28 August 2018, Volume 37 Issue 18
    

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  • Lian Ji-jian 1,2,Rong Qin-biao 1,2,Dong Xiao-feng 1,2,3,Wang Hong-zhen 1,2,Liu Zhuo 1,2
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 1-8.
    Abstract ( 373 ) Download PDF ( 264 )   Knowledge map   Save
    Aiming at suppressing mode mixing in the traditional empirical mode decomposition (EMD) method, a combined method called as FM-CEEMD based on the complementary ensemble empirical mode decomposition (CEEMD) and signal frequency modulation (FM) methods was proposed considering the generating mechanism of mode mixing.The effectiveness of the combined decomposition method was verified by using simulation signals.The modified mode decomposition method was then applied to the Hilbert-Huang Transform (HHT), replacing the traditional EMD method, in order to obtain an improved HHT structural dynamic parameter identification method for suppressing mode mixing.The identified results both from the simulation experiment and an actual arch dam show the improved HHT method can not only avoid the loss of modal information to improve the parameter identification accuracy, but also be suitable to the researches on the structural modal identification of real hydraulic projects.

  • ZHU Jingyuan1,2,WANG Jian1,2,DING Zehua1,2, ZHOU Hui1,2,CAO Yi1,2,3,4
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 9-17.
    Abstract ( 222 ) Download PDF ( 87 )   Knowledge map   Save
    In order to study the effect of joint clearance on the dynamic characteristics of parallel mechanisms, a 3-CP_aRR parallel mechanism was taken as an example.First, the kinematics of the parallel mechanism was studied synthetically by analyzing the constraints.It shows that the cylindrical pair of the parallel mechanism can be equivalent to a driving-sliding pair and a passive-revolute pair.Next, a normal distribution statistic model was used to establish the kinematic model of the revolute joint with clearance in radial direction and axial direction, and a branch kinematics model was also established.The normal contact force between the joint elements was evaluated based on the Flores contact model, and the tangential contact force was evaluated according to the modified Coulomb friction model.Then, the dynamic model of the parallel mechanism with joint clearance was established based on the non-holonomic systems Lagrange equation method.Finally, the effect of revolute joint clearance on the parallel mechanism’s kinematics and dynamic response was analyzed in detail through a numerical example.In addition, compared with the parameter of standard normal distribution model, the physical meaning of defining the initial contact clearance value as μ was analyzed.The research provides a new research approach and builds a theoretic foundation for the analysis of multi-body systems with clearance.

  • LIU Xiaohui1,HU You1,YAN Bo2,CAI Mengqi3
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 18-29.
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    The calculation formulas for natural frequencies of continuous spans conductors based on the vibration theory were proposed, and the mode shapes based on the sub-structure approach were obtained.The natural frequencies and mode shapes calculated by the formulas under different span numbers and tension forces were in good agreement with the results of the finite element method, and thus the reliability of the theoretical formulas was verified.The influence of geometric parameters of continuous spans conductors on the dimensionless frequencies was revealed.The conditions for the resonance between different modes of continuous spans conductors were investigated and it is shown that the multi-mode coupling conditions were obviously different from those of single span ones.The motion equations of continuous spans conductors were discretized by using Galerkin procedure, then the non-linear ordinary-differential equations for the multi-mode coupled vibration were obtained.These results establish the base for the study of bifurcation behaviors in the strong internal resonance of continuous spans conductors.
  • LUO Ziwei 1,YU Ling 1,2,LIU Huanlin 1 PAN Chudong 1
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 30-35.
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    Using the space sparsity of structural damage is prevalent to identify structural damages in the field of structural health monitoring.Based on the sparse regularization, first-order sensitivity analysis can detect damage locations and quantify damage extents effectively.However, the misjudgments and stiffness hardening would occur under the influence of noises.A new structural damage detection (SDD) algorithm, based on the norm normalization and sparse regularization constraints, was proposed to solve these problems.It can reduce misjudgments, make the damage detection results more rational and improve identification accuracy by adding the norm normalization and sparse regularization constraints to the process of iteration as well as adding, the constraint of Newton iteration method and the total damage reduction factor to the model.The numerical simulation results from three different structures indicate that the damage detection identification are obviously improved after adding the norm normalization and model constraints.The new SDD method can effectively identify damage locations and extents under different level noises and get high robustness to noises.
  • LIU Haining1,SONG Fangzhen1,DOU Renjie1,HUANG Yixiang2,LIU Chengliang2
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 36-42.
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    The shortage of prior faulty data or the incompleteness of sample space, which leads to a "small data" trap, is a common situation encountered when implementing intelligent condition monitoring and fault diagnosis of machines.To overcome this problem, a domain adaptive fault diagnostic scheme was proposed based on the geodesic flow kernel method.With prior data samples as the source domain and monitored data as the target domain, status features of the machine were extracted and selected separately to construct the subspaces of machine conditions.By embedding the subspaces in a Grassmann manifold, the structural similarity of subspaces was evaluated based on the geodesic flow kernel to achieve the domain adaptive fault diagnosis.The verification based on the bearing vibration data demonstrates that the domain adaptive fault diagnosis based on the geodesic flow kernel can effectively reduce the impact of the variety in working conditions and the physical differences underlying sampling populations, so that the accuracy of fault diagnosis can be improved.
  • CAO Jianhua1,2,LIU Yongshou1,LIU Wei1
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 43-47.
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    In order to model the uncertainty of clamps of a pipeline in the aviation industry, a nonparametric method was adopted to model, simulate and predict the vibration characteristics of a fluid-conveying pipe.The clamp was modelled as simply supported and attached with a torsion spring.The wavelet-based finite element method was used to discretize the governing differential equations of the fluid-conveying pipe with clamps at two ends.The random global stiffness matrix, which models the effect of uncertainties of clamps, was generated by the nonparametric method.As shown in the numerical results, the confidence interval of the frequency response curves of the nonparametric model contains the mean model’s curves perfectly.As the frequency increases, the greater the influence of uncertainty at higher frequencies.For the case of the first four frequencies varying with the fluid velocity, the confidence interval of the curves of nonparametric model also contains the mean model’s curves perfectly.With the fluid velocity increasing, the influence of uncertainty on the real part of frequencies becomes smaller while the influence of uncertainty on the imaginary part of frequencies becomes greater.However, the uncertainty has no effect on the divergence and flutter instability.
     
     
  • KANG Zhuang,ZHANG Cheng,FU Sen,XU Xiang
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 48-58.
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    To predict the amplitude response and other important characters of the vortex-induced vibration of a cylinder quickly and accurately, a high order nonlinear oscillator model was proposed.Based on the Lagrange second dynamic equations and the Taylor expansion formula, the vibration equation of the cylinder fixed by four symmetrical springs was derived, where the axial tensile nonlinearity and coupling nonlinearity were considered.Then, the fluctuating lift and drag in the vortex-induced vibration were obtained in accordance with the discrete point vortex theory, and the mathematical quantified relationship between the fluid forces was established.The improved Van der Pol equation was used to simulate the fluid oscillator, and then the coupling equations of the nonlinear structure and fluid oscillators were established.On this basis, the vortex-induced vibration for cylinders with different mass ratio and damping ratio was predicated, and the results were compared with testing data to verify the correctness and universality of the model.Finally the sensitivity of the parameters in model was analysed.
  • SU Liang,SONG Mingliang,DONG Shilin
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 59-66.
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    A convolutional neural network (CNN) methodology was proposed to automatically interpret stabilization diagrams.Once the stabilization diagrams of different structures had been obtained, they were equally distributed into several frequency bands according to the accuracy requirements of each frequency identification, which were called single mode stabilization diagrams.These frequency bands samples were used as learning samples of the CNN.After that, these learning samples were expanded with some technical methods such as translating and changing the label of stable poles on the stabilization diagram.Then, the preprocessed learning samples were substituted into the constructed CNN.The parameters of CNN, such as learning ratio, were tuned by tracking the changing rule of losing function during the learning process.Finally, a CNN which can automatically eliminate the spurious modes on the stabilization diagram was obtained.The constructed CNN was verified by a 3 degree of freedom(DOF), a 7DOF spring-mass model as well as the accelerometer data of a reinforced concrete frame structure and the Swiss Z24 bridge.The robust learning and prediction results prove that the constructed CNN is effective for analyzing any stabilization diagram of different structures.It can automatically and accurately eliminate the spurious modes on the stabilization diagram immediately without  extracting any characteristic parameters or setting any thresholds of them.
     
  • LIU Chuang,LIU Hongzhao,ZHANG Lei,LI Lai
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 67-72.
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    To explore the wear law of a circuit breaker mechanism system in SF_6 atmosphere, experiments were done on a self-developed pin-bushing friction and wear tester with the orthogonal test method, and a wear prediction model was established based on the neural network.Considering the clearances in revolute joints, the kinematic parameters were got by using the ADAMS simulation software based on an elastic-damping contact force model, then the trained Elman model was employed to predict the wear of dangerous joints through repeated iteration.It can be seen from analysis that wear occurs seriously in some special areas on the bushing surface, and more seriously in the test atmosphere than in the air.The research provides the theoretical basis for the optimization and fault diagnosis of the circuit breaker mechanism, and also offers a method to analyze the couple phenomena between various kinematic parameters and the joint wear. 
     
  • YANG Boya,L Xilin
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 73-77.
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    Self-centering structures can undergo large deformation with minor residual displacement under the strong earthquake excitations, exhibiting flag-shaped hysteretic behaviors.The dynamic elastic-plastic analysis of the  systems of bilinear elastic (EP) model and self-centering (SC) model was conducted to acquire the ductility demand factor μ for different seismic modification factor R.It is shown that self-centering systems develop greater ductility demands than cast-in-place RC systems when the lateral strength and post-yielding stiffness keep the same.When the post-uplifting stiffness and hysteretic energy dissipation capacity of the self-centering systems are increased, the ductility demands decrease obviously.
  • WU Haipeng1,2,CAO Wanlin1,DONG Hongying1,YIN Fei1,LI Xiangyu1
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 78-85.
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    In order to study the seismic behaviors of special-shaped CFT mega bifurcate columns coupled with multiple cavities in different cross sectional direction, five specimens were tested under a twice repeated horizontal low cyclic load.In the tests, three types of loading directions were considered, including long axial, short axial and 45 degree directions.And there are two types of joint core region constructions including a basic one and an enhanced one by increasing the quantity of steel tube cavities.The test results show that the arrangement of welding seams leads the failure trend under accumulated damage.The failure features appear as steel plate tearing caused by crazing and extending of welding seams at the lower horizontal partitioning steel plate of lower columns.The specimens in long axis possess higher bearing capacity, stiffness, deformability and energy dissipating ability than those in short axis, while the specimens in 45 degree directions take the middle seismic performance.The enhanced construction can increase bearing capacity, stiffness and energy dissipating ability in some degree.The bearing capacity degradation is slight under the same repeated load.The upper columns are the main parts of deformation and energy dissipation, and the proportion is between 60% and 70%.Each specimen possesses good elastic-plastic deformability, and can be used in the seismic design of mega frame structures in super high-rise buildings.
  • YAN Guiyun1,FANG Yiwen1,WU Yingxiong2,XIAO Xiaofei1
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 86-94.
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    Far-field harmonic-alike ground motions, in which multiple cycle pulses resembled harmonic vibrations were generated at the later stage of ground motions, were characterized by long duration and rich low frequency components.Its adverse influence on the seismic performance of long-period structures, such as the isolated structures, should be revealed and validated.To this end, the peak ratio of ground motion acceleration, duration and response spectrum characteristics of far-field harmonic-alike ground motions were discussed.Then, a single-tower steel frame structure with a large chassis was designed to form three test models, namely the aseismic structure, base-isolated structure and mid-story isolated structure.One-dimensional shaking table tests and numerical simulations were performed adopting common and far-field harmonic-alike ground motions as its external excitation input.The impacts of long-period components and harmonic-alike components on the story drift, acceleration and isolation layer deformation of these test models were explored.Further, the vibration characteristics of the single-tower isolated structures with horizontal indentation size proportions of 1∶1.5, 1∶2, 1∶2.5 and 1∶3 were examined.The results show that the dynamic responses of the aseismic and isolated structures when subjected to far-field harmonic-alike ground motions are 2-3 times as large as those when subjected to common ground motions, and the seismic-reduction performance under far-field harmonic-alike ground motions are not as good as that under common ground motions.The deformation of the isolation layer is also enlarged 3-4 times, which will result in the destruction of the isolation bearing owing to its excessive deformation.Further, there is no obvious difference in the vibration characteristics of the seismic-isolation structures with different horizontal indentation size proportion.
  • FANG Zhiwei1,2,HOU Hailiang1,LI Mao1,LI Dian1
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 95-99.
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    In order to investigate the anti-penetration mechanism of an aluminum foam sandwich,dividing the process of bullet impact on the structure into three stages: the plugging of facet plate, aluminum foam failure in the mode of through-thickness shearing with tearing and back face sheet failure in local disc deformation—shear plugging.According to the failure model for the components of the aluminum foam sandwich, a theoretical analysis model was deduced based on the Newton’s laws of motion and energy conservation.Using the theoretical analysis model, the energy absorption of each component part of the structure was studied.The results show that the analysis model results are in good agreement with the experiment ones and the error is less than 10%.Analyzing the absorbed energy by different component part of the sandwich structure, it is found the aluminum foam absorbs the most energy.The aluminum foam core consumes 48.9% of the total energy.The consumed energy of the back facet plate is the next and that of the front facet plate is least.The different deformation and failure modes of both facet plates are the main reason that causes the difference in energy absorption proportion.
  • WANG Renfeng,YOU Yunxiang,CHEN Ke,HU Xiaofeng
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 100-107.
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    Considering the potential impact of aspect ratio on the vibration of structures, the classical Theodorsen equation for the motions of two-degree-of-freedom foils was derived with the modification of its mass parameter and circulation parameter.The time-history curves and the phase orbits of the hydrofoil system at different values of inflow velocity were obtained by solving the equation through MATLAB programming.As the inflow velocity increases, the shape of phase orbits tends to be flattened, which means that the kinetic energy of the system can be transformed into a larger potential energy.Moreover, the finite volume method and semi-implicit integration method were used to discretize the computational domain, and the discrete governing equations were solved with the SIMPLE algorithm.Based on the results of numerical simulation, the transient motion of the hydrofoil system induced by fluid was solved, and the variation of the flow distribution around the hydrofoil during fluttering was analyzed.It is shown that the vortex between the leading edge and the elastic axis on the upper surface gradually spreads towards the trailing edge, forming a vorticity layer.The vorticity layer covers the whole upper surface of the hydrofoil, which is different from attenuated vibrations. As the hydrofoil pitches up, new vorticity layers are generated near the leading edge, and meanwhile the vorticity layer at the trailing edge moves downstream, forming a starting vortex nearby.
  • HE Dawei, PENG Jingbo, HU Jinhai, LI Tenghui JIA Weizhou
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 108-114.
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    Aiming at the problems of small samples and dataset imbalance in fault diagnosis, an optimized cost-sensitive support vector machine (CS-SVM) model was proposed and an improved fly optimization algorithm (FOA) was applied to select the best regularized constants C_+,C_-, and the kernel function parameter g, by increasing the penalties for the misclassification of fault dataset, so as to raise the diagnostic accuracy of the fault samples.The proposed method was verified by combining the stochastic resonance and KPCA feature extraction methods, taking the  experimental data of a IMS aviation bearing as an example.The results show that the CS-SVM can effectively deal with unbalanced samples of small fault class in bearing fault diagnosis, and improve the diagnosis accuracy.It can also be further expanded to other fields of fault diagnosis.
  • FAN Lulu,YOSHINO Tatsuo,LIN Ye,LIU Huan,YU Zhenglei
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 115-120.
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    A systemic investigation was done for the improvement of the crashworthiness of an automobile front rail structure, that was a S-shaped thin-walled beam with square section, by introducing inducting grooves and stiffeners, as well as by realizing lightweight design based on material properties.Eight finite element models were established according to the position distribution, number of inducting grooves and the position distribution of stiffeners.Considering the total mass as a constraint condition and geometrical parameters as design variables, the crashworthiness optimization design of the S-shaped thin-walled beam with stiffeners was carried out based on high precision surrogate models.The validity of the optimization model was verified by the comparison between simulated and theoretical force-displacement curves.The material of the stiffeners was changed to magnesium-aluminum alloy to realize lightweight design.The results provide a novel strategy for crashworthiness optimization and lightweight design of thin-walled beam structures.

  • YANG Jianfeng1,2,SHI Gege1,ZHOU Tianqi1,GAO Fengyang1
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 121-125.
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    Aiming at the crucial problem of ending effect which can lead to waveform distortion for double signals in the decomposition process of Empirical Mode Decomposition (EMD), a novel method for restraining the ending effect was proposed based on the self-adaptive sequential similarity detection of waveform matching extending.In the method, the introduction of cut-off precision threshold makes the algorithm intuitive and fast.And the folded self-adaptive threshold adjustment further reduces the time used for traversal.A simulation and analysis were carried out on analog signals and practical engineering signals, respectively.The results indicate that the algorithm proposed is able to effectively restrain the ending effect in the decomposition process of EMD and improves the overall decomposition efficacy.
     
  • MENG Chaomei1,2, LIU fei1, JIANG Zhigang1, SONG Dianyi1, TAN Qinghua1
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 126-131.
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    Steel-tube-confined concrete (STCC) targets have superior anti-penetration performance over ordinary unconfined concrete targets.The penetration progress and confined mechanisms of hexagonal and circular STCC targets were analyzed by using the finite element-smoothed particle hydrodynamics method in the finite element package ANSYS/LS-DYNA to reveal the influence of steel-tube shape on penetration mechanisms.The results show that the steel-tube confinement effect consists of the stress wave effect and predominate displacement constraint effect on concrete during the cavity expansion progress.The profile of steel tube has influence on the distribution of stress and displacement of the steel tube.The stress distribution along the circumference of circular STCC targets is nearly uniform and the steel tube is in simple tensile state under radially uniform pressure for the case of normal penetration without any eccentricity, while there are in-plane tensile deformation and out-plane bending deformation for polygonal steel tubes under non-uniform inner pressure.Furthermore, the corners of hexagonal steel tubes expand little due to the bending displacement, which enhances the confinement to concrete and develops high-compressive regions near the diagonal in polygonal STCC targets.Thus, the penetration resistance is increased and the anti-penetration performance is improved.
  • TANG Jun 1 ZHAO Bo 2
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 132-137.
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    In the process of the ultrasonic assisted grinding of carbon fiber composites, the self-sharpening of the grinding wheel can be guaranteed, and the producing of defects of the carbon fiber composites can be suppressed.Therefore, an ultrasonic machining system, suitable for machining the special-shaped and deep cavity combustion chambers of a supersonic propeller, was investigated.Based on the one-dimensional vibration theory and the thin plate vibration theory, the frequency equations for a muti-section horn and a special grinding wheel were established, and the ultrasonic machining system with the special grinding wheel was created by using the software MATLAB 7.1.Then, the finite element analysis and natural frequency test of the designed ultrasonic machining system were carried out, and the results show that the frequency error between the analysis and test results is less than 1.4%.An example workpiece made of carbon-fiber composite was processed with the designed ultrasonic assisted grinding system, and better machining results were obtained.

     
  • XIA Lifu YANG Deqing
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 138-144.
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    A new type of double cylindrical shell with lightweight auxetic metamaterial ribs was designed under the premise of ensuring the load-bearing capacity to explore its application in the submarine cabins for reducing the vibration and noise caused by the working of equipments.By adjusting the width of auxetic ribs, the overall stiffness and load-bearing capacity were adjustable.At the same time, keeping unchanged the weight of basic functional primitives, the effect of the number of layers of cell unit on the double shell’s vibration isolation and acoustic radiation performance were studied.The structure strength, natural frequency, acceleration response, vibration level difference, radiation pressure and vibration transmission rate were provided with different width of auxetic ribs, different Poisson ratio and various layer number of cell unit.By comparing with conventional double shell structures, the lightweight performance, good vibration performance and fine acoustic performance of the double shell structure with auxetic metamaterial ribs were confirmed.
     
  • YE Wenxun, YU Zhefeng,
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 145-151.
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    It is meaningful to identify the threshold load generating the delamination growth in the determination of the impact energy causing the damage of composite laminates subjected to small mass impact.The simulation results based on the analytical model show that the contact force drops sharply when the local contact rigidity is decreased, while the decrease of flexural rigidity of the whole plate does not introduce this feature into the response.A tester for small mass impact was fabricated and the impact tests were conducted on the laminates with variant energies.The contact force was detected by measuring the impactor responses and the laminate deflection at the impact point.It is shown that the contact force drops sharply at the theoretical delamination threshold load once the significant delamination is generated, and then goes up again.This phenomenon can be employed to identify the growth of delamination during the impact.To capture the sudden drop of the contact force obtained from the plate deflection, the sampling rate should be no less than 200 kHz.Otherwise, one may lose the sudden drop instant of the contact force curve slope. 
  • SUN Chuanzong 1, YANG Rui 1, CHEN Yushu 1, HOU Lei1, 2
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 152-157.
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    A high-accuracy solid finite element model, which is beneficial for expressing complicated geometrical features, was established by using ANSYS software for analysing a certain casing-dual-rotor test rig.The Craig-Bampton mode synthesis method was applied to the model order reducing processes of the casing and rotors, and the whole assembly model was obtained accordingly.The validity of the reduced model was verified under critical speeds and modes.By means of 3D spectrograms and whirl orbits, the steady-state responses were investigated.Finally, the numerical results were compared with the experimental results.The results indicate the modeling and reduction of the casing-dual-rotor test rig are accurate and effective.The work provides a reference to the dynamic study of actual dual-rotor aero-engines.
  • FU Haiqing 1, 2,YUAN Xiaoming 1,WANG Yunlong 1
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 158-164.
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    Based on the self-developed in-situ liquefaction testing technology, two different types of in-situ liquefaction tests were carried out.The pore pressure-shear strain relationship of saturated sand was studied and its quantitative expression was presented.Besides, the simulation results were compared with the dynamic triaxial test results and the in-situ liquefaction test results by others.The main conclusions are as follows.The acceleration slightly affects the pore pressure-shear strain relationship of saturated sand, but its influence is larger than that of the relative density.An equation, [U=1-exp(aγ+b), U≥0], Which is consistent with the mathematical expression of the physical process of soil liquefaction, was proposed to quantitatively describe this relationship.When the shear strain of saturated sand is at the range of 0.03%~0.30%, the residual pore pressure increases quickly.Furthermore, when the shear strain of saturated sand is about 0.5%, the residual pore pressure ratio can reach the maximum value 1.These results are consistent with those obtained from strain-controlled dynamic triaxial tests by Dobry, but have discrepancy with these obtained from in-situ liquefaction tests by Chang.The unexpected results were analyzed and it is found the discrepancy is caused by the unadapted computation method for shear strain adopted by Chang.In the process of soil liquefaction, large deformation occurs, and it is unreliable to calculate the shear strain by the finite element method.

  • HU Qin WANG Jinhua LV Juan XING Zhiyuan WU Yueyi
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 165-169.
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    A kind of metal-confined ceramic composite in which the matrix alloy is 6061 aluminum and the diameter of Al_2O_3 ceramic ball is 6 mm was fabricated by squeeze casting.The ballistic efficiency factor of the composite material was obtained through 12.7 mm and 30 mm armor piercing experiments and the anti-ballistic mechanism and damage mechanism were investigated.The results show that the mass efficiency of the metal-confined ceramic composite armors with average density about 3.3-3.4 g/cm3 resisting against 12.7 mm and 30 mm armor piercing bullets exceeds 2.2 and 1.7 respectively.A concentrated shock load on the surface of composite materials might be tranfered to a locally uniform load due to the impacts among ceramic balls.On the other hand, an array arranged alternately by flexible 6061 aluminum ball and hard Al_2O_3 ceramic ball in composite materials could disperse energy and increase the shock-wave reflection, resulting in the improvement of the ballistic performance of composite target.The energy absorbing mechanism reveals that the innovated armor is able to protect against projectiles, together with the benefit of weight saving.

     
  • FAN Liang GAO Jingbo WANG Cong
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 170-176.
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    Three kinds of simulation conditions were designed to study the high stability index assignment of a spaceborne SAR antenna according to the practical environment of the antenna on orbit.By analyzing the SAR antenna with the multi-body dynamics software ADAMS, the pointing accuracy was rationally allocated by the probabilistic method.The results show that the influence of disturbances on the pointing accuracy of the SAR antenna is greater if the disturbing load is acting on the area closer to the antenna.And the order of their influence degree is as follows: vibration isolator disturbance, CMG disturbance and SADA disturbance.The influence degree of the three angles on the pointing accuracy of the antenna is in the following order: pitch angle, direction angle, and distance angle.Improve the performance of the vibration isolator, reduce the effect of the payload disturbance on the pointing accuracy and improve the pitch angle control in the process of switching between various imaging modes, the SAR satellite antenna will be able to improve the SAR satellite image quality and help the satellite overall to select the adjustable posture institution.
  • TANG Xiaowei 1 BAI Xu 1 HU Jilei 2
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 177-183.
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    Based on the Bayesian network method, a Bayesian network model for assessing seismic liquefaction-induced settlement was constructed, in which 12 significant factors including earthquake parameters, soil parameters and field conditions combining with the liquefaction potential and liquefaction potential index were considered.Through some cases study, it is shown the Bayesian network model has obvious advantages in the assessment performance, comparing with the RBF (Radial Basis Function) neural network method and I & Y (Ishihara & Yoshimine) simplified calculation method.The Bayesian network model not only has better assessment accuracy and reliability, but can also perform reverse causal reasoning.In the analysis of sensitive factors to the two machine learning models, the ground peak acceleration, duration of earthquake and standard penetration test blow count are more sensitive among the 12 factors, which are the same as those considered in the I & Y simplified calculation method.
     
     
  • LIU Zhihao,GAO Qinhe
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 184-192.
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    The experimental modal analysis, dynamic modeling and structural parameter identification on the  in-plane vibration modals of heavy loaded radial tires with different inflation pressure were put forward.The in-plane bending characteristic, axle pre-tension caused by the inflating pressure and sidewall radial stiffness sensitive to the  inflation pressure were taken into consideration and the coupled kinematic equation for the flexible tread, distributed sidewall elements and rim was modeled based on Euler beam theory.In-plane experimental modal tests and analysis under different inflation pressure were presented and experimental modal parameters under different inflation pressure were obtained.Taking the error between the experimental modal resonant frequency and analytical modal resonant frequency as the object, structural parameters of the tire were identified by the genetic algorithm based on the experimental and analytical modal parameters obtained and the higher order modal frequencies were predicted with the analytic model. The experimental and theoretical results show that: the  in-plane vibration of heavy loaded radial tires can be charactered as the coupled vibration of flexible tread and distributed sidewall elements, and the vibration within 0-180 Hz appears in the same-direction modes, while the vibration within 180-300 Hz is shown in the opposite-direction  modes; the modal resonant frequency increases with the increase of inflation pressure; the in-plane vibration characteristics under different inflation pressure can be featured using the axle pre-tension of flexible tread caused by the inflating pressure and the sidewall radial stiffness sensitive to the inflation pressure.
  • HAN Qihao, WANG Dayang, ZHANG Yongshan
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 193-200.
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    A traditional composite steel plate shear wall is assembled with single concrete slab, which has larger dimensions and is difficult for lifting and transporting.The single concrete slab was replaced by multi-precast concrete slab in this paper, and the composite steel plate shear wall with assembled multi-concrete slab was proposed.Three 1/3 scaled composite steel plate shear wall specimens were made: The composite steel plate shear wall with vertical assembling mode(V-CSPSW), composite steel plate shear wall with horizontal assembling mode(H-CSPSW) and traditional composite steel plate shear wall(CSPSW).The cyclic loading tests on specimens were performed.The failure characteristic, hysteretic behavior, ductility, energy dissipation capability and stiffness degradation were investigated.The test results show that the CSPSW with assembled multi-concrete slab has lower lateral stiffness and energy dissipation capacity, but it can reduce the harmful effects of the additional moment on frame columns that the steel plate generates.The V-CSPSW presents bending-shear failure mode, which is ductile failure.The tearing failure appears in the horizontal gaps that between the precast concrete slabs of the H-CSPSW, it presents obvious shearing failure mode.Comparing the horizontal and vertical assembling modes, the ductility coefficient of V-CSPSW is smaller, but other seismic performance indexes such as the energy dissipation capacity, bearing capacity and stiffness are more superior.
  • ZHANG Junfeng1, 2, YANG Junhui1,GE Yaojun2, ZHAO Lin2
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 201-208.
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    For further interpretation of the features of wind dynamic effects on hyperbolic cooling towers (HCTs), the dynamic responses were calculated and the features were analyzed.The analysis focused on the background component σ_B and resonance components σ_R, and their contributions to the total gust response σ.Then, the parameters of damping ratio ζ, velocity V and meridian correlation coefficient ρ were altered respectively to study their influences on the gust responses and the influence mechanism.It is shown that the coupling effects of σ_ and σ_R could be neglected for all responses.The contribution of σ_R to σ varies with responses and locations.If σ_R is neglected, the σ of F_X and F_Y decrease about 10% in the middle and bottom shell but about 20% in the top shell, and the σ of M_X decreases about 20%-30% for the whole shell height.With the increase of ζ, the σ_R  of all responses decreases remarkably and the decrease amount could be determined roughly by a simple equation.However, the decrease of σ is slight because the contribution of σ_R  to σ is limited, especially for F_X and F_Y.It is also found that σ_R is proportion to V3.The meridian correlation influences σ_B directly and then σ indirectly, so this influence is mainly on the σ_B of F_X and F_Y, which is predominant in σ.Nonetheless, σ_B of F_Y increases with the coefficient ρ, but σ_B of F_X decreases.Finally, in structural reinforcement designs, the resonance effects of meridian internal forces could be neglected and that of latitude internal forces couldn’t be neglected.
  • CHEN Jianjun1,ZHENG Enming2, CHEN Xinhua2
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 209-215.
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    Under the same frequency unit, according to the different contribution of  different target radiated signals to each subspace, a weighted detection method based on the extremum fluctuation feature of subspace spatial spectrums was proposed for the sake of  detecting unknown unequal strength targets.In the method, an eigen decomposition was made on the covariance matrix of received data of a linear array to get the sub-covariance matrix of each subspace.The spatial spectrums were obtained by performing the beam-forming on each submatrix, and the extremum fluctuation differences between subspace spatial spectrums were atilized to determine the weight values.Then, with the weight values, the normalized spatial spectrum of each subspace was processed statistically and thus to form the final spatial spectrums, in which the proportion of the weak target subspace was increased.The theoretical analysis, numerical simulation and experimental results show that, the method can further restrain the spatial spectrum disturbances by noise subspaces, enhance the proportion of weak target subspace in the spatial spectrum, make the proportion increase from σ2_s,w/(σ2_s,all+σ2_n/N) to nearly 1/L, where N is the number of array elements, L is the number of targets, σ2_s,w is the energy of weak target, σ2_s,all is the energy of all the targets, σ2_n is the energy of background noise, decrease the spatial spectrum difference between different target subspaces from σ2_s,s/σ2_s,w to nearly 1, where σ2_s,s is the energy of strong target, improve the detection performance of conventional beam-forming for unknown unequal strength targets under the same frequency unit, and effectively detect unknown unequal strength targets in the same beam diagram.
  • SUN Ying1, WAN Yuting1, CHEN Lifen1, GUO Qiwei2
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 216-223.
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    For large-scale nonlinear structures with local single-sided limitation, the fundamental frequency response characteristic is often closely related to the position and size of the limitation.The analysis method for nonlinear structures was mainly studied.The frequency domain characteristics of nonlinearity were characterized by the describing function first appeared in the nonlinear control.The inverse matrix updating method was used to reduce the processing dimension, which greatly improves the computational efficiency of frequency domain response.The numerical method Runge-Kutta was adopted to verify the effectiveness of the method.The first-order frequency response curve of a T-shaped beam was analysed by simulations and experiments.

  • QIAN Weiji,HUANG Zhiqiang
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 224-230.
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    The friction coefficient has an important influence on the formation of friction-induced self-excited vibrations.However, in the experimental process, it is difficult to make an accurate control on the friction coefficient between two sliding surfaces.A finite element model of a metal reciprocating sliding system was established.The friction-induced vibrations during a reciprocating sliding process were simulated using the transient dynamic analysis and complex eigenvalue analysis.In the simulation, the friction coefficient between two friction contact surfaces was controlled precisely.The dynamic transient analysis results indicate that the friction coefficient has a significant effect on the continuation and magnitude of the friction-induced self-excited vibrations and it has a little influence on the frequency of friction-induced self-excited vibrations.The complex eigenvalue analysis results show that with the increase of the friction coefficient, the vibration mode of the metal reciprocating sliding system changes significantly.
  • ZHUANG Chao1,2, Liu Hanguang1,2,Kang Kaixuan1,2,SU Junshou1,2
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 231-235.
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    A boundary element method for acoustical problems based on point cloud data was proposed, which combines the reverse engineering with the acoustic boundary element numerical algorithm.The irregular point cloud grid obtained by scanning was optimized to a regular grid element model with well shape, suitable for numerical calculation.The CAD geometrical model was seamlessly connected with the CAE simulation analysis.An example of the acoustic propagation problem for a small suction sweeper van body was given in detail.Comparing the results with those of the traditional acoustic boundary element simulation, the validity and feasibility of the method were proved.
  • XU Hailiang,ZHOU Yongxing,XU Cong,ZHAO Hongqiang,XU Shaojun
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 236-242.
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    In order to study the cuttings removal performance of a bundling-reaming pneumatic impactor, a cuttings flow field model was established, the computational fluid dynamics theory and FLUENT simulation software were employed to simulate the gas-solid two-phase flow field and the impact of different drilling speed and the mass flow of exhaust gas on the cuttings removal performance were analysed.The gas phase characteristics, the distribution of debris flow, the particle concentration distribution under different drilling velocity and inlet gas flow rate were discussed.The results show that:once the exhaust enters into the field, its speed will slow down, the field pressure will maintain in a gradient distribution and gradually decrease from the entrance to exit; cuttings particles will be gathered around the bottom and there is minor variation in their average concentration as they are distributed in the contrary direction against the entrance, while the maximum concentration descends along the same direction and finally becomes stable; during construction, the maximum drilling speed should be less than 8.4 m/h, as the mass flow rate of exhaust gas increases, the carrying ability increases as well.

  • WANG Feng 1 WU Zhiqiang 2 LI Yajie 2
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 243-250.
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    Due to highly non-linear magnetic linkage,a switched reluctance motor (SRM) generates a severe torque ripple,and a large radial force appears when the stator coil commutates.The bending vibration of its rotor will happen when the radial force is exerted on the rotor, which leads to the continual changes of air gap and electromagnetic force.The motion of the rotor becomes very complicated.Therefore, the rotor dynamics of the motor in coupling situation has become a research hotspot.The electromagnetic force function of the rotor was obtained by the empirical formula for the single-tooth force of the rotor.The bending vibration equation of the rotor was established by the finite element method.The critical rotational speed of the rotor under different bearing stiffness was analyzed by using the Campbell diagram.The numerical simulation of the rotor motion trajectory was carried out and the influence of the rotational speed on the maximum displacement of the rotor was discussed.The results show that the maximum displacement at the rotor intermediate nodes in normal speed range is not greater than the gap size, and the energy distribution of the vibration displacement spectrum is closely related to the rotational speed and low order natural frequency of the rotor.The rotor motion rule of switched reluctance motors could be grasped through this study, which provides a dynamic evaluation for the design of switched reluctance motors.
     
  • XIONG Shiyong1 CHEN Chunjun1 WANG Feng2 XIA Yin2
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 251-256.
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    The dynamic detection of rail cants can efficiently guide the railway operation and maintenance.Reasonably setting rail cant angle is beneficial to ensure the reasonable contact between rail head and wheel tread, therefore increasing the rail service life.A method was proposed based on the laser camera technology, which can continually extract the contour of rail on line.Considering the influence of the camera lens distortion on the rail contour image, a nonlinear calibration resolver model for the spatial attitude relationship of two laser camera sensors was established.By using the data fusion function of the Kalman filtering algorithm, a state space model for the multi-sensor signal fusion was established to eliminate the effect of car body vibration on the calculating results of rail cants.At last, a GJ-4 type track inspection vehicle was taken to perform the real vehicle test and it is verified the rail cant calculation method proposed is feasible and practical.The sensor data after Kalman filtering can compensate the results of the rail cant angle calculation very well.
     
  • LI Xiaowei1, HE Guanghui2
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 257-265.
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    Aiming at improving the efficiency of finite element method (FEM) in the dynamic characteristics and transient responses analyses of partial-interaction composite beams, firstly, the primary unknowns and their derivatives of the composite beams were discretized by the differential quadrature method, and the differential quadrature element equations were formulated, using the principle of virtual work on the Timoshenko composite beams’ dynamic problem.For comparing the analysis efficiency between the proposed quadrature element method (QEM) and FEM, parabolic interpolation finite element equations were also provided.Then, the computational efficiency of FEM and QEM were compared through the eigenvalue analysis on free vibration and the direct integration analysis on seismic time-history, after the verification of the proposed FEM and QEM algorithms.The numerical results show that comparing with the FEM, the efficiency of the natural frequency analysis is increased by 479 times by using the presented QEM and that for the time-history response prediction by 42 times.
  • DU Ye1 LI Qiang2
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 266-270.
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    The impact energy release characteristics of an energetic jet was analysed based on the building of a dynamic energy acquisition system.The overpressure versus time curves produced by the energetic jet impinging plate were obtained under different impact conditions, and the composition of reaction products was determined.The results show that with the increase of the impact energy, the overpressure peak and energy release formed by the jet both show a tendency to increase progressively, and there is an upper limit of impact energy which can make the energetic material reach the staurated state of chemical reaction.The average amount of heat that the jet can release is 65.4 kJ containing 4.4 g, which is enough to achieve damage.
  • LIU Zhihuai1,2 QIN Fang3 LIU Na4 HUANG Zukun1 LIU Xubin5
    JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 271-276.
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    In terms of the problems existing in steel rope broken wire quantitative testing, making full use of the advantages of principal component analysis (PCA) and BP neural network, a quantitative testing method for broken wire in steel rope was established.Inducting principal component analysis method to pre-analyze the original character attributes of broken wire signal for steel rope, and using the principal components of original character attributes as the input of BP neural network, the relationship between the principal components of original character attributes of broken wire signal for steel rope and the number of broken wire were estimated and the number of broken wire were predicted.Principal components method cut down the dimensions of original character attributes and eliminated the correlation among original character attributes.Meanwhile, the structure of BP neural network was also simplified by the principal components of original character attributes.Testing results show that BP neural network based on principal component analysis method compared with conventional BP neural network improves the prediction precision of broken wire in steel rope and reduces neural network training time.