25 October 2014, Volume 33 Issue 20
    

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  • LIU Zhang-jun;LIU Ling
    . 2014, 33(20): 1-6.
    Abstract ( 383 ) Download PDF ( 580 )   Knowledge map   Save
    Based on two classical simulation methods for stationary stochastic processes, including the spectral representation methodology and the orthogonal expansion method, through defining these standard orthogonal random variables in the two classical simulation methods as the orthogonal function form of a given basic random variable, so the original stochastic process can be represented by one basic random variable. In order to research a stochastic process from the set of its sample functions, discrete representative points of the basic random variable need be selected, and sample functions with assigned probability can be generated directly by the spectral representation methodology and the orthogonal expansion method, respectively. The two innovated methods are used to simulate random ocean state, and the simulated results are in excellent agreement with the prescribed probabilistic characteristics. Finally, some features of these two kinds of innovated simulation methods in applications are stated and compared.
  • ZHANG Jun-hong;YANG Shuo;LIU Hai;LIN Jie-wei
    . 2014, 33(20): 7-11.
    Abstract ( 336 ) Download PDF ( 277 )   Knowledge map   Save

    Fatigue cracks generated during operation would alter the aero-engine blade vibration characteristics, manifested as frequency veering and mode shape switching. Study on the frequency veering can lead us to a further understanding of the blade crack evolution process. After building the FEM of aero-blade, the influence of crack parameters (crack location and length) on blade natural vibration and forced vibration characteristics was studied based on structural modal vibration theory, focusing on the variation laws of vibration frequency and mode shapes in the frequency veering area. The research shows that crack location and length variation would affect the blade frequencies and mode shapes, and thus lead to complex frequency veering, mode coupling and mode shape switching characteristics, which explains why mode shapes alter with the crack length and location in the same vibration mode.


  • LI Xu;HUO Lin-sheng;LI Hong-nan
    . 2014, 33(20): 12-15.
    Abstract ( 363 ) Download PDF ( )   Knowledge map   Save

    The focus of this paper is to analysis the fracture and damage characterize of reinforced concrete (RC) column subject to dynamic and static loading based on acoustic emission (AE) technique. The multi-dimensional dynamic/static loading test of RC columns is conducted with the loading rate of 40mm/s and 0.1mm/s respectively. By b-value analysis, the moment of macro-crack opening is acquired, and by which, the ratio of macro-crack opening load to maximum load is proposed to evaluate the damage condition. In addition, the load condition and damage accumulative rate of RC column subject to both dynamic and static loading are analyzed. The results are shown that: the distribution of AE amplitude, which also can be seen as b-value, can capture the moment of macro-crack opening in RC column. The macro-crack subject to dynamic loading needs smaller external load compared with the one subjected to static loading. The dynamic loading is more likely to lead the formation of macro-crack. The time parameter of AE event accumulation can clearly reflect the damage accumulate rate of RC column. Moreover, the damage accumulate rate in high loading rate specimen is larger than the one in loading rate specimen. And the high loading rate is more easily to make and aggravate the structural damage.

  • WANG Yu-tao;LIU Dian-shu;LI Sheng-lin;FENG Ya-fei
    . 2014, 33(20): 16-19.
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    Through the high temperature heating system of C30 and C50 two kinds of strength grade of concrete under different temperature conditions of uniform heating and after natural cooling, using Φ 75 mm SHPB experiment device, ultrasonic measurement technology and test press to impact dynamic and static compression test of concrete specimens before and after the high temperature. The experimental results showed that: With the increase of temperature, vertical wave, static compressive strength and elastic modulus are both the decrease of the different degree,the overall trend is consistent.Damage increased with the temperature increasing and the temperature of 400 ℃ and 700 ℃ is the turning point of its obvious change;After different high temperature cooling, the dynamic damage of concrete strength is decreasing but the peak of strain is increasing.Stress-strain curve becomes more smooth and the plastic flow phenomenon, this phenomenon with the rising of temperature is more and more obvious.
  • NIE Xue-yuan;LIU Zhong-yu;YANG Guo-wei
    . 2014, 33(20): 20-25.
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    Unsteady aerodynamic reduced order model based on computational fluid dynamics (CFD) can either improve computational efficiency or remain the same computational accuracy as CFD. However, modeling ROMs based on the identification technology is strict with the loading method and/or frequency spectrum of the excitation signals. To overcome the shortcoming and improve the identification efficiency, the random white noise signal was taken as excitation to model unsteady aerodynamic forces with one-mode-at-a-time loading way. The multiple-input multiple-output (MIMO) model can be obtained by linear superposition of identified single-input multiple-output (SIMO) autoregressive moving average (ARMA) models. By exerting different frequency and shape excitation signals to identified model, the simulation results from ROM and direct CFD computation were compared and indicate that the same computation accuracy as CFD can be acquired by ROM. Coupled with structural model, the ROM was used to predict the flutter boundaries of AGARD445.6 wing. The numerical simulations show that the flutter results predicted by the ROM are in general agreement with those from direct unsteady Navier-Stokes equations computation and wind-tunnel experiments, and verify that ROM can provide a high efficient method for transonic aeroelastic numerical analysis.
  • GUO Ya;TANG Wen-yong;ZHENG Shao-wen;LI De-cong;SU Yi-ran
    . 2014, 33(20): 26-30.
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    A method considering both the shock wave and jet load is proposed for the ship underwater near-field explosion. Firstly, the numerical simulation of near-field underwater explosion bubble motion process is being carried out to establish the jet impact model, and then the jet load is simplified. Jet load is automatically added to the fluid-structure coupling simulation model after the shock wave phase to form a complete calculation process of the underwater near-field explosion process. Finally, a shell frame structure finite element model simulated by the MSC.Dytran software is established. This numerical example validates the feasibility of the method. The proposed method considering both the shock wave load and jet load at the same time is a more realistic simulation of the underwater near-field explosion process.
  • SHI Wen-pu;WEI Juan;
    . 2014, 33(20): 31-34.
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    Multi-coordinate transform, Graf addition formulae, wave function expansion are employed to study the Green function solution of SH-wave scattering of the several circular cavities in the circular domain to the steady out-of-plane pulse acting on the out boundary of the circular domain.At first, the scattering wave function of every circular cavity in the circular domain is given, and the superposition principle is used to give the total wave field of the circular domain medium, and a linear algebraic equation system of the unknown coefficients can be obtained by the boundary conditions of the problem and Graf addition formulae and Fourier transform, it can be solved by limited trunction according to the computation precision, then the Green function solution can be ensured. The results of the given example show the feasibility of the method here.
  • ZONG Yuan;ZENG Yu-min;ZHANG Meng;LI Peng-cheng
    . 2014, 33(20): 35-39.
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    This paper presents a new framework based on eliminating falling trend for improving average magnitude difference function (AMDF) pitch detection algorithm in speech signal processing to conquer the defect of the conventional AMDF which may generate error pitch. In the framework, linear polynomial is employed to represent the falling trend of AMDF. Then a modified AMDF algorithm based on least square (LS) method within the proposed framework is showed. LS method is performed to fitting the linear polynomial based on AMDF and the modified AMDF called LSAMDF is obtained by subtracting the falling trend, namely, the linear polynomial from AMDF for pitch detection. The simulated results show that the performance of LSAMDF is much better than that of many improvements of AMDF and validate the correctness of the proposed framework and the rationality of linear polynomial based falling trend representation.
  • MENG Zong;CAI Long
    . 2014, 33(20): 40-46.
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    The traditional independent component analysis is too difficult to solve the problems of underdetermined blind source separation(BSS) and statistically correlated sources separation existed in mechanical fault diagnosis.Assuming some sub-components of correlated machine vibration sources are independent,a novel blind source separation method based on subband extraction of ensemble empirical mode decomposition(EEMD) is proposed to solve the problem of single-channel statistically correlated mechanical signals separation. Firstly in this method,the single-channel signal is decomposed into a series of subband observed signals by ensemble empirical mode decomposition,then the number of source signals is estimated by singular value decomposition and Bayesian information criterion.Secondly,the new observed signals are reconstructed by the subband observed signals with high independence according to the mutual information criterion and the number of sources,the dimension of the new observed signal is increased.Finally,The source signals are estimated through the reconstructed observed signals by using whitening process and joint approximate diagonalization.The simulation and experiment testify the validity of the proposed method.

  • CUI Wei;YAN Bo;YANG Xiao-hui;Lü Zhong-bin
    . 2014, 33(20): 47-51.
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    Finite element models of three-phase transmission lines with triangle and vertical conductor arrangements are set up, and the anti-galloping efficiency of the interphase spacers mounted on the transmission lines is numerically investigated by means of the ABAQUS software. Galloping responses of the transmission lines in steady wind flow and stochastic wind field are simulated, and the necessity to take the stochastic wind field into account in these analyses is illustrated through the comparison of the dynamic responses of the two transmission lines in the two kinds of wind fields. The anti-galloping efficiency of the inperphase spacers in the transmission line with triangle and vertical conductor arrangements are analyzed based on the numerical simulation results.
  • CHEN Chang;TANG Bao-ping;Lü Zhong-liang
    . 2014, 33(20): 52-56.
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    A new prediction method is proposed based on Weibull distribution and least squares support vector machine to describe the rolling bearing degradation trend. The shape parameter of Weibull distribution is used as bearing recession performance indicators. The indicators act as the input of the least squares support vector machine and then a prediction model is constructed. Due to the model parameters of least square support vector machine has an important influence on the predictive ability of the model, the proposed method choose particle swarm(PSO) algorithm to optimize the model parameters. The rolling bearing run-to-failure tests are carried out to inspect the prediction model, and the results demonstrate the effectiveness and accurateness of the proposed method.
  • BAO Xing-xian;LI Chang-liang;LIU Zhi-hui
    . 2014, 33(20): 57-62.
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    Measured output signals are inevitably contaminated with noise. A low rank approximation of a Hankel matrix method was proposed to remove noise from the measured data, and then modal parameters were estimated from the filtered data. In the method, a Hankel matrix was constructed based on the impulse response function and then the singular value decomposition (SVD) was used to obtain the relative change ratio of the decreasing singular values. Theoretically the maximum change ratio corresponds to the model order. An iterative low rank approximation method was applied to get the filtered signals. The effects of chosen size of a Hankel matrix on the performance of the noise reduction and computational time were investigated. The effectiveness of the proposed method was verified by using measured signals from model test of a cantilever beam.
  • HU Fang;ZHANG Zhi-yi;WU Tian-xing;HUA Hong-xing
    . 2014, 33(20): 63-69.
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    Suppressing the vibration ofshafting bearings is an effective measure to reduce vibration transmission from the shaftingto its elastic support. This paper investigates active vibration transmission control of ashaftingsystem,which cosists of water-lubricated rubber bearings and a thrust bearing,and presents an activecontrol scenario,which uses inertial electromagnetic actuatorsto tranquilizethe thrust bearing. The active controlmethod employs an online identification and filtering algorithm to establish the control channel model influenced by the shaft-speed-dependent characteristicsof the rubber bearings. A simplified physical model is presented to explore the mechanism of the speed- dependent characteristics. The LMS-based adaptive identification algorithm and the subspace filtering algorithm are applied toderive for the control channel anFIR modelwithout noise contamination caused otherwise by the speed-modulated periodical disturbances.Transmission suppression is realized via the Filtered-x LMS algorithmenforced with two additional units fordisturbance reconstructionand saturation alleviation.The simulation and experimental results have demonstrated that the online identification of the FIR model is effective and the active control mthod is able to suppress the speed-modulated periodical vibration of the shafting bearing.
  • CHEN Xiao-an;ZHANG Peng;HE Ye;LIU Jun-feng
    . 2014, 33(20): 70-74.
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    The processing quality of vertical machining workpiece is affected by the rotor’s axial vibration of high-speed motorized spindles. This paper presents a dynamic model by the finite element to discuss the dynamic behaviors of high-speed motorized spindles. It has been found that the axial rigid vibration is the first natural mode of vibration and the first natural frequency of axial vibration is lower than radial vibration. The good agreement between the theoretical results and the experimental data indicates that the model can describe the dynamic characteristics of the axial vibration. Finally, the axial vibration active suppression theory of high-speed motorized spindles has been carried out based on the linear quadratic optimal control theory. The simulation result shows that the axial vibration amplitude of closed-loop system will attenuate fast compared with the open-loop system.
  • LI Jing;CHEN Jian-yun;LI Xue-lei
    . 2014, 33(20): 75-80.
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    Damage and Crack were the key factors that affecting the dam’s safety under seismic excitation. Take Koyna arch dam as example, two different forms of seismic reinforcement schemes are presented. According to the plastic-damage concrete damage model, and based on the embedded model of reinforced concrete, the seismic responses of concrete gravity dam are calculated under different reinforcement schemes. The results verified the necessity and practicality arranging reinforcement for seismic resistance at the weak parts of the dam.
  • MA Xing-guo;ZHANG Ren;YOU Xiao-mei;YE Ming;GONG Xue-lian
    . 2014, 33(20): 81-85.
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    For studying the performance of hydro-pneumatic spring and hydraulic buffer and their effect on a suspension system, the dynamics model of single-wheel suspension system of a tracked vehicle was established by RecurDyn. Based on the vehicle dynamic and the crash theory, the cushioning and absorbing of the crash energy of the suspension system were studied. The results show that a dynamics model of single-wheel suspension system used for simulating is valuable for studying the properties of the suspension system, which can replace a whole vehicle’s simulation to some extent. The hydro-pneumatic suspension system has non-linear and large damping properties which have a strong ability to cushion and absorb the crash energy in a large amplitude vibration.
  • CHI Yu-lun;LI Hao-lin
    . 2014, 33(20): 86-90.
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    The machine tool deformation is one of important factors which affect the workpiece surface quality. The paper proposed a method to optimize the milling parameters based on dynamic stiffness measurement and milling force model. The machine tool dynamic stiffness is obtained by step response experiment, and the milling force model coefficient is defined through orthogonal experiment. At last, the paper designed the tool online measurement and the milling force online measurement setup to verify the optimized parameters, and its validity and feasibility are proved.
  • WANG Ping-ping;LIU Lei;LUAN Xiao-na
    . 2014, 33(20): 91-94.
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    The working performance of smart actuators is affected by the hysteretic effect nonlinearity. Thus, it is necessary to identify and compensate the hysteresis nonlinearity to achieve precision motion. At first, based on the singular value decomposition (SVD) method, the parameters of the Preisach model are identified using the de-signed harmonic input signals with varying amplitudes to satisfy PE condition. Then, based on the identified Preisach model, the mode-inversion feedforward is designed to compensate the hysteresis nonlinearity. Finally, the piezoelectric stage is used to validate the proposed identification and compensation methods. The experimental re-sults indicate that the hysteresis nonlinearity has been identified using the SVD method, the tracking error has been reduced by 89.5% using the model-inversion compensator. The proposed identification and compensation ap-proaches have been verified.

  • WANG Shu-xin;LUAN Xin;SONG Da-lei;WANG Yong-fang;SU Zhao-long;YAN Qi-zhi
    . 2014, 33(20): 95-98.
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    The submersible buoy with turbulence instrument is an effective and a long-term observation platform of the turbulence in deep sea and plays an important role in marine scientific research. The current development of turbulence instrument at home and abroad and shear probe measurement principle were briefly introduced, according to the measurement data with the turbulence instrument submersible buoy. The factors affecting the measurement results of flow vibration instrument were analyzed. The methods to reduce noise pollution were discussed. According to the noise caused by the vibration of cable transmission, the method of application of low temperature water damping material was proposed. The damping experiment data analysis indicated that adding damping material can effectively reduce the influence of vibration on the measurement accuracy.
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  • CHE Kai-kai;ZHANG Zhen-guo;ZHANG Zhi-yi;HUA Hong-xing;
    . 2014, 33(20): 99-104.
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    The coupling between nonlinear friction and bending-torsion vibration can induce self-excited vibration in shaft system with water-lubricated rubber bearing, which can result in abnormal noise. The present researches are mainly based on single-point bearing to establish the dynamic model, which cannot analyze the influence of distributed bearing force and bearing inclination on the vibration characteristics of shaft system. In order to solve this problem, the dynamic model of a shaft system is developed, which is based on distributed bearing model and velocity dependent friction represented by Stribeck curve. The equation of motion is derived using Lagrangian approach and Modal Synthesis Method. Using numerical method, the paper analyzes the relationship between the nonlinear dynamic response and the system’s physical parameters. What’s more, the effects of contact force, rotational speed and the inclination of bearing are also discussed. According to the simulation results, the self-excited vibration in shaft system can be easily obtained for the inclined bearing if other conditions, like contact force, rotational speed and friction parameters, are the same.
  • YU Tao;;WANG Jiao;LI Ying-jie;SUN Wei;HAN Qing-kai
    . 2014, 33(20): 105-110.
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    The dynamic model of simplified-concentrated-mass based Jeffcott rotor system with slowly-varying mass is build. Analytic processing for rotor system with slowly-varying mass is introduced by adopting the asymptotic method. And the analytic solutions for response of the rotor system are deducted detailedly. With the analytic solutions and Reassigned Morlet scalograms, the nonlinear dynamics of rotor system with slowly-varying mass are discussed. The specific nonlinear dynamic characteristics for rotor system with slowly varying mass can be referred for research on slowly-varying parameter system and diagnosis of corresponding faults.
  • LIU Feng;PANG Fu-zhen;HAN Duan-feng;MIAO Xu-hong
    . 2014, 33(20): 111-117.
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    Based on principle of structural dynamics analysis, the unitary of force and moving boundaries is proved by using the “equipment-base” vibration system as an example. By constructing “virtual force” to keep the consistency of moving boundaries of structure with dynamic parameters locally unknown, moving boundary similarity method (MBSM) is thus proposed to solve structural dynamics prediction problem of given moving boundary conditions with structural dynamic parameters locally unknown. The effectiveness of MBSM is also verified. On that basis, MBSM is applied to the research of ship structural underwater vibration and noise radiation. The underwater noise radiation characteristic of a ship is analyzed. Result shows that the underwater vibration and sound radiation of a ship are highly related with the location and frequency of excitations and other factors. On the one hand, ship structural borne noise radiation is mainly concentrated in the vicinity of excitation source in the middle and aft region of ship hull, followed by the aft of ship hull, and the underwater noise radiation of bow has the minimum effect. On the other hand, the underwater noise radiation is more uniformly distributed along the ship length in low frequency band; however, the inhomogeneity and directivity of the underwater noise radiation gradually increases as excitation frequency increases.
  • WANG Shi-ping.;ZHANG A-man;WU Chao.
    . 2014, 33(20): 118-122.
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    Bubble collapse under different boundary conditions has long been a hot topic in research on bubble dynamics. The Bubble motions between two parallel plates and in cylinder region are studied experimentally with low-voltage electric spark bubble generator and high-speed camera. Bubbles are generated at the center of the region to ensure its symmetric motion. Between parallel plates, the bubble will be teared apart from the middle into two smaller bubbles, with the jets of both directed towards the plates. As the dimensionless distance between two plates decreases, the following three motion patterns are observed: rebound and split, adverse jet, and connected jet. In cylinder and square cylinder regions, the bubble evolves into a red blood cell shape and a ring-bubble is generated at the end of jetting with its jet points towards cylinder wall. The study on bubble motion characteristics presented here could be useful references for researches on collapse patterns near different types of boundaries.
  • CHEN Shang-you;LU Ping;LIU Gao;XIA He
    . 2014, 33(20): 123-128.
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    A dynamic analysis model of coupled train-bridge-road vehicle system is established, in which the train and road vehicles are modeled by multi-rigid-body system, the bridge is modeled by spatial beam and bar elements, the wheel-rail corresponding assumption and the creep theory are used to deal with the wheel-rail contact relationship, and the bridge deck and the vehicle tires are assumed to be in point-contact and without separation. A computer simulation code is developed. With a rail-cum-road bridge as an example, the coupling vibration responses of the train-bridge-road vehicle system are analyzed. The results show that when trains and road vehicles pass the bridge simultaneously, with the increase of vehicles, the maximum vertical acceleration, derailment factor and offload factor of the train are significantly increased, showing an adverse influence of the road vehicles on the running safety of the trains.
  • WANG Zhi-hao;;CHEN Zheng-qing;WANG Xu;WANG Zhao-yang
    . 2014, 33(20): 129-132.
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    Traditional tuned mass damper (TMD) adopted for vibration control model test of civil engineering structures has several obvious disadvantages. It can’t well separate the damping and stiffness components, and the damping coefficients can’t keep the same during the movement of the TMD. In addition, it is difficult to adjust the damping coefficient during the control performance tuning in the test. By performance tests and analysis, it is proved that the developed tiny TMD with eddy-current damping can successfully solve the above three problems. The great advantage of the proposed TMD is that its damping ratios can be easily adjusted by changing the thickness of conductor plates. Finally, model test on lateral vibration control a footbridge has further demonstrated the feasibilities and effectiveness of the developed TMD based on identified modal damping ratios of structure subjected to both free vibration and forced vibration excitation, structural dynamic response magnification as well as the phase between the main structure and TMD in the forced vibration excitation tests.
  • SHI Zhen;WANG Jia-xu;XIAO Ke;LI Jun-yang;GUAN Hao
    . 2014, 33(20): 133-139.
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    To a planetary reducer with small tooth number difference, a coupling multi-body dynamics virtual prototype model was established, the dynamic correlation method was used to validate the virtual prototype model and the accuracy of the virtual prototype model was verified; the equivalent stress and vibration response of planetary reducer were analyzed under various conditions, and its vibration characteristics were tested by vibration test equipment. The results show that with the increase of rotational speed of the planetary reducer, the equivalent stress has no distinct change, but the eccentric motion of the eccentric shaft is increasingly obvious, which enhances impact to meshing gear leading to more serious vibration and impact amplitude, the simulation analysis results are consistent with the experimental results.
  • ZHANG Ju-hui;GUAN Zhong-guo
    . 2014, 33(20): 140-145.
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    Structural performance indices of the regular continuous girder bridges under different damage states were discussed and constructed by displacement ductility ratio. Based on the OpenSees platform, a structural dynamic analysis model was established by using the nonlinear fiber beam elements. 100 earthquake ground motion records were selected, and the nonlinear time-history analysis was performed, thus the fragility curves under different damage states were constructed. Through parametric analysis, the effects of pier height, bearing types and transverse reinforcement ratios on the fragility curves were studied. The results show that the ductile development degree of the continuous bridge has a great effect on the structural seismic vulnerability. The fragility curves obtained under both minor damage and moderate damage seem to be very close; while under extensive damage, the bridge shows a good performance against earthquake forces. With the increase of the pier height, the lower level of damage probability of the structure is observed; meanwhile, the improvement in the fragility by using the plate rubber bearings is excellent for a short-pier bridge, but very limited for a high-pier one. The effect of increasing the transverse reinforcement ratio on fragility curves can be neglected for structural damage in early stages, but can significantly increase the structural capacity from collapse.
  • LI Hong-bo;ZHOU Jian-jun;WANG Zhu-feng;
    . 2014, 33(20): 146-150.
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    The shield is widely used in underground projects. The cutting-tool wear of shield machine has become a key problem that affects the engineering quality and progress. Acoustic emission(AE) as a nondestructive detection method has been widely applied in all kinds of field. Acoustic emission signal which has rich multi feature information can reflect accurately the detection member state. In the study of acoustic emission signal, How to distinguish between effective signal characteristics of acoustic emission and how to use the characteristic information to evaluate is a hot research at home and abroad. Based on the comprehensive experiment platform of rock and machine, By acquisiting emission signal of different shield cutter wear, The adaptive filter and acoustic emission detection are applied to detect the field shield cutter and use information entropy multi feature fusion technology assessment. According to the state of the database tool wear information entropy and the corresponding can clearly understand the wear condition of shield cutter.

  • CHEN Ai-jun;ZHANG Jia-sheng;HE Jian-qing;WANG Zhi-bing
    . 2014, 33(20): 151-156.
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    Vibratory compaction is commonly used compaction method in embankment, Dynamic response tests of vibratory compaction are the basis of vibration compaction mechanism study. For Sansui-Liping highway Weathered Slate embankment test section in Guizhou province, through buring earth pressure boxes at different depths in the embankment, Using two vibrating roller compaction, Vertical and horizontal dynamic response of different depth is tested in field. The results showed that: when the shock wave is propagating in the soil closely the frequency remained constant or decreased slightly, Soil particles is in pressure-unloading cycle under dynamic stress; Rollers for power generating topsoil and cause a significant role in pushing the loose surface filler, High-power roller produce significant push effect for topsoil and loose skin fillers; Dynamic stress diffuses in the soil down to a certain diffusion angle, different roller has different diffusion angle; according the wave theory getting the law that dynamic stress is decaying with depth natural numbers exponentially in the soil, the conclusion has been verified and the test data, the attenuation coefficient of vertical dynamic stress is twice the level of dynamic stress; Dynamic stress levels generated by super power roller are far greater than the heavy roller, heavy roller resonance phenomenon in the soil; Measured dynamic lateral pressure coefficient is not a fixed value, it Increases linearly with increasing depth.
  • LI Fa-zong;TONG Shui-guang;WANG Xiang-bing;CHENG Xiao-min
    . 2014, 33(20): 157-163.
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    Structure of marine excavator’s mechanical armwasapproximatedasa flexible cantilever beamwith tip mass.Lagrange theorem is used toestablishrigid-flexiblecouplingdynamic equations of mechanical arm, sensitivity of the first natural frequency for the geometric parameters related is calculated by applying the numerical solution method,the change relations between vibration natural frequency and associated parameters for the mechanical armwere gotten.the rigid-flexible coupling model of hydraulic excavator’s mechanical arm is established and simulated by the simulation software ADAMS and NASTRAN ,thevirtual prototype model of marine excavator with flexible boom,flexible luffing rope,flexiblegraphoisting rope,rigidframe,rigid rotation platform.The dynamics simulation is conducted based onthe structure and working condition characteristics ofthe marine excavator’s mechanical arm system,the system displacement, velocity, acceleration,aswell as the hinged connection force points and the dynamic stress ofmechanical arm etc.The research resultswas is demonstrated by contrasting, and the basis from the research results is provided for the further researchon the job stabilityand motion error control of mechanical arm.
  • LI Zhe;HU Ji-quan;WANG Dong
    . 2014, 33(20): 164-169.
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    According to the dynamic similarity theory to design the reasonable scale model, take dynamic test analysis of the container crane structure by shaking table. In the scale model, the length of each component (beam) size can be based on the size of the prototype, but the cross-section thickness cannot change according to the same scale narrowed, causing distortion model. Finite element prediction coefficient method can get the prediction coefficient which using to the distortion model predict the dynamic characteristics of prototype. In order to verify the effectiveness of distortion coefficient that obtained by the finite element prediction coefficient method, made a distortion model that the thickness of the cross-section distorted and a hammering modal test and a series of seismic sharking table tests were successively carried out. The results showed that the experimental results similar to the calculation results, the maximum acceleration and strain in the same position, distortion coefficient of prediction is reasonable.

  • QIU Dong-hai;JIA Hong-guang;MA Wu-yuan;GAO jiu-zhou;ZHOU Ling
    . 2014, 33(20): 170-175.
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    To improve the shock absorbing performance of UAV landing gear, dynamic analysis and optimization for a cushioning mechanism of articulated landing gear is performed. Firstly, based on the establishment of mathematic model of UAV ground movement and the stress analysis of landing gear when it is under braking control, the behavior and scheme of cushioning mechanism is discussed. Secondly, the software of multidisciplinary design optimization (iSIGHT) combined with the dynamic software(Adams) are applied to the optimization of cushioning mechanism. Then, by taking the requirements of braking condition and shimmy containment as constraint, the size of cushioning mechanism and the spring stiffness are optimized by using the method of point-by-point comparing at macrocosm combined with sequential quadratic programming method. Finally, the taxiing test and stiffness test for the optimal landing gear are carried out. The results show that the compression displacement meets the desired requirement and the efficiency of buffer is increased by 71.5%. The analysis and optimization method provide guidance for the design of UAV articulated landing gear.

  • KONG Yan-ping;TIAN Ruo-meng;LIU Jin-xi
    . 2014, 33(20): 176-182.
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    This paper investigates the propagation of SH waves in the layered plate structure consisting of a functionally graded piezoelectric layer and a piezomagnetic half space. The change of the functionally graded piezoelectric material is exponential form along x2 direction. The electrical boundary conditions is short circuit and open. Based on the dispersion equations, the numerical examples are presented to show the influence of variations of material properties, piezoelectric layer thickness and electrical boundary on the phase velocity. The resach results can provide theoretical reference for high performance acoustic devices.
  • LIU Wei;SUN Xiao-xia;SHEN Rui-qi;YE Ying-hua
    . 2014, 33(20): 183-186.
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    The dispersion effect in the Hopkinson pressure bar high-g loading technique was caused by the lateral inertia motion of the particle, leading to an inaccurate acceleration in peak and duration. Based on the Fast Fourier Transform (FFT) approach, the dispersion effect was corrected. Then, acceleration pulses at different locations along the pressure bar were compared to check the dispersion effect. In addition, before and after dispersion correction, the acceleration pulses on the specimen were obtained under different pulse loading, and the errors of the peak and duration were analyzed. Results show that the acceleration pulses at different locations of the bar are different in peak and duration due to the dispersion effect, and the errors of the peak acceleration on the initiator are more than 10%. The errors of the acceleration duration depend on the pulse shape, but the absolute errors are all less than 6μs. As for the dispersive pulse, dispersion correction is a necessary procedure to obtain a more accurate acceleration pulse.

  • WANG shi-ming;LIU yu;REN Shun-qing
    . 2014, 33(20): 187-191.
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    The impact of external environmental factors on centrifuge stability is analyzed when centrifuge is working, and the influences of environmental temperature, angular inclination modifications and linear vibration of foundation on the specific force generated by centrifuge are discussed respectively, the results show that three errors should be real-time monitored and measured while inertial devices are calibrated on the centrifuge, and the calibration accuracy of inertial devices on centrifuge can be raised through compensating for these three errors.
  • YANG Juan;LI Xing
    . 2014, 33(20): 192-197.
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    The scattering of SH wave on cracks in magneto-electro-elastic composites substrate was studied. Considering the electric permeable boundary conditions, by using the Fourier cosine transform, the problem was transformed to a pair of dual integral equations, which were then reduced to the Fredholm integral equation of second kind by the using the Copson methods, and the normalized dynamic stress intensity factor at the crack tip was obtained. Finally, numerical results showed the influence of the length of the crack, the thickness of the strip, the frequency of SH wave and the incidence angle upon the normalized stress intensity factor.
  • FENG Lei;MA Tie-hua;
    . 2014, 33(20): 198-203.
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    It is common that only the accelerometer is calibrated in high impact test, so the measurement error caused by the accelerometer assembling is neglected. First, analyzes the reason transverse effect arise and the instrument overall mechanical model. Use Hopkinson bar to do the impact test on each axis of the accelerometer to study the transverse effect. And then use ANSYS to analyze the instrument structural response under the load of 20000g acceleration. The results show that the instrument mechanical shell vibrates and the measurement error caused by assembling of the accelerometer cannot be neglected.