15 April 2014, Volume 33 Issue 7
    

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  • Yaoqing Gong Yejun Li Lumin Wang Qikeng Xu Jun Chuai
    . 2014, 33(7): 1-3.
    Abstract ( 385 ) Download PDF ( 394 )   Knowledge map   Save
    The computational model of a set of reinforced concrete silos with tubular foundations is built, simplified into a combination of vertical generalized Timoshenko beams with n segments. The deflection of the neutral surface and the cross-sectional rotation around the neutral axis of each segment of the beam are chosen as basic unknown functions. By applying an energy principle, the motion equations for the free vibration problem of a set of reinforced concrete silos with tubular foundations are then translated into a group of ordinary differential equations composed by the unknown functions, which can be solved by an ordinary differential equation (ODE) solver. Thereupon, the natural frequencies and mode shapes of the set of reinforced concrete silos are obtained. The comparison between the numerical solutions and the results of the corresponding tests demonstrates the efficiency and precision of the analysis. Thusly, a new computational method for the analysis of dynamic performances of a set of reinforced concrete silos with tubular foundations is provided.
  • Zhang Jing;Liu Rong-qiang;Guo Hong-wei;Deng Zong-quan
    . 2014, 33(7): 4-10.
    Abstract ( 508 ) Download PDF ( 216 )   Knowledge map   Save

    A purely bending model considering the clearance, stiffness, damping of joints and nonlinear cables, is derived to show the nonlinear dynamic characteristics of jointed deployable structures. The Taylor series expansion of nonlinear differential equation and harmonic expansion of variables are used to convert the nonlinear dynamic equation to nonlinear algebraic one. The response of the deployable structures can be analyzed by iteration method. The numerical analysis by Runge-Kutta method for deployable structures is employed to validate the incremental harmonic balance (IHB) method. IHB method is used to analyze the stability of response for deployable structures when the exciting frequency changes, which is based on the nonlinear dynamic model. The stability of deployable structure response are presented in a frequency range when the clearance and stiffness of joint, exciting force and cable change. The IHB method can be used for multi-degree deployable structures to obtain the steady response and nonlinear dynamic characteristics, which provides a method for further research of the dynamics of jointed deployable structures.



  • Zhang Jun Liu Xian-zeng
    . 2014, 33(7): 11-17.
    Abstract ( 371 ) Download PDF ( 242 )   Knowledge map   Save

    A multibody dynamic model for helical planetary gear train (HPGT) is proposed and the dynamic performance of the HPGT system is analyzed. The free vibration characteristics, steady-state dynamic responses and effects of design parameters on system dynamics are investigated through numerical simulations. The free vibration of the HGPT is classified into 3 categories according to modal properties such as eigenvalue multiplies, modal coordinates of central components and coordinates ratios of planets. The classified vibration modes are demonstrated as axial translational and torsional mode (AT mode), radial translational and rotational mode (RR mode) and planet mode (P mode) followed by the characteristics of each category. The simulation results agree well with those of previous discrete model when neglecting the component flexibilities, which validates the correctness of the present multibody dynamic model. The steady-state dynamic responses indicate that the dynamic meshing forces fluctuate about the average static values and the time-varying meshing stiffness is one of the major excitations of the system. The parametric sensitivity analysis shows that floating sun gear and reducing circumferential error of planets are two effective solutions for vibration control of the HGPT.



  • Chen Yongsheng;Wu Bin;Wang Zhen;Xu Guoshan;Zeng Cong
    . 2014, 33(7): 18-23.
    Abstract ( 331 ) Download PDF ( 350 )   Knowledge map   Save

    As the tool of Hybrid Simulation(HS), Hybrid Testing System(HTS) is developing toward distributed and complex direction. It is difficulty for the beginners to understand the process of HS and for the researchers to focus on a particular field. Herein a basic HTS is studied. Firstly, Simulink simulation environment is introduced. Then, the basic principle of HS and the framework of HTS is elaborated, A HTS based on Simulink simulation environment is proposed, and some key problems in HS are discussed. Finally, HTS simulation and validation are carried out using a simplified loading system model and a real loading system respectively. The results indicate that the modules of the HTS can work together and it can easily implement hardware in the loop simulation.


  • Liu Shuai;Weng Da-gen;Zhang Ruifu
    . 2014, 33(7): 24-30.
    Abstract ( 474 ) Download PDF ( 220 )   Knowledge map   Save

    Based on the finite element analysis program ANSYS, the three-dimension integral finite element model of pile-soil-LNG storage tank interaction system was established, the effect of considering the pile-soil interaction on the seismic performance of LNG storage tank was analyzed in the soft site of class IV. Analysis results show that the peak shear force, peak overturning moment and the maximal Von Mises equivalent stress for the inner steel wall of the LNG storage tank were reduced by different degrees, but the maximum sloshing wave height of the liquid was increased. In addition, the effect of different insulation layer stiffness on the seismic response of LNG storage tank was also analyzed, by contrast, the variation of insulation layer stiffness had important influence on the seismic response of LNG storage tank. With the increase of insulation layer stiffness in a certain range, the peak shear force, peak overturning moment and the maximum sloshing wave height have minor changes, but the maximal Von Mises equivalent stress for the inner steel wall was reduced significantly.



  • Han Ning;Gu Ming
    . 2014, 33(7): 31-36.
    Abstract ( 348 ) Download PDF ( 203 )   Knowledge map   Save

    Based on wind tunnel tests of two square tall buildings, the characteristics of wind pressure spectra on the isolated and interfered building were investigated. Firstly experiments on a single square tall building in C terrain were carried out, then tests on the same building with 16 different locations and 3 different height ratios of an interfering building were conducted and wind pressures on the interfered building were obtained. In these foundations, the interference effects on wind pressure spectra of the typical taps of the interfered building were analyzed in frequency–domain with different spacing ratio and height ratio in tandem configurations. The results show that wind pressure spectra energy on the center line of the windward face of the isolated building is distributed over a wide frequency range; however, that near the edges on the face has sharp peaks. Energy at high reduced frequency near the trailing edges on the side face of the isolated building is significantly greater than that near the leading edges. The sharp peak amplitudes were dampened dramatically when the spacing ratio is small in tandem arrangements. The lower interfering building leads to larger energy at low reduced frequency, while the taller interfering building mainly affects the energy at high reduced frequency.


  • WU Jun-da;DONG Da-wei;YAN Bing;SUN Yu-hua;WANG Yuan-wen
    . 2014, 33(7): 37-44.
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    In order to study dynamic response characteristics and swing-arm fatigue strength of heavy hydraulic modular trailer, a rigid-flexible coupling multi-body dynamic model of trailer was established based on finite element analysis method and rigid-flexible multi-body dynamics theory. The model was simulated with excitation signal by road roughness and verified by vibration experiment results. Dynamic response simulation analysis of trailer was carried out with different operational conditions, as the road roughness and trailer speed. The stress time histories of swing-arm, which are necessary for fatigue analysis, were calculated by using finite element analysis method with dynamic load, as the results of multi-body dynamics simulation. Fatigue life of swing-arm were predicted based on local stress-strain analysis method. The calculation results show that, stress concentration positions of swing-arm appears at cross section of fracture failure location and stress level has entered into plastic state. With operational conditions of trailer on B grade, C grade and D grade roads, the fatigue life of risk points are greater than the service life of trailer. However, on sinusoidal uneven roads, the fatigue life of risk points decreases obviously with the augmentation of sinusoidal amplitude and trailer speed. Reasonable operating conditions, which could enhance trailer’s operation security and transportation efficiency, are proposed from swing-arm fatigue life simulation results.


  • WANG Yi-jia;ZENG Jing;LUO Ren;WU Na
    . 2014, 33(7): 45-50.
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    According to the measurement of wheel profile by line test for high speed train, the contact geometry of new and worn wheel profiles S1002GCN with different wear mileages are studied .The relationship between contact angle difference and equivalent conicity of wheel/rail contact is analyzed, which provide a basis for stability study when wear profiles are difficulty to obtain. A high speed dynamic model is established and the stability of vehicle is analyzed with the new and the worn wheel profiles respectively. The results showed that: the relationship between the equivalent conicity and contact angle tend to a constant with wheel wear. Equivalent conicity, the longitudinal stiffness of the primary suspension affect the amplitude and the form of bifurcation. From the simulation results we can see that rail cant, track gauge and rail grinding have nonlinear relationship with the contact geometry between the worn wheel profile and rail.


  • WU Wen-bing;JIANG Guo-sheng;DOU Bin;WANG Kui-hua;HUANG GEN-sheng
    . 2014, 33(7): 51-57.
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    Based on plane strain model and Reyleigh-Love rod model, the calculating model and governing equation of rock-socketed pile embedded in layered soil is established when there is arbitrary vertical exciting force acting on the pile head. Combined the boundary conditions and initial conditions, the analytical solution of vertical dynamic impedance at the head of rock-socketed pile is derived by means of Laplace transformation and impedance function transfer method. By means of parametric study method, the influence of rock-socketed characteristics on the vertical dynamic impedance of rock-socketed pile is investigated within the low frequency range. The results show that, for a certain depth of overlaying soil, the dynamic stiffness decreases as the rock-socketed length increases while the dynamic damping increases as the rock-socketed length increases. When the radius of rock-socketed segment is equal to pile radius, it can be seen that the dynamic stiffness and dynamic damping increase as pile radius increases. When the radius of rock-socketed segment is less than pile radius, it can be seen that the dynamic stiffness decreases as the radius of rock-socketed segment decreases, but the dynamic damping increases as the radius of rock-socketed segment decreases. It can also been shown that the dynamic stiffness increases and the dynamic damping decreases as the shear wave velocity of bedrock increases.
  • WANG Jun;WANG Zhi-wei;LU Li-xin;CHEN An-jun;
    . 2014, 33(7): 58-62.
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    An generalized inverse subsructuring method was develped for multi-component coupled system, the back-caculating formula for four-component coupled system was obtained as an example. Then, the mothod was verified by a lumped parameter model, the FRFs of the components and coupling stiffness were predicted by the system-level FRFs applying the developed method and compared with the given value, showing perfect agreement. The results indicated that the propsed method is effective to model the multi-component coupled system.


  • JIANG Jin-ke;FANG Zong-de;Wang Feng
    . 2014, 33(7): 63-67.
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    An approach based on the minimum amplitude of loaded transmission error, meshing impact force and acceleration of vibration with drive diagonal modified helical gears was proposed to reduce vibration and noise. Firstly, the modified tooth surfaces was represented by a sum of two vector functions that determined the theoretical tooth surface and the deviations surface, which was fitted by 3 B Spline based on tooth surface grid data established by the deviation curve. Secondly, with the tooth bearing deformation ascertained by TCA and LTCA, the meshing force and meshing stiffness were established according to the meshing impact theory. Finally, a dynamic model with a pair of helical gear was built, and used genetic algorithm to optimize the parameter of curve to get the best deviation surface. The results shows that the diagonal modified helical gears can greatly reduce the vibration and noise due to the positions changing and small loads under approaching meshing, as well as higher coincidence degree than other type modified gears.


  • TANG Gui-ji;DENG Fei-yue;HE Yu-ling;Wang Xiao-long
    . 2014, 33(7): 68-72.
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    There have periodic impulses in vibration signals of bearing, so a new method, so called time-wavelet energy spectrum entropy, is proposed for rolling element bearing fault diagnosis. Firstly, the impulse response wavelet is constructed to extract wavelet energy spectrum in time domain by using continuous wavelet transform, then energy spectrum entropy which represents vibration signals quantitatively change with time is calculated along the time axis, bearings with different faults have different variation complexity, and the entropy is different. To identify the fault pattern and condition of bearing, entropy of different fault signal could as input vectors of support vector machine. Practical examples showed the method can diagnose efficiently faults of rolling element bearings.



  • WANG Su-juan;LEI Zheng-bao;ZHAO Jian
    . 2014, 33(7): 73-78.
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    For the data-processing reliability problems in risk-assessment group decision-making, the importance of the expert weights for the data processing was proposed. From the industry characteristics of automotive crash safety research, based on expert social factors indicators, by using two analysis methods of system clustering and K-means clustering, clustered the experts according to expert-authority-weight; Based on the data consistency and the consistency degree of individual and group from expert opinions, by using the method based on information entropy, clustered the experts according to expert-opinion-weight; Two clustering results were compositely clustered to get the final weight of the experts. The results show that the expert weights got by the composite clustering have good proportionality and reliability, based on compositing expert-authority-weight and expert-opinion-weight, it lays a foundation for the study of systems projects.



  • WU Shao-wei;;XIANG Yang;XIA Xue-bao;
    . 2014, 33(7): 79-85.
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    Fictitious acoustic sources have to be placed inside a structure apart from the surface in conventional wave superposition method. Otherwise, the singularity of Green’s function for self-terms would arise in the algorithm, leading to worse sound field calculation. To solve this problem, a meshless acoustic superposition method based on discretized radiating surface of vibrating structure is studied. The singularity problems of Green's function when the source and receiver point coincide are overcome by removing singular point, replacing part integration region and invariant imbedding separately. Non-singular expressions for the pressure and velocity self-terms are obtained. Then the source strength and pressure could be determined according to velocity boundary conditions. The pressure and velocity self-terms can be correctly calculated by the approximate analytical expressions, validated by an example of pulsating sphere. Thus the prediction of sound field could be realized.
  • WANG Jun;YAO Xiong-liang;GUO Jun
    . 2014, 33(7): 86-91.
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    Impact assessment test for large-medium sized shipboard equipment should be carried out through the floating shock platform, and the structure form of the floating shock platform can make the difference between a successful or unsuccessful test. But the IFSP (intermediate floating shock platform) has not been started the construction in China. So the structural design of IFSP is analyzed. The response of the IFSP is calculated through nonlinear doubly-asymptotic approximation. Several structure forms of the floating shock platform are put forward and their strength and shock environment are analyzed. The results show that the main response of the IFSP is the rigid body motion and the structure form of IFSP with box girder and outer plate dissection has the best strength. The spectrum displacement and spectrum velocity of shock environment provided from the inner bottom are consistent with the specification. The spectrum acceleration requires the filtering of deck simulator to meet with the specification. Analysis results are expected to be useful for the construction of IFSP for the impact assessment of large-medium sized shipboard equipment.



  • Hai Yu;Yushu Chen and Qingjie Cao
    . 2014, 33(7): 92-98.
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    Crack fault is an often occurred complex high-dimensional nonlinear problem in large rotating machinery system. In this paper, a low-pressure rotor system of an aero engine with a pair of liquid film lubricated bearings is modeled into a twenty-two degree of freedom nonlinear system using Lagrange method. This high dimensional nonlinear system can be reduced into a two degree of freedom system preserving the crack fault oil-film oscillation property by introducing the modified POD method. Numerical simulations demonstrated the efficiency of the method is shown by comparison with the computed results given for both the original and the reduced systems. C-L method is also employed to obtain the dynamical behaviours of the reduced system, which reflect the natural property of the crack fault.
  • Shi Wankai Liu Jing Gong Jianchun
    . 2014, 33(7): 99-104.
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    Based on the method of gear system dynamics and Lagrange equation, a coupling dynamic model of the Co-axial Counter-rotating Epicyclic Transmissions(CCET) is built by lumped-parameter method, and the support stiffness, elastic coupling and power flow of the gear train is considered in the model. Under the action of the gear pair run-out error, meshing-frequency error and time-varying mesh stiffness together, time-domain dynamic characteristics about displacement response and speed response are achieved by numerical analysis method, and the load sharing is compared between ordinary gear train and differential gear train, which provides the basis for dynamic performance optimization and noise and vibration study of CCET.

  • Zhicheng Huang Zhaoye Qin Fulei Chu
    . 2014, 33(7): 105-113.
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    Because of its structure characteristics of "light" and "thin",the thin-walled structures vibrate more easily compared with the common thick-walled components. Using viscoelastic damping material to control the vibration of thin-walled member is an effective means,and for decades the vibration problem of thin-walled structures with viscoelastic damping layer treatments has been a hot issue, and especially in the last ten years made considerable progress. Selected dozens of literatures in this field since 2000, and then divided them into six categories to summarize the new progress on vibration problems of thin-walled structures with viscoelastic damping layer treatments. The conclusions and prospects will provide valuable reference for researchers in this area in the future.
  • HU Jian-guo;MA Da-wei;LE Gui-gao;ZHAO Jie
    . 2014, 33(7): 114-119.
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    Honeycomb is one of the most used buffer medium in buffer device of lunar lander, studying on the mechanical properties has an important significance to buffer device and ascender's stable take-off. Firstly, analysis the in-plane and out-of-plane equivalent mechanical properties of honeycomb, and the rate-dependent transverse isotropic constitutive model is built considering the rate-dependent features of honeycomb structure. Secondly, the user subroutine of rate-dependent transverse isotropic constitutive model is written based on FEM, and the reliability is verified. Finally, taking the four legs hanging rack lander as the research object, the influence of rate-dependent coefficients on landing impact performance is studied. The results show that with the increase of rate-dependent coefficient, the energy absorption of buffer device increases first and then decrease, and reach the maximum when the coefficient is 0.6; the biggest impact acceleration of lunar lander increase, and when the rate-dependent coefficient is large, the growth rate of the biggest impact acceleration is bigger than that when the rate-dependent coefficient is small.
  • ZHANG Dapeng;LEI Yongjun;DUAN Jingbo;XIE Yan;ZHENG Jian
    . 2014, 33(7): 120-125.
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    The establishment of scientific finite element mode for soil plays a pivotal role in simulating and analyzing the landing impact of space capsule. The LS-DYNA was used to simulate the landing process of space capsule, and the effect of main parameters in soil mode on impact characteristic was analyzed through orthogonal test. The results demonstrate that bulk modulus and parameter A2 significantly influence the maximum impact acceleration and pulse width, parameter A0 A1 and their interaction are not significant. These conclusions can provide some references to both the study on ground test in the landing process and the structural optimization of space capsule.

  • XUE Kun;XU Jun-biao;BAI Chun-hua
    . 2014, 33(7): 126-132.
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    Particle jets driven by the central explosion determine the dispersal of particles in the blast flow. We tracked the dynamic fragmentation of sand shells with different saturation subject to the central explosion, and obtained the onset of jet formation and the characteristics of jets. The stretch and dissolution of particle jets can be studied by virtue of the analysis of the vibration acceleration of targets generated by the impact of jets. We found the interstitial fluid plays an important role in both formation and evolvement of particle jets.

  • Liu Wenguang;YAN cheng
    . 2014, 33(7): 133-137.
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    The modeling method of an elastic plate under vibration with cracked effects is proposed according to dynamic problems of cracked plates. The crack is replaced by an external force approximately on the basis of deformation equivalence. The motion equation of an elastic plate considering crack is derived via the principle of mechanical equilibrium, and the cracked terms is derived through the stress relations that are introduced by Rice and Levy. Therefore, Galerkin method and Berger’s experience are used to simplify the cracked plate into a nonlinear one single freedom nonlinear vibration system, and the dynamic character of a simply support plate is analyzed. Then, a case study is carried out for the impact of crack size, plate dimension, damping and loading point on the vibration nonlinear and response. Results indicate that vibration response is affected by the plate dimension and crack size obviously; the stress response amplitude is controlled by damping and loading point.
  • FANG Zhi;JI Zhen-lin
    . 2014, 33(7): 138-146.
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    The two-dimensional finite element method is used to calculate the transversal modes of perforated tube dissipative silencer, and the numerical mode matching method is developed to predict the acoustic attenuation performance. The corresponding formulation is derived and the computational code is written. For a circular concentric configuration, the transmission loss results from the numerical mode matching method, the three-dimensional finite element method and experiment agree well, which demonstrated the accuracy of the 2-D finite element method in calculating the transversal modes and the numerical mode matching method in predicting the transmission loss of perforated tube dissipative silencer, respectively. The numerical mode matching method is then used to investigate the effects of hole diameter, porosity, density of the sound-absorbing material and offset of the perforated tube on the transversal modes and acoustic attenuation characteristics of the circular straight-through perforated tube dissipative silencer. The results showed that smaller hole diameter or higher porosity or bigger offset of perforated tube may lead to wider effective frequency range of plane wave domination, and better acoustic attenuation performance in the high-frequency range, but worse acoustic attenuation performance in middle-frequency range. Increasing the filling density of sound-absorbing material may improve the acoustic attenuation in the mid to high frequency range.
  • Lin Youxin;Jia Ziguang;Ren Liang;Li Hongnan;Cheng Mingtao;Zhang Peng
    . 2014, 33(7): 147-152.
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    This paper presents an experimental method to simulate stiffness reduction of compressed member using magneto-rheological damper (MR damper). The compressional stiffness is changed by current regulation of MR damper. In a transmission tower partial truss model dynamic experiment, simulation of instantaneous compressional stiffness reduction is carried out based on this approach. The dynamic response is processed by joint time frequency analysis, through which the damage time is to be figured out precisely. The result shows that this method is effective in model experiment.
  • Wang Xin;Hu Wei-bing;MENG Zhao-bo
    . 2014, 33(7): 153-159.
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    Ancient wood structure damage was simulated with the finite element under random incentive based on Xi’an bell tower, the node acceleration response signal on beam was decomposed with wavelet packet, the wavelet packet energy curvature difference index of ancient wood structure was proposed to decide the damaged localization. The results show that the index is more sensitive to ancient wood structural damage and can accurately determine the damage location under no noise, the injury degree is greater, the index is greater. When SNR is bigger or equal to 40db, the index can decide the damage location, it has a certain degree of noise immunity. The function relation between damaged index and extent is obtained to decide the damage extent, and the applicability is verified, so it provides theory basis for damage warning of Xi’an bell tower under environment excitation.
  • ZHANG Yong;WANG Ning
    . 2014, 33(7): 160-164.
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    The stability analysis for a class of typical second-order oscillatory systems is presented. The effect of signal transmission delay to the performance of closed loop control systems with unit negative feedback and unit positive feedback are analyzed respectively. The relationship between the time-delay and the stability of closed loop control system is obtained via drawing and analyzing Nyquist plots in the different value regions of relative damping coefficient. The simulation examples of unit step response for every situation are processed and the simulation results show that the analysis is correct.
  • XU Yonggang LU Ming FU Sheng ZHANG Jianyu
    . 2014, 33(7): 165-169.
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    As a new non-stationary signal process method, The intrinsic time-scale decomposition method (ITD) can decompose a complex non-stationary signal into several proper rotation components (PRCs), but there will be involved end effect in some PRCs. Five end effect mitigation methods to deal with the end effect is proposed in this paper. Including adaptive extension、AR prediction method、 mirror extrema extending、polynomial fitting extending method、anti-symmetric extensions method. Five methods are compared by mathematical simulation. The best one is applying in the simulated signal and bearing fault vibration signals, the results show that the new method can be used to solve the end effect effectively and the fault feature of the mechanical equipments can be extracted .

  • ZHANG Zhao-jun WANG Xiao-ming LI Wen-bin
    . 2014, 33(7): 170-173.
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    On the study of projectile perforating concrete target, mesoscale model is able to describe the effect of various mediums on the concrete mechanical properties. Algorithms for generating and distributing random 3D sphere coarse aggregate were proposed. The 3D finite element mesoscale concrete model, which consists of mortar matrix and coarse aggregate, was established based on the theory of background element and material identification. The interfacial transition zone was simplified as a kind of contact between elements. Based on this model, continuous finite element code was used to simulate the process of rigid projectiles perforating concrete targets and the effect of 3 different coarse aggregate on residual velocities was analyzed. This work indicate that the strength and density of coarse aggregate affects the residual velocity under lower and higher impact velocity respectively.

  • . 2014, 33(7): 174-180.
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  • ZHANG Yong-fang;LIU Cheng;WANG Dong;WU Peng
    . 2014, 33(7): 181-186.
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    More and more sliding bearings operate in turbulent regime due to the requirements of higher speed, higher power in rotating machinery. In order to analyze the lubrication characteristics of sliding bearings efficiently and save computational cost, an approximate solution of load-carrying capacity of oil film of finite length turbulent flow bearing is proposed based on Sommerfeld and Ocvirk number. Reynolds equation in lubrication of finite length turbulent journal bearing is solved based on multi-parametric perturbation principle. Load-carrying capacity of nonlinear oil film is obtained and comparison of the results obtained by different methods is made. The validation of the proposed method is verified. Then the influence of the change of the eccentricity and the width-to-diameter ratio on the load-carrying capacity and pressure distribution is discussed. The numerical results show that the proposed method not only approximates the load-carrying capacity of sliding bearings with varied width-to-diameter ratios efficiently, but also is suitable for those situations with large eccentricity ratio and high load.
  • LI Rong;JIAO Xiao-Hong;YANG Chao
    . 2014, 33(7): 187-193.
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    Robust disturbance attenuation problem based on output feedback is investigated for the half-car hydraulic active suspension system. First, the dynamic model of the half-car hydraulic active suspension system is established. Then, in the light of direct measurement not suitable for the position and velocity of car body, the pitch angle and angular velocity automobile body, the position and velocity of front- and rear-wheels, besides, nonlinearity and external disturbance, a dynamic output feedback control strategy with robust disturbance attenuation is proposed. The effectiveness of the designed controller is demonstrated by both theoretical analysis and simulation results. By comparison with the conventional PID algorithm, the improvement in ride comfort as well as the enhancement in handling and stability of vehicle can be further achieved by the controller in this paper.
  • Qiao Baijie;Zhao Tong;Chen Xuefeng
    . 2014, 33(7): 194-198.
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    A test rig is performed to measure power flow and estimate vibrational energy in this paper. Both force signal and acceleration signal of the same location and direction of one point could be simultaneously captured by inserting an impedance head. Subsequently, the power flowing into the foundation is calculated by the time average method, the fundamental frequency method and the second harmonic frequency method respectively. Experimental investigation shows that the harmonic vibration should be controlled, if the operating frequency of vibration source is the fractional frequency of natural frequency. However, due to the negative value which is inevitable during the measurement process of power flow, this study attempts to interpret the cause of the negative power flow from multi-degree of freedoms vibration. Due to the difficulty of measurement, the vibrational energy of the foundation is estimated via the driving impedance and mobility. Finally, the relationship between power flow and vibrational energy is examined by the loss factor.



  • Dan Wang Yushu Chen Qingjie Cao Yeping Xiong
    . 2014, 33(7): 199-205.
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    Blades of turbomachine are important components to produce power like turbines or pressure compressors working in a complicated condition with high pressure, high temperature and three dimensional air flows as well. The aeroelastic problem like flutter may occur during different working states. Flow-induced vibration of the blade with the coupling of bending and torsion is investigated to reveal the mechanism of flutters. Averaging method and power flow approach are used to demonstrate the flutter behaviours of interaction between an isolated blade and the quasi-steady flow. The relation between amplitudes and the frequency of blades vibration is given to predict flutters, which is beneficial to aeroelastic designs of the turbomachine.


  • Junchuan NIU;Feng YANG;Yong LI
    . 2014, 33(7): 206-209.
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    Due to the fact that the existing isolation theories and technologies have many defects to isolate multi-dimensional vibrations, they are unable to meet the needs of the isolation in practice engineering, in which the excitation and the environment maybe change frequently. A novel metamorphic parallel mechanism is presented as the main body of the multi-dimensional vibration isolation system, in which some springs and dampers are installed on the active joints. The presented mechanism has two configurations, or can change to 3-CRR mechanism or CRU-2CRR parallel one, just by adjusting the configurations of the rT joint. The kinematics and dynamics equations of the presented isolation system are deduced, and then the modes, dynamics characteristics and vibration isolation of the isolation platform are studied. The simulations show that the system has good vibration effect in both two configurations, and it can isolate two sets of multi-dimensional vibrations.


  • Wu Jie Yang Weidong Yu Zhihao
    . 2014, 33(7): 210-214.
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    Based on finite rotation hypothesis, a rigid-flexible rotor dynamic model is developed. Comparing with classical finite element model, this model introduces three rigid degrees of freedom for hinge rotations coupled with blade elastic deformations and thus has potential advantages over the small rotation beam model. Generalized aerodynamic forces are tightly coupled with structural rigid rotations and elastic deformations. Structural loads are computed using three load calculation methods (force integration method, reaction force method, and curvature method) while equations of motions are solved on each step. The loads are examined by analysis results of BO105 model blade and flight test data of SA349/2 Gazelle helicopter. All load methods can handle the structural load calculation without aerodynamic forces applied. Force summation method loses some power at sections near the blade root especially when transient aerodynamic forces are taken into account. Results from curvature method and reaction force method are nearly the same at the nodes of finite element method. Accuracy of reaction force method depends on the response solutions and only shows efficient to predict loads at the nodes. Since curvature method simplify considers the bending and torsion deflections, it requires higher order shape functions to satisfy the continuity of second derivatives. To speed up convergence and decrease accumulated errors, extrapolation technique is introduced to implement numerical integration algorithm.

  • NI De;ZHU Ru-peng;JIN Guang-hu;LI Fa-jia
    . 2014, 33(7): 215-220.
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    The description method of spatial motion for helicopter maneuver flight and helicopter tail drive shaft was proposed and the corresponding coordinate systems were established. The lateral bending vibration model of the helicopter oblique tail drive shaft during maneuvering flight was established by using the extended Hamilton’s principle, and the partial differential equations were converted into the ordinary differential Equations by using Galerkin calculation method. The horizontal shaft could be regarded as a special case of the oblique tail shaft, and the dynamical equations of horizontal shaft could derive from the oblique tail drive shaft by using a coordinate transformation matrix. The effects of spatial maneuver flight on the vibration characteristics of the tail drive shaft were discussed by the combination of mathematical model and numerical simulation. The study results reveal that the spatial maneuver flight of helicopter will produce additional stiffness effect, damping effect and external excitation force, which may change the center position and size of the motion orbit of the tail drive shaft, on the bending vibration of helicopter tail drive shaft.
  • ZHOU Tieming;CHEN Enwei;LU Yimin;LIU Zhengshi;CHEN Wuwei
    . 2014, 33(7): 221-226.
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    In order to better use the magnetorheological damper in the semi-active vibration control of magnetorheological damper coupling system, an accurate dynamic model of magnetorheological damper need to be established. Existing polynomial model of magnetorheological damper can fit the damping force-velocity curve accurately, but high-order polynomial fitting will lead to Runge phenomenon and violently oscillation at both ends of the fitting curve. To eliminate the Runge phenomenon, a piecewise cubic polynomial model is proposed in this paper and its parameters are identified by least square method. Compared with the experimental data, the piecewise cubic polynomial model can fit the damping force-velocity moer accurately and eliminate the Runge phenomenon.