28 March 2020, Volume 39 Issue 6
    

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  • ZHOU Jianting1,2,LI Xiaoqing1,XIN Jingzhou1,2,YANG Shanqing1,ZHOU Yingxin3,4
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 1-7.
    Abstract ( 281 ) Download PDF ( 163 )   Knowledge map   Save
    The structural damage identification based on monitoring data plays a fundamental role in the bridge health monitoring system to exert the benefit of perception and early warning.To further improve the accuracy of structural damage identification, a new method was proposed which integrates the Kalman filtering and generalized autoregressive conditional heteroskedasticity (GARCH) model.First, the Kalman filter was used to de-noise the raw acceleration data, and a linear recursive autoregressive model (AR) was established to identify the structural damage.Then, the nonlinear recursive GARCH model was introduced to further improve the identification accuracy.Finally, the time-history data obtained in the tests of corroded RC beams was used to verify the effectiveness of the proposal algorithm.The results show that the residual variance ratio of the time series model can be effectively used to identify the structural damage.Compared to Kalman-AR model, the Kalman-GARCH model can explain the nonlinear characteristics and make up the recognition error caused by neglecting the heteroskedasticity of data.The accuracy can be improved by 14.2%.The results provide a new way for bridge structure state perception based on massive data.
  • LIU Xianbo1,HE Enyuan2,LONG Xinhua1,MENG Guang1,3
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 8-14.
    Abstract ( 386 ) Download PDF ( 483 )   Knowledge map   Save
    During the machining process, such as turning, milling and drilling, due to the regenerative cutting effect, the equation of motion of the tool-workpiece system suffers time delay effects, which causes changes in dynamic characteristics of the system.The responses of a linear delay differential system with single degree of freedom were studied when subjected to external excitation.Via deriving the transfer function of the system with time delay and delayed stiffness, the frequency response functions were obtained in the parameter space.The results show that the time delay changes the operating mode of the system, and multiple formants appear on the amplitude-frequency response diagram.The delayed stiffness mainly affects the peak value of the formant, while the time delay amount mainly affects the number of formants.Meanwhile, by analyzing the equations of the ridge clusters of formants, the distribution of formants in the parameter space was presented.In addition, the numerical solution yields a distribution of the number of formants.The results show that as the delayed stiffness and the amount of time delay increase, the number of formants increases from 1 to infinity with a continuous interger increment.Finally, modal hammering tests on a turning test platform verify the relevant conclusions of the time-frequency response characteristics in the paper.The research can serve as a basis in machine tool modal analysis and machine dynamic response analysis.
  • LIU Xiang1,2,JIANG Lizhong1,2,XIANG Ping1,2,MAO Jianfeng1,2,WEI Minglong1,2
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 15-21.
    Abstract ( 197 ) Download PDF ( )   Knowledge map   Save
    In the construction and manufacturing process of railway concrete bridges, the randomness of structural parameters (such as concrete elastic modulus, density, etc.) inevitably exists, the randomness of passengers and cargo may cause the randomness of train-body, mass, and these randomness cannot be ignored in the random dynamics analysis of train-bridge systems.The model of a train-bridge coupled system was established, and the Newmark-β integral method was used to calculate the first four central moments of random train-bridge dynamic responses based on a new point estimate method which was based on adaptive dimensional decomposition.The results of the comparison with Monte Carlo method show that the new point estimate method can calculate the random response of the train-bridge system efficiently and accurately, and the efficiency is improved by 2—3 orders of magnitude.After obtaining the corresponding first four moments, the probability density function of the response can be fitted by using the cubic normal transformation technique.The method provides a reference to the train bridge limit state design.
  • SHEN Guohui1,YAO Jianfeng1,GUO Yong2,XING Yuelong2,LOU Wenjuan1
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 22-28.
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    In order to study the aerodynamic coefficients and flow characteristics of a smooth circular cylinder, wind pressures on the cylinder were measured at different wind speeds in a uniform flow simulated in a wind tunnel.The variation of the drag coefficient, lift coefficient, surface wind pressure distribution, wind pressure correlation coefficient and Strouhal number of the cylinder with respect to the Reynolds number were obtained.And the above results were compared with those of the previous researches.The results show that the fluctuation of the lift coefficients is larger than that of the drag coefficients, indicating that the vortex shedding induced by cross-wind excitation is more significant than that induced by along-wind turbulence.When the Reynolds number is in the critical flow region, the wind distribution around the cylinder experiences a symmetry-asymmetry-symmetry transition, revealing a whole changing process from laminar flow separation to turbulent flow separation.When the Reynolds number equals 352 000, a critical flow with laminar flow separation on one side and turbulent flow separation on the other side occurs and the wind pressures around the cylinder present a unilaterally asymmetrical bubble form.The characteristics of wind pressure correlation during laminar flow separation and turbulent flow separation were obtained.The wind pressures on the same side of the cylinder are highly correlated in the laminar flow separation case.Whereas, the wind pressures in the flow region before the separation point are highly correlated and those in the flow region after the separation point are weakly correlated in the turbulent flow separation case.The spectrum of lift coefficient has an obvious peak in the turbulent flow separation case, indicating that the fluctuation of the wind pressures is induced by the periodical vortex.The spectrum of lift coefficient has no obvious peak in the turbulent flow separation case, indicating that the fluctuation of the wind pressures is induced by the random vortex.
  • WANG Yurong1,2,WU Tianxing1
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 29-36.
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    Short pitch rail corrugation(25 mm—30 mm) has been observed at both curved and tangent tracks of metro, where high-elastic rail fasteners were used.To address it, the time-domain model for a slab track system coupled with four wheels was developed to determine the vertical dynamic wheel-rail interaction forces due to wave reflections, which were considered to have the main effects on the formation of corrugation.The non-linear rolling contact between the wheels and rail was modeled as a two-dimensional model, in which the wear at the longitudinal slip zone was assumed to be proportional to the frictional work done by tangential stresses.Combinedly using the transient wheel/rail dynamics, contact mechanics and long-term wear, mechanism, the evolution processes of rail corrugation under single and multiple wheel/rail interaction were simulated for the slab track systems with high-elastic rail fasteners as well as with normal rail fasteners respectively.The results show that wave reflections between moving wheels and rail lead to the dramatical fluctuation of contact forces and thusly the abnormal growth of uneven rail corrugation.Finally, the effects of tuned rail damper(TRD) on this specific rail corrugation were investigated.The simulation results show that wave reflections among wheels may be attenuated effectively by TRD and thereby short pitch rail corrugation may be mitigated as well.
  • CAI Chang1,2,HE Xuhui1,2,JING Haiquan1,2,QIN Chengwen3
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 37-43.
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    The background of this study is a real cable-stayed bridge.A special support system was designed for wind tunnel tests.The effects of incidence angle and yaw angle on the wake induced vibration of two flexible staggered and unparalleled stay cables were investigated.Large wake galloping has been observed.The incidence angle and yaw angle of cables have significant impact on the amplitude and trajectory of the wake galloping.When the incidence angle equals 5° and the yaw angle equals 10°, the downstream cable is more prone to wake galloping.Therefore, this configuration is considered to be the most unfavorable case.Three suppression measures were applied to this unfavorable case.They are rigid connection rod, flexible connection rod, and additional damping.The results show that the rigid connection rod and the flexible connection rod successfully suppress the wake galloping of the downstream cable, while the effect of a little increase in additional damping is not apparent.
  • DENG Zhouquan1,TANG Haojun1,LI Yongle1,HUANG Jing2,WANG Yichao1,LIN Taiyi2
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 44-50.
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    In order to decorate cities' night view, it has become a trend to install lighting fixtures on the existing long-span cable-stayed bridge.But, the installation of lighting fixtures will significantly change the aerodynamic shape of stay cables, affecting the structural aerodynamic stability.In order to ensure the safety and durability of bridges, the wind resistance of a stayed cable installed with lighting fixtures was studied bymeans of wind tunnel tests, and the influence of the lighting fixtures on the existing stay cable was evaluated.Taking three different diameter stay cables as the research object, wind tunnel tests for force and vibration measurement were carried out around a segment model with a scale ratio of 1∶1.The experimental results show that the presence of lighting fixtures will significantly change the aerodynamic shape of stay cables, increasing the frequency of vortex shedding at the leeward side, so that stay cables have the possibility of vortex-induced resonance at a lower inflow wind speed.In addition, the influence of lighting fixtures on the rain vibration of stay cables is finite, and it has a certain inhibitory effect on dry galloping.
  • FU Xiaoqiang1,2,YANG Renshu3,CUI Xiuqin1,2,LIU Xing1,2,LIU Jifeng1,2,LEI Zhen4
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 51-58.
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    Considering that the multi-fractal analysis based on the partition function is not conducive to highlighting the local scale characteristics,the multi-fractal detrended fluctuation analysis (MF-DFA) method was introduced into the field of blasting vibration signal analysis.The results show that the vertical shaft blasting vibration signal has multi-fractal characteristics, the MF-DFA spectrum and multi-fractal singular spectrum have significant diversity for the explosive loading form in the cases of different settlement types of peripheral holes, so, they can be used as characteristic parameters to distinguish the structure form of peripheral charge.The MF-DFA spectrum diagram and related parameters can characterize the vibration response state of the shaft lining under different blasting schemes.The study provides an effective method for the identification and classification of blast hole charge structure and charge parameters.
  • ZHU Lin1,CHEN Min2,JIA Minping3
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 59-63.
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    The structural health assessment in the crack propagation process was studied.Considering the wide existence of Weilbull distribution data characteristics in the assessment process, an approach for structural health assessment based on the Bayesian theory was proposed through combining the data of the type of Weibull distribution with the Bayesian theory.The numerical solutions for the complex posterior problems were provided by using the MCMC algorithm.The acoustic emission approach was adopted to collect the health assessment data for an industrial component.The health result obtained by the proposed model shows that two fractile parameters of 5% and 95% constitute the 90% of confidence interval of the assessment parameter for structural health.The posterior parameters are centrally distributed and the confidence level is up to 90%, which verifies the accuracy of the health assessment method.
  • SONG Hong,HUANG Weiping,FU Xuepeng
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 64-73.
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    The vortex-induced vibration of flexible tandom cylinders with large aspect ratio and low mass ratio was studied by model tests and CFD numerical simulations.By analyzing the characteristics of the tandem cylinders such as amplitude, vibration frequency, force characteristics and flow field structure, the effects of flow velocity and distance between tandem cylinders on the vortex-induced vibration characteristics of downstream cylinder were investigated.It is found that the amplitudes of vortex-induced vibration of the upstream and downstream cylinders, are rather different and the dominant frequencies are also different when the velocity is greater than a certain value.Thus the concept of separate reduced velocity Ur was proposed.Both the velocity and spacing affect the effect of upstream wake on downstream cylinder.The velocity affects the strength and development of the upstream wake, and the spacing affects the development space of the upstream wake and the contact position between upstream wake and downstream cylinder.
  • FANG Bo1,ZHONG Shuncong1,2,LIN Jiewen1,CHEN Weiqiang1,ZHONG Jianfeng1,ZHANG Qiukun1,3
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 74-81.
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    A two-dimensional frequency-domain optical vibration tomography system (2D-FOCVT) was used for the modal analysis of added-mass cantilever beams and finally to do mass detection.Based on describing the theory and method for the natural frequencies of lumped mass cantilever beams, the first three order natural frequencies of a cantilever beam with different added mass were analyzed, and the sensitivity of the additional lumped mass to the first three order natural frequencies was investigated.Subsequently, the relationship between the additional lumped mass and the first three order natural frequencies measured by the home-made 2D-FOCVT system was achieved by using the  numerical fitting method.The variation of the sensitivity along with the change of the additional lumped mass was discussed.On this basis, a mass weighing method using the sensitivity of the first order natural frequency was proposed by virtue of the 2D-FOCVT system.The experimental results show that the home-made 2D-FOCVT system exhibits a good performance with nano-scale high resolution; also, it is a novel application of 2D-FOCVT in the modal analysis for mass weighing.
  • LI Pan,CAO Lihua,SI Heyong,MENG Bin
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 82-88.
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    Taking one stage of a steam turbine as the research object, a three-dimensional unsteady numerical simulation was adopted to analyse the leakage vortex characteristics of rotor tip labyrinth seals.The pressure fluctuation in labyrinth seal cavities affected by leakage vortexes was also studied.The results show that there are multi-scale vortices in the labyrinth seal cavities, which are composed of circumferential spiral vortexes and wall vortexes.The position and the influence range of the vortexes experience complicated changes over time.The frequencies of pressure fluctuation in tip seal cavities contain both the blade passing frequency and the high frequency induced by the tip leakage flow dispersing into small scale vortexes.The uneven circumferential pressure in tip seal cavities is caused by the multi-scale vortex structure of the tip seal leakage flow and the spread of alternately changing pressure field between the stator and rotor blades in the tip clearance.
  • JIA Chuanguo1,2,GUO Yingqi2,LI Jianguang2,ZHOU Yue2,LI Yingmin1,2,YANG Pu1,2
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 89-98.
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    Accurately estimating additional equivalent damping coefficients is foremost for designing structures with viscous dampers.Based on the linearization theory and damper-structure coupling analysis, an estimation method was proposed by applying the inter-history iteration and energy dissipation equivalency.The proposed method exhibits clear physical meaning, with full consideration of the influence of both damping parameters and structural dynamic responses.Moreover, it also has a fast convergence speed and high accuracy.The reliability of the proposed method was validated by the simulations of several case studies and the comparison with an accurate method.
  • JIAO Bolong1,2,ZHONG Zhixian1,2,LIU Yixin1,2,WANG Jiayuan1,2,ZHU Changsheng3
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 98-103.
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    A method for rotor crack fault diagnosis based on variational mode decomposition(VMD) with bat algorithm (BA) optimization parameters was proposed, aiming at overcoming the difficulty in identifying rotor crack fault features.The global optimization of parameter K and penalty factor α in variational mode decomposition was carried out by applying the bat algorithm.The optimal (α, K) combination of VMD was searched by using the BA and the local minimum envelope entropy was used as a fitness function in the iteration process.The simulation results show that the BA-VMD method can achieve the adaptive acquisition of VMD parameters (α, K), and has obvious advantages in anti-modal aliasing and anti-noise interference.Finally, the displacement signal of a cracked rotor was analyzed by the BA-VMD method.The results show that the frequency spectrum processed by the BA-VMD method can fully describe the frequency characteristics of the signal, and the fault characteristics of the cracked rotor can be easily identified by the frequency structure characteristics.
  • HU Junfeng,HE Jiankang,YANG Mingli
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 104-110.
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    In order to describe the rate-dependent hysteresis nonlinearity of piezoelectric multi-dimensional micro-positioning stages, a modeling method was proposed based on the Hammerstein model.The dynamic model of a two-dimensional micro-positioning stage was composed of a static hysteretic nonlinear part and a linear dynamic system in series.The static nonlinear part was described by an modified Prandtl-Ishlinskii model (MPI), and the linear dynamic system was described by the autoregressive model with exogenous input (ARX).The model parameter identification method was also given out.In order to verify the validity of the Hammerstein model, an experimental platform was set up for experimental verification.The experimental results show that the relative errors between the predicted displacements derived by the Hammerstein model and measured displacements is 1 %—5 % by applying different frequency voltage signals to the stage.The predicted displacements are close to the measured displacements, which shows that the presented model can accurately describe the rate-dependent hysteresis characteristics of the micro-positioning stage.
  • ZHOU Huilin1,ZHANG Jianfu1,FENG Pingfa1,2,YU Dingwen1,WU Zhijun1
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 111-124.
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    In order to improve its vibration transmission and amplitude output characteristics, a horn for rotary ultrasonic machining with a tapered locating nodal surface was designed based on the analytical method, and optimized by the prestress modal analysis and harmonic response analysis.27 optimization design points were established making use of the response surface optimization method.The first, second and third optimization objectives are maximizing the amplification factor, minimizing the maximum equivalent stress and closing the resonant frequency to the theoretical design frequency, respectively.A 5-order modal frequency response surface validation method was proposed, and the optimal solution of the optimal design points was verified by the results of (2—6) order 5-mode frequency response surface analysis.The results show that, based on the proposed method, the optimized horn can improve the amplification coefficient, reduce the maximum equivalent stress, make the resonant frequency close to the theoretical design frequency, and improve the energy efficiency of ultrasonic machining.It has a certain guiding significance for the research and development of the performance of rotary ultrasonic machining equipments.
  • WANG Bo1,XIE Junwei1,ZHANG Jing2,GE Jiaang1
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 117-124.
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    In the process of suppressing the interference outside the platform which is close to the target position, the main lobe distortion of MVDR beamformer was analyzed when the number of array elements is large and the number of fast shots is insufficient.The CSB sin-FDA receiving array structure was used to replace the ULA-FDA receiving array.When the number of snapshots is insufficient, the modified covariance matrix was introduced into the fuzzy RBF neural network to calculate the optimal weight vector, which avoids the matrix inversion operation.Compared with the MVDR beamformer based on PA and FDA-BFF, in the case of low snapshot, the main lobe pointing can be kept in the target position while the effective zero notch is formed at the interference position.And the pattern only forms a single main lobe peak at the target position, which lays an important foundation for fuzzy elimination in a series of subsequent analysis of target parameter estimation.Numerical simulation verified the effectiveness of the proposed method.
  • LI Jianzhao1,SHEN Haichuan1,SONG Yulin1,LIU Wei1,LIU Bingxiang2
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 125-131.
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    The use of vibration isolator is an important means for improving the anti-shock performance of marine experiments, and its second impact problem under certain condition is one of the main concerns in impact analysis.Therefore, it is necessary to choose reasonably restrictor parameters, such as the stiffness of restrictor and the restricted displacement, to fulfill the allowable impact response condition.At the same time, the consideration of the rigidity of installation foundation has a great influence on the anti-shock performance of marine experiments.In the paper, an undamped system with one degree of freedom and an undamped system with two degrees of freedom were taken as the analysis objects.Based on the piecewise function method, the influences of foundation stiffness on impact responses and different restrictor parameters were discussed.The results provide a more accurate basis for choosing vibration isolators.
  • PAN Hongxia,ZHANG Yuxue
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 132-137.
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    For the complicated signal components in the early failure of the supply and delivery missile system, the  failure symptoms are usually difficult to identify.Aiming at this, an intelligent fault diagnosis method was proposed based on the texture features of synchrosqueezing wavelet transform(SST)time-frequency distribution images.The EEMD method was adopted to preprocess the vibration signal of the projectile delivery system, and to calculate the correlation coefficient of the decomposed components.The first four layers with high correlation coefficient were selected to reconstruct the signal for reducing the noise effect.Then, the vibration signals of different states of the transmissive bomb system were dealt with by the time-frequency analysis with the synchrosqueezing wavelet transform to obtain two-dimensional time-frequency images reflecting different operating states, and the gray-scale processing was performed.The gray level co-occurrence matrix method and the gray gradient co-occurrence matrix were used to extract the texture features.In order to compare with the traditional method, the energy percentage of the first four layers with large correlation coefficient of the original signal was taken as a feature after the signal was decomposed by EEMD.The method of kernel-based fuzzy C-means clustering, was used to do the classification and recognition of the image texture features and the image features of three different state vibration signals of the supply and delivery bomb system respectively, and the results were compared with those of the fuzzy C-means clustering.The experimental results show that the method can effectively recognize the early failure of automatic missile systems and the recognition accuracy is 91.21%.
  • XU Wenbiao1,2,WANG Ailun1,2,LIAO Zeyu2,LIU Le1,2
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 138-146.
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    The nonlinear vibration phenomenon of a circumferential rod-fastened rotor with cracked rod is of nonlinear property.The stiffness model of the cracked rod was established based on the supposition of Paris crack propagation and the model of the disk interface contact stiffness was also established, by which the preloading effect of the rod was characterized.On this basis, a nonlinear dynamics model of the connection interface of the rotor with cracked rod was completed by refering to the Capone short bearing model.The solution was analysed by virtue of the Poincare section surface method.It is found that the system alternates between the periodic doubling bifurcation and the quasi-periodic bifurcation in the e-n bifurcation set obtained under the influence of the factors of rotational speed and eccentricity.The solution distribution of bifurcation points on the η-n bifurcation set obtained under the influence of crack propagation and rotational speed is discontinuous.At different rotational speed, the bifurcation trajectory of displacement along with the crack propagation is rather complicated, and the presence of rod crack will accelerate or decelerate the occurrence of the bifurcation point.The results show that the mechanism of the effect of rod crack on rotor stability is affected by the system parameter set.The conclusion has certain significance for parameter design and fault identification of rod-fastened rotors.
  • ZHANG Gang,TIAN Fuqing,SHE Bo,LIANG Weige
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 147-153.
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    The traditional physic health indicator(PHI) has poor monotonicity and is insensitive to the incipient fault.Aiming at this, a virtual health indicator(VHI) construction model, was proposed based on the information entropy of a specific frequency band and the restricted Boltzmann machine(SEI-RBM).The model consists of two layers: physic health indicator construction layer and features fusion layer.In the physic health indicator construction layer, a method based on the information entropy of a specific frequency band was proposed to construct the physic health indicator.In the features fusion layer, the monotonicity metric was used to select parts of the PHIs to form feature sets, which were then fused by the restricted Boltzmann machine to get a VHI.The experiment results show that the proposed model could make a VHI, being able to effectively enhance the monotonicity of the degradation assessment curve and promote the remaining useful life prediction accuracy of rolling element bearings.
  • LIN Peng1,LIU Heyun1,HU Dong1,LIU Meiqing2,WANG Shu1,ZHAO Wensheng2
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 154-160.
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    The influence of blade angle on the vibration of an axial-flow pump under normal operation and in starting state was studied by comparing the vibration signal characteristics of the pump station running under normal operation and in starting state at different blade angles.This could serve as a reference to ensure the safe and stable operation of the unit.The results show that under normal operating conditions, the general vibration amplitudes of the outer cylinder and the lower frame increase gradually as the blade angle increases from -8° to +8°.The amplitude of  spindle slips is almost constant.The main frequency components of vibration signals in the flow direction include 2.5 Hz and 10Hz.And the main frequency components of vibration signals in the vertical flow direction and axial direction are 2.5 Hz, 10 Hz and 20 Hz, presenting a multiple relationship with the rotational frequency of the pump (2.5 Hz).When the blade angle increases from 2° to 8°, part of the peak values of vibration gradually exceeds 50 μm, entering into the C area, which indicates that the pump should not run continuously at large angle.
  • XIAO Longjiang,HUANG Jianliang
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 161-166.
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    The nonlinear dynamics of a fixed-fixed buckled beam with low initial deflection subject to uniform hamonic base excitation was concerned, which was governed by a coupled nonlinear equation with both quadratic and cubic nonlinearities.The Galerkin method was employed to discretize the governing equation, and the incremental harmonic balance (IHB) method with variable excitation force was used to track the dynamic response of the buckled beam.The Floquet theory was used to analyze the stability and bifurcation of the solution.It is found that at low initial deflection, the anti-symmetric modes cannot be excited,however, period-doubling and saddle node bifurcations will occur and lead to snapthrough of the solution.The results obtained by incremental harmonic balance method agree very well with those by the numerical integration using the fourth-order Runge-Kutta method.
  • LI Zhichao1,SHANGGUAN Wenbin1,Subhash Rakheja1,LIU Jie2,TAN Meng1,AHMED Waizuddin1
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 167-175.
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    The finite element model of a foam-filled thin-walled square tube for calculating its energy absorption capacity was  established.The measured energy absorption performance of the tube subjected to axial load was used to verify the model.The effects of different type and number of introduced crush initiators on the axial deformation mode, the initial peak force and the energy absorption capacity of the foam-filled thin-walled square tube were studied.The results show that the introduced crush initiators can improve the energy absorption capacity, reduce the initial peak force, increase the crush force efficiency and even change the deformation mode.Moreover, by increasing the number of crush initiators along the axial direction of the square tube, these advantages can be further enhansed.Using the grade evaluation method, it can be determined that by designing 4 sets of four-corner-holes along the axial direction, the foam-aluminum-filled thin-walled square tube attains the best comprehensive energy absorption characters.
  • DU Fei1,2,3,MA Tianbing1,2,3,LIU Jian3,LUO Zhi3
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 176-180.
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    In the active vibration control of a stiffened plate, the sensing piece and the actuation piece are in a relative position pasting form.Experiments show that there is local strain effect in this way, which will lead to the attenuation of vibration control effect and even the divergence of control.Aiming at this, a local strain compensation scheme was constructed and an improved power law approaching sliding mode control algorithm based on local strain compensation was designed.The vibration mode of the stiffened plate was taken as the control object.An active vibration control experiment of the stiffened plate was carried out on the NI-CompactRIO 9024 platform.The experimental results show that the vibration suppression effect of the improved power law approaching sliding mode control algorithm based on local strain compensation could reach 13.16 dB for the first mode of the stiffened plate, which is 2.57 dB higher than the 10.59 dB of the uncompensated improved power law approaching sliding mode algorithm.
  • ZHU Zhiwen,LI Hongbo
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 181-188.
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    One of major concerns, when carrying out bridge sectional model tests, is the effect of model corner fabrication errors on the aerodynamic forces and vortex shedding property of a shallow box girder, which has not been addressed at current time.The Reynolds-averaged Navier-Stokes equations and SST  k-ω turbulent model were used to do the simulation of the flow field around the rigid box girder section of the main span of the Great Belt East Bridge.For different kinds of corner rounding radius, the flow pattern around the girder section, the mean aerodynamic coefficients and vortex-shedding frequency were obtained.The results show that the increase of corner rounding radius can decreas the flow separation intensity, while the flow separation point will no longer keep fixed.The simulated mean aerodynamic coefficients and Strouhal (St) number indicate the minor influence of different corner rounding configuration.The further study shows that the leading edge rounding presents small and negligible Reynolds number effect on the mean aerodynamic coefficients and St number.It is suggested that the effects of corner rounding with small radius can be neglected in bridge wind resistant design.It is also suggested that corner rounding with small radius at the leading edge can be adopted in CFD simulation, which will help decrease grid number, improve mesh quality and reduce CFD computational cost.
  • YU Chao1,2,LAN Diandian1,2,WANG Fang1,2,WANG Bingyu1,2,LI Guibing3,LI Fan4,PENG Yong5
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 189-197.
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    The head/brain injury occurs frequently in a car-to-pedestrian impact accident.The impact between the pedestrian head and the windscreen is a leading cause of the head/brain injury.The effect of windscreen inclination angle of a typical small passenger car on the pedestrian head/brain injury was numerically investigated.The THUMS (Total HUman Model for Safety, developed by Toyota Central R & D Labs) head-neck finite element (FE) model and TNO multi-body (MB) pedestrian model were coupled to construct a new numerical pedestrian impact model.By simulating a real-world car-to-pedestrian impact accident, the new coupled model was validated in terms of the pedestrian/vehicle kinematics reconstruction of such accident.Based on the above model, the impact simulation matrix was set up, the variation range of the windscreen inclination angle was set to be 24°—50° (an increment of 2°), the impact locations of the pedestrian with the vehicle were defined as the 1/2 and 1/3 of the front of the bumper, and the impact velocity was considered to be 45 km/h.The results show that the coupled pedestrian model could predict the pedestrian kinematics effectively.The predicted head/brain injury when the pedestrian is impacted at the 1/2 of the bumper seems to be more severe than at the 1/3 location.It is also suggested that the head/brain injury risk decreases firstly and then increases with the increasing windscreen angle within the predefined range, and the angle between 32°—34° produces the lowest head/brain injury risk.
     
  • LUO Haitao1,CHEN Shipeng2,FU Jia1,LIU Guangming1
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 198-204.
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    The high-speed impact penetrator dives into the interior of a planet in a collisional manner.Due to its high landing speed, the overload generated by the collision is severe.In order to ensure that the scientific instruments can work well after collision, the buffer protection must be designed.The vibration damping structure of a penetrator was designed.The nonlinear finite element technique was used to simulate the penetrating process of the penetrator, and the landing speed of the penetrator was then determined.The dynamic response and energy absorption of the main vibration-damping structure, foam-filled aluminum thin-walled tubes, under impact loads were investigated.From the analysis results, foam-filled thin-wall structures, used as an impact energy absorber, has excellent performance in terms of shock isolation efficiency and total energy absorption.
  • YIN Aijun,ZHANG Zhiyu,LI Haizhu
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 205-209.
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    In order to detect rolling bearing abnormities earlier and quantify the degree of performance degradation, a new evaluating method was proposed based on the synchroextracting transform and complex wavelet similarity (SET-CWSS) index.The time-frequency analysis of a vibration signal at current moment was performed by the synchroextracting transform (SET) to get a more concentrated time-frequency graph.The time-frequency graph obtained after SET and the SET time-frequency graph of the fault-free vibration signal when the bearing was just put into operation were compared on the basis of complex wavelet structural similarity (CWSS).And then, the SET-CWSS index for the assessment of rolling bearing performance degradation at current moment was achieved.Through the fatigue test verification and comparisons with other performance degradation assessment methods, the results show that the SET-CWSS index can effectively describe the performance degradation process of rolling bearings, quantify the degree of performance degradation and is more sensitive to the early abnormities of rolling bearings.
  • CAO Xincheng1,CHEN Binqiang1,YAO Bin1,HE Wangpeng2
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 210-219.
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    Multiresolution dictionary is an important tool to decouple the multitude of vibration modes with weak spectral coherence in vibration measurement.However, there is lack of systematic theory that enables continuous spectral refinements around fixed analyzing center.To address this problem, a novel theory of topology fractal multi-resolution (TFMR) was proposed based on the nearly analytic wavelet theory.With the concept of nested centralized wavelet packet space (NCWPS), the amazing capability of simultaneous multi-object tracking with respect to mechanical fault features was ensured.Mathematically, it is proved that: ① Any NCWPS is a topology space of the original spectral domain; ② All NCWPSs share the self-similar fractal property.The research reveals the important intrinsic relation between the classical dyadic multiresolution and TFMR, that is, any dyadic wavelet packet uniquely belongs to a NCWPS.In the sense of augmented NCWPS, the wavelet packet space is regarded as a subset to the theory of TFMR.Combining the technique of TFMR with the component damage model, a novel sparsity promoted learning dictionary for repetitive transient features due to mechanical damages was proposed.The algorithm has been applied to analyze signals from the mechanical system with rub-impact fault, and the periodic impact features in the form of mono-component were successfully extracted in the presence of strong background noises.Compared to the methods represented by fast kurtogram and periodic group sparse optimization, the enhanced noise resistibility of the proposed method was validated.
  • CAO Jinggu, ZHANG Tao
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 220-224.
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    To increase the computational efficiency and accuracy of the meshless method for solving vibration problems, a new meshless time domain adaptive algorithm was developed.In the method, a time domain adaptive algorithm was used and variables were expanded in terms of time within each time interval.The variables could be more accurately described over time by adopting higher expansion order.The time-space problem of vibration would be transformed into a series of boundary value problems solved by the meshless method.The method can improve the computational efficiency and compensate for the loss of precision caused by different time steps, and its efficiency and accuracy were verified by numerical examples.
  • ZHANG Yongliang, FENG Pengfei, CHEN Xingchong, LIU Zhengnan, JI Richen
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 225-229.
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    To study the effect of high-order modes on the seismic response of long-span steel truss arch bridges,a deck-type steel truss arch bridge with a span of 490 m was taken as the research object.By virtue of the software MIDAS Civil to build the finite element model of the whole bridge,based on the fundamental principle of mode analysis spectrum method,the separation method for the seismic response of the bridge with high-order modes was introduced by combinedly using the dynamic analysis and static analysis.On this basis,the influence of main control orders on the longitudinal seismic response of the main arch ring of the bridge was analyzed,and the seismic response mechanism was revealed.The results show that the influence of the same vibration mode on different internal force components at the same position of the chord bar under the main truss is different.The same vibration mode has different influence on the same internal force component in different areas of the chord under the main truss.Viewing the overall internal force distribution on the lower chord of the main truss,the influence of different modes on the axial force and bending moment on the lower chord is similar,but the influence on the shear force is obviously different.For the axial force and bending moment,in the region from L/8 to arch foot,the high-order vibration mode has a significant impact.For shear force,in the region from middle-span to L/4,the influence of high-order modes is significant,and the effect of multi-mode coaction is obvious.

  • YU Huijie, ZHU Yixuan, XU Yahui
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 230-235.
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    Theoretical and experimental researches on the transfer characteristics of a nonlinear metal-rubber isolator were carried out.Based on a nonlinear hysteresis model with dry friction damping, the averaging method was used to get the frequency-response function.The transfer rate in different motion states and the probability of realizing no resonance in the system were inspected.The critical dry friction force and unlocked frequency were determined through the frequency-response function.Dynamic tests of the isolator were performed,and the mechanics parameters of the isolator were identified by the test data.Finally,the theoretical results were verified by vibration tests.The results provide a new way to the design of metal rubber isolator and its applications.
  • FAN Chen, WANG Ying, LI Zhaoxia
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 236-242.
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    Taking the cable-stayed bridge of Runyang Yangtze River Highway Bridge at the north branch as an engineering background, based on the finite element software ANSYS and the numerical calculation software MATLAB, a series of technical problems in the vehicle-bridge coupling dynamic analysis of long-span steel box-girder bridges were discussed, which include the vehicle-bridge coupling vibration modeling method and dynamic stress analysis method aiming at fatigue analysis, the fatigue evaluation method based on vehicle-bridge coupling dynamic stress, the comparison of different bridge stress analysis methods, and the influence of road roughness on the fatigue condition of the bridge.The results show that the coupled dynamic analysis method  can be effectively applied to the fatigue state assessment of long-span steel box-girder bridges, and can meet the need of local fatigue damage cumulative simulation.By comparing the dynamic stresses by using different calculation methods and different road roughness, it is shown that the effect of vehicle load on bridge is local but has a significant effect on the local fatigue accumulation.More accurate results can be obtained by the use of vehicle-bridge coupling dynamic analysis in bridge fatigue condition evaluation.
  • CAI Yannian1, YU Hongliang1,2, YAN Jin2, LIAO Jianbin2
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 243-248.
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    In order to explore the vibration energy flow and distribution characteristics of composite structures under external excitation, the vibration energy visualization technology for a glass fiber reinforced plastic(GFRP) sandwich plate was studied based on the structural intensity method.The structural intensity vectors of the GFRP sandwich plate element were calculated according to the laminate theory based on the concept of structural intensity.The realization process of structural intensity visualization based on finite element method was presented by virtue of the Python and Matlab Language.The calculated natural frequencies, mode shapes and structural intensity vectors were compared with the references to validate the proposed numerical method.The analysis of the GFRP sandwich plate gives an example to show the graphic information of structure intensity field which provides the location of excitation source and the distribution characteristics of vibration energy flow for composite structures.The contributions of the shear component, twist component and bending component to the structural intensity vectors were extracted which intuitively show the dominant role of shear component in the energy transfer of vibration.
  • PENG Zhaiming, CHENG Longsheng, ZHAN Jun, YAO Qifeng
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 249-256.
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    In order to improve the running efficiency of rotating machinery and to identify its potential failure, a fault classification method based on the multi-feature extraction and improved Mahalanobis Taguchi system (MTS) was proposed.The methods of time domain, frequency domain and the complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) were combinedly used to obtain a multi-dimensional feature set.Integrating the advantages of the MTS and the directed acyclic graph (DAG), a DAG-MTS multi-class classification model was constructed and applied to bearing fault diagnosis.The effectiveness and applicability of the model was verified by using experimental data.The results show that the model can quickly and accurately identify the fault of rolling bearings.
  • ZHANG Xiaohua, ZHOU Haiyang, WU Zhibiao
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 257-262.
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    A method for sensor location selection was proposed for the response reconstruction of a substructure.According to the structure of a system, the whole structure was disassembled into several substructures to reduce the number of degrees of freedom (DOFs).Then the sensor location optimization and response reconstruction of each substructure were conducted separately.Since the number of DOFs of each substructure is far less than that of the whole structure, the method can improve the efficiency of sensor location optimization and response reconstruction.The sensor locations were determined by minimizing the reconstruction errors between the reconstructed and analyzed responses.The results of numerical and experimental investigations demonstrate that the reconstructed response by using finite measurements match well with the analyzed or measured responses both in time and frequency domains.The proposed method does not reuqire to isolate the substructures and consider the complicated boundary conditions, which is beneficial for its application in large-scale civil engineering structures.
  • ZHANG Mian, WANG Kesheng, LI Yaxin
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 263-270.
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    The fault diagnosis of planetary gearboxes is a challenging issue due to the complexity and variety of vibration responses generated by the relative motions of internal gears which are much different from the case of fixed-shaft gearboxes.When the damage occurs on a tooth, due to the time-varying transfer paths caused by the dynamic fault meshing behaviors, the captured fault induced information on a fixed-sensor may exhibit unique irregularity.Before properly making use of these fault induced information for fault diagnosis, the period of fault meshing behaviors should be focused and analyzed, because a certain period included in the analyzed data may involve complete fault information for fault detection.In the paper, a method was introduced to determine the period of sun gear fault-meshing positions based on the kinematics of the internal gears.Two conditions were considered: planet gears were all different; planet gears were identical.Generalized mathematical expressions for the number of rotations of the sun gear and the carrier under above two conditions were derived respectively.The proposed expressions can also be applied to ring gear fixed planetary gearboxes.Finally, experimental studies were carried out to suggest the minimal measured data length to ensure an effective fault diagnosis.
  • CUI Shuangshuang1,2, SUN Hao1, CHEN Weihong3, HAN Xu1, SONG Pengyan4
    JOURNAL OF VIBRATION AND SHOCK. 2020, 39(6): 271-276.
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    Structural response modification factor implied in our country’s current aseismic design code is a constant R≈3.0.Here, to assess whether or not the chosen value of structural response modification factor for RC frames be reasonable, a capacity-demand ratio λ was introduced.17 RC frames with different stories and fortification intensities were designed according to our country’s current aseismic design code.Based on the finite element platform OpenSees,Pushover analysis method was used to analyze these frames’ structural anti-collapse capacities, and obtain capacity values of their structural response modification factors under critical collapse state.The static capacity spectrum method and dynamic capacity spectrum one were used to analyze structure’s demand under rarely occurred earthquake, and obtain demand values and variation laws of structural response modification factors.Then, the capacity-demand ratios λ was obtained, and it was shown that its value always is larger than 1.The results showed  that RC frames designed can satisfy the expected safety performance objective against collapse under rarely occurred earthquake;response modification factors of structures designed according to 8° fortification intensity are more reasonable, while those of structures designed according to 7° fortification intensity are more conservative;those of structures designed according to 6° fortification intensity are too conservative, and they can be safely increased.