluidic droplet actuation by means of electrowetting-on-dielectrics (EWOD) and provides a technique for modeling and simulating a microfluidic device by using the computational fluid dynamics (CFD) program, Flow3D. Digital or droplet microfluidics implies the manipulation of droplets on a scale of nanoliters (10-9 L) to femtoliters (10-15 L), as opposed to continuous microfluidics that involve the control of continuous fluid within a channel. The two operations in focus here are droplet translocation (moving) and droplet fission (splitting), in which the pressures and velocities within the droplet are analyzed and compared to existing works, both theoretical and experimental. The variation in the pressure of the leading and trailing faces of a droplet indicates the variation in surface energy—an important parameter that explains how a droplet will move toward a region of higher electric potential. The higher voltage on one side of a droplet reduces surface energy, which leads to an induced pressure drop, thus resulting in fluid motion. Flow3D simulations are for both water and blood droplets at voltages between 50 V and 200 V, and the droplet size, surface properties (Teflon coated), and geometry of the system are kept constant for each operation. Some peculiarities of the simulation are brought to light, such as instabilities of the system to higher voltages and fluids with higher dielectric constants, as well as the creation of a tertiary droplet when the applied voltage causes a large enough force during fission. The force distribution across the droplet provides a general understanding of the electrowetting effect and more specifically allows for a comparison between the effects that different voltages have on the forces at the droplet surface. The droplet position and mean kinetic energy of the droplet are also investigated and compared to other works, proving the dynamics of a droplet motion found here.

  • RESEARCH ARTICLE
    Jan BOHá?EK, Ale? HORáK

    The steel hot rolling process is inseparably connected to an oxide layer called “scale” at high temperatures. Hydraulic descaling of rolled material is a part of all rolling trains. Surface quality after descaling is fundamental for the final surface quality of a rolled product. The process itself is not theoretically well described; various different approaches have been used to clarify the descaling problem. This paper describes the dynamics of high-speed impact between the compressible water droplet and the steel scale layer. The phenomenon is known as water hammer effect. The purpose of this study is to numerically verify the fact that impact stress can be a significant factor during the descaling process. Considering a high droplet impact speed (100–300 ms-1), inferential extremely short time interval (0.1–5 μs) peaks in impact pressure reaching 300 MPa can be found. Droplet dynamics was simulated with the help of LS-Dyna solver, whereas the stress analysis was performed in ANSYS interface. The extreme pressure peaks of very short duration in an impact area are a new phenomenon in the descaling theory.

  • RESEARCH ARTICLE
    Huijun ZOU, Qinghua LIANG, Qing ZHANG

    Conceptual design is the most critical and creative phase of design. Recently, increasing attention has been directed to supporting conceptual-level computer aided creative design and its theories and methodologies. Specifically, for conceptual design of mechanical products, this paper presents a novel function solving model for mechanical product design and highlights the importance of systematic synthesis to achieve creative design. Then it builds a framework as a function-effect-process-action- mechanisms (FEPAM) mapping process, which enables creative design on the basis of conceiving different action schemes. After that, several key points are elaborated including 1) representing and decomposition methods of functions and motion behaviors; 2) action scheme representing method based on network plan techniques; and 3) variation and creation methods based on action scheme transformations.

  • RESEARCH ARTICLE
    Chuntao JI, Lipeng DENG

    The behaviors of electrode displacement and force during spot welding under various conditions, such as different weld currents, electrode forces, and welding times, were studied. Tests were conducted on a 170?kVA MFDC spot welder. Data were collected via a multichannel high-speed data acquisition system and were analyzed with MATLAB. Behaviors of 5182 aluminum and mild steel in spot welding were compared. Results show that nugget expansion rate does not reach zero for aluminium as it does for mild steel as nugget grew to a certain size. A linear relationship is found between the nugget size and maximum expansion that facilitates online weld quality evaluation. An electrode force peak is observed and believed relevant to the sufficient nugget size.

  • RESEARCH ARTICLE
    Qiushuang LIU, Xiaoli XU

    Because it is difficult for the traditional PID algorithm for nonlinear time-variant control objects to obtain satisfactory control results, this paper studies a neuron PID controller. The neuron PID controller makes use of neuron self-learning ability, complies with certain optimum indicators, and automatically adjusts the parameters of the PID controller and makes them adapt to changes in the controlled object and the input reference signals. The PID controller is used to control a nonlinear time-variant membrane structure inflation system. Results show that the neural network PID controller can adapt to the changes in system structure parameters and fast track the changes in the input signal with high control precision.

  • RESEARCH ARTICLE
    Zhengbao LEI, Shubin WEI, Qingyun DU

    To obtain the explicit function for optimizing the cutting-screw-thread (CST) in crash, the simulations of frontal crash at the speed of 56 km/h have been carried out in VPG. The peak acceleration in crash has been taken as the evaluation index of energy absorption characteristics. First, the single factor experiment was taken based on six parameters affecting on the absorption characteristics of CST. Second, the peak acceleration function of each parameter by using response surface method (RSM) is obtained. Third, the explicit resultant peak acceleration function of six parameters by using RSM again is obtained. A dual RSM-based explicit method is proposed. According to this function, the best size dimensions of CST in different crash conditions could be easily obtained. Finally, an example shows that the values of the calculation errors for simulation value and target value (40 g) are 3.6% and 1.3%, respectively. This method can satisfy the demand for engineering accuracy.

  • RESEARCH ARTICLE
    Min WANG, Jianzhong HU, Tao ZAN

    The theory and algorithm of the homogeneous transformation matrix (HTM) method are applied in establishing the kinematic error model of five-axis machining tool with two-axis turntable. Based on this model, a new method for the kinematic error separation in five-axis numerical control (NC) machining tool is proposed. In this study, three types of simultaneous three-axis control motions are designed for each rotary axis to identify the deviations. In the measurement, two translational axes and one rotary axis are simultaneously controlled to keep a constant distance between the tool and the worktable. Telescoping double ball bar is used to measure the relative distance between the spindle and the worktable in the motion of NC machining tool. Finally, the value measured by telescoping double ball bar is substituted into the model to obtain kinematic error of NC machining tool. Comparison has confirmed that the proposed method is high precision and can be applied to effectively and conveniently measure the five-axis machining tool.

  • RESEARCH ARTICLE
    Lezhi YE, Desheng LI, Bingfeng JIAO

    An eddy current retarder for vehicles generates much heat when it works continuously, which leads to serious decline in braking torque. This paper proposes a novel permanent magnet retarder (PMR) for vehicles, whose cooling system connects with engine cooling-water. A three-dimensional finite element model is developed to model the electromagnetic behavior of a permanent magnet retarder under a constant speed. The magnetic field and eddy current field in PMR are numerically solved by a finite element method. By accounting for the nonlinear permeability of the rotor and the weakened effect in the magnetic field that is generated by the eddy current magnetic field, the calculation accuracy of air-gap magnetic field is enhanced. Experiment shows that the temperature of the retarder is less than 150°C, and the braking torque keeps the hard characteristics curve. The calculated air-gap magnetic flux density is fairly good agreement with the measured one.

  • RESEARCH ARTICLE
    Bingfeng JIAO, Desheng LI, Yunkang SUI, Lezhi YE

    The main purpose of this research is to perform a magnetic analysis on the magnetic equipment of permanent magnet retarder (PMR) and optimize the structure of magnetic equipment with the commercial FEM software ANSYS and its design optimization module. The FEM model is built as an axisymmetric model according to the characteristics of the structure of magnetic equipment. Using this model, the magnetic field distribution and magnetic force are calculated by ANSYS. The mathematical model of structure optimization is also built. The design variables are structural parameters including the dimensions of permanent magnets and magnetic yoke, and the objective function is the magnetic force. The unconstrained optimization model takes the maximum value of magnetic force as the objective. A first-order optimization method is used to determine the optimum design of this problem. The optimization process works entirely with the ANSYS parametric design language (APDL). The design tools are used to understand design space and the behavior of the dependent variables. It is shown that designing a structure with the ANSYS optimization module and its design tools is an effective means to improve the structure.

  • RESEARCH ARTICLE
    Bing TU, Desheng LI, Enhuai LIN, Bin LUO, Jian HE, Lezhi YE, Jiliang LIU, Yuezhong WANG

    Rotation magnetic beacons magnetic field strength is very important to drill parallel horizontal twin wells in steam assisted gravity drainage (SAGD). This paper analyzes a small magnet with a diameter of 25.4 mm. At each end, there is a length of 12.6 mm with permanent magnet, and in the middle, there is a length of 78 mm with magnetic materials. The magnetic field strength generated by the magnetic material of 1J12, 1J50, and 1J79 is analyzed, respectively. ANSOFT software is used to simulate the magnetic field strength generated by different magnetic materials above, which also be tested through experimental methods. The comparison of the simulation and experimental results show that experimental and simulation results are basically consistent, and the results can meet the specific requirements of engineering applications.

  • RESEARCH ARTICLE
    Cunfu HE, Huanyu ZHAO, Ruiju WEI, Bin WU

    This paper theoretically and experimentally studies the existence of complete band gaps in two-dimensional (2D) phononic crystal consisting of parallel steel rods in water with square lattice. The band structure of phononic crystal is calculated by a plane wave expansion (PWE) method. Based on the well-known ultrasonic immersion transmission technique, the overlapping transmission spectra of acoustic waves, a complete band gap, is experimentally measured along the two high-symmetry directions of the first irreducible Brillouin zone. There is a very good agreement between the experimental result and the range of frequencies of the complete band gap.

  • RESEARCH ARTICLE
    Yarong CHEN, Zailin GUAN, Yunfang PENG, Xinyu SHAO, Muhammad HASSEB

    The use of techniques and system of constraint programming enables the implementation of precise, flexible, efficient, and extensible scheduling systems. It has been identified as a strategic direction and dominant form for the application into planning and scheduling of industrial production. This paper systematically introduces the constraint modeling and solving technology for production scheduling problems, including various real-world industrial applications based on the Chip system of Cosytec Company. We trend of some concrete technology, such as modeling, search, constraint propagation, consistency, and optimization of constraint programming for scheduling problems. As a result of the application analysis, a generic application framework for real-life scheduling based on commercial constraint propagation (CP) systems is proposed.

  • RESEARCH ARTICLE
    Jianxin LIU, Huaiyun ZHAO, Wanming ZHAI

    A single wheelset drive model and 2-DOFs torsional vibration model were established to investigate the self-excited torsional vibration of a locomotive driving system. The simulation results indicate that the self-excited torsional vibration occurs when the steady slip velocity is located at the descending slope of the adhesion coefficient curve. The principle of energy conservation was used to analyze the mechanism of the self-excited vibration. The factors affecting on the amplitude of the self-excited vibration are studied.

  • RESEARCH ARTICLE
    Hongxue XU, Hong ZHENG, Xiuying GUO

    A modular architecture model of a computer-supported collaborative design (CSCD) system is proposed on the basis of the hierarchical structure characteristics of a distributed collaborative design system and advanced component object technology. The model mainly regards the module as the core organizing and managing design objects and uses the common object request broker architecture (CORBA) specifications as an interactive platform to achieve object communication. The browser/server computing model deals with the remote heterogeneous collaborative design problem. Product design strategies and mechanisms for collaborative design are separated to facilitate the application of distributed collaborative design environment for quick implementation. The open design framework for CSCD system developers can support the implementation of distributed collaborative design to improve product design speed and reduce product development time. The modular CSCD system (MCSCDS) model and its implementation are achieved in the modular CSCD, a prototype system.

  • RESEARCH ARTICLE
    Yongjie LU, Shaopu YANG, Shaohua LI

    The tire-road contact mechanics is the key problem in vehicle ride comfort and road-friendliness research. A flexible roller contact (FRC) tire model with the enveloping property is introduced to reflect the contact history between the tire and the road. Based on D’Alembert principle, an integral balanced suspension (IBS) model is established, considering mass and moment of? inertia of? the stabilizer rod. ?The sprung mass accelera- tion and tire dynamic force for balanced suspension and the traditional quarter-vehicle model are compared respectively for frequency and time domain responses. It is concluded that the quarter-vehicle model can be used to evaluate the ride comfort of vehicles; however, it has some limitations in evaluating the vehicle road-friendliness. Then, the dynamics performances for IBS model are analyzed with the single point contact (SPC) model and FRC model, respectively. These works are expected to propose a new idea for the vehicle-road interaction research.

  • RESEARCH ARTICLE
    Lixin GAO, Lijuan WU, Yan WANG, Houpei WEI, Hui YE

    This paper presents an intelligent system that is necessary for diagnostic accuracy and efficiency in the iron and steel industry. A rule-based reseaning (RBR) intelligent diagnostic system has been developed based on many successful diagnostic applications. It can solve the difficulty in knowledge acquisition and has more precision. Its application results prove that the usability of the system is good and it will increasingly attain perfection.