RobustLongitudinalVibrationSuppressionofSteelWireRopeofFrictionHoist

ZHUZhencai,SHENGang,DINGXingya,TANGYu,LIXiang

(School of Mechatronic Engineering, China University of Mining and Technology Xuzhou, 221116, China)

AbstractUnder high-speed and heavy-load operating conditions, the vibration of wire rope inevitably occurs due to the error of the wire rope itself and external interference, which greatly affect the service life of the wire rope and the comfort of passengers. In this paper, a friction hoist is taken as the research object, Hamilton principle is used to establish the dynamic model of the system, and adaptive robust theory is used to design the boundary control strategy of the longitudinal vibration suppression of the hoisting wire rope, and Lyapunov theory is used to prove the stability of designed controller. The simulation results show that the designed adaptive robust controller can effectively compensate the vibration displacement shift caused by the elastic deformation of the wire rope, and obtain a faster convergence rate of vibration suppression than traditional proportion integration differentiation (PID) algorithm.

Keywordsfriction hoist; Hamilton principle; longitudinal vibration; adaptive robust; vibration suppression

FractalWearModelofContactMechanicalSeal

LIXiaopeng,YANGZemin,PANWujiu,WANGLinlin,XUJinchi,WENBangchun

(School of Mechanical Engineering & Automation, Northeastern University Shenyang, 110819, China)

AbstractBased on fractal theory, the contact between the surface of dynamic and static rings is simplified as the one between a rough surface and an ideal rigid plane. The characterization methods of surface topography of the contact mechanical seal is discussed, and then the contact mechanical seal wear model is established. Finally, the effects of fractal parameters, the material parameters and the working parameters on the established model are analyzed to obtain some results as follows. The relationship between the fractal dimensionDand the wear rateγof the contact mechanical seal is bathtub shaped. The characteristic length scale parameterGis directly proportional to the wear rateγ. The unit loadpgis directly proportional to the wear rateγ. The comprehensive elastic modulusEof the contact mechanical seal is inversely proportional to the wear rateγ. The rotation rate ofnis directly proportional to the wear rate of contact mechanical seal. Moreover, the model data are compared with the experimental data.

Keywordsfractal theory; contact mechanical seal; surface topography; wear

ExperimentalStudyonAerodynamicCharacteristicsofTwoTandemSquareCylindersinDifferentArrangements

DUXiaoqing1, 2,CHENRuyi1,XUHanlin1,MAWenyong3

(1.Department of Civil Engineering, Shanghai University Shanghai, 200444, China)

(2.Wind Engineering and Aerodynamic Flow Control Research Center, Shanghai University Shanghai, 200444, China)

(3.Wind Engineering Research Center, Shijiazhuang Tiedao University Shijiazhuang, 050043, China)

AbstractWind tunnel tests are conducted to investigate aerodynamic characteristics of two tandem square cylinders in horizontal and diagonal arrangements at a Reynolds number ofRe= 8.0×104and spacing ratios ofP/B= 1.75 ～ 5.00, wherePis the center-to-center spacing of the two cylinders andBis the width of the square cylinder. The surface pressure distributions on cylinders in two arrangements are obtained. Efforts are mainly devoted to the aerodynamic characteristics of two diagonal tandem cylinders, and the comparison with those of the two horizontal tandem cylinders. The results show that the mean drag coefficients on the downstream cylinder for the horizontal arrangement discontinuously vary from a negative value to a positive one when the spacing ratio increasing from 3.00 to 3.50, while the mean drag coefficients for the diagonal arrangement remain negative in all spacing investigated. ForP/B< 3.00, the mean and fluctuating aerodynamic forces, the maximum of mean negative pressures and the fluctuating pressures of two diagonal tandem cylinders are generally larger than those for the horizontal tandem cylinders, whereas the scenarios are completely contrary forP/B> 3.00. Furthermore, the Strouhal numbers of the diagonal cylinders are significantly smaller than those of the horizontal ones at the same spacing. It is interesting to note that there are multiple peaks in the lift power spectra for the diagonal cylinders forP/B< 3.00.

Keywordstwo tandem square cylinders; wind tunnel test; horizontal arrangement; diagonal arrangement; aerodynamic characteristics

DieselEngineFaultDiagnosisMethodBasedonOptimizedVariationalModeDecompositionandKernelFuzzyC-meansClustering

BIFengrong1，TANGDaijie1，ZHANGLipeng2，LIXin1，MATeng1，YANGXiao1

(1.The State Key Laboratory of Engines, Tianjin University Tianjin, 300072, China)

(2.Tianjin Internal Combustion Engine Research Institute Tianjin, 300072, China)

AbstractTo solve the diesel engine fault diagnosis problem, a fault diagnosis method based on the combination of variational mode decomposition (VMD) and kernel fuzzy C-means clustering (KFCM) is proposed. This paper optimizes the selection of decomposition levelKin VMD algorithm, and proposes an adaptive choosing method forK. Then, three key components are selected from the decomposition results of the optimized VMD algorithm to calculate the maximum singular values, which are input into the KFCM algorithm as three-dimensional eigenvectors for classification and recognition. The optimized VMD method，VMD method and empirical mode decomposition (EMD) method are used to decompose and recognize the simulated signal and the experimental data of a diesel engine. The results show that the proposed method obviously improves the accuracy of pattern recognition. The joint algorithm proposed in this paper has better application prospects.

Keywordsdiesel engine；vibration signal；fault diagnosis；variational mode decomposition (VMD)；kernel fuzzy C-means clustering (KFCM)

OperatingFrequencyofFreePistonStirlingEngine

MOUJian1,LINMingqiang1,2,CHIChunyun1,2,HONGGuotong1,2，CHENHoulei1

(1.Key Laboratory of Space Energy Conversion Technology, Chinese Academy of Sciences Beijing, 100190, China)

(2.University of Chinese Academy of Sciences Beijing, 100049, China)

AbstractThe operating frequency is key to free piston Stirling engine. The free piston Stirling engine is different from the traditional crank link Stirling engine, that the frequency is decided by the dynamic parameter and thermodynamic parameter, such as charge pressure, moving mass, stiffness of spring, damped coefficient. So, it is not easy to calculate the operating frequency of free piston Stirling engine. In this paper a model that includes dynamic and thermodynamic methods is used to study the characteristics of frequency. The pressure is lineared to get the computational formula of frequency. The influence of main parameters to frequency is studied through the model, and the model is validated byrelative experiments. At last, the reason why the frequency is unable to increase by enhancing the stiffness of spring is analyzed. The natural frequency of spring has a big effect on the operating frequency of engine. To increase the operating frequency of engine, a new spring is designed to increase it from 35 Hz to 60 Hz.

Keywordsfree piston Stirling engine; operating frequency; linearization; dynamic model

NewIdentificationMethodforNonlinearTime-VaryingSystemBasedonSubsystem

CHENTengfei1,HEHuan1,HECheng2，CHENGuoping1

(1.State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics Nanjing, 210016, China)

(2.Key Laboratory of Unmanned Aerial Vehicle Technology, Nanjing University of Aeronautics and Astronautics Nanjing, 210016, China)

AbstractIn this paper, a new identification method for nonlinear time-varying system based on subsystem is proposed. This new method can be used to locate and estimate the nonlinear characteristics of the multi-degree-of-freedom (MDOF) dynamic system without a priori knowledge regarding the system. A MDOF system can be partitioned into a number of different subsystems with a continuous-time model provided by the new method. All the information about the masses and linear or nonlinear connections in the subsystems can be determined with an orthogonality algorithm and an error reduction ratio (ERR) calculation. In this identification process, the time expressions of the time-varying parameters are also given. This new method is demonstrated by a 3 DOF lumped mass system and a mechanical arm structure. This new proposed identification method has a wide application prospect in practical engineering for its simplicity and efficiency.

Keywordsnonlinear time-varying system; parameter identification; subsystem；orthogonal-triangular decomposition； error reduction ratio (ERR) calculation

TensionMeasurementofArchBridgeSuspenderConsideringEnvironmentalTemperatureandOtherFactorsInfluence

HERong1,YANPengpeng1,HEWei1,CHENHuai2

(1.School of Civil Engineering and Communication, North China University of Water Resources and Electric Power Zhengzhou, 450045, China)

(2.School of Civil Engineering, Zhengzhou University Zhengzhou, 450001, China)

AbstractBased on the Euler-Bernoulli beam theory, analytical expressions for tension and vibration frequencies of hangers are established by considering the effects of bending stiffness, length, damping pad, additional mass, elastic support, adhesive sheath and environmental temperature. Firstly, a boundary influence coefficient method is put forward to. The boundary influence coefficients are calculated under different boundary conditions and a practical expression of suspender tension under boundary influence is given. Secondly, taking the Liujiang Yellow River Bridge as an example to verify. Finally, the results show that during the construction period, the maximum error of the long hanger is 1.10% and the middle and short hanger is no more than 1.12%, when the tension expression of the suspender is established under the influence of various factors is adopted; the maximum relative error of the hanger tension is no more than 2.38% when the suspender tension is calculated by the boundary influence practical expression. During the operation period, considering the influence of temperature, the computation accuracy under complex boundary conditions is increased by 11.39% and the accuracy of the calculation is improved by 11.38% using practical expression. The expression established by the boundary influence coefficient method is not only high accuracy, but also is an explicit form, which is convenient for engineering applications.

Keywordsarch bridge; suspender; tension; frequency; influence coefficient of boundary condition

OscillationPerformanceandPropulsionMechanismsofBiomimeticUnderwaterPropellerActuatedbyMacroFiberComposites(MFC)

LINHuangxu1,RENXiaorong1,LOUJunqiang1, 2,JIAZhen1

(1.Faculty of Mechanical Engineering and Mechanics, Ningbo University Ningbo, 315211, China)

(2.State Key Laboratory of Industrial Control Technology, Zhejiang University Hangzhou, 310027, China)

AbstractFiber-based piezoelectric composites offer the advantages of excellent flexibility and geometric scalability in the applications of bio-inspired locomotion and flexible actuation. A biomimetic underwater propeller mimicking the body or caudal fin (BCF) oscillating behavior of carangidae fish is proposed, and macro fiber composites (MFC) are used as actuators. Oscillation performance of the propeller is presented at different actuation voltage levels. Experimental results show that the maximum oscillating displacement of the proposed propeller in air is 45 mm (peak-to-peak value), with the actuation of 1 000 V (peak-to-peak value) at 17.7 Hz. The distributions of flow field and vortexes around the propeller tip in a steady oscillating cycle are obtained by the use of computational fluid dynamics (CFD) technologies. The anti-Karman vortex street phenomenon is revealed during the time sequence of vortices generation, expand, shed and breakdown processes. Meanwhile, a jet flow ejecting downstream the tip between the two counter-rotating vortices is observed. Accordingly, the propulsion locomotion of the propeller is achieved with the reactive force of the jet flow. Thus, the propulsion mechanism of the proposed biomimetic underwater propeller is demonstrated. The average propulsion force at the end of the propeller in thexdirection is up to 1.5 mN.

Keywordsbiomimetic underwater propeller; macro fiber composites (MFC); body or caudal fin (BCF) oscillating propulsion; computational fluid dynamics(CFD) analysis; anti-Karman vortex street

DynamicCharacteristicsofCantileverSelf-tuningVibrationAbsorberwithVariableStiffness

CAORuizhi,SHAOMinqiang,CHENWeidong

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

AbstractA new type of cantilever self-tuning vibration absorber with variable stiffness driven by piezoelectric material is designed, which is based on the principle that the natural frequency of the cantilever structure varies under different axial forces. The progressive optimization and genetic control algorithms are used to adjust the natural vibration frequency of the absorber in real time, and the dynamic simulation analysis is combined with the actual controlled system. Finally, the dynamic properties of the vibration absorber is further evaluated installed on wind tunnel aerodynamic models based on the effective vibration suppression of simulation analysis. The results show that the absorber can effectively attenuate vibration in a wide frequency range, and the highest damping effect reaches more than 40 dB, that has a better kinetic performance than other types of vibration controllers.

Keywordsself-tuning vibration absorber; vibration control; genetic algorithm; progressive optimization algorithm

ReinforcementLearningLongandShortTimeMemoryNeuralNetworkforStatePrediction

LIFeng1, 2, 3,CHENYong1,TANGBaoping2,WANGJiaxu2, 3

(1.School of Mechanical Engineering, Sichuan University Chengdu, 610065, China)

(2.The State Key Laboratory of Mechanical Transmissions, Chongqing University Chongqing, 400044, China)

(3.School of Aeronautics and Astronautics, Sichuan University Chengdu, 610065, China)

AbstractA new method for predicting the degradation of rotating machinery is proposed based on the reinforcement learning 3-state combined long and short time memory neural network (RL-3S-LSTMNN). The degradation of a rotating machinery is divided into three monotonic parts, naming stationary unit, descending unit and ascending unit, by a monotone trend discriminator based on the least square linear regression method. Moreover, by virtue of reinforcement learning, the proposed method select LSTMNNs with the number of hidden layers and hidden layer nodes number suitable for each monotone trend unit, which improves the generalization performance and nonlinear approximation ability of RL-3S-LSTMNN to obtain a higher prediction accuracy. Besides, different hidden layer and node numbers and three monotonic trend units represent the action and status of the Q table, and the output error of LSTMNN is associated with the update of the Q table to avoid the blind search of agent (i.e., decision function) and accelerate the convergence rate of RL-3S-LSTMNN. Accordingly, the higher computational efficiency can be obtained for the proposed prediction method. A state degradation trend prediction of rolling bearing demonstrates the effectiveness of the proposed method.

Keywordsreinforcement learning; long and short time memory neural network; singular spectral entropy; trend prediction; rotating machinery

CharacteristicsofInductionMotorCurrentSignatureforCentrifugalPumpLoad

GONGBo,YUANShouqi,LUOYin,HANYuejiang,DONGJian

(National Research Center of Pumps, Jiangsu University Zhenjiang, 212013, China)

AbstractChanges in the operating conditions of the centrifugal pump cause fluctuations in the hydraulic load torque, which stimulates current in the motor stator when transmitted to the motor through the rotor shaft system. In light of the relationship between the operating conditions of the centrifugal pump and the stator current of the motor, the hydraulic load torque characteristics of the centrifugal pump under different operating conditions are analyzed through numerical simulation. The hydraulic moment changes periodically, its mean value increases with the increase of the flow rate, and the root mean square of the hydraulic moment pulsation intensity increases as the operating conditions deviate from the design conditions. Furthermore, theoretical analysis shows that the characteristics of torque are reflected in the motor stator current by power frequency modulation. Finally, the motor stator current is measured through experiments, the root mean square of the stator current is calculated, and the power frequency signal of the power grid is eliminated by the singular value decomposition method to realize the extraction of current characteristics for centrifugal pump running state. The results show that the root mean square of the stator current is consistent with the root mean square of the hydraulic load torque. The calculation of total harmonic distortion (THD) shows that it tends to increase as the operating conditions of the centrifugal pump deviate from the design conditions.

Keywordscentrifugal pump; hydraulic torque; stator current; singular value decomposition; total harmonic distortion

EngineFaultsDetectionBasedonOptimizedVMDandEuclideanDistance

ZHANGHailong1, 2,SONGYedong1, 2,LIXin3,BIFengrong3,BIXiaobo3,TANGDaijie3,YANGXiao3,MATeng3

(1.State Key Laboratory of Engine Reliability, Weichai Weifang, 261061, China)

(2.Weichai Power Co. Ltd. Engine Research Institute Weifang, 261061, China)

(3.State Key Laboratory of Engines, Tianjin University Tianjin, 300072, China)

AbstractIn light of the problem to distinguish multiple engine faults through the same method using a single channel signal, the existing algorithms are optimized to extract fault characteristics from vibration signals. First, in view of the difficulty in selecting the decomposition level of the variational mode decomposition (VMD) decomposition levels selection, the initial value of the center frequency iteration is optimized based on the frequency characteristics of several different types of faults, which improves calculation efficiency and convenience while ensuring accuracy. Then, the robust independent component analysis (Robust ICA) is introduced to analyze different signal sources in the same frequency. The fourth-order cumulant of the restructured signals from VMD and Robust ICA is taken as failure indexes. Finally, the cluster center determined by fuzzy C-means clustering is used as the reference point. The Euclidean distance between each test points and the center is used to distinguish fault types. The results show that this method achieves high recognition rate.

Keywordsdiesel engine; fault diagnosis; vibration signal; variation mode decomposition; signal processing

DesignandApplicationofStrainDecoupledandSensitizedFBGTemperatureSensor

LIWuyi1,YANChuliang2,LIULihong1

(1.Institute of Aeronautics and Astronautics，Nanjing University of Aeronautics and Astronautics Nanjing, 210016, China)

(2.China National Machinery Industry Corporation Beijing, 100083, China)

AbstractIn order to measure the temperature parameters accurately in the flight test of aircraft load spectrum, a strain decoupled and sensitizing fiber Bragg grating (FBG) temperature sensor is designed. The new structure sensor is designed through mechanical modeling analysis, the sensor's FBG is sensitized, and aluminum 7075-T6 is selected as the substrate for full-coverage packaging. The indirect contact between the packaging position of FBG and the structure part is proposed to eliminate the influence of structural deformation on the temperature sensor. The temperature sensitive speed of the calibrated test sensor is 40.4 pm /℃, which is 4 times that of the ordinary fiber grating. Then, the test system is built to explore the performance and the decoupling characteristics are verified on the tensile testing machine. The deformation of the tensile test piece has no influence on the temperature sensor, which is consistent with the theoretical analysis. Finally, sensors are attached to the aircraft cockpit for practical engineering applications. The experimental results show that the maximum temperature difference measured by the sensors is no more than ±1 ℃, which meets the requirements for accurate measurement of temperature parameters in the actual flight test of the aircraft load spectrums and allows the sensor to be used for actual temperature measurement.

Keywordsflight test; strain decoupled; sensitized; fiber Bragg grating; temperature sensor

PerformanceofVehicleSuspensionBasedonHydraulicPistonInertialContainer

YANGXiaofeng,ZHAOWentao,LIUYanling,SHENYujie,YANLong

(School of Automotive and Traffic Engineering, Jiangsu University Zhenjiang, 212013, China)

AbstractThe basic structure, working principle and the characteristics of large bearing capacity of hydraulic piston type inertial container are expounded, and the nonlinear mechanical model of an inertial container is established considering friction force, parasitic damping and oil elasticity effect. The mechanical performance test of the hydraulic piston inertial container is carried out on the numerical control hydraulic servo vibration table. Then, based on the test results, the parameters in the nonlinear mechanical model are identified by MATLAB parameter identification toolbox. Finally, a dynamic model of the vehicle inertial-container-spring-damper (ISD) suspension including the identified nonlinear factors is established and simulated. The results show that the root-mean-square value of the vehicle body acceleration of the vehicle ISD suspension system increases by 5%, while the root-mean-square value of the dynamic tire load and suspension working space slightly decreases, which reduces the driving comfort of the vehicle.

Keywordshydraulic piston inertial container; nonlinearity; parameter identification; ride comfort

AdaptiveCompressedSensingofMechanicalVibrationSignalsBasedonSparsityFitting

YANGZhengli,SHIWen,CHENHaixia

(School of Mechanical and Electrical Engineering，Sanjiang University Nanjing，210012，China)

AbstractThe fault diagnosis and state monitoring of the mechanical vibration signal often struggle with large amount of sampled data, large storage capacity, high transmission bandwidth and low signal reconstruction accuracy. In light of this problem, an adaptive compressed sensing of mechanical vibration signals based on sparsity fitting method is proposed. First, the multi-scale wavelet packet transform is carried out on the mechanical vibration signal, and its sparsity is obtained by zeroing the wavelet packet coefficient at a certain threshold value. Then, the iterative method is adopted to obtain the minimum sampling rate that meets the requirements of reconstruction signal accuracy under each sparsity degree, and the sparsity degree and sampling rate are fitted with the least square method to eliminate the signal measurement error for an optimal signal sampling rate. Finally, an over-complete dictionary adapted to each signal block is constructed by K-singular value decomposition algorithm, and the signals are reconstructed by orthogonal matching pursuit algorithm. Experiments show that the signal compression rate and reconstruction accuracy of this algorithm are greatly improved compared with the traditional compression algorithm.

Keywordsmechanical vibration signals; adaptive compressed sensing; wavelet packet transform; sparsity fitting; super-complete dictionary

AbnormalNoiseofCompressor-SupportSystem

SHANGGuoxu1,2，SHIWenku1，CHENZhiyong1，LIUGuozheng1，LIXiaoyan3，YANGJiahong3

(1.State Key Laboratory of Automotive Stimulation and Control, Jilin University Changchun, 130022, China)

(2.Dongfeng Nissan Passenger Vehicle Technical Center, Dong Feng Motor Co., Ltd. Guangzhou, 510800, China)

(3.Technical Department, Mudanjiang Futon Automotive Air Conditioning Co., Ltd. Mudanjiang, 157000, China)

AbstractIn light of the abnormal noise in the cab generated by the air conditioning (AC) compressor when the engine speed is 1 573 r/min, a prototype car is tested, analyzed and diagnosed. The analysis and diagnosis of the car and its compressor-support system are carried out, and the improvement scheme is verified in order to solve. The LMS instruments are applied to collect the vibration and noise signals. The spectrum analysis and order tracking diagram are obtained by test. The results of data analysis and modal simulation show that the twenty-first harmonic frequency of compressor shaft is close to the third-order modal frequency of compressor-support system, which leads to the abnormal noise in the cab. The third-order modal frequency is increased by optimizing the support structure, and the input torque fluctuation of the compressor is mitigated by replacing the rubber drive plate. The improved structure is tested and the results indicate that the internal noise is reduced by 2.5 dB(A) when the AC is turned on at a constant speed. In uniform acceleration conditions, the peak internal noise is eliminated when the AC turned on during an engine speed between 1 500 r/min to 1 650 r/min . Under the engine speed is outside the range, the internal noise rarely changes, and the internal noise fluctuates smoothly.

Keywordsautomobile; air conditioning compressor; noise; test analysis and diagnosis; rubber drive plate

DynamicAnalysisoftheRotorSystemoftheCuttingHeadoftheRoadheaderUnderTwoLoads

HUANGZhilong1,2,SONGGuiqiu1,ZHANGZhongchao1,FUJiaxing3

(1.School of Mechanical Engineering & Automation, Northeastern University Shenyang, 110819, China)

(2.School of Mechanical and Electrical Engineering, Shaoxing University Shaoxing, 312000, China)

(3.Tiandi Science and Technology Company Ltd. Beijing, 100013, China)

Abstractn light of the dynamic characteristics of the cutting head and cantilever system of the roadheader under different pick loads (sharp picks and blunt picks), the bending-torsional coupling nonlinear dynamic model of the cutting head-rotor-bearing system of the roadheader is established. Considering the spline meshing clearance between the cutting head and the rotating shaft, and the nonlinear factor of the rolling bearing contact, the dynamic differential equations of the cutting head rotor system of the roadheader are derived. Then, the dynamic response characteristics of the cutting head rotor system under time-varying load are analyzed. The results show that under the condition of sharp picking, the cutting head rotor system is in chaotic and quasi-periodic motion state at low speed between 15 and 20, and the system is in periodic motion after the speed is increased. While the picks are blunt, the vibration of the cutting head rotor system is obviously aggravated, the chaotic motion range is increased, and the frequency amplitude fluctuates significantly. The system changes from chaotic motion to periodic motion with the increase of cutting speed at the given premise of cutting coal seam hardness and cutting thickness. The dynamic analysis results provide a theoretical basis for the vibration reduction and dynamic design of the roadheader.

Keywordscutting head rotor system; bending-torsional coupling; spline meshing clearance; blunt picks; nonlinear vibrations

PredictionoftheInstantaneousMillingForceofBallEndMillingCutterforConvexSurfaceofSplicingMold

WUShi,ZHANGTianyuan,LIUXianli,LIUHairui,YANGLin

(Key Laboratory of Advanced Manufacturing and Intelligent Technology, Ministry of Educatio,Harbin University of Science and Technology Harbin, 150080, China)

AbstractDuring the milling of the ball-end milling cutter in the splicing area of the curved surface mold, the tool load changes greatly, and the transient milling force has a sudden change, which affects the machining accuracy and surface quality of the splicing area of the mold. In light of the prediction of its transient milling force in the splicing area, a transient undeformed chip thickness model is established based on a three-dimensional trochoid trajectory equation of the ball-end milling cutter considering impact vibration. Then, based on the idea of milling microelement, the transient milling force model for ball-end milling cutter of the convex curved surface and double hardness stitching mold is established. The model comprehensively considers the influence of impact vibration, the change of hardness and contact angle of the tool workpiece in the splicing area on the transient milling force. Finally, the milling experiments of ball-end milling cutter in the splicing area of convex surface is carried out. The results show that the predicted transient milling force and experimental measurements are consistent in magnitude and trend. The maximum milling force prediction error value is less than 15% during steady cutting. The experimental results verify that the model can effectively predict the transient milling force of the ball-end milling cutter in the splicing area of the convex surface of the splicing mold.

Keywordssplicing mold; ball end milling; impact vibration; three-dimensional trochoid；milling force prediction

InstantaneousFrequencyIdentificationofaStructureUsingVariationalModeDecompositionandGeneralizedMorseWavelets

WANGChao1,MAOLing2

(1.School of Civil Architecture and Environment, Hubei University of Technology Wuhan，430034, China)

(2.School of Civil Engineering and Architecture, Wuhan University of Technology Wuhan，430070, China)

AbstractCivil engineer usual appear time-varying characteristic, it is very important to identify instantaneous frequency for structural health monitoring and safety evaluation. A method about instantaneous frequency identification of a structure based on variational mode decomposition (VMD) and generalized morse wavelets (GMW) is proposed. Firstly, fast iterative shrinkage-thresholding algorithm is used to reduce noise, which utilize the sparse feature of signal by transforming to wavelet region. And then, an identification theory of time-varying parameter based on VMD and GMW is presented. A numerical stimulation is used to validate the effectiveness of the method. Finally, an experiment model of moving vehicle across a beam is built. The modal test is proceed and the finite element model is calibrated. The measured stain data is used to estimate the position of vehicle on beam at any time, and the accelerate response is used to identify the instantaneous frequency by proposed method. The results show that the proposed method has good validation and accuracy to identify the instantaneous frequencies.

Keywordstime-varying structure; instantaneous frequency; wavelet transform; generalized Morse wavelets; fast iterative shrinkage-thresholding algorithm; variational mode decomposition

ShockResistanceofVibrationIsolationSystemwithHydraulicDisplacement

WANGPeng1，YANMing1，ZHANGChunhui2，LIUHaichao1

(1.School of Mechanical Engineering, Shenyang University of Technology Shenyang, 110870, China)

(2.Naval Research Institute Beijing, 100161, China)

AbstractThe maximum relative displacement of shipboard equipment can be effectively limited when a limiter is installed in vibration isolation system. However, traditional rubber limiter is liable to produce serious secondary shock on the system. Firstly, the mathematical model of hydraulic limiter is established and the shock response characteristics are simulated and analyzed by Duhamei integral method. Secondly, the test devices of vibration isolation system with hydraulic limiter are designed and the effects on shock resistance with different limiter parameters are studied by the actual shock test. Finally, the shock response characteristics of vibration isolation system with both hydraulic and rubber limiter are compared and analyzed. The results show that: compared with non-limiter vibration isolation system, the hydraulic limiter can reduce the maximum relative displacement response by 60%; there is an optimum throttle aperture, which can make the system obtain the optimum vibration isolation effect; compared with rubber limiter vibration isolation system, the hydraulic limiter can reduce acceleration response by 44.5% when the relative displacement response is approximate equal. Therefore, hydraulic limiter can substantially improve the shock resistance of shipboard equipment.

Keywordshydraulic displacement limiter; vibration isolation system; shock resistance; throttle orifice; shipborne equipment

FuzzyFaultTreeAnalysisofUnderwaterPMTExplosionProtectionExperimentSystem

TANRunze1,LIXiaobin1,DUZhipeng2,HEMiao3,YUEJingxia1

(1.School of Transportation, Wuhan University of Technology Wuhan, 430063, China)

(2.Naval Academy of Armament Beijing, 102401, China)

(3.Institute of High Energy Physics, Chinese Academy of Sciences Beijing, 100049, China)

AbstractTo estimate the failure probability of the photomultiplier tubes (PMT) underwater explosion test system, a method using information from fault tree analysis and uncertainty of data is presented. Based on the fuzzy set method and possibility theory, fuzzy fault tree method is a mathematical approach to model inaccuracy and uncertainty of the failure. The proposed model is able to quantify the fault tree of PMT explosion protection experiment system. In order to effectively investigate basic event failure probabilities without crisp quantitative historical failure data, fuzzy logic theory combined with expert judgement method is employed. The failure probability of the top event and the importance measures of basic events is also illustrated. The result demonstrates that the approach is apposite for the assessment of system failure. The research results can help professionals to decide whether and where to take preventive or corrective actions and help improve the underwater explosion-proof performance of PMT protective cover and fault diagnosis of test system.

Keywordsphotomultiplier tubes; fuzzy fault tree; fault diagnosis; underwater explosion

EffectofVSRonSurfaceIntegrityofStructuralParts

GAOZicheng,YUTian,LIAOKai,MINShuhui,LILijun,TANGXiaohong

(School of Mechanical and Electrical Engineering, Central South University of Forestry and Technology Changsha, 410004, China)

AbstractIn order to reveal the influence of vibration stress relief (VSR) on the surface integrity including residual stress, hardness and microstructure of structural parts, the 7075 aluminum alloy structural parts is taken as the research object. The software ANSYS is used to build VSR finite element model, the optimum excitation frequency and sample clamping position are obtained by modal analysis. On this basis, three thin-walled components are placed in different positions of the platform for VSR, and the effect of VSR on the surface properties of the samples is obtained. The results show that when the sub resonance frequency is 112 Hz, the stress release rate of the specimen is 27% at the middle position of the excitation source and at the max amplitude position. At the same time, electron backscattered diffraction (EBSD) electron microscope observation shows that there is obvious orientation area change in the surface structure grain after VSR, the change of energy and dislocation proliferation brought by grain growth, and the increase of recrystallization grain improves the surface performance, making the surface hardness of the material promote about 10%～17%. The results show that VSR with platform can change and optimize the surface integrity of materials.

Keywordsvibration stress relief; structural parts; stress relaxation; electron backscattered diffraction; surface integrity

TestAnalysisofConcrete-FilledDoubleSkinMetalTubularMembersUnderLateralImpact

SHIYan1,3,LIXuanying2,3，ZHANGJunbo2,LIUFeifei2,ZHANGJigang2,3

(1.College of Civil Engineering, Fujian University of Technology Fuzhou,350118,China)

(2.College of Civil Engineering,Qingdao University of Technology Qingdao,266033,China)

(3.Cooperative Innovation Center of Engineering Construction and Safety in Shandong Blue Economic Zone Qingdao,266033,China)

AbstractBased on the improvement of ice resistance of offshore platform structure, a new type of concrete-filled double skin metal tubular jacket leg members is proposed. The method of theoretical analysis, test and simulation is used to study its impact resistance under lateral impact load. The outside tube materials of the members are respectively Q345 steel, grade 304 austenitic stainless steel and T6061 aluminum alloy. The single impact and continuous impact are adopted for the impact form. The time-history curve of impact load and time-history curve of mid-span deflection are recorded and compared with those of hollow pipe members. The results show that the impact resistance of combined members is better than that of hollow pipe members, and the overall impact resistance of aluminum alloy combined members is poor. The ultimate bearing energy of stainless steel under single impact is more than 18.83 kJ, and the number of bearing impact times under the continuous impact of small energy is the most, so the impact resistance of stainless steel combined members is the best. In addition, combined with the finite element ABAQUS software, the single impact members are modeled and the calculation results are basically consistent with the test results.

Keywordsoffshore platform; concrete filled double skins metal tube; jacket leg; impact resistance

UnsteadyAerodynamicLoadsofLow-PressureTurbineUnderRotor-StatorInteraction

YANGChenghao1,FENGHeying1,PENGYehui2,LIHongguang1,3

(1.Hunan Key Laboratory of Mechanical Equipment Health Maintenance, Hunan University of Science and Technology Xiangtan, 411201, China)

(2.School of Mathematics and Computational Science, Hunan University of Science and Technology Xiangtan, 411201,China)

(3.State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University Shanghai, 200240, China)

AbstractIn order to study the control effects of axial gap and trailing edge serrated structure on the unsteady aerodynamic loads of low-pressure turbine blades under rotor-stator interaction, the internal flow field of the last stage of the E3low-pressure turbine is numerically simulated. The variation regularity of unsteady aerodynamic loads on the down-stream rotor blade surface is studied by changing axial gaps and adopting serrated trailing edge stator. The following facts are revealed: the unsteady aerodynamic loads on the rotor blades surface can be inhibited when increasing the axial gaps, because the blending of the wake and the mainstream can be enhanced with the increasing of the axial gaps, which results that the non-uniformity of the airflow is eliminated; the stator trailing edge serrated structure can not only strengthen the blending of the wake and the mainstream, but also change the vortex structure at the trailing edge, which will cause a destructive interference effect on the leading edge of the downstream rotor blades, lower its maximum load fluctuation by about 30%, reduce the speed loss in wake by 75.7 m/s, and improve the circulation capacity and time-averaged efficiency of turbine. Compared with the straight trailing edge stator, the serrated trailing edge stator blades can not only improve the rotor-stator interference effects and aerodynamic performance greatly, but also shorten the axial gaps of turbine by 10% without loss of the turbine efficiency.

Keywordslow-pressure turbine; rotor-stator interaction; axial gap; trailing edge serration; aerodynamic loads

FaultDiagnosisofTractionConverterforHigh-SpeedTrain

GUJia1, 3，HUANGMing2，GUANYue4

(1.School of Mechanical Engineering, Dalian Jiaotong University Dalian, 116028, China)

(2.Software Technology Institute, Dalian Jiaotong University Dalian, 116028, China)

(3.IT Department, CRRC Qingdao Sifang Co., Ltd. Qingdao, 266111, China)

(4.National Engineering Laboratory for High-Speed Train, CRRC Qingdao Sifang Co., Ltd. Qingdao, 266111, China)

AbstractAccording to the problem of traction converter fault caused by the abnormal condition of cooling filter for high-speed train, a fault diagnosis method based on multi task deep learning is proposed by comprehensively analyzing the correlation between fault classification of traction converter and filter blockage degree. Firstly, a multi-task deep neural network (MT-DNN) including the main task of traction converter fault diagnosis and the sub task of filter blockage degree is constructed. Then, in order to accurately predict the failure and degradation trend of traction converter, the prediction results of MT-DNN and self-organizing mapping (SOM) method are combined to construct the multi-task deep neural network self-organizing mapping model (MTDNN-SOM). This method defines the degradation state curve according to the evolution law of characteristic variables of historical fault data, which directly reflects the relationship between fault characteristics and degradation state, and finally realizes fault diagnosis and maintenance prediction for the cooling filter of traction converter. The experimental results show that the proposed method is superior to the single task or traditional fault diagnosis method in both accuracy and efficiency, and has achieved good results.

Keywordshigh-speed train; traction converter; fault diagnosis; multi-task deep neural network; self-organizing map

EffectofPreloadonPerformanceofPiezoelectricActuatedTrackedMobileSystem

WANGLiang1,CHENDi1,WANGXin1,ZHANGQuan2,JINJiamei1

(1.State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics Nanjing, 210016, China)

(2.School of Mechatronic Engineering and Automation, Shanghai University Shanghai, 200072, China)

AbstractTo improve mechanical output performances of the sandwich piezoelectric actuated tracked mobile system, a U-shaped preload adjusting mechanism is proposed, and experimental investigations on the relationship between the preload and the output performance of the sandwich piezoelectric actuated track mobile system are carried out in this study. At first, finite element simulation analysis is conducted to study the influence of the installation of the U-shaped preload adjusting mechanism on the vibration characteristic of the sandwich piezoelectric actuator. Additionally, the optimal preload force corresponding to the maximum traction force of the sandwich piezoelectric actuated tracked mobile system prototype with the installation of the U-shaped preload adjusting mechanism is experimentally determined. Finally, traction characteristics, obstacle crossing performances, and motion characteristics in the simulated lunar soil environment are experimented for the tracked mobile system prototype under the optimal preload force state. Experimental results indicate that the mechanical output performance of the sandwich piezoelectric actuated tracked mobile system is improved when it worked in the optimal preload force state. These provide the technology support and experimental basis for the future application of the piezoelectric actuated tracked mobile system on lunar rovers.

Keywordspreload force; piezoelectric actuation; piezoelectric actuator; tracked mobile system; lunar rover

EvaluationMethodofBearingHealthStateBasedonVariationalAuto-Encoder

YINAijun1,WANGYu1,DAIZongxian2,RENHongji1

(1.State Key Laboratory of Mechanical Transmissions, Chongqing University Chongqing, 400044, China)

(2.Chongqing Institute of Metrology and Quality Inspection Chongqing, 401120, China)

AbstractAiming at the problems such as high loss of characteristic information, weak generalization ability, and strong data dependence commonly existed in existing data-driven based methods for bearings health status evaluation, a new evaluation model based on variational auto-encoder (VAE) which allowing high-entropy characteristic input is proposed. By learning the high-dimensional potential probability distribution of the bearing vibration signal spectrum point in characteristic space, our model can quantitatively evaluate the bearing operating health state. First, the health status evaluation model based on VAE is theoretically elaborated. Afterward, a state assessment index based on the lower bound of variational evidence is established. As a consequence, it is proved that the variational auto-encoder has good accuracy in dealing with the evaluation of bearing running state and is more sensitive to the abnormal state through comparative experiments. Additionally, there is no need to extract features and set complex parameters artificially, also without setting and adjusting specific parameters for a specific system. Furthermore, it retains good robustness even with small training data sets as well as showcases certain promotion value of engineering application.

Keywordsvariational auto-encoder; anomaly detection; prognostics and health management; bearing fault diagnose