Dec 2009, Volume 4 Issue 4
    

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  • Research articles
    Creep of brazed plate-fin structures in high temperature compact heat exchangers
    Shantung TU, Guoyan ZHOU
    2009, 4(4): 355-362. https://doi.org/10.1007/s11465-009-0065-2
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    In recent years, the need for high temperature heat exchangers to improve the efficiency of power and chemical conversion systems has been growing. However, the creep design of the high temperature compact heat exchangers has been a primary concern because the working temperature can be well above the creep limit of the materials. To establish the high temperature design criterion for compact heat exchangers, creep behavior of the plate-fin structures and brazed joints are investigated in this paper. The time-dependent deformation and bending stress of the plate-fin structures are obtained analytically by simplifying the fins to elastic springs. The creep damage evolution inside the brazed joint is studied by coupling the finite element method with a damage constitutive equation. The significant effect of creep property mismatch in the brazed joint on the creep strength is demonstrated.
  • Research articles
    Design considerations and experimental studies on semi-active smart pin joint
    Yancheng LI, Jianchun LI, Bijan SAMALI, Jiong WANG,
    2009, 4(4): 363-370. https://doi.org/10.1007/s11465-009-0074-1
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    Hostile dynamic loadings such as severe wind storms, earthquakes, and sudden impacts can cause severe damage to many civil engineering structures. An intelligent structural system equipped with smart structural members that are controllable in real-time is an effective solution to structural damage and failure during such situations. Civil intelligent structures with controllable properties to adapt to any changes due to dynamic loadings can lead to effective protection of structures and their occupants. In this paper, design and testing of a semi-active magnetorheological (MR) pin joint, in which the moment resistance can be controlled in real-time by altering the magnetic field, is reported with the view of using it as a potential candidate for smart members in the development of intelligent structures. Design of prototype smart pin joints includes theoretical analysis related to the radius of the rotary plate, the property of MR fluids and the gap between the rotary plate and the casing based on the requirements of the dynamics of MR pin joints. FEM analysis was deployed to study the distribution of the magnetic field along the gap. It is found, from the theoretical analysis and experimental verification, that the MR pin joint with a diameter of 180 mm can produce a torque of up to 30 Nm, which meets requirements for semi-active members in a multi-storey prototype building model in the next stage of research and development.
  • Research articles
    Design approach for single piston hydraulic free piston diesel engines
    Wei WU, Shihua YUAN, Jibin HU, Chongbo JING,
    2009, 4(4): 371-378. https://doi.org/10.1007/s11465-009-0069-y
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    The operating characteristics of a single piston hydraulic free piston diesel engine differ significantly from conventional diesel engines and this provides a theoretical basis for controlling and optimizing the design of the engine. The design of the proposed engine intended as a power supply for a hydraulic propulsion vehicle is presented. An engine performance forecast model was generated in AMESim. The performance of the prototype engine is predicted and the predictive results are verified with experiments. The particular features of the engine are discussed. The dynamic characteristics of the prototype engine are analyzed and the results indicate the rationality and feasibility of the engine design parameters. The features of the controllable working frequency and the intermittence output flows are provided. The flow capacity characteristics of the hydraulic valves on the prototype engine are offered. The methods for starting and the operation after misfire are presented.
  • Research articles
    Singularity loci of an orthogonal spherical two-degree-of-freedom parallel mechanism
    Jialun YANG, Feng GAO,
    2009, 4(4): 379-385. https://doi.org/10.1007/s11465-009-0075-0
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    Singularity analysis plays an important role in the design of robots, especially for parallel robots. In this paper, the direct and inverse kinematics of an orthogonal spherical two-degree-of-freedom parallel mechanism is proposed based on the modified Euler angles. All the singular poses of the mechanism are achieved through the direct kinematic analysis. Self-motions, which are different from the general spherical 5R parallel mechanisms, are also discussed. Singularity loci in the joint space and Cartesian space are plotted according to the Jacobin of the mechanism. Result shows that the singularity loci at the joint space are two circles and one line, whereas at the Cartesian space are a circle.
  • Research articles
    New decentralized control technique based on substructure and LQG approaches
    Ying LEI, Ying LIN,
    2009, 4(4): 386-392. https://doi.org/10.1007/s11465-009-0041-x
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    Decentralized control is more suitable for structural control of large-scale structures. In this paper, a new decentralized control technique is proposed based on the linear quadratic Gaussian (LQG) and substructure approaches. A large-scale structure is divided into a set of smaller substructures. Each substructure is controlled by its own local controller with interaction forces at substructural interfaces, which are considered as “unknown external inputs” to the substructure concerned. An algorithm of recursive least squares estimation for the unknown excitation is proposed. A numerical example of the decentralized control of a tall building is studied to illustrate the new proposed algorithm. Simulation results show that the proposed decentralized control provides satisfactory control performance when comparing with the conventional centralized LQG control algorithm and is viable for the future structural control of large-scale structures.
  • Research articles
    Development of electrorheological chip and conducting polymer-based sensor
    Xianzhou ZHANG, Weihua LI, Weijia WEN, Yanzhe WU, Gordon WALLACE,
    2009, 4(4): 393-396. https://doi.org/10.1007/s11465-009-0043-8
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    This paper presents the development of an integrated sensor using two types of smart materials: electrorheological (ER) fluids and conducting polymers (CPs). The developed ER chip worked as an actuator, and it was driven by different voltages and control frequencies. When the four electrodes are controlled synchronously, the diaphragm acts as a vibrator whose frequency can be adjusted in accordance with the frequency of the electrical signals. The response signals of the CP sensor were recorded, and its properties were analyzed. Experimental results show that the amplitude decreases monotonically when the frequency increases, owing to the time delay in the pressure buildup in the ER chip. However, the displacement fluctuation of the diaphragm below 20Hz can be detected clearly even if the value is very low. When the vibration frequency is larger than 20Hz, the CP sensor can hardly detect the displacement fluctuation. Thus, the upper limit frequency that the CP sensor can detect is about 20Hz. The practical applications of this microdevice are also discussed.
  • Research articles
    Vibration analysis of a simply supported beam under moving mass based on moving finite element method
    Zhuchao YE, Huaihai CHEN,
    2009, 4(4): 397-400. https://doi.org/10.1007/s11465-009-0044-7
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    In this paper, a moving finite element (MFE) method is proposed to perform the dynamic analysis of a simply supported beam for a moving mass (MM). The MFE method treats the moving mass as a moving part of the entire system, so that the transverse inertial effects caused by the moving mass may easily be taken into account. The solution to the beam’s dynamic behaviors including its displacement is obtained via a Newmark-β method; the effects of the velocity and weight of the MM on the beam’s dynamic behaviors are further discussed. The numerical examples show that the inertial effects of the MM significantly affect the transverse responses of the simply supported beam.
  • Research articles
    Low crosstalk switch unit for dense piezoelectric sensor networks
    Lei QIU, Shenfang YUAN,
    2009, 4(4): 401-406. https://doi.org/10.1007/s11465-009-0047-4
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    Structural health monitoring (SHM), on the basis of piezoelectric (PZT) sensors and lamb wave method, is efficient in estimating the state of monitored structures. Furthermore, to monitor large-scale structures, dense piezoelectric sensor networks are required, which usually contain many piezoelectric sensor pairs called actuator-sensor channels. In that case, considering the few data acquisition channels especially in the data acquisition board with a high sampling rate and limited quantity of signal amplifiers used in an integrated computer system, a switch unit is adopted to switch to different channels. Because of the high frequency and power of the lamb wave excitation signal, there exists a crosstalk signal in the switch unit. A large crosstalk signal is mixed into the response signal so that the on/off-line signal processing task is difficult to achieve. This paper first analyzes the crosstalk signal phenomenon, describes its production mechanism, and proposes a method to reduce it. Then a 24-switch channel low crosstalk switch unit based on a digital I/O board PCI7248 produced by Adlink technology is developed. An experiment is implemented to validate it. Its low crosstalk characteristics make it promote the real application of the SHM based active lamb wave method. Finally, a general software program based on LabVIEW software platform is developed to control this switch unit.
  • Research articles
    Efficiency characteristics of piezostack pump for linear actuators
    Junwu KAN, Kehong TANG, Chenghui SHAO, Guoren ZHU, Taijiang PENG,
    2009, 4(4): 407-414. https://doi.org/10.1007/s11465-009-0049-2
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    A piezostack pump for linear actuators is presented and studied in terms of mechanical energy efficiency (MEE), energy conversion efficiency (ECE) and design method. MEE is defined as the ratio of the output mechanical energy to that converted from input electrical energy, and ECE is the ratio of output mechanical energy to input electrical energy. The analysis results show that both MEE and ECE decrease with the increase of stiffness of the chamber diaphragm (ks), which is a function of the radius ratio (rigid disk radius to chamber radius). There is respective optimal external load (Fc) for them to achieve peak value for a given piezostack with blocked force (Fb) and stiffness (ka). The optimal force ratio (Fc/Fb) is a constant of 0.5 for maximum MEE, and between 0.57 and 0.5 for maximum ECE. Considering the deflection of the pump chamber and dynamic response of the piezostack, the stiffness ratio (ks/ka) should be limited between 0.3 and 1, and the relative radius ratio is between 0.7 and 0.8. With the increase of the radius ratio in the range, the maximal MEE decreases from 0.38 to 0.25, and the peak ECE decreases from 0.20 to 0.14.
  • Research articles
    Performance investigation on ultrasonic levitation axial bearing for flywheel storage system
    Taijiang PENG, Zhigang YANG, Junwu KAN, Fengjun TIAN, Xiaohong CHE,
    2009, 4(4): 415-419. https://doi.org/10.1007/s11465-009-0051-8
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    The bearing is an important basic mechanical part for supporting a shaft. A flywheel storage system needs a type of noncontact support bearing to enhance the speed of the axis. A magnetic suspension bearing is one type of noncontact bearing but has electromagnetic interference to other electric equipment. Based on the performance research of ultrasonic levitation technology, a novel noncontact bearing called ultrasonic bearing is presented, which consists of a special piezoelectric vibrator supporting the load. Experiments are carried out to study the relationships among the amplitude of the vibrator and levitation clearance, the highest speed of the axis, and the frictional moment of the axis. Results show that the levitation clearance becomes smaller gradually with increasing load; the rotation speed is up to 8946 r/min, and the friction moment is only 2.095×10−5 N·m when the levitation clearance is 8.53 μm. The ultrasonic bearing is highlighted because of its simple structure, strong levitation ability, and low friction moment.
  • Research articles
    Present situation and classification of piezoelectric pump
    Fang YE, Shouyin WANG, Wei CHENG, Qixiao XIA, Jianhui ZHANG,
    2009, 4(4): 420-429. https://doi.org/10.1007/s11465-009-0052-7
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    According to the present classification method for a piezoelectric pump, this paper reviews the development and present situation of piezoelectric pumps in the latest 30 years and finally puts forward a new classification. A volumetric piezoelectric pump, which belongs to traditional volumetric pumps, can be divided into a piezoelectric pump with or without valves. A new valveless piezoelectric pump nowadays becomes a hot issue in scientific research. It is constructed by using no-moving-part valves, which can induce positive flow resistance and negative flow resistance different, and in which the inlet and outlet are connected all the time. New forms of piezoelectric pumps, different from traditional ones, are only at the stage of conception and principle, and no practical application has been reported.
  • Research articles
    Performance of ionic polymer-metal composite (IPMC) with different surface roughening methods
    Ning JIN, Bangfeng WANG, Kan BIAN, Qi CHEN, Ke XIONG,
    2009, 4(4): 430-435. https://doi.org/10.1007/s11465-009-0053-6
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    Based on permeation and double chemical reduction technology, this paper researches the manufacture of Pt-ionic polymer metal composites (IPMC) and the effect of three types of surface roughening methods on the manufacture and performance of IPMC. The roughening methods include manual polishing, sanding machine polishing, and plasma surface treatment. The appearance and scanning electron microscopy (SEM) features, electro-active deformation and surface resistance characteristics of these IPMC specimens were obtained and compared through specimen tests. The results of the tests indicate that surface roughening technology obviously influences the performance of IPMC. The uniformity and compactness of the metal deposited on the surface and inside the Nafion film are improved by improving surface roughening uniformity. However, the electro-active deformation capability and surface resistance of the specimens decrease at the same time. There is an approximate linear increase relationship between the driving voltage and the bending deformation of the IPMC specimen within a certain voltage range. Under the same specimen dimension, constraints, and driving voltage (3V), the maximum electro-active bending deformation angles of the specimens are about 60°, 45°, and 15° for manual polishing, sanding machine roughening, and plasma treatment, respectively.
  • Research articles
    Preparation and performance of soft actuator based on IPMC with silver electrodes
    Qi CHEN, Ke XIONG, Kan BIAN, Ning JIN, Bangfeng WANG,
    2009, 4(4): 436-440. https://doi.org/10.1007/s11465-009-0054-5
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    The surface electrodes of traditional ionic polymer-metal composites (IPMC) are made of platinum. To reduce the production cost, nonprecious metals such as silver is proposed. A new approach of electroless silver plating based on chemical deposition method is adopted, getting two types of IPMCs, Pt-Ag IPMC, and Ag-Ag IPMC. The microscopic analysis, driving abilities tests, and their surface-electrode resistance analysis show that Ag and Pt particles penetrate inside Nafion membrane with gradient distribution throughout the membrane. The maximum electro-active bending deformation angles of the specimens, which are obtained under the same specimen dimension and constrains, are about 60° for Pt-Pt IPMC and Pt-Ag IPMC and 90° for the Ag-Ag IPMC, respectively, corresponding to the driving voltage of 3 V, 4 V, and 1.5 V. The surface-electrode resistance of Ag-Ag IPMC is the lowest and the most stable, which shows that the proposed approach is valid. The experiments show that the IPMC technology based on the silver electrode is feasible.
  • Research articles
    Vibration control efficiency of piezoelectric shunt damping system
    Dan WU, Zhichun YANG, Hao SUN,
    2009, 4(4): 441-446. https://doi.org/10.1007/s11465-009-0055-4
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    The piezoelectric shunt damping technique based on the direct piezoelectric effect has been known as a simple, low-lost, lightweight, and easy to implement method for passive damping control of structural vibration. In this technique, a piezoelectric material is used to transform mechanical energy to electrical energy. When applying the piezoelectric shunt damping technique to passively control structural vibration, the piezoelectric materials must be bonded on or embedded in host structure where large strain is induced during vibration, thus to ensure vibrational mechanical energy to be transformed into electrical energy as much as possible.
    In this paper, the concept of vibration control efficiency of a piezoelectric shunt damping system is proposed and studied theoretically and experimentally. In the study, PZT patches are used as energy converter, and the vibration control efficiency is expressed by the vibration reduction rate per area of the PZT patches. Emphasis is laid on the effect of the generalized electromechanical coupling coefficient K31 on the vibration control efficiency. Four PZT patches with different sizes are bonded on the geometrical central area of four similar clamped aluminum plates, respectively, and vibration control experiments are conducted for these plates using the R-L shunt circuit. The results indicate that the bigger the coupling coefficient K31, the larger the rate of vibration reduction, and hence, the higher the vibration control efficiency. It also shows that the vibration responses of the first mode of the plates bonded with different PZT patches can be reduced by about 30.5%，48.58%，85.47%, and 89.91%, respectively. It comes to a conclusion that the vibration control efficiency of the piezoelectric shunt damping system decreases with the increase of the area of the PZT patch, whereas the vibration reduction of the plate increases with the area of the PZT patch. Therefore, it is necessary to make topology optimization for the PZT patch in the vibration control utilizing the piezoelectric shunt damping technique.
  • Research articles
    Deformation analysis of shape memory polymer for morphing wing skin under airflow
    Weilong YIN, Jingcang LIU, Jinsong LENG,
    2009, 4(4): 447-449. https://doi.org/10.1007/s11465-009-0062-5
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    The method for analyzing the out-of-plane deformation of a flexible skin under airflow is developed in this paper. The aerodynamic analysis is performed using the CFD software, and the structural analysis is performed using finite element method. The chief aim of the present study is to investigate the out-of-plane deformation of the shape memory polymer (SMP) skin at different temperatures. Numerical results show that the maximum out-of-plane displacement of the SMP skin increases with increasing temperature. When the SMP skin is heated to 53°C, the maximum out-of-plane displacement is about 7 mm. It decreases by 72%, when the SMP skin is applied with a uniform pre-strain of 0.1.
  • Research articles
    Extended stochastic resonance (SR) and its applications in weak mechanical signal processing
    Niaoqing HU, Min CHEN, Guojun QIN, Lurui XIA, Zhongyin PAN, Zhanhui FENG,
    2009, 4(4): 450-461. https://doi.org/10.1007/s11465-009-0072-3
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    To catch symptoms of machine failure as early as possible, one of the most important strategies is to apply more progressive techniques during signal processing. This paper presents a method based on stochastic resonance (SR) to detect weak fault signal. First, a discrete model of a bistable system that can demonstrate SR is researched, and the stability condition for controlling the selection of model parameters of the discrete model and guarantee the solving convergence are established. Then, the frequency range of the weak signals that the SR model can detect is extended through a type of normalized scale transformation. Finally, the method is applied to extract the weak characteristic component from heavy noise to indicate the little crack fault in a bearing outer circle.
  • Research articles
    Smart optical-fiber structure monitoring based on granular computing
    Guan LU, Dakai LIANG,
    2009, 4(4): 462-465. https://doi.org/10.1007/s11465-009-0073-2
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    Using an optic fiber self-diagnosing system in health monitoring has become an important direction of smart materials and structure research. The buried optic fiber sensor can be used to test the parameters of the composite material. The granular computing method can reach the requirement of damage detection by analyzing digital signals and character signals of the smart structure at the same time. The paper investigates an optic fiber smart layer and presents a method for realizing optic fiber smart structure monitoring and damage detection by using granular computing. After the analysis, it is presumed that optic fiber smart structure monitoring based on granular computation can identify the damage from complex signals.
  • Research articles
    Overall HIEs deconstruction method and its application
    Li LIN, Chengqi XUE,
    2009, 4(4): 466-471. https://doi.org/10.1007/s11465-009-0076-z
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    Based on the human interface elements (HIEs) as the emotional carriers, this paper researches the general analysis steps of hierarchical HIEs and puts forward a new systematical deconstruction method for Kansei engineering fields. A mobile phone is taken as the research subject, the emotional design rules are inferred based on the multiple-orientation information of human interfaces, and the emotional change law is grasped from a new perspective. The research on the deconstruction method promotes the study of Kansei engineering and is a significant guide and reference for the theory and practice of related product design fields.
  • Research articles
    Development of an electrorheological chip and conducting polymer based sensor
    Xianzhou ZHANG, Weihua LI, Weijia WEN, Yanzhe WU, Gordon WALLACE,
    2009, 4(4): 472-472. https://doi.org/10.1007/s11465-009-0077-y
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