英文摘要

TheStatusandProspectsofFlexibleTransducersinUltrasonicWaves-BasedStructuralHealthMonitoring

GUOShifeng1,2,3,LIYehai1,2,3,LIZhen1,2,3,FENGWei1,2,3
(1. Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences Shenzhen, 518055, China) (2. Shenzhen Key Laboratory of Smart Sensing and Intelligent Systems Shenzhen, 518055, China) (3. CAS Key Laboratory of Human-Machine Intelligence-Synergy Systems Shenzhen, 518055, China)

AbstractStructural health monitoring (SHM) technology is of great significance in ensuring structural safety, reducing maintenance costs, and extending the service life of structures. Conventional transducers, which are made of brittle material and installed with additional couplant and fixtures, are difficult to be applied in real engineering structures because of their poor reliability, heavy weight, and excessive volume. Flexible transducer technology is the important direction to solve the existing structural health monitoring problems. The flexible transducers and sensing network, made of polymer materials, can be directly fabricated and integrated on the structures of interests by using advanced additive manufacturing technology, with the advantages in high sensitivity and consistency, light weight and low volume, and good flexibility with complex profiles. For applications in ultrasonic waves-based structural health monitoring,the flexible transducers can form large and condense transducer network on structures, possess wave tuning capability, and qualify for multiple forms of monitoring tasks (including active and passive damage detection), therefore providing solid foundation for health monitoring technology in real engineering structures such as aerospace, railway transportation and oil pipelines.

Keywordsflexible transducer; sensing network; ultrasonic waves; structural health monitoring

ModelingandExperimentalStudyofGalloping-BasedPiezoelectricEnergyHarvester

ZHAODaoli,HUXinyu,SUNWeipeng,GUOPengcheng
(State Key Laboratory of Eco-hydraulics in Northwest Arid Region of China,Xi′an University of Technology Xi′an, 710048, China)

AbstractBased on the distributed parameter model of piezoelectric energy harvester, the vibration and power of cantilever piezoelectric energy harvester under galloping are further theoretically analyzed, meanwhile the analytical solution of tip′s onset speed and harvested power from onset to galloping are obtained in this paper. The cantilever piezoelectric energy harvesters with a regular tri-prism tip and a regular quad-prism tip are tested in a closed direct-flow low-speed wind tunnel. The experimental results show that their harvested power reaches 0.125 9 mW and 0.248 5 mW, respectively. Comparing the harvested power and its history curve, it is found that the theoretical solutions are in good agreement with the experimental ones, showing a high accuracy of the theoretical model.Thought the theoretical model analysis, the larger the wind speed and the smaller the tips mass are, the higher the power of energyharvester will be. For the energy harvester at different conditions, there are optimal external load resistance values, and there are also two optimal external load resistance values at low wind speed.

Keywordsgalloping; piezoelectric energy acquisition; the distributed parameter model; closed direct-flow low-speed wind tunnel

VibrationMechanismandCharacteristicsofCompositeDampingPlateswithElasticConstraints

AIZhen1,2，HUANGYizhe2，LIZhuang2，HUANGQibai2
(1.State Key Laboratory of Vehicle NVH and Safety Technology Chongqing, 401120, China) (2.School of Mechanical Science & Engineering, Huazhong University of Science and Technology Wuhan, 430074, China)

AbstractA new composite viscous damping material is developed to reduce the vibration and noise of car body. To analyze the mechanism of vibration and energy dissipation of the new type of viscous damping material on car body, the essay, based on the studies of the classic free damping layer and constrained layer damping, a composite damping layer with elastic constraints, composite shear, and its bending energy dissipation mechanisms is proposed.. Based on the displacement continuous relations of layers and thin plate theory, the displacement and strain energy equationsare established. According tothe boundary conditions of local damping equipped and four edges simply supported, the composite damping plate motion differential equation and the eigenvalue equation of the vibration frequencyare deduced by combined with the assumption mode method.The natural frequency and the loss factor of the composite damping plate are also obtained.The composite damping layer can be used to study the different parameter characteristics of single-phase materials and the performance comparison of multiphase materials. In addition, the elastic layer moves up, the vibration damping performance is better.The derivation of the composite energy dissipation mechanism formula also provides a theoretical basis for its applications in automobiles.

Keywordspartial coverage； viscoelastic； composite damping； vibration mechanism； parameter studies

Time-VaryingMeanWindExtractionofDownburstBasedonEnergyValley
SearchingEmpiricalWaveletTransform

LIChunxiang,LIZhou
(Department of Civil Engineering, Shanghai University Shanghai, 200444, China)

AbstractExtreme wind such as downburst has strong non-stationary characteristics, which brings challenges to the analyses of wind field characteristics and structural response. Empirically, this non-stationary wind can be divided into a time-varying mean wind and a zero-mean fluctuating wind, which are effective methods to deal with non-stationary wind speed signals. In this paper, the advantages and disadvantages of several common time-varying mean extraction methods are summarized. On this basis, an empirical wavelet transform method based on energy valley search is proposed to extract the time-varying mean wind velocity of downburst. The extracted time-varying mean wind and fluctuating wind are used to analyze the non-stationary response of the top of a high-rise building. The results of two groups of downburst analyses show that compared with empirical mode decomposition and discrete wavelet transform, the time-varying mean wind extracted by energy valley searching empirical wavelet transform is more in line with expectations, and the corresponding structural response is on the safe side.

Keywordsdownburst; time-varying mean; nonstationary response analysis; empirical wavelet transform; energy valley

MachineryFaultClassificationMethodBasedonFeatureContributionRate

MABo1,2,ZHAOYi1,2
(1.Beijing Key Laboratory for Health Monitoring and Self-Recovery of High End Mechanical Equipment,
Beijing University of Chemical Technology Beijing, 100029, China)
(2. Key Laboratory of Ministry of Education for Engine Health Monitoring and Networking,
Beijing University of Chemical Technology Beijing, 100029, China)

AbstractIn order to improve the accuracy of fault classification of complex machinery such as reciprocating compressor and aeroengine, an analysis method combining Dirichlet process mixture model(DPMM) with Bayesian inference contribution(BIC) is proposed according to the characteristic that the sensitivities of feature parameters are vary from fault to fault. It is used to self-learn the statistical distribution model of high dimensional features of the mechanical vibration signals by DPMM method, and the contribution rate of each feature to the model is calculated according to the BIC theory. The fault classification is realized by analyzing the differences between the feature contribution rates of the observed data and different kinds of fault data. The results indicate that the average classification accuracy of the proposed method increases by 19.29% compared with the fault diagnosis method based on Gaussian mixture model(GMM), and increases by 32.71% compared with the fault diagnosis method based on Relief algorithm. Furthermore, this method has characteristics of high timeliness and strong generalization performance. It can effectively classify the complex mechanical faults.

Keywordsfault diagnosis; feature contribution rate; Dirichlet process mixture model; Bayesian inference

ModificationoftheDynamicMechanicalModelofDampingMaterials
inSupramolecularInteraction

DUANYuxing,ZHAOMiaomiao,SUBo,DONGWanyuan
(Aircraft Strength Research Institute of China Xi′an, 710065, China)

AbstractThe effect of damping materials on supramolecular interaction is studied, and a fractional derivative Kelvin-SI model with supramolecular corrected item is established. Then the properties of the materials at various frequenciesand temperature environments are studied by characterizing the dynamic mechanical properties using the new model. Furthermore,the storage and the loss moduli of the materialscanbe accurately described at various temperatures (240～420K) and different frequencies (1～100Hz) according to the new model. It is shown that the calculation by using the uncorrected fractional Kelvin-Voigt model is inconsistent with the measured values and the R-squared value is only 0.787 3. However, the new corrected model is fitted well and the R-squared value is above 0.98. Finally,the dynamic moduli are both decreasing when the temperature is increasing or the frequency is decreasing. The parameters of the modified model canbe fitted with the physical phenomenon, and the change of the dynamic performance can be precise characterized by varying the parameters of the modified model.

Keywordsdynamic mechanical model; fractional derivative model; loss modulus; supramolecular interaction

ImprovedAlexnetBasedFaultDiagnosisMethod
forRollingBearingUnderVariableConditions

ZHAOXiaoqiang1,2,3，ZHANGQingqing1,2
(1.College of Electrical and Information Engineering, Lanzhou University of Technology Lanzhou, 730050, China)
(2.Key Laboratory of Gansu Advanced Control for Industrial Processes Lanzhou, 730050, China)
(3.National Experimental Teaching Center of Electrical and Control Engineering,
Lanzhou University of Technology Lanzhou, 730050, China)

AbstractRolling bearings in rotating machinery often work in the environment with variable loads and strong noise. Traditional fault diagnosis methods of rolling bearings are difficult to adaptively extract the favorable features under complex conditions, so a fault diagnosis method of rolling bearings with variable conditionsis proposedbased on improved AlexNet. Firstly, one-dimensional time-domain signals are translated into two-dimensional feature maps using transverse insert samples method to satisfy the requirements of the improved AlexNet input.Compared with the existing longitudinal insert samples method or two-dimensional spectrums method, the time series and correlation of vibration signals are preserved during feature extraction automatically. Secondly, the functional layer of AlexNet convolutional layer is improved and adjusted,andthe profitable characteristics for the state identification of rolling bearingscanbe automatically extracted via the convolution and sampling operations of improved AlexNet from the two-dimensional feature maps. Finally, the softmax cross entropy is considered as a loss function and Adam is used to realize the fault diagnosis of rolling bearings according to a small batch iterative optimization method. Compared the diagnosis effects with other methods for 12 kinds of states of different positions and damage degrees of rolling bearings under variable loads and strong noise, the results show that the proposed method has a higher accuracy of fault diagnosis of rolling bearing and its robustness is stronger.

Keywordsfault diagnosis; rolling bearings; deep learning; variable loads; convolutional neural network

MonitoringtheOperatingConditionofPipelineofPumpingStations
BasedonRecurrenceTheory

ZHANGJianwei1,2,3,CHENGMengran1,2,3,MAXiaojun1,2,3,WANGLibin1,2,3,ZHANGYina4
(1. College of Water Conservancy, North China University of Water Conservancy and Electric Power Zhengzhou, 450046, China)
(2. Collaborative Innovation Center of Water Resources Efficiency and Protection Engineering Zhengzhou, 450046, China)
(3. Henan Provincial Hydraulic Structure Safety Engineering Research Center Zhengzhou, 450046, China)
(4. School of Civil Engineering and Communication，Yellow River Conservancy Technical Institute Kaifeng, 475004, China)

AbstractAiming at the abnormal operation of pipeline caused by unfavorable factors, anoperational monitoring method of pipeline based on Recurrence theory is proposed. First of all, the vibration sensor is used to extract the measured information of key parts of the pressure pipeline and fuse the data of different directionsat the same position to obtain a set of comprehensive data that reflect the overall dynamic characteristics of the structure. And then, embedding dimension (m) and time delay (τ), these two parameters of the phase space reconstruction, are selectedby using false nearest neighbor methodand mutual information method, respectively. Finally, the recurrence plot and recursive quantification indexes which represent the dynamic characteristics of pipeline are drawn and calculated. The method is applied to the operational monitoring of the second stageseventh pipeline of Jingtaichuan project, andit is verified by setting different operating conditions. The results show that the recurrence plots of the pipeline vibration signalspresentdifferent modes under the conditions of switching unit transient and stablely operating. The recursive quantification indexes and thedeterminism, the diagonal average length, the recurrence rate and the recurrence entropy also shows significant differences, whichcan effectively distinguish the pipeline vibration state. Therefore, the method provides a new idea for the non-destructive dynamic monitoring of pressure pipeline.

Keywordspumping station pipeline; vibration; recurrence plot; recursive quantification indexes; signal analysis; on-line monitoring

StudyonSeparationofAerodynamicNoisefromHighSpeedTrainBogies

ZHULeiwei1,GUOJianqiang1,ZHAOYanju1,SONGLeiming2
(1.CRRC Qingdao Sifang Co., Ltd. Qingdao, 266111, China)
(2.School of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University Beijing, 100044, China)

AbstractThere are aerodynamic noise, wheel/rail noise and equipment (structure) noise in the bogie area of high-speed train.In order to separate the noise, the operationaltransferpathanalysis (OTPA) is used in the bogie area. In the low-speed operation condition, the noise in the bogie area of the train is mainly the wheel-rail noise, and the structure noise generated by power equipment such as motor, axle box, gear box, etc. The aerodynamic noise is negligible,so the transfer function of the wheel-rail and the structure acoustic paths can be obtained by analyzing the transmission path of test data. In the high-speed operation condition, the response point noises of the bogie area in the transmission path analysis include the contribution of the two types of noises and the aerodynamic noise. The contributions of the wheel-rail and the structure noises under high-speed operation can be obtained by using the transfer function of the two types of noises obtained at the low-speed condition.Compared with the calculated total values, the contribution of aerodynamic noise can be accurately separated. The separation results show that the turning point of velocity dominated by aerodynamic noise occurs at the speed level of 200 km/h. However, at the speed level of 350 km/h, the contribution of the aerodynamic noise reaches 60%, and that of wheel-rail noise is about 30%, which cannot be ignored.

Keywordsaerodynamic noise； high-speed train； transfer path analysis； contribution

CFD/CSDFullyImplicitTightlyCoupledStudyonLimitCycleFlutterofWing

HUANGJie1,YAOWeixing1,2,JIANGZhiping3,ZHOUDanfa1
(1. State Key Laboratory of Mechanics and Control of Mechanical Structures,
Nanjing University of Aeronautics and Astronautics Nanjing, 210016, China)
(2. Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle,
Nanjing University of Aeronautics and Astronautics Nanjing, 210016, China)
(3. AVIC ShenyangAircraft Design and Research Institute Shenyang, 110035, China)

AbstractA fully implicit tightly coupled numerical method is developed for the limit cycle flutter of the wing. The Roe scheme and dual time stepped method are adoptedin the spatial and time discretization of flow field, respectively. The Newmark method based on the finite element method is adopted in the structural transient response. The geometrical nonlinearity of the wing under the large deformation is also considered, and the implicit time marching scheme is used in theanalyses of flow field and structure.On the basis of the traditional loosely coupled method, the pseudoiteration is added in the tightly coupled method.When the pseudo-iteration converges, the physical iteration related to the real time step is sequentially analyzed, which can reduce the time lag effect caused by the frozen boundary conditions in the analysis of traditional loosely coupled method.The transonic limit cycle flutter of the cropped delta wing is also analyzed. The results show that the limit cycle flutter amplitude and the frequency of wing tip obtained by the tightly coupled method are better than the traditional loosely coupled method,closer to the test results.Therefore, the tightly coupled method can eliminate the accumulated errors inthe time marching and has a higher coupled time precision.

Keywordslimit cycle flutter； numerical method； tightly coupled method； geometrical nonlinearity； pseudoiteration

AnalysisofQuasi-zero-StiffnessVibrationIsolatorwithVariableLoad

KANGBingbing1,LIHaijun2,LINXuesen1,WANGJinglin3,DENGLi2
(1. Aviation Foundation Institute, Naval Aviation University Yantai, 264001, China)
(2. Coast Defense Army Institute, Naval Aviation University Yantai, 264001, China)
(3. Aviation Key Laboratory of Science and Technology on Fault Diagnosis
and Health Management Shanghai, 201601, China)

AbstractA quasi-zero-stiffness vibration isolator with a variable load is designed to make up for the weakened ability to isolate vibration caused by the changed load. First, the principle of the vibration isolator is discussed in terms of its static characteristics based on its mathematical model. Then, the main resonance response is analyzed by the averaging method including the amplitude-frequency characteristic function of relative displacement and the displacement transfer rate of vibration. Besides, the rules of vibration changing with the parameters are investigated. The results show that the vibration isolator adapts to load by changing the angle of the quasi-zero-stiffness spring when the resonance is weakened and the initial isolation frequency is reduced with increasing angle. The vibration isolator is also characterized by gradual hardening, which compresses the resonant frequency bandwidth and reduces the descending frequency so that the quasi-zero-stiffness isolator with variable load excels the normal one in the low-frequency isolation performance.

Keywordsquasi-zero-stiffness; vibration isolator; averaging method; variable load

AMulti-resonanceComponentFusionBasedConvolutionalNeuralNetwork
forFaultDiagnosisofPlanetaryGearboxes

TANGBaoping,XIONGXueyan,ZHAOMinghang,TANQian
(State Key Laboratory of Mechanical Transmission, Chongqing University Chongqing, 400044, China)

AbstractIn light of the aliasing of vibration signals, and the incipient fault features covered by stronger harmonic components at different levels and environmental noise, a fault diagnosis approach is proposed for planetary gearboxes using a multi-resonance component fusion-based convolutional neural network (MRCF-CNN). First, the vibration signal is decomposed using resonance-based signal sparse decomposition (RSSD) for the high resonance components containing the harmonic components of the gears and the low resonance components that may contain the impulse components of bearing faults. Then, a convolution neural network with multi-resonance component fusion is constructed from which the obtained high and low resonance components are adaptively fused with the original vibration signals at the feature level. Finally, the supervised model is trained to diagnose the faults of planetary gearboxes. The experimental result shows that the proposed method can classify failures of rolling bearings and gears in planetary gearboxes, diagnose the planetary gearbox failure, and enhance the ability of convolution neural networks to detect fault information from vibration signals.

Keywordsresonance-based signal sparse decomposition (RSSD); convolutional neural network (CNN); multi-resonance component fusion; planetary gearboxes; fault diagnosis

StiffnessPropertiesandTuningAnalysisfortheSmoothTypePneumatic
Quasi-zeroVibrationIsolator

CHENChun1,GAOXue2,TENGHandong2
(1. Eastern China Subsidiary of Sinopec Marketing Co., Ltd. Yangzhou, 225002, China)
(2.Aerospace Engineering College, Nanjing University of Aeronautics and Astronautics Nanjing, 210016, China)

AbstractLight of the mechanical equipment of heavy-duty and low dynamic frequency, the pneumatic quasi-zero stiffness nonlinear vibration isolation technique is proposed. The presented technique employs negative gas pressure to produce the static bearing capacity, and the low dynamic stiffness is provided by the elastic bellows structure. Hence, the given isolator possesses the high-static-and-low dynamic (HSLD) stiffness. First, the structure and the working principle of the smooth type isolation device is introduced. Then, the isolator′s nonlinear stiffness model is derived based on the gas state equation. Furthermore, the influence of physics parameters including gas proportion and gas pressure on the elastic restoring force is discussed. The results show that a proper gas proportion can tune the low dynamic stiffness of the isolator, and limit the maximum amplitude. Moreover, the effects of overloading acceleration on the inherent frequency of the isolation system are examined. It is found that overloading acceleration diverges the static equilibrium position away from its original point. As a result, the corresponding change of the natural frequency of the linearized system deteriorates the performance of vibration isolation which should be taken into consideration in engineering.

Keywordslow frequency; heavy duty; quasi-zero stiffness; nonlinear dynamics; overloading acceleration

ResearchonParameterIdentificationMethodofFriction
ModelforElectricLoadSimulator

LIChengcheng1,WANGGuanglin2,PANXudong2,LIYuefeng2
(1. School of Mechatronics Engineering, Lanzhou Jiaotong University Lanzhou, 730070, China)
(2. School of Mechatronics Engineering, Harbin Institute of Technology Harbin, 150001, China)

Abstractlight of operation affected by friction, parameter identification of a continuous differentiable friction model is introduced based on an improved cuckoo search algorithm (ICSA) to precisely control electric load simulators. First, the experimental prototype of an electric load simulator is set up, and the dynamic mathematical model is established in the way of a continuous friction model instead of the discontinuous common one. Second, the traditional CSA algorithm is improved by adjusting the values of the decision probability and the step size during the identification process, which accelerates the convergence speed and increases the accuracy. Then, the friction-velocity data with the speed range of [-1, 1] rad/s is obtained by the point-by-point experiment method, and six parameters of the friction model are identified using the ICSA. Finally, verification experiments are conducted. The results show that the six parameters of the friction model are identified correctly and quickly by ICSA. The convergence speed and accuracy are improved compared with that of the traditional CSA, and the value of the cost function ICSA algorithm is reduced by 45.2% when the number of iterations reaches the maximum value.

Keywordselectric load simulator(ELS); improved cuckoo search algorithm(ICSA); continuously friction model; parameter identification

StructuralDamageIdentificationUnderLoadBasedon
ElectromechanicalImpedanceCo-integration

JIEXiaoluo,XIAOLi,QUWenzhong
(Department of Engineering Mechanics, Wuhan University Wuhan, 430072, China)

AbstractThe high-frequency electromechanical impedance (EMI) method creates active motivation by piezoelectric transducers (PZT) affixed to the surface of the structure, and monitor the structure's health by continuous monitoring and analyzing changes of admittance signals of PZT. However, the EMI method is susceptible to environmental and operational variations, leading to false alarms of structural damage. In light of this problem, the impact of the structural workload on the electromechanical impedance signatures is eliminated by the time series co-integration method. This method is based on the non-stationary characteristics of the PZT impedance spectrum admittance signal under the dynamic load of the structure. The non-stationary time series of the impedance spectrum under the influence of the dynamic load is transformed into a stationary time series by linear combination and the health of the structure is determined according to the co-integration margin sequence. The experiments of loose bolt damage identification of aluminum beam structure under dynamic stress are carried out to verify the effectiveness of the proposed method. The results show that the method can isolate damage-sensitive features from stress variations to detect the existence of bolt loosening. The EMI co-integration method can eliminate the impact of load on structural health monitoring and time to identify structural damage.

Keywordsstructural health monitoring (SHM); electromechanical impedance (EMI); influence of load; co-integration; bolt loosening

ExperimentalStudyonControllingVibrationofPipeline
withIntegralSqueezeFilmDamper

DINGJichao,HELidong,JIPeiyao
(Beijing Key Laboratory of Health Monitoring and Self-Recovery for High End Mechanical Equipment,
Beijing University of Chemical Technology Beijing, 100029, China )

Abstractlight of the pipeline vibration, an integral squeeze film damper is designed and the rules of stiffness are analyzed. The damping effect is simulated with SAP2000 software. The integral squeeze film damper is installed on a two-dimensional gate-type pipeline vibration test bench to study the rules of vibration in the pipeline. The results show that the integral squeeze film damper performs best with a 51.83% decrease in amplitude when installed at the excitation source and being parallel to the plane of the excitation force, while the damper acts worst when installed at the excitation source and being vertical to the plane. Besides, two integral squeeze film dampers perform better than one does, and the damper installed at the excitation source excels the one away from the source in vibration attenuation.

Keywordsintegral squeeze film damper; damping vibration control; pipeline system; installation plan

DynamicModelandCharacteristicAnalysisofPre-compressedPiezoelectricBimorph

CHENHeng，CHENChao，LIUShixiang，CHENGGang
(State Key Laboratory of Mechanics and Control of Mechanical Structures,
Nanjing University of Aeronautics and Astronautics Nanjing, 210016, China)

AbstractThe dynamic model of the system is established based on the Hamilton principle where the bimorph is simplified into a 3-layer piezoelectric laminated beam according to the hypothesis of Euler beams. The analytical expressions of the output characteristics of the bimorph under different axial forces is derived from the solution of the partial differential equation and specific boundary conditions of the axial pre-compressed piezoelectric bimorph At the same time, the simulation is conducted to verify the correctness and gain the credibility of theoretical analysis. At last, the static and dynamic properties of bimorphs are studied experimentally. It is proved that the bending stiffness and natural frequency of the bimorph are reduced by the application of axial force. The electromechanical coupling efficiency is significantly increased and the output capability is improved. While the axial force affects the peak displacement of the bimorph at start-up, it has little effect on the response time and bandwidth. The bimorphs still have advantages over high bandwidth and fast response under large axial force.

Keywordsaxial pre-compression; Hamilton principle; dynamic model; piezoelectric bimorph； electromechanical coupling

UncertaintyModelUpdatingofFrequencyResponseFunctionBasedon
ApproximateLikelihoodFunction

DENGZhenhong1，ZHANGBaoqiang1，SUGuoqiang1，GUOQintao2
(1. School of Aerospace Engineering, Xiamen University Xiamen, 361005, China)
(2. College of Mechanical and Electrical Engineering, Nanjing University
of Aeronautics and Astronautics Nanjing, 210016, China)

AbstractAn uncertainty model updating method, which is targeted at frequency response function and using an approximate likelihood function, is proposed under the Bayesian framework. Compared with modal parameters, the frequency response function contains more structural information which offers advantages in finite element model updating of structural dynamics. However, the current uncertainty model updating methods rarely work well with a target of the frequency response function. In light of this problem, the uncertainty model updating theory under the Bayesian framework is introduced. An approximate likelihood function suitable based on the approximate Bayesian computational method is presented for the uncertainty model updating with e tfrequency response function. The proposed uncertainty model updating method is verified on a vibration system with three-degree-of-freedom and an unsymmetrical H-shaped beam. The DREAM algorithm is introduced to identify the parameters. The results show that the upper and lower bounds of updated parameters as well as the frequency response function of the updated model vary little from the desired values. The uncertainties are well updated under noise, which verifies the effectiveness of the proposed method.

Keywordsmodel updating; frequency response function; Bayesian; approximate likelihood function; uncertainty

ImprovedPCAAlgorithmandItsApplicationinRotorFeatureExtraction

LIWeiguang1,GUOMingjun1,YANGQijiang2,ZHAOXuezhi1,LIGuochen3
(1. School of Mechanical & Automotive Engineering, South China University of Technology Guangzhou, 510640, China)
(2. School of Marine Engineering, Guangzhou Maritime University Guangzhou, 510725, China)
(3. Training Center of Dongguan Polytechnic Dongguan, 523808, China)

AbstractThe traditional principal component analysis (PCA) method selects the primary components according to the prior knowledge. In light of this shortcoming, the covariance matrix eigenvalue difference spectrum is introduced to describe the differences between the primary and secondary components. First, a square relation between singular value and eigenvalue is discovered by theoretical deduction. Second, the principle of PCA signal processing with the Hankel matrix is further studied by difference spectrum theory. Finally, a PCA algorithm based on differential spectrum theory is proposed, and the effectiveness of the algorithm is verified by simulation. The results show that the number of active principal components can be selected automatically according to the maximum peak of the difference spectrum of the eigenvalues of the covariance matrix, and different frequency components can be extracted from the combination of the component signals between different spectral peaks. The PCA algorithm is used to purify the axis trajectory of the rotor of a large sliding bearing testbed and present better performance than that of the traditional PCA algorithm.

Keywordsprincipal component analysis； difference spectrum of eigenvalues； contribution rate； axis trajectory； feature extraction

AMulti-labelFaultClassificationMethodforRollingBearingBasedonLSTM-RNN

CHIYongwei1,YANGShixi1,JIAOWeidong2
(1. School of Mechanical Engineering, Zhejiang University Hangzhou, 310027,China)
(2. College of Engineering, Zhejiang Normal University Jinhua, 321004, China)

AbstractThe fault classification method based on long short-term memory recurrent neural network (LSTM-RNN) model is improved based on multiple labels in light of higher accuracy and less training samples when classify rolling bearing faults based on the traditional algorithm. First, a simulation model of rolling bearing fault signal is established, and the spectrum and classification of the rolling bearing fault simulation signal are analyzed. Second, the spectrum feature vectors of the rolling bearing are coded based on the structural characteristics of the multi-label LSTM-RNN model. The effectiveness of a multi-label classification method based on LSTM-RNN is verified by the simulated fault signal. Finally, a test platform is established to collect rolling bearing faults at three different speeds. The multi-label LSTM-RNN classification method and single-label method are compared based on nine groups of data extracted by three methods. The experimental results show that the average classification accuracy of multi-label LSTM-RNN classification increases to 99.21% from 69.07% of the single-label method. The sample size reduces by 69.55% compared with that of the single-label method when the correctness rates of the two classification methods are similar. The multi-label classification method based on LSTM-RNN is suitable for complex vibration signals, which is practically useful in realizing fast and accurate fault diagnosis of rotating machinery.

Keywordsrolling bearing; fault classification; multi-label classification; recurrent neural network (RNN); long short-term memory (LSTM)

HelicopterMainReducerAnti-vibrationIsolationTechnology

WANGZhiwei，WANGKe，DENGTing
(Institute of Vibration Engineering, Nanjing University of Aeronautics and Astronautics Nanjing, 210016, China)

AbstractAccording to the existing theory of main anti-resonant vibration isolation and active control, a new type of helicopter main vibration isolation prototype is designed. With the change of the operating frequency of the helicopter and the change of the frequency of the vibration isolation system, the mass position of the vibration isolator will be automatically adjusted, so that the system will always have the effect of vibration isolation. Taking the helicopter prototype as the object, using the neural network-based control method, the dynamic characteristics of the experimental object are calibrated to obtain the relationship between the position of the mass and the operating frequency. By studying the frequency tracking algorithm and the combination of the neural network and frequency tracking algorithm, a LabVIEW program that can acquire signals and identify frequencies is created. The experimental results show that the vibration isolation effect and control effect of the new main vibration isolation system are in line with expectations and can play a guiding role in the design of the active vibration control system for helicopters.

Keywordshelicopter main reducer； anti-resonancevibration isolation； semi-active control; neural network

Adaptive-PassiveMultipleTunedMassDamperonLarge-SpanFloorStructure

WANGLiangkun1,SHIWeixing1,ZHANGQuanwu2,ZHOUYing1
(1. Department of Disaster Mitigation for Structures, Tongji University Shanghai, 200092, China)
(2. Shanghai RB Vibration Science and Technology Co., Ltd. Shanghai, 200092, China)

AbstractMultiple tuned mass damper (MTMD) are often used to control the vertical vibration of large-span floor structures. In order to improve their shortcoming of highly sensitive to frequency deviation and difficult to retune frequency, an adaptive-passive multiple TMD (AP-MTMD) system is proposed. Each adaptive-passive TMD in the system has a variable mass and a servo control system, which consists of an acceleration sensor, a control circuit board and a drive device. Under environmental excitation, the control circuit board collects the acceleration signal from the main structure through frequency identification method based on wavelet transformation (WT) to identify the structural first order frequency, and then starts the drive to change the quality of TMD to retune it to the primary structural frequency. A long-span floor structure is proposed as an example. By field measurement, the finite element model is updated, and then according to the original finite element model, an AP-MTMD system is designed, and the robustness of frequency adaptive adjustment is verified. Finally, by applying several pedestrian loads, vibration control effects of MTMD system before and after the adaptive adjustment on the updated model are compared. The results show that the AP-MTMD can automatically retune its frequency and improve the vibration control effect to the floor structure.

Keywordsfloor structure; adaptive-passive multiple tuned mass damper; wavelet transformation; in-situ test; response

CharacteristicFrequencyofExternallySqueezeOilWhirlof
ElasticSupportonTurbo-ShaftEngine

LINXuesen1,LIBenwei2,WANGJinglin3,ZHANGYun2,KANGBingbing2
(1. Naval Research Academy Beijing, 100161, China)
(2. Aeronautical Foundation Institute, Naval Aviation University Yantai, 264001, China)
(3. Aviation Key Laboratory of Science and Technology on Fault Diagnosis and Health Management Shanghai, 201601, China)

AbstractIn view of the fact that the frequency spectrum components of a turbo-shaft engine are numerous and unclear for vibration source or modulation, when it tested on test bed, the vibration data is filtered by empirical mode decomposition (EMD). It is found that the low-frequency component contains more significant information from the original data. After further multi-sensor and multi-state measurement and time-frequency analysis, it is demonstrated that the frequency component is the subsynchronous frequency of the gas generator combined with the rotor, and the ratio between them is 0.443. Finally, through the elimination method and the oil interruption of the whole engine, it is determined that this component is the characteristic frequency of the externally squeeze oil whirl of front elastic support on the gas generator combined withthe rotor.

Keywordsturbo-shaft engine; squeeze film damper(SFD); oil whirl; characteristic frequency

DevelopmentofFiveChannelsTesterDetectingFerromagneticObjects
andBlockageDetectiononBoilerTubes

WANGXirun1,2,ZHANGShuangnan1,CAIGuixi1,LIJiankui1,ZHANGBo1,
YANGLiang1,WUYupeng1,2
(1. Institute of Metal Research, Chinese Academy of Sciences Shenyang,110016, China)
(2.College of Materials Science and Engineering, University of Science and Technology of China Hefei, 230026, China)

AbstractThe development and applications of the tester detecting ferromagnetic objects is described. The tester can be used to detect and evaluate quantitatively blockages by rust in superheater tubes and reheater tubes so as to avoid explosion of the tubes. By using the magnetic measurement method,five points where blockage detection will be made are set on tube surface along a circumference. Simulations by finite element method and calculation of calibration curves are conducted. The results of calculation are verified by experiments. Comparing with the calculated values, the standard error of the measured values, which is named as the relative error, is 5.2%. The standard error of the field-measured proportion of blocked area in the tube to the area of the cross section of the tube bore is 3.9%, compared with that measured by X-ray photography, which is named as absolute error. Blockage detections on tubes have been implemented for the five power plants. More than 30 blockages the area percentage of which is more than 30% have been found. Cutting the tubes and removing the blockages out of the tubes indicates that no false report of blockage have happened. It is concluded that blockage detection on the tube using the tester is effective for prevention of the tube from explosion accident.

Keywordstester detecting ferromagnetic objects; superheater tube; reheater tube; detection of blockage by rust fragments

OilIntelligentAnalysisandHealthMonitoringofRotaryDrillingRigEquipment

RENSong,XUXueru,OUYANGXun,WANGXiaoshu
(State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University Chongqing,400030,China)

AbstractIn order to improve the extraction efficiency of the oil information related to the running status of the equipment, a new analytical technique called oil filtergraphy technology is proposed in this paper. A further discuss is made of its main content, implementation process and engineering significance. Firstly, the filtergram is prepared based on the filtergraphy, then the image segmentation technology, automatic counting algorithm and fuzzy support vector machine are used to realize the automation of analysis process. The intelligent extraction of oil information is completed and the key information reflecting the running state of the equipment is obtained at the same time. Applying the technology to the condition monitoring of rotary drilling rig equipment, the lubricant state and wear condition for the current stage are assessed after analyzing the suspended particles from hydraulic oil and gear oil. According to the results of qualitative and quantitative analysis, some useful guidance is provided for its repair and maintenance. It is indicated that oil filtergraphy technology can extract the complete information contained in the oil to reflect the running status of the equipment. It has the advantage of high detection efficient and abundant analysis content, and can be extended to other equipment for oil monitoring and fault diagnosis.

Keywordsfiltergraphy technology; rotary drilling rig; image segmentation; automatic counting algorithm; fuzzy support vector machine; condition monitoring

ExperimentalStudyonDampingCharacteristicsofBetaDampingLine
forLargeSpanTransmissionLines

WANGFeng1，HUANGYucheng2，CHENChi1，BAIXiaolu2，DUANHongbo1
(1. Hubei Key Laboratory of Disaster Prevention and Mitigation, China Three Gorges University Yichang, 443002, China)
(2. Central Southern China Electric Power Design Institute Co., Ltd. Wuhan, 430071, China)

AbstractIt is a key issue to accurately grasping the vibration damping characteristics of Beta damping lines in the design of anti-vibration of long-span transmission lines. Based on the characteristics of aeolian vibration of damping line, the calculation formula of resonance frequency and lace length of Beta damping line is derived, and the reasonable range of lace length of damping line is analyzed. Combined with IEEE vibration test guide for transmission line, the test model of vibration damping characteristics of Beta damping line for long-span transmission line is designed and made. The influence of the length and the quantity of lace and the sag of lace on the aeolian vibration of long span transmission line is studied. The results show that the lace length of Beta damping line is closely related to the resonance frequency, mass and bending rigidity of materials, and the lace length should not be too long; the lace length of damping line has a great influence on the aeolian vibration of transmission line. The lace length is different, the vibration attenuation effect is also different under different excitation frequency, and the damping line with multiple lace combination has a wider anti-vibration frequency band and anti-vibration effect than that with single lace damping line. The influence of lace sag of Beta damping line on the aeolian vibration of transmission line is small.

Keywordslarge span transmission line； Beta damping line； vibration damping test； lace length； resonant frequency

Near-FaultVelocityPulseMotionsonSeismicResponsesoftheRCFrame

ZHANGYing1，2，SUNGuangjun2，LIHongjing2
(1. Hua Tian Engineering and Technology Corporation, MCC Nanjing，210019, China)
(2. College of Civil Engineering, Nanjing University of Technology Nanjing, 211816, China)

AbstractA behavior analysis on reinforced concrete frame structures under near-fault velocity-pulse ground motions is numerically performed by using simulation software and finite element method (FEM). Firstly, three frame models are established considering the effects of different heights by PKPM software. Then, the FEM, together with the plastic hinge model, is applied to simulate numerically the whole process of dynamic responses on the structures suffered with near-fault motions, and the effects of velocity pulse and non-pulse motions are compared. Finally, the damaging factors of the velocity pulse are demonstrated. The results show that the structural damage degree is related to the high-frequencies and the peak ground accelerations of velocity pulse motions. Moreover, when seismic responses of structures step into the plastic stage, the structural responses to the ground motion with velocity pulse are increased by considerable magnitudes compared to the motions without velocity pulses.

Keywordsnear-fault; velocity pulse; frame structure; seismic response; high-frequency