25 February 2014, Volume 33 Issue 4
    

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  • WANG Xiao-dong;CHEN Yu-shu
    . 2014, 33(4): 1-6.
    Abstract ( 499 ) Download PDF ( 917 )   Knowledge map   Save

    The nonlinear dynamics phenomena of a Single-Machine-Infinite Bus power system with periodical load disturbance were studied in this paper: the method of multiple scales was used to develop an approximate primary resonance solution; the stability of the periodic motion was analyzed. According to the bifurcation equation, different bifurcation models of primary resonance with different systematical parameters were presented directly by using C-L method, which shown that the occurrence of this phenomena are closely related to the operational parameters and structural parameters of the power system. The numerical simulation results show that with the amplitude of the excitation changing, this system possess rich dynamic behaviors characterized by period-doubling bifurcations, which are precursors to chaos and loss of synchronism. The results can provide theoretical guidance for the synchronous operation, oscillation and out-of-step of a synchronous generator.


  • Li Zhinong;;Zhao Kuang;Wu Guanhua
    . 2014, 33(4): 7-10.
    Abstract ( 423 ) Download PDF ( 311 )   Knowledge map   Save

    Based on the deficiencies of traditional self-adaptive equalization, a new self-adaptive equalization method based on kernel recursive least-square(KRLS) is proposed. In the proposed method, the original nonlinear data are mapped to high-dimensional feature space by introducing kernel function. Then standard least-square algorithm is implemented in high-dimensional feature space. the proposed method is compared with the other self-adaptive equalization methods. The simulation results show that the proposed method is supiror to raditional self-adaptive equalization method. The proposed method can effectively eliminate the influence of transer channels. Finally the proposed method is applied to the extraction of weak inpact fault in the rotor system, the experiment results further verify the validity of the proposed method.



  • Zhong Xianyou;Zhao Chunhua;Chen Baojia;Zeng Liangcai
    . 2014, 33(4): 11-16.
    Abstract ( 543 ) Download PDF ( 382 )   Knowledge map   Save

    Frequency slice wavelet transform (FSWT) is a new time-frequency analysis method,and the noise in the signal will reduce frequency resolution of the FSWT. In order to improve the accuracy of analysis,a method based on morphological filtering and delayed autocorrelation analysis was proposed and applied to the bearing fault diagnosis successfully. In this method,a multi-structure element difference morphological filtering and time-delayed autocorrelation method was used to reduce the noise,and the bearing vibration signal was decomposed by applying frequency slice wavelet transform,and then time and frequency slice interval was selected for detailed analysis according to the bearing fault characteristic frequency to extract fault characteristics. Simulation signal and bearing fault diagnosis analysis of examples demonstrate the effectiveness of the method.



  • LI Xiao-peng;ZHAO Guang-hui;YANG Hao-tian;WEN Bang-chun
    . 2014, 33(4): 17-21.
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    In order to consider the influence of nonlinear characteristics of the joint surface on the dynamic characteristics of whole machine, the composite beam is taken as a research object, and the nonlinear pre-stressed modal analysis method is provided based on ANSYS. The nonlinear characteristics of the joint surface are proved to have an important influence on the natural frequency of the composite beam. Moreover, the influence of normal load and friction coefficient on the natural frequency is revealed with single variable method. The results show that the natural frequency is decreased by normal load and friction coefficient, and friction coefficient is the dominant. Finally, the modal test is conducted and the mode shape of composite beam got by the modal test and pre-stressed modal analysis is coincided. The natural frequency error between them is in an acceptable range which demonstrates pre-stressed modal analysis is correct.


  • Yuan Xin;Zheng Wei Yang Hao Wu Yibin
    . 2014, 33(4): 22-26.
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    In order to research the real mechanical behavior of the supporting system during urban bridge long stroke synchronous jack-up under specific boundary conditions, the comparative stress analysis of space calculation results and truss structure calculation is adopted. From the perspective of the simulation calculation method, this paper carries on analysis on the simulation calculation method of the lifting support system which is constituted by the steel support, pile caps, artificial dig-hole pile three a whole. The results show that the accuracy of the traditional support system calculation method which is based on elastic foundation beam hypothesis is not high and often cannot reflect the space mechanics state of supporting system. In this paper, the ABAUQS space simulation is adopted to lifting support system during which the nonlinear characteristics of the structure is considered, the convergence is good .The space calculation method of the lifting support system which is constituted by the steel support, pile caps, artificial dig-hole pile is more accurate than “m” method.


  • Wang Feng Lin Gao Zheng Bao-jing Hu Zhi-qiang LIU Jun.
    . 2014, 33(4): 27-31.
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    A meshless local Petrov-Galerkin (MLPG) method basing on the moving Kriging interpolation is employed for solving two-dimensional structural dynamic problems, in which the Heaviside step function is used as the test function in each sub-domain and the precise time step integration method is selected for the time discretization scheme. The essential boundary conditions can be implemented directly as the shape functions possess the Kronecker Delta property. This method does not involve the sub-domain and singularity integral in generating the global stiffness matrix except for the boundary integral. Numerical examples have shown that the MLPG method basing on the moving Kriging interpolation has the advantage of easy implementation and high accuracy.


  • Zheng kan Xiao xingzhi Liao wenhe
    . 2014, 33(4): 32-36.
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    According to the machining problems for zirconia ceramics dental prosthesis which were exposed, such as complex process, difficult to control shrinkage and so on, a new method which used ultrasonic vibration assisted grinding presintered zirconia ceramics was proposed. Firstly, the macro kinematic characteristic is investigated from theoretical analysis. Then, an experimental study on machining presintered zirconia ceramics with ultrasonic vibration assisted grinding and diamond grinding is conducted to analysis the feasibility for the new method. Effects of spindle speed on material removal rate, surface roughness and edge chipping size are obtained, according to the machining characteristics of dental prosthesis. The experiment results demonstrate that the assistant for ultrasonic vibration not only increases the material removal rate, but also reduces the surface roughness and restrains the edge chipping effectively. Therefore, ultrasonic vibration assisted grinding might be the high efficiency and low-damage method for presintered zirconia ceramics.



  • CAO Guang-qun;WANG Jian-zhong;DUO Ying-xian;ZENG Zhi-yin
    . 2014, 33(4): 37-41.
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    To study the affection on the vibration of wheeled self-propelled gun chassis during running firing, a nonlinear shock absorber damper model was built in this paper based on the basic theory of fluid and hydraulic mechanics. And the damping coefficient and stiffness coefficient expressions of the shock absorber were deduced, with its nonlinear damping characteristics included. In addition, according to the specific structural characteristics of wheeled self-propelled gun, expressions to calculate equivalent damp coefficient and equivalent stiffness coefficient were developed. And tests on wheeled self-propelled gun during running firing were done. Based on the tests data and the theory developed, numerical simulations in two conditions, the damping and stiffness coefficient calculated by linear expressions and by nonlinear expressions, were done respectively. The result shows that, simulations in the nonlinear condition match well with the experiments data, but simulations in the linear condition have a deviation to the experiments data. As a conclusion, the damping coefficient and stiffness coefficient has a considerable affection on the vibration of wheeled self-propelled gun chassis. This method can be popularized to studies on the simulation of vibration of other gun chassis.



  • HOU Shuang;LEI Jinfang;Ou Jinping
    . 2014, 33(4): 42-47.
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    A vehicle load monitoring method for asphalt concrete (AC) pavement based on smart aggregates (SA) is proposed. Firstly, the cyclic stress is applied on an AC block embedding a piece of SA by a servo-hydraulic machine. During the loading, a variety of frequencies is used to consider the vehicle speed variation. The SA sensitivity in the given boundary condition is obtained and the influence of the loading rate on the sensitivity is studied. Secondly, the finite element (FE) model of the AC block embedding the SA is established with the real boundary condition of the loading test. The stress distribution in SA is analyzed and the SA sensitivity is obtained based on the numerical method. Finally, the influence of the AC Young’s modulus variation on its sensitivity is studied through the numerical simulation approach. This study demonstrates that the SA output varies linearly with the applied dynamic stresses, and in normal atmospheric temperature the variation of the SA Young’s modulus barely change the SA sensitivity. Thus, it can be concluded that the proposed monitoring method for vehicle load on the AC pavement is feasible and reliable.


  • CUI Kun-peng;XIA He;XIA Chao-yi;WU Xuan
    . 2014, 33(4): 48-53.
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    Due to the quick development of elevated overpass bridges on highway, railway, urban overpass nowadays, the probability of vehicle collision with piers also increases sharply. An analysis model for truck-pier system is set up using the finite element software ANSYS LS_DYNA, to analyze the collision force characteristics of the truck at different speeds. In this paper, four calculation methods for equivalent static force of truck-pier collision have been presented, including the global average method, the local average method, the equivalent displacement method, and the simplified pulse method. Using these methods, the equivalent static forces are calculated, and the results are compared with the allowances given in AASHTO-LRFD, Chinese Railway Code and Chinese Highway Code, based on which the adapted scope and the accuracy of different methods are pointed out, providing references for engineering design.

  • QIAN Ji;SUN Limin;JIANG Yong
    . 2014, 33(4): 54-59.
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    Through tension testing in single wire and cables, acoustic emission (AE) waveform were gained from wire crack expansion, wire breakage and cables damage. Comparing the waveform, spectrum and time-frequency characteristics in different sources, the results illustrate that, energy and continuous time of wire breakage are more higher than crack expansion signals, however, its amplitude is largish to the most value of crack expansion; The spectrum peak of wire breakage is very obvious, mostly at 43KHz, the vast majority energy distribute in a equal frequency banding in whole continue time; The spectrum of crack expansion signal contain four frequency band, maximum energy at 50-60KHz, and the high frequency part appear at the front wave, which will quickly disappears along with the time increase; While the wire breakage source propagate in the cable, its energy will attenuates and energy contained in low frequency will increase relatively..


  • GUO Xiao-ling;TANG Guo-qiang;;LIU Ming-ming;LU Lin;;TENG Bin
    . 2014, 33(4): 60-69.
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    Based on the FEM solution of incompressible viscous Navier-Stokes equations in the frame of Arbitrary Lagrangian-Eulerian (ALE), a two-dimensional numerical model is developed to investigate the vortex-induced vibration of twin tandem circular cylinders at low Reynolds number. In the numerical simulations, the upstream cylinder is fixed, while the rear cylinder is allowed to freely oscillate in both transverse and stream-wise directions. The damping ratio 0.007 and the reduced velocity varying from 3.0 to 12.0 are used for the computations. The effects of the in-line center-to-center distance (LX / D = 3.0、5.0、8.0) and the mass ratio (m* = 5.0、10.0、20.0) on the displacement and forces of the downstream cylinder are examined. The numerical simulations indicate that the spacing ratio (LX / D) has great influence on the VIV responses in terms of the lock-in band, displacement and fluid forces. Several flow modes under different spacing ratios and reduced velocities are observed, which are closely related to the VIV responses. It was also found that the change of the mass ratio may give rise to different characteristics of VIV responses for the twin cylinders in tandem at low Reynolds number.


  • Xinghui Zhang;Jianshe Kang;Jinsong Zhao;Xiao Lei;Duanchao Cao
    . 2014, 33(4): 70-76.
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    A new approach for identifying the wear degree of gear based on Mixture of Gaussians Bayesian Belief Network (MoG-BBN) was proposed. The inference algorithm was established through combining the variable elimination algorithm with expectation maximization algorithm. Then, one can recognize the gearbox wear states through identifying the hidden state of MoG-BBN which best fits the observations. Aiming at the local convergence problem of expectation maximization, a modified algorithm was proposed. According to the non-linear dependencies between features, the curvilinear distance analysis was used for dimension reduction. Finally, the data of gear’s wear experiment were used to demonstrate the proposed methods. The results showed the classification accuracy was 99%.



  • Jiang Huanjun;* Zhu Jianmei Chen Qian
    . 2014, 33(4): 77-83.
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    Based on the seismic damage distribution characteristics and evolution law of different types of structural components in a typical ultra-tall steel-concrete composite building structure, a seismic damage model at the story level was proposed aimed at the research of steel reinforced concrete frame-concrete tube composite structure, considering the different importance of different types of components. Then based on the above model, combining the weighting coefficients of the story position and the damage index, the global damage model was established, which can reflects the distribution characteristics of story damage. At last, as a case study, the nonlinear earthquake responses of a steel-concrete composite structure was calculated with the aid of Perform-3D program, the features of damage distribution and evolution were analyzed, and the damage indices of individual level were determined by the damage model proposed in this study, which verifies the reasonability of the damage model.


  • LIU Hai-ying;ZHANG Qi-chang;HAO Shu-ying
    . 2014, 33(4): 84-89.
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    The ratio of every coefficient of nonlinear stiffness terms to coefficient of linear stiffness term at different horizontal tension is analysed,which in the first three vibration mode.Through discussion relationship between amplitude of vibration and horizontal tension,linear restoring force as well as nonlinear restoring force,the main factors that influence strong or weak geometric nonlinearity of icing conductor system were determined.On the basis,the steady state amplitudes and vibration frequency of system were calculated with undetermined natural frequency method,numerical results show the amplitudes of vibration increase with wind velocity increase in each vibration mode,and frequency of each order vibration mode would deviate from original fundamental frequency while system was subjected effect of geometric strong nonlinearity.The analysis results of conventional normal form was difficult to meet accuracy requirements of model analysis,and the analysis results in this paper could relatively accurately grasp vibration characteristics of model.


  • Chi Yulun;Li Haolin
    . 2014, 33(4): 90-93.
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    The milling chatter is a kind of instability vibration, which usually affects the workpiece surface quality and productivity efficiency. The paper proposed a method to determine the milling stability lobe diagrams based on theory model and experiment design. The genetic algorithm is used to optimize and determine these constant parameters based on measurement data and theory calculation. Then, the stability lobe diagrams can be made to be consistent with the experiment results. So, the stability lobe diagrams can be used to choose the parameters for the milling machine, and it has an importance significant to improve the milling efficiency and process quality.
  • WANG Lu-yan;WANG Qiang;LU Dong-lin;ZHANG Mei-jun;MAO Di
    . 2014, 33(4): 94-99.
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    Waveform matching extension is considered to be an effective method to improve the end effect of empirical mode decomposition (EMD). According to those deficiencies of existing matching extension methods, this paper proposes a self-adaptive triangular waveform matching extension method for EMD,which ameliorated both the matching degree algorithm of triangular waveform and the searching algorithm for optimal triangular waveform. The new matching degree algorithm not only promoted the extension’s smoothness but enhanced the relationship between the data near the end-point and waveform inside. By the new searching algorithm, we firstly searched for intercepting time to cut out the local optimal wavelet in each wave band corresponding to the fixed extreme point, and then searched for the global optimal wavelet in the local optimal wavelets. Based on the simulated signals and experimental signal analysis, it is suggested that the method could effectively mitigate the end effects of EMD and significantly improve the precision of decomposition.



  • Yin Bang-hui;Wang Min-qing;Wu Xiao-dong
    . 2014, 33(4): 100-106.
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    The technologies of reverse filtering, backward integral and energy level average are used to build the damping test data processing system for decay method; the relationship between the decay method test results and frequency-band damping in the sense of statistical energy analysis and the effect of modes outside the frequency band on damping test results are studied; in the end of this paper, a plate’s transient impact response data from finite element simulation are used to verify the relevant conclusions. The main conclusions include: if the difference of the modal damping of the modes in the frequency-band is small, the decay method results are close to frequency-band damping in the sense of statistical energy analysis while on the contrary the decay method results are less than frequency-band damping in the sense of statistical energy analysis; if there are modes with small damping outside the considered frequency-band, the damping test results will be strongly influenced by the mode; if the damping of each mode gently changes with frequency, the decay method test results are accurate, while on the contrary a large error will be caused.



  • LIU Yang;LIU Wenguang;HE Wenfu;YANG Qiaorong
    . 2014, 33(4): 107-112.
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    Yunnan museum is in the high-intensity seismic area, and its structure form is complex, overrun and irregular steel reinforced concrete structure. It is significant for this kind of structure with special function to use seismic isolation technology. In order to confirm the vibration isolation effect and damage mechanism of museum isolation structure, shaking table tests of a scaled model (1:30) are accomplished. The dynamic characteristics of isolated bearing and fixed bearing model structure and seismic responses of model structure under fortification intensity and rare earthquake are tested and compared. Test results show that dynamic characteristics of isolation structure under different performance level earthquakes are stable, and vibration absorption effect is good. Horizontal peak accelerations of every storey of superstructure are less than that of table. Compared with non-isolated structure, acceleration responses of isolated structure are less. The drifts of every storey of superstructure meet requirements limit. Torsion responses of structure are small. The structure has no failure. Isolation bearings hysteretic curves are full and symmetric, and have no damage. Isolation technology can be applied into large, complex museum structure.


  • Liu Fu;Zhang Jia-zhen;Tong Ming-bo;Hu Zhong-min;Guo Ya-zhou;Zang Shu-guang
    . 2014, 33(4): 113-118.
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    Stress-strain curves at quasi-static and high strain rate of 2024-T3 aluminum alloy are measured using dynamic tensile tests by the electronic universal testing machine and split Hopkinson tensile bar (SHTB). Constitutive model of aluminum alloy is described by Johnson-Cook model which can reflect strain and strain rate hardening effect. 4 parameters in Johnson-Cook equation are fitted by the stress-strain curves at different strain rates. By coupling Smooth Particle Hydrodynamics (SPH) method and Finite Element (FE) method, combining with the Johnson-Cook equation of 2024-T3 aluminum alloy, the numerical model of bird impact on a 2024-T3 aluminum alloy square plate is established using the transient dynamic software PAM-CRASH. Dynamic responses of the plate by numerical calculation agree well with the experimental results, which shows that the numerical calculation is reasonable and reliable. The analysis process including material dynamic mechanical test, numerical calculation and bird impact experimental verification provides reference for anti-bird impact design and analysis of aircraft structure.


  • LI Jian-yang;WANG Hong-yan;RUI Qiang;HONG Huang-jie;CHI Bao-shan
    . 2014, 33(4): 119-123.
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    The self-inflating airbags were unfolded and inflated by the self-weight of buffer system at landing. The airbags have some advantages, such as simple structure, convenient usage and higher reliability, and so on. In this paper, the influence of landing velocity and mass on cushioning characteristics for normal opened and bonding self-inflating airbags were studied by indoor experiments. And so did the inflenece of the status of exhaust orifice on cushioning characteristics for bonding self-inflating airbags. The results show that the maximum pressure is directly proportional to landing velocity and mass, the peak acceleration is directly proportional to landing velocity, and inversely proportional to mass. The cushioning performance is better when the vent is bonding.



  • Li Jiawu Fang Cheng Hou Liming Wang Jie
    . 2014, 33(4): 124-130.
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    With increasing span length of bridge, bridge construction quality is more and more light, structural stiffness is more and more small, structural damping is more and more low, which led to the sensitivity of the wind-induced role is more and more big. Based on the main girder static coefficients measured by wind tunnel tests and wind load nonlinear, and considering geometrically nonlinear, the whole process of the static wind instability of long-span suspension bridge will be analyzed, as well as large-span cable-stayed bridge; Then the sensitivity aerostatic stability parameters of long span cable supported bridge, which contains of static coefficients, the initial wind angle of attack, the bridge tower wind loads and the rope wind loads and side cross wind load, were investigated.



  • OUYANG Huimin UCHIYAMA Naoki SANO Shigenori ZHANG Guangming WANG Deming MEI Lei
    . 2014, 33(4): 131-137.
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    This paper aims at the problem of two dimensional load sway caused by horizontal motion of booms in rotary crane systems, and proposes a control method using only horizontal boom motion for achieving boom positioning control and load sway suppression control simultaneously. Firstly, we derive a partial linearized dynamic model of a rotary crane by using a disturbance observer. The model has robustness with respect to varying parameters such as joint friction and load mass. Next, we design a nonlinear controller on the basis of the model, and confirm the stability of the control system via Lyapunov stability theory. Finally, comparative simulations and experimental results demonstrate the effectiveness of the proposed method. A kind of rotary crane without an actuator for vertical boom motion can be achieved by using the proposed method, therefore, the structure of cranes can be simplified and their production cost can be reduced.


  • Li Hai-sen;Li Shan;Zhou Tian;
    . 2014, 33(4): 138-142.
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    In some multi-beam bathymetric sonar applications, accuracy of the DOA estimation algorithms presently used reduces for the seafloor backscattering signals dissatisfying the point sources assumption, while the DOA estimation algorithms based on assumption of distributed source model have a potential to solve it well. However, most existing distributed source algorithms fail to distinguish incoherent sources apart. Although Toeplitz method has been proposed and tested effective to the problem, it has low estimation accuracy and can’t estimate the parameters of angle expansion. Aiming at the DOA estimation problem of multi-beam bathymetric sonar, a generalized MUSIC algorithm based on spatial smoothing is proposed and proved to be effective by formula derivation. Its accuracy and performances under different SNR are given via computer simulation. Finally, the method is tested with experimental data of multi-beam bathymetric sonar.



  • Yin Bang-hui;Wang Min-qing
    . 2014, 33(4): 143-148.
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    The spectral finite element method is used to analysis propagating wave types and their damping loss factor (DLF) in the beam with a non-constrained damping layer (NCDL). Every wave type’s exciting condition is studied by the analysis of characteristic wave shapes. The finite element method is used to compute the strain energy for every element of long beam with a NCDL, the DLF is computed by strain energy method and the relationship between structure DLF and load types is studied. In the end the boundary reflected waves’ effect on the DLF is studied. The study showed that: the vertical excitation mainly excites the highest order bending waves or lower order longitudinal waves whereas the longitudinal excitation mainly excites the highest order longitudinal waves; when the beam becomes longer and the displacement between the exciting point and the boundary becomes more far, the effect of boundary reflection on structure DLF become smaller; the DLF on different boundary condition are always the same except some special frequency; the structure DLF of a beam with a NCDL is decided mainly by the wave types and influenced a little by boundary reflection .


  • XIAO Huifang;SHAO Yimin;XU Jinwu
    . 2014, 33(4): 149-155.
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    The dynamic response and energy dissipation characteristic at rough contact interface are of great importance to the interface dynamic mechanism. In this paper, the vertical contact vibration model for rough interface is proposed and the corresponding calculation method is presented to study the contact dynamic responses and energy dissipation at rough contact interface. Results of contact force and deformation are obtained using the finite element method and are presented for contacting surface with varying topographies. Expression relating the contact force and the deformation is established and good correlation with calculated results is obtained and compared with that for the Hertz contact law. The dynamic motion equation is further established and the dynamic response quantities and energy dissipation characteristics for contacting interface with different surface topographies are determined. The obtained results explain theoretically the experimental results on energy dissipation observed for vertical contact vibration.


  • ZHANG Qinghua;GU Ming
    . 2014, 33(4): 156-160.
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    Wind-induced responses of a 500kV single-circuit transmission tower are computed based on wind forces acting on the tower obtained from wind tunnel tests using high-frequency-force-balance technique in a wind tunnel and the modal decomposition method. The results show that the dynamic displacements,accelerations and base bending moments (BBM) are all large in both along and across wind directions, and furthermore, the across wind dynamic responses are generally larger than the along wind responses. The first mode has dominant contributions to the total responses respectively in both A and B directions. In addition, gust response factors corresponding to displacement and BBM have similar trends. The maximum displacement gust response factors of critical nodes are no more than 1.8, and the maximum moment gust response factors are about 1.5.


  • Zhang Miao Yu Lan Ju Wei
    . 2014, 33(4): 161-166.
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    Firstly, by introducing modal coordinate transformation and matrix function transformation, the original damped system is transformed into a non-damped system. Secondly, by analyzing the properties of mode parameters with respect to non-damped system, the Frequency Response Matrix is worked out. Furthermore, by using inverse matrix transformation and inverse mode coordinate transformation, the precise response of originally damped system is derived. When the presented algorithm is applied to the classically damped system, the analytic equivalence to mode superposition method is obtained. And then the analytic expression involving non-classically damped system which can’t be done with by mode superposition method is obtained as well. Finally, the correctness and effectiveness of the methods given here are demonstrated by considering two examples respectively.



  • Zheng Shan-suo;Sun Long-fei;Si Nan;Yang Wei;Qin Qing
    . 2014, 33(4): 167-172.
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    By researching the failure mechanism of the structure under seismic action, recognizing and optimizing structural failure modes, the desired failure mode of the structure can be achieved, which will improve the seismic performance and reduce casualties and property losses in the earthquake importantly. By using OpenSEES—the Open System for Earthquake Engineering Simulation, and utilizing IDA analysis method together, the seismic response of the steel reinforced concrete frame structure is gained in this paper, and some methods are proposed to identify the failure modes for the structure. Farther, some optimization algorithms are given to improve the failure modes, which have certain theoretical significance for corresponding engineering application.


  • MENG Dan;ZHU Chong-zhao
    . 2014, 33(4): 173-177.
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    Based on the practice of Qingdao subway tunnel under-passing building,get the concrete structure stress distribution under the influence of blasting vibration through the finite element calculation. Take the derivation of yield approach index model that suitable for concrete material based on the two kinds of concrete failure criteria. And then get the concrete structure damage distribution and evolution process combined with yield approach index function of Ottosen and GUO-WANG failure criterion. The fundamental ground moving parameters are obtained by using inverse analysis method based on ground surface measurement data of prophase excavation. Thus realize the quantitative evaluation and control of building structure damage under the influence of different settlement and vibration quantity. As a whole, settlement impact is much greater than the blasting vibration for damage evolution in building structures.


  • ZHAI Xi-mei;HUANG Ming
    . 2014, 33(4): 178-184.
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    Dynamic finite element software ANSYS/LS-DYNA was used to set up a typical finite element model for Kiewitt8 single-layer reticulated shell which contained reticulated shell member, purlin hanger, purlin, rivet, roof boarding, wall and ground. The dynamic response of structure subjected to internal eccentric blast loading was studied by using ALE (Arbitrary-Lagrange-Euler) algorithm, four response types are defined, that is: No Impairment, Member Developing Plasticity, Large Deformation of Reticulated Shell and Destruction with explosion relief. The response rules of the structure under internal eccentric blast loading with different explosion point position, section size of reticulated shell member, rise-span ratio, supporting condition and thickness of roof boarding are obtained through the comparison of the plastic strain, the plastic development degree and displacement of structure. The result offers the theoretical basis for reasonable defense design of reticulated shell structure for resisting blast.


  • SHI Dongyan WANG Qingshan SHI Xianjie LI Wen Long GU Jingjing
    . 2014, 33(4): 185-189.
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    In this investigation, an analytical method is presented for the free vibration analysis of T coupling plates with general boundary conditions. The in-plane vibration and out-of-plane vibration have been taken into account at the junction via four types of coupling springs of arbitrary stiffnesses. Regardless of boundary conditions, the transverse and in-plane vibration displacement functions are sought as a new form of trigonometric expansion with accelerated convergence. The displacement functions can overcome all the relevant discontinuities of the elastic boundaries. The expansion coefficients are considered as the generalized coordinates, and determined using the Rayleigh-Ritz method. The free vibration analysis of T coupling plate with various boundary and coupling conditions are carried out using the current method. The reliability and accuracy of the current method are validated with FEM results. This study provides a reliable and theoretical basis for the vibration control of coupling plate structure.



  • SUN Ya-jun;LIANG Ji;Yang Fei;ZHANG Jun-jie
    . 2014, 33(4): 190-194.
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    An advanced region jet is designed with supercritical wing. The transonic flutter characteristic is one of the critical techniques of supercritical wing. The wind tunnel test of flutter model is the effective test for civil aircraft airworthiness compliance. A transonic flutter model is designed and used to research the transonic flutter of wing through the model wind tunnel test. Meantime, the test result is used to evaluate the academic flutter calculation for the model, including the subsonic flutter calculation and lift slope analysis. Comparisons show that the test result is satisfied with the theoretical analysis well and the maximal Mach effect factor is small. The test result is applicable to airworthiness compliance certification.



  • LIU Shi;XU Jinyu;
    . 2014, 33(4): 195-198.
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    By using of the high temperature split Hopkinson pressure bar apparatus which is composed of traditional Φ100 mm SHPB and the high-temperature device,the test of granite chosen from shaanxi Qinling mountain under high temperatures and dynamic loadings is carried out. The change rules of the peak stress, peak strain and elastic modulus are studied. It is demonstrated that during 25 ℃ to 600 ℃, temperature has a little effect on the peak stress. But the peak stress drops rapidly with the temperature increment from 800 ℃ to 1000 ℃, and therefore the possible critical temperature is included from 600 ℃ to 800℃. As the temperature increases, the peak strain increase gradually, and the elastic modulus generally presents decreasing trend. All in all, the peak stress and peak strain still show significant strain rate effect at high temperatures.



  • Wang Dongpo;He Siming;Wu Yong;Li Xinpo;
    . 2014, 33(4): 199-203.
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    Impressive cushioning effect of EPS cushion structure on the rock-shed hole have been shown in engineering practices, while detailed research is needed on its mechanisms and quantitative evaluation. In this study, a comparative study on dynamic responses of soil cushion and EPS structure under impact load of rock-fall was performed. Contact force-indentation relationships between various cushion structures and rock-fall, under loading and unloading conditions, were obtained through static indentation numerical test and were introduced into the impact power control equation to calculate the dynamic responses of different cushion structures. Theoretical resolutions obtained in this study were compared with those of the dynamic finite element method and the two were quite in consistent with each other, which indicates that theoretical method can be used to analyze dynamic responses of sheds subjected to impact load of rock-fall. Results in this study showed that EPS cushion structure showed satisfactory cushioning effect in rock-fall impact loading which was more significant when the material is of low density and large thickness.


  • Wang Ya-nan;Li Hui; Du Yong-feng;
    . 2014, 33(4): 204-209.
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    Based on energy balance principle, the energy response anlysis of the hybrid control system which is consisted of base-isolation and TMD is carried out, and the vibration control effectiveness of the hybrid control system under seismic ground motions with different pulse periods is studied. The Bouc-Wen model is adopted to simulate the isolation layer’s nonlinear force-deformation behavior. The motion equation and the relative energy balance equation are established. A eight-storey base-isolated structure is employed herein as an numerical example. The seismic response and energy response of the base-isolated structure with and without TMD are calculated using the fourth-order Runge-Kutta method and the trapezoidal rule, respectively. Input energy’s transformation and dissipation process of the hybrid control system are analyzed. Analysis results show that TMD’s control effect on the isolation layer’s peak displacement is not good. From the standpoint of the energy, TMD’s control to the input energy of the primary structure, especialy to the isolation layer’s hysteretic energy is very effective, and it’s the result of the energy dissipation by TMD’s damping. TMD shows different control effectiveness under seismic ground motions with different pulse periods, and the influence of the seismic grond motion’s characteristics should be considered when solving TMD’s optimum prameters.



  • XU Feng;LIU Yun-Fei;PAN Hui-Xin
    . 2014, 33(4): 210-214.
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    Fundamental frequency extraction of acoustic signal is a key step for determination of elastic modulus of wood by acoustic-ultrasonic technology. Calculation of elastic modulus by fundamental frequency extracted by the existing fast Fourier transform (FFT) method is about 20% bigger than one which acquired by the standard mechanical method for noise and sensor resonant frequency and other factors. For this, the largest common divisor algorithm was proposed for extraction of fundamental frequency to construct an improved method of measuring elastic modulus of wood, and gave the detailed process of extracting the fundamental frequency. The poplar core samples were tested respectively by application the method proposed in the paper and FFT method. The calculated values of elastic modulus(Eu), as determined by the method proposed in the paper, and the calculated values of elastic modulus(Ef), as determined by FFT method, were in the range of 8.23~40.32Gpa and 7.94~51.87Gpa. Comparing with measured value of static modulus of elasticity (Es), ranged from 6.72Gpa to 36.35Gpa, as determined by the standard method of mechanics, error was decreased by 10% or so. Linear correlations were observed respectively, with a coefficient of determination of 0.94 between Eu and Es, and with a coefficient of determination of 0.86 between Ef and Es. Results showed significant correlations. The measured data show that compared with elastic modulus acquired by mechanical method, testing values are more consistent and better correlations by the method proposed in the paper than one by FFT method.