25 April 2014, Volume 33 Issue 8
    

  • Select all
    |
    论文
  • WU Zhi-qiang;CHEN Shi-dong;LEI Na;GONG Ming-xu
    . 2014, 33(8): 1-3.
    Abstract ( 503 ) Download PDF ( 650 )   Knowledge map   Save

    Experiments on internal and combinational resonances of a three-story structure are investigated. The frequency ratio between the first and the second modal of the structure is set near 1:3 by modal design. The internal resonance behaviors are found when the excitation frequency is near that of the first or second modal frequency. Meanwhile, several types of combinational resonances are found in this structure. These results made a foundation for future modification of the nonlinear vibration equipment.


  • XU Yan;WANG Bo;LI Peng
    . 2014, 33(8): 4-10.
    Abstract ( 343 ) Download PDF ( 167 )   Knowledge map   Save

    A new method to determine delay time is proposed, which is called nonlinear multiple autocorrelation function method. The method uses a high order multiple autocorrelation function, R(τ), to calculate the nonlinear correlation of system and estimates the optimal delay time by finding the first local minimum value of R(τ). The time complexity is low and the dependence on the length of data is not strong. The performance of the algorithm is tested by being applied to five noisy chaotic time series. The time series are generated by four chaotic maps adding different noise level Gauss white noise. The numerical results show that, the method is more appropriate and robust to noise.



  • CHEN Jun;WANG Hao-qi;PENG Yi-xin;
    . 2014, 33(8): 11-15.
    Abstract ( 395 ) Download PDF ( 335 )   Knowledge map   Save

    Using three-dimensional human motion capture system and three-dimensional force plates, a series of experiments on dynamic properties of human-induced walking load at seven different walking frequencies was conducted. Seventy three test subjects had participated the experiments leading to 5 004 records of single footfall trace. The continuous time history of walking load is synthesized with single-step force by using its exact landing time. Based on the experiment measurements, the first five orders of dynamic load factors and phase angles from Fourier-series Model of both vertical and lateral walking load are given. By comparing with existing models from other countries, different characteristics of walking are noticed. The model proposed in this paper could be provided for structural design and analysis of long-span structures considering the problem of serviceability caused by human walking.



  • TAN Li-hui;TAN Hong-wu;MAO Zhi-qiang;CUI Xiao-mei;XU Tao
    . 2014, 33(8): 16-21.
    Abstract ( 426 ) Download PDF ( 149 )   Knowledge map   Save

    This paper took the metal thin-walled components as the investigation tool on the basis of different inducing grooves. The maximization of the Specific Energy Absorption (SEA) and the minimization of the maximum peak force ( ) were considered as the multiobjective functions, the radius of the inducing grooves|, distance between inducing grooves and free end, distance of inducing groovs were chosen as design variables. The optimization was based on the minimization of and the maximization of SEA. The objective functions were constructed based on the Radial Basis Function (RBF), the multiobjective optimization for the thin-walled with the different inducing grooves, which was presented by using the ideal point method, and considering the impact on the SEA and of the convex grooves, indentations, alternately convex grooves and indentations. After the optimization we can get the ideal indentations.



  • WANG Jie-fang;AN Wei-guang;SONG Xiang-hua
    . 2014, 33(8): 22-28.
    Abstract ( 332 ) Download PDF ( 267 )   Knowledge map   Save

    Firstly, the supercavitating vehicle was simulated by a cylindrical thin shell which was loaded with a axial dynamic load, and the dynamic stability differential equations and the unstable regions of structure were deduced. Secondly, the safety margin equations of dynamic buckling were given and linearized by limit step length iteration method when the randomness of axial load was taken into account, and step-by-step searching method was proposed in search of those effective safety margin equations. Finally, the reliability index of dynamic buckling was calculated with step-by-step equivalent plane method. Through numerical results, the influence of the change of load frequency, velocity and the coefficient of load rate to the dynamic buckling reliability were discussed. The calculate result give a theory foundation to how to choose the safety range of load frequency, velocity and the coefficient of load rate.

  • YUE Er-tuan;GAN Chun-biao;YANG Shi-xi
    . 2014, 33(8): 29-24.
    Abstract ( ) Download PDF ( )   Knowledge map   Save

    This paper investigates the vibration characteristics of the rotor system of permanent magnet synchronous motor with air-gap eccentricity. A dynamic model of the rotor system is built. According to the distribution of magnetic flux density generated by permanent magnet and armature current under load, Unbalanced Magnet Pull (UMP) is calculated with the Maxwell stress tensor and is substituted into the dynamic model. From several illustrating numerical examples, the effects of different eccentricities and loads on rotor vibration are discussed in detail. The results show that, the mass unbalance weakens the effect of the UMP while aggravates the vibration of the rotor, the magnitude and orientation of the initial eccentricity can also change the vibration characteristic of the rotor, and the vibration will be weakened when the orientation of initial eccentricity is close to the direction of the gravity. As the load changes, the corresponding vibration components will be excited with the same frequencies as those of the load.



  • PANG Ming;;ZHANG Li-jun;;MENG De-jian;;YU Zhuo-ping;
    . 2014, 33(8): 35-41.
    Abstract ( ) Download PDF ( )   Knowledge map   Save

    A large number of structural, material, operational and environmental factors would have great influence on automotive brake squeal induced by friction, and the intrinsic influencing mechanism is a significant and challenging issue needs to be solved. Selecting a certain type of drum brake as the research object, a drum brake finite element model for frictional squeal is established using ABAQUS, a free-free modal test of individual brake components and the brake squeal bench test are performed to verify the model, and on the basis of which, the impact of Young’s modulus of shoes’ linings, brake pressure and friction coefficient on the squeal propensity is analyzed By introducing the contact pressure distribution properties between the drum and shoes, the intrinsic influencing mechanism of the factors above on squeal propensity is studied based on the complex eigenvalue theory. Results show that: (1) the squeal propensity of the drum brake decreases with the increase of Young’s Modulus of linings, while increases with the increase of friction coefficient and brake pressure; (2) the nonuniformity of contact pressure distribution is closely related to the squeal propensity and could make an unified explanation on the intrinsic influencing mechanism of the factors above; the squeal propensity decreases as the nonuniformity of contact pressure distribution increases, and the system tends to be more stable.



  • LU Tao;JIANG Dong;WU Shao-qing;FEI Qing-guo;
    . 2014, 33(8): 42-47.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    By using the large commercial finite element software NASTRAN, a method that the elastic parameters of a 2.5D C/SiC composite plate are determined by parameter identification based on the modal test data is proposed in this paper. An optimization problem is formulated with the model updating technique in which the objective function is defined as the sum of squares of the discrepancy between measured and calculate modal frequencies, the initial value of the elastic parameters are obtained by adopting stiffness averaging method which makes full use of the prior information of the material parameters. Finally, the accurate elastic parameters of the composite plate are identified through a iteration process by using sensitivity analysis method. The accuracy of the first 1-4 modal frequencies of C/SiC composite plate are significantly improved by identification, while the predictive accuracy of the 5-8 modal frequencies can also be guaranteed. Results show that the proposed method can accurately identify the 2.5D C/SiC composite elastic parameters, and the method proposed in this paper can provide effective references for dynamic design and equivalent modeling of C/SiC composite.

  • JIAO Chi-yu;LONG Pei-heng;LI Shi-luo;HOU Su-wei;LIU Lu-yu
    . 2014, 33(8): 48-54.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Transves collisions between restrain block and main girder under earthquake excition are the important factors that affect the seismic response of the bridge. Recent researches lack of dicussion on the lateral collision problems related to the Double-Column and Box-Girder Bridge(DCBGB) which is widely used in urban viaduct. Taking a bridge as an example, this paper established the spatial finite element model, the lateral collision is accurately simulated through the Kelvin-model. Then the key factors that affect the seismic responses of the DCBGB, such as the impact stiffness, the restrain block - main girder gap, height of bridge pier, site category, quality ratio of the upper structure to cap beam.The research shows that: the impact stiffness and impact clearance have greater influence on the internal forces of the double column pier bottom. The factor should be confirmed by testes as far as possible. The design parameters such as site features, quality ratio of the super structure to cap beam and pier height also have great influence on the bridge seismic force, therefore design parameters should be carefully adjusted when the bridge were designed. Choosing hard site, higher piers and lightweight main girder structure system will be a good choice. In all, this research conclusion can provide technical support for the design of similar viaducts bridges.

  • LUAN Qiang-li;CHEN Zhang-wei;XU Jin-rong;HE Hui-nong
    . 2014, 33(8): 54-60.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Deeply research the Three-Variable Control (TVC) algorithm of seismic simulating shaking table, and study the correction action on the system characteristics of shaking table played by the three-variable feedback and three-variable feedforward step in detail. Through simulation and field test methods verify the improvement effect for system frequency response characteristics of seismic simulating shaking table taken by the TVC algorithm: expand the system bandwidth by introducing the velocity feedback of TVC; effectively increase the system damp by introducing the acceleration feedback of TVC; eliminate the system pole near to the imaginary axis of system closed-loop transfer function and further extend the system bandwidth by introducing the three-variable feedforward control. Finally, by conducting the seismic wave reproduction test on the three-variable controlled shaking table prove the TVC algorithm could achieve high-precision seismic wave reproduction test.
  • XIA Hu;ZHUANG Jian;ZHOU Fan;YU De-hong
    . 2014, 33(8): 61-65.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Feature selection is necessary for high-dimensional features in fault diagnosis since it can improve the efficiency and accuracy. However, traditional feature selection algorithm always has a strong bias towards a single criterion, which is harmful to the quality of feature selection. An unsupervised feature selection algorithm based on multi-objective evolutionary model was proposed to solve this problem. A relevance objective based on entropy measure and a redundancy objective based on correlation coefficient were simultaneously optimized. Both initialization process and mutation operator were also designed by utilizing the distribution of samples in each feature. Besides, an ensemble method was proposed to obtain the importance order. Experiments on five UCI and three valve fault of reciprocating compressor datasets demonstrated better performance of the proposed algorithm.

  • Pan Jin;Zhang Min;Xu Ming-cai
    . 2014, 33(8): 66-71.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The aim of this paper is to investigate the design method of protection device for single bridge pier in order to against 1 000 DWT ship collision. The nonlinear FE analysis is used to simulate the collision procedure between the Yangtze River standard bulk carriers and the steel box of bridge protection. The influences of slope angle of the protection device bow on the absorption characteristics and the collision force are investigated. The results of analysis could be as reference for designing steel box of bridge protection against ships collision. The Boltzmann equation is adopted to fit the relationship between velocities of the striking ship and collision forces of bridge pier, which could be used for rapid assessment of collision forces in the primary design for this kind of protection device.

  • XIONG Rui;LIU Xiang-dong
    . 2014, 33(8): 72-77.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    We consider a hysteresis closed-loop control system with PID controller. A model based on Backlash neutral network is adopted to represent the hysteresis relation of the system. After dynamic model is established,nonlinear principle resonance of this control system is studied. The bifurcation equation is obtained by averaging method, and then the system’s singularity is analyzed completely, the transition sets and bifurcation plots are shown in parametric space. The corresponding relations between the unfolding parameters and the system parameters are given and the theoretical basis for analysis and control in dynamical behaviors of the system is provided.
  • LIU Peng-peng;LI Yu-long;LIU Jun;JIANG Yu;LI Qiang
    . 2014, 33(8): 78-82.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to design the rear observation window glass on aircraft cockpit under bird impacting, the experiment of bird impact on rear observation window was carried out. In experiment the time histories for strain on two points were measured. A full-scale finite element model of bird impacting on rear observation window was established to simulate the experimental process by using large-scale commercial impacting analysis software PAM-CRASH. The strain results of simulation and test were compared, the good agreement between simulation and test indicated that the numerical model established in this paper was rational. Then the dynamic response of rear observation window structure impacted by bird was studied in which the observation window has different thickness of inside and outside glass layer as well as middle air layer. Some influence tendency was obtained which can provide technical guidance for the design of rear observation window glass impacted by bird.
  • WANG Bao-yuan;XU Yao-feng;ZHOU Fa-ming;HENG Gang;HONG Li-na
    . 2014, 33(8): 83-87.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to investigate the phenomena of obviously deflection in horizontal plane to the dispersion center of vertical target of antiaircraft gun, a series of experimental research methods are adopted, such as fault representation, reason analysis, method propose and results verification. In the firing experiments, the projectile exit time is obtained by testing the floating displacement of receiver, and the displacement curves of muzzle vibration are obtained by displacement transducers. Further more, the vertical target dispersion coordinates are detected by the graphics vertical target dispersion testing system, and the natural frequency of muzzle vibration is computed by frequency analysis of the displacement curves of muzzle vibration. Based on the works above, the law of vertical target dispersion influenced by muzzles vibration is summarized. It can be seen from the research results, because of the mismatch between nature frequency of gun structure and firing frequency, muzzle resonance is induced, so it follows that the projectile exit time is the same time when the muzzle vibration at it’s max. displacement. Therefore, the phenomenon of deflection to the dispersion center of vertical target is observed. In the following experiments, the phenomenon of muzzle resonance is eliminated by optimizing the structural stiffness, and it can be seen from the result that the phenomenon of deflection to the dispersion center of vertical target is basically disappeared.
  • SONG Wei-wei;LIANG Shu-guo;ZOU Liang-hao;WEN Si-qing
    . 2014, 33(8): 88-95.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Wind tunnel tests of surface pressure scanning with a rigid model and vibration measurement with a stick-like aero-elastic model of a 100-meter-high diamond-shaped cross-section monument were conducted, and then the frequency domain wind load model was established based on the pressure measurement data and the wind-induced response of the structure was calculated by the method of random vibration theory; meanwhile, the aerodynamic damping ratio were identified by applying Random Decrement Technique (RDT).When the aerodynamic damping ratios were considered in the structural complex frequency response function, the calculation results of wind-induced dynamic responses agree well with the aero-elastic model test results. As the difference between the structural actual mode shape and the linear mode shape of the stick-like aero-elastic model may cause error, mode shape correction factors were adopted to modify the aero-elastic model test results, and then acquire actual structural responses. The analysis results show that, frequency domain response analysis method of a actual high-rise structure, in which wind load model is established by the surface pressure scanning test of a rigid model, combined with the aerodynamic damping identification by the aero-elastic model vibration measurement test, can accurately assess the wind-induced aero-elastic responses of the low-frequency small-damping high-rise structures under strong wind actions.

  • ZENG Xin;ZHOU Ke-dong;HE Lei;JIN Yong-xi;CUI Hai-lin;WANG Hao-sheng;LI Bing-cang
    . 2014, 33(8): 96-99.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To investigate the internal pressure transmission in body caused by the small caliber projectile under non-penetration, the non-penetration firing tests were conducted with different impact velocities and different protected targets including Landrace and gelatin to measure the pressure value in the targets at different locations by dynamic acquisition system of pressure. The results show that the pressure is higher when the impact velocity becomes greater, and the peak pressure decays exponentially with the distance between impact point and the measurement position, and the pressure attenuation speed in the Landrace is greater than that in the gelatin target, and the energy absorption ability of skin has great relationship with impact velocity. The test results have important significance in the wound treatment, the injury standard establishment, and the bullet design modification.
  • HU Teng;YIN Guo-fu;SUN Ming-nan
    . 2014, 33(8): 100-108.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to improve the operation stability of spindle system, it is significant to investigate the dynamic performance, affected by centrifugal force and gyroscopic moment effects of "shaft-bearing" system which runs in high-speed field. An integrated "shaft-bearing" system digital dynamic model considering both centrifugal force and gyroscopic moment effects of shaft is presented based on the coupled stiffness matrices of rolling bearings, which are obtained by expanding Harris' nonlinear rolling bearing analysis model. Impact modal experimentation is selected to verify the accuracy of this dynamic model. Effects of centrifugal force and gyroscopic moment of shaft and operational stiffness of rolling bearings on the dynamic performance of "shaft-bearing" system which runs in high-speed field are discussed. It is shown that when bearing being in the case of extreme light (EL) preload, the high-speed effects of shaft are more influential than the shifts of the operational stiffness of rolling bearings to the varying dynamic performance of "shaft-bearing" system, especially where the gyroscopic moment effect of shaft is the most remarkable influence factor.
  • GU Xiao-hui;YANG Shao-pu;LIU Yong-qiang;LIAO Ying-ying
    . 2014, 33(8): 109-114.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The response of a rotor supported on ball bearings which considering nonlinearity such as surface waviness, internal radial clearance and Hertzian contact force is analyzed and the result is presented in the form of bifurcation diagram, power spectra and Poincaré map. The effect of maximum amplitude of waviness and speed on the dynamic of the rotor response is mainly studied and the characteristic frequency of surface waviness is analyzed. G-P method is used to calculate the correlation dimension at different maximum amplitudes. The result shows that the correlation dimension will increase with the addition of amplitude of the waviness when the system in chaos and it’s implied that the correlation dimension can be usefully applied to the diagnosis and quantitative identification of the fault of waviness.
  • LI Kun;SHI Qing-xuan
    . 2014, 33(8): 115-119.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Elastio-plastic dynamic analyses of 9 reinforced concrete frame-core wall structures with different structural characteristics were carried out under several sets of ground motions. The earthquake total input energy of the structure under ground motion, and the regularity of the total input energy between hysteretic energy and damping energy were discussed; the distribution of hysteretic energy among shear wall, coupling beams and frames were studied, as well as the distribution of hysteretic energy along different stories. The results show that the hysteretic energy is increased with the peak ground acceleration. The earthquake records with different spectrum characteristics have a great influence on hysteretic energy. Although the total hysteretic energy among different structural members are steady, the distribution of hysteretic energy among shear wall, coupling beams and frames may vary significantly. It is found that the bottom portion of shear walls and coupling beams in middle floors are the predominant energy dissipated area.
  • LIU Zhang-jun;WANG Yong;ZENG Bo
    . 2014, 33(8): 120-124.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Based on the orthogonal expansion of stochastic processes, and the idea of random function, a hybrid orthogonal expansion-random function approach is proposed to simulate fluctuating wind. In this method, these standard orthogonal random variables in the orthogonal expansion formula can be denoted by the orthogonal function form of a basic random variable. Through investigating the form of orthogonal random functions, the original stochastic process can be readily functioned by a single basic random variable. Utilizing the proposed approach, schemes for simulation of fluctuating wind processes are presented. The results show that the proposed approach can accurately capture the second-order statistics of fluctuating wind processes using only a basic random variable, and show the effectiveness and advantages of the orthogonal expansion-random function method.
  • LUO Zhong;ZHOU Xin
    . 2014, 33(8): 125-129.
    Abstract ( ) Download PDF ( )   Knowledge map   Save

    The absorption character in low frequency can be improved by adding cavum. The affect factor of absorption coefficient was studied, by three type of acoustic system model of stealth structure. Using the pulse tube system, the resonance peak and peak frequency of samples with cavum, different distance, shapes, and depth, were analyzed. The results show that the cavum enhance absorption in low frequency, and the first resonance peak is higher, peak frequency in lower in smaller cavum distance in air backing, and the result is opposite in water backing, and the first resonance peak is lower, peak frequency in lower in smaller cavum volume.

  • ZUO Shu-guang;HU Qing;HAN Hui-jun;KANG Qiang
    . 2014, 33(8): 130-133.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The regenerative blower’s inner flow field is simulated by using a three-dimensional model, and the dynamic pressure of every blade can be attained. Then by the FW-H function calculation and with blades’ dynamic pressure as sound resource, far field aerodynamic noise caused by blades is obtained. And with blade’s dynamic pressure as excitation source, vibration noise radiated by blades is calculated. The change rule of blade’s far field aerodynamic noise and vibration noise is calculated and analyzed when blade thickness varies from one millimeter to four millimeters. The result is that the blades’ noise is mainly aerodynamic noise and structural noise can be dismissed through analysis.
  • LI He;LIU Dan;JIANG Lai;ZHAO Chun-yu;WEN Bang-chun
    . 2014, 33(8): 134-140.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The conditions of self-synchronization and motion stability regarding a dual-motor drive vibrating mechanism with a two-stage vibration isolation frame are studied. Owing to the effect of the two-stage vibration isolation, this mechanism enables not only enough oscillation amplitude of the material box to screen the material but also reduces the dynamic load transmitted to the foundation. This paper begins with utilizing Lagrange equation to establish differential motion equations of the vibrating mechanism, and follows with a modified average small parameter method to obtain the dimensionless coupled equation of the eccentric rotors. Then the condition of existence for zero solution of dimensionless coupled equation of the eccentric rotors is used to achieve the condition to implement self-synchronous motion of the vibrating mechanism, and the stability condition of self-synchronous motion is obtained by the Routh-Hurwitz criterion. Finally, the numerical simulations are carried out to verify the correctness of the theoretical analysis.

  • KOU Lei;BAI Yun
    . 2014, 33(8): 141-147.
    Abstract ( ) Download PDF ( )   Knowledge map   Save

    Based on the two-parameter Pasternak model of elastic foundation, the two-parameter model of viscoelastic foundation was derived by using fractional derivative. The equation of elastic and viscoelastic rectangular plate under the dynamic load on two-parameter viscoelastic foundation with the fractional Kelvin model was established. The equation of elastic and viscoelastic rectangular plate with four edges simply supported was solved by the Galerkin method and the segmented numerical method, the correctness of the solution was verified by the example of free vibration. The influences of the fractional order, viscosity parameter, horizontal shear parameter and modulus parameter on the displacement of the fractional Kelvin model with impact load were analyzed. The results show that the fractional derivative viscoelastic model may describe the mechanical behavior of different viscoelastic materials; the displacement response of rectangular plate appears different attenuation formation before and after the fractional order value of 0.5; the attenuation speed of the displacement response increases with the increasing of the viscosity parameter, horizontal shear parameter and modulus parameter.

  • WU Zi-ying LIU Hong-zhao WANG Sheng LIU Li-lan
    . 2014, 33(8): 148-155.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In view of the development of the feed servo system of CNC machine tools, some mechanical structures of the feed system are introduced first, including the application and characteristics of each kind of structure. Then, the methods of the performance prediction and detection for the feed system are described in detail. Several mechanical models of the feed system are presented as well as their characteristics. Moreover, the effects of the nonlinear factors on the dynamic performance of the feed servo system are introduced. The different control and compensation methods for friction and backlash are also summarized. Last, some problems to be further studied are pointed out. This paper can provide some references for the research of the feed servo system in the future.
  • ZHANG Jun-jie;WANG Yong-Quan;CHEN Hua-Ling;ZHANG Hao
    . 2014, 33(8): 156-160.
    Abstract ( ) Download PDF ( )   Knowledge map   Save

    Aiming at the two different installation modes of the screw nut at the condition that the screw is fixed at one end and only supported at another, this paper mainly presents a comparative study about their influences on the load distribution of the ball screw. The different load states of the screw at the two nut installation modes are firstly analyzed qualitatively. Then, a ball screw load distribution model considering the variations of actual contact angle is established. Using the model, the influence laws of the nut installation modes on the the screw’s load distribution, specifically, the normal load and actual contact angle of each steel ball, are quantitatively investigated. The numerical results show that the distributions of the normal load and contact angle both more balanced when the connecting flange of the nut is installed away from the screw’s fixed end. In addition the nut installation have no significant effect on the axial stiffness of ball screw.The conclusion of this study will provide a theoretical guide for reasonable installation or maintenance of ball screws, which may be significant for enhancing the performance of these functional components, as well as prolonging their life.

  • LIU Xiao-bing;YANG Qun;LIU Zhi-wen
    . 2014, 33(8): 161-164.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A series of wind tunnel test were performed to investigate flutter stability of twin streamline-liked sections in tandem. The test results were compared with those of single streamline-liked section. The study result show that flutter critical wind speed of twin streamline-liked sections is lower than that of single streamline-liked section and decreases with smaller distance; flutter frequency of twin streamline-liked sections is higher than that of single streamline-liked section and increases with smaller distance; the soft flutter characteristic of twin streamline-liked sections is more obvious compared with that of single streamline-liked section.

  • FANG Zhan-Peng;ZHENG Ling
    . 2014, 33(8): 165-170.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The topology optimization model is established to obtain an optimized layout of constrained layer damping material on the plate with Passive Constrained Layer Damping (PCLD) treatment. The maximum of modal loss factor is considered as the objective function to enhance damping dissipation of this plate. The volume fraction of constrained layer damping material is selected as constrained condition in the model. The sensitivity of the objective function to design variables is deduced by using the modal strain energy method. The Bi-directional Evolutionary Structural Optimization (BESO) method is proposed to search the optimized layout of constrained layer damping material. The numerical example is illustrated to demonstrate the effectiveness of the proposed BESO method. The results are compared with that from the conventional Evolutionary Structural Optimization (ESO) method. It is demonstrated clearly that the proposed BESO method can achieve higher modal loss factor for the plate with PCLD treatment than conventional ESO method through an optimized layout of constrained layer damping material on the plate. The damping dissipation of the plate is enhanced and the effectiveness of the proposed BESO method is thus identified.
  • ZHANG Xing-hui;KANG Jian-she;ZHAO Jin-song;XIAO Lei;CAO Duan-chao;LIU Hao
    . 2014, 33(8): 171-179.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A new approach for equipment health state identification and remaining useful life prediction based on Mixture of Gaussians Bayesian Belief Network (MoG-BBN) was presented. The inference algorithm was established based on variable elimination (VE) and expectation maximization (EM). State number was optimized based on cluster validity measures. One can recognize the equipment health state through identifying the MoG-BBN that best fits the observations. Then, the remaining useful life (RUL) prediction method was presented at the recognition base. Finally, the 50 bearing test-to-failure simulation data and 3 bearing test-to-failure experimental data were used to demonstrate the proposed methods. The results showed that the proposed method can identify degradation states and predict RUL effectively.
  • GONG Dao;ZHOU Jin-song;SUN Wen-jing;CHEN Hong
    . 2014, 33(8): 180-185.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    FE models of fully-equipped car bodies and a high-speed railway vehicle rigid-flexible coupled model including the flexibility of car body are built, the influences of devices suspended forms on modal parameters of fully-equipped car bodies are analyzed, the design procedures of rubber parameters of suspended device are proposed, and the relations between car body eigenmodes and suspended equipment natural frequencies are researched. Results show that, car body eigenmodes can be promoted observably with devices of elastic suspension; reasonable suspension parameters of device may effectively suppress car body flexible vibration, the example in this paper shows that when the static deflection of rubber is set at 8~9 mm, the bounce and roll frequencies of device can be separated from the first vertical bending and the diagonal distortion frequencies of car body, respectively, the devices which have vibration sources can achieve a good effect of vibration reduction at high frequencies, the vehicle can obtain a good ride quality and the device vibration is not fierce.
  • LI Chun-yin ;WANG Shu-lin
    . 2014, 33(8): 186-191.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The discharge valve is one of the key parts of the vane compressor for automotive air conditioner, as well as one of the main vibration noise sources. Through the analysis of the movement of Discharge Valve structure, a mathematical model of the vibration of the valve was constructed, and the natural frequency and the forced vibration were solved. Calculating by the UG NX Nastran, the natural frequency and the mode of vibration of the discharge valve were identified. The testing results has verified that the shell vibration acceleration, noise and exhaust pulsation are lower than the upper limits of the GMW standards of the General Moors Corp., USA, having proved the reliability of the working condition of the discharge valve. However, the results of the research indicates that the ultimate displacement of the vibration of the valve is relatively close to the height of restrictor plates. Therefore, there still remains some space for raising the height of the restrictor plates or limiting the vibration amplitude for further control of the exhaust pulsation and noise of the system. The result of this analysis has a reference value for the vibration analysis and fault diagnosis of the discharge valve even the overall vane compressor.

  • LI Wei;ZENG Zhi-song;HAN Xu
    . 2014, 33(8): 192-195.
    Abstract ( ) Download PDF ( )   Knowledge map   Save

    Generalized Differential Quadrature Rule(GDQR)was applied to investigate the stability of a complex elastic supported beam on an elastic foundation subjected to a partially tangential force. Based on the motion equations and boundary conditions of an elastic supported beam, the matrix eigenvalue equation consisted of the dynamic equations and boundary conditions was obtained after discreted by GDQR.After analyzing the corresponding eigenvalue equations,the effects of the elastic foundation modulus, shear coefficient, complex boundary conditions on critical load were discussed ,for a clamped-elastic supported beam,the influence of elastic foundation modulus and supported spring stiffness to the instability area was studied and some useful conclusions were obtained. It shows that GDQR is an effective way for solving the stability of such system.


  • SUN Qi-chen;LV Xiao-bin;YUE Yue-zhen;TIAN Jun-tao;KONG Xiang-zhi
    . 2014, 33(8): 196-201.
    Abstract ( ) Download PDF ( )   Knowledge map   Save

    This paper studies the validity of using impact-echo method to test the dynamic modulus of elasticity of concrete for standard prismatic specimens. It is found that the P-wave speed in a standard prism obtained from the impact-echo test well corresponds to the theoretical one-dimensional P-wave speed, and the dynamic elastic modulus obtained from the impact-echo method are essentially equal to those from the conventional transverse resonant frequency method. This paper adopts impact-echo method to detect the variation of P wave velocities of concrete specimen with the increase of freezing and thawing cycles, which is compared with the variation of fundamental vibration frequencies, thus to conduct parallel evaluation of the decline of relative dynamic elastic modulus using these two methods. The experimental results and theoretical analysis show that using impact echo method to detect the frost resistance of hydraulic concrete is feasible and can be used for durability assessment of hydraulic concrete.



  • ZHAO Zhi-gang;YOU Bin-di;ZHAO Yang
    . 2014, 33(8): 202-208.
    Abstract ( ) Download PDF ( )   Knowledge map   Save

    A new vibration reduction control strategy is presented, which integrates modified negative input shaping (MNIS) technique with optimal control for active vibration control of the flexible systems such as flexible manipulator. An optimal state feedback controller is designed for the flexible manipulator maneuver and the vibration eliminating. To improve the performance of the vibration control and reduce the system response time duration, the designed modified negative input shaper as feed-forward controller which utilizes the frequency and damping ratio of the whole closed loop system under linear quadratic regulator (LQR) controller. Combining the feed-forward control and feedback control and utilizing the respective advantages, the performance of the control system can be improved. Both analytical and numerical results are presented to demonstrate the effectiveness for vibration suppression of the hybrid control strategy. It can reduce the time delay and thus increase the speed of the response of the system.



  • CHEN Hui;WANG Shao-feng;HE Bin;HUANG Ya-pin;YANG Jun;GAO Tao
    . 2014, 33(8): 209-214.
    Abstract ( ) Download PDF ( )   Knowledge map   Save

    The shock load imposed on the equipments is multidirectional. At the same time, the isolators installed under equipments will appear multidirectional distortion. In this condition, the shock characteristics of isolators are distinct from the results in the unidirectional shocks in lab. The studies about the influence multidirectional shocks experts upon shock characteristics of isolators are little both home and abroad at present, and it is necessary for us to conduct groping works about this problem. Therefore, the shock characteristics along two directions of BE120 and EA120 isolators are tested using drop hammer impact test machine. The results show that the stiffness of isolators have dependencies on the main axle direction stiffness. While, the results can’t represent all isolators for the lack of sampling tests.