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2020 Vol. 39, No. 5
Published: 2020-03-15
1
Review of uncertain nonparametric dynamic modeling
FENG Wei1,2,LIU Baoguo1,2,DING Hao1,2,SHEN Huipeng1,2
Various uncertain factors unavoidably exist in engineering applications, and adopting uncertain models can more accurately reflect dynamic systems’ characteristics.Dynamic modeling of parametric uncertainty has received full attention in last 30 years, while uncertain non-parametric dynamic modeling as a newer study field receives attention in recent years.This field has obtained a lot of study achievements up to now.It is necessary to comprehensively review the status of research and development at home and abroad in this field.Here, the research status and advances for approaches, theoretical basis, modeling process and application of uncertain non-parametric dynamic modeling were reviewed systematically.The existing problems now were summarized and development directions of future study in this field were pointed out.
2020 Vol. 39 (5): 1-9 [
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335
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10
Laser ultrasonic identification method for surface cracks on cylindrical metal components
LIU Xuekun,YANG Shixi,LIU Yongqiang,CHI Yongwei, HE Jun
Here, in order to effectively identify cylindrical surface cracks with laser ultrasonic technique, a method of cylindrical surface wave signal enhancement and wavelet packet-singular value decomposition (WPT-SVD) was proposed to identify location and depth of surface cracks on cylindrical metal components.A laser ultrasonic explicit finite element model for a cylinder was established to analyze effects of cylindrical surface cracks on mode transformation of surface waves.The position of a cylindrical surface crack was identified using the phenomenon of laser ultrasonic scanning signal being enhanced during cylindrical surface crack being near excitation source.After crack location was identified, time-frequency characteristics of crack detection signal were analyzed, and these time-frequency characteristics were extracted using WPT-SVD.The parameter kr was defined to characterize crack depth change, and cylindrical surface crack depth was identified.Here, a laser ultrasonic cylindrical surface crack detection test system was built to conduct test study.The test results showed that the proposed method of cylindrical surface wave signal enhancement and WPT-SVD can be used to identify position and depth of cylindrical surface cracks.
2020 Vol. 39 (5): 10-17 [
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167
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18
Dynamic modeling and operation performance of wind turbine set based on its front-end speed regulating mechanism
YIN Wenliang,RUI Xiaoming
Based on advanced mechanical speed regulating and servo control techniques, a hybrid-drive wind turbine (WT) set with a generator front-end nonpolar speed regulator was proposed to realize its working mode of variable-speed constant-frequency (VSCF).The dynamic model for the WT’s transmission system was established using the lumped mass method and Lagrange’s equations.Based on the derived dynamic equations, The Simulink simulation model for a 1.5 MV WT set with front-end speed-regulating was built to deeply study its operation characteristics including speed-regulating accuracy, power consumption, current harmonic wave pollution and low-voltage ride-through (LVRT) capability.The results showed that under condition of different wind speeds, the proposed WT set can not only output constant-frequency electric power with smaller power dissipation (less than 15.25% of output power) of speed regulating, but also effectively suppress current harmonic wave pollution and improve the WT set’s LVRT capability; the practicability and superiority of the proposed WT set are verified with theoretical analysis and simulation study.
2020 Vol. 39 (5): 18-24 [
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158
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25
Spatial correlation of across-wind wind fluctuating wind load of a lattice tower
LI Feng1, ZOU Lianghao1, LIANG Shuguo1, CHEN Yin2
Here, to study spatial correlation of across-wind fluctuating wind load of a lattice tower, based on two typical segmental models of a certain lattice tower’s synchronous high-frequency force-measuring balance wind tunnel tests and synchronous wind speed measuring wind tunnel tests, two models’ base shear force, bending moment and wind speed time histories were measured.Coherence functions of across-wind fluctuating wind load and fluctuating wind speed were calculated with the data-processing method, and these coherence functions’ characteristics and variation laws were analyzed contrastively.The results showed that coherence function of across-wind fluctuating wind load of a lattice tower is related to frequency, horizontal distance, and vertical distance; there is a certain deviation between this coherence function and those of existing high-rise buildings and conical chimneys.Finally, the nonlinear least square method was used to deduce the empirical formula for across-wind fluctuating wind load coherence function.It was shown that the calculation results with this fitted formula agree well with test ones; the study results provide a reference for analyzing across-wind fluctuating wind load and wind-induced response of lattice towers.
2020 Vol. 39 (5): 25-31 [
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163
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32
Lumped parametric modeling and model modification for fixed decoupling hydraulic engine mount
ZHOU Dawei, ZUO Shuguang, WANG Jun, HU Kun, WU Xudong
Here, in order to improve dynamic characteristics prediction accuracy of a fixed decoupling hydraulic engine mount (HEM), a novel lumped parametric model and a modified lumped parametric model were proposed, respectively both considering effects of decoupling film stiffness on volume flexibility of upper liquid chamber, and the former made decoupling film be equivalent to an explicit spring with two added parameters of decoupling film stiffness and equivalent pump suction area, while the latter modified flexibility of upper liquid chamber with a more concise form according to decoupling film stiffness based on conventional lumped parametric model.Then the finite element method was employed to identify decoupling film stiffness, upper liquid chamber’s equivalent volume flexibility and other lumped parameters.Finally, all identified lumped parameters were substituted in the two models and to perform simulations.The results showed that both two proposed models can correctly predict dynamic stiffness and lagging angle of a fixed decoupling HEM, while the conventional lumped parametric model of HEM can’t do.
2020 Vol. 39 (5): 32-44 [
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230
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37
Robust optimization design model for vehicle body crashworthiness based on parametric interval analysis
WANG Qiong, LIU Guiping
A robust optimization design model for vehicle body crashworthiness considering tolerances was proposed based on interval analysis to effectively reduce sensitivity of crashworthiness to fluctuation of design parameters, and realize maximization of tolerances’ ranges.Firstly, uncertainties of design parameters, such as, size, position and shape of vehicle body’s key collision resistant parts in vehicle collision model were described with symmetric tolerances.Then, parametric design was combined with tolerance design to establish a multi-objective optimization model with robustness evaluation indexes and tolerance evaluation indexes taken as optimization objectives, and synchronous optimization of nominal values of design variables and their tolerances.Thirdly, the interval possible degree was used to deal with uncertain constraints, and the optimization model with uncertainties was converted into a deterministic multi-objective optimization one.Finally, the proposed model was applied in two vehicle crashworthiness optimization design problems, and they were solved using the sequence quadratic programming method and the improved non-dominant sorting genetic algorithm.The results showed that the proposed robust optimization design model and method are feasible and practical.
2020 Vol. 39 (5): 37-44 [
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245
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45
Extended SVD packet and its application in wheelset bearing fault diagnosis of high-speed train
HUANG Chenguang1, LIN Jianhui1, YI Cai2, HUANG Yan1, JIN Hang1
Combining decomposed structure of the multi-resolution SVD package and singular value distribution characteristics of a rolling bearing fault signal’s Hankel matrix, the extended singular value decomposition (SVD) package was proposed.The core of this method included matrix recurrence construction and matrix reconstruction.Component signal energy was taken as an index to propose the screening criterion of effective component signals.Then based on the proposed criterion, a fast algorithm for the extended SVD packet was further proposed.The simulation results showed that the extended SVD packet has good decomposition ability for resonance frequency band components in a signal; the method has a strong robustness and greatly improves modal aliasing appearing in the SVD packet.The test data for high-speed train’s wheelset bearing were used to verify the proposed method.The results showed that this method can effectively separate different resonant frequency band signals in high speed train wheelset bearing compound fault signals, and perform envelope analysis for screened effective component signals to effectively extract different types fault feature frequencies and their harmonics; compared to the SVD package, the proposed method makes resonance bands’ aggregation property and faults’ characterizing ability be significantly improved.
2020 Vol. 39 (5): 45-56 [
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195
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57
Finite element analysis and tests for a high torque radial standing wave type ultrasonic motor
JIANG Chunrong1, ZHOU Liangzhi1, DONG Xiaoxiao2, LU Danhong1, JIN Long2
A high torque radial standing wave type ultrasonic motor was proposed to realize large torque output and keep compact structure feature.Firstly, the motor structure was designed and its working principle was analyzed.The finite element method was used to analyze its stator vibration characteristics.Then a motor prototype with diameter of 32 mm was fabricated.Its stator’s resonance frequency and radial vibration amplitude were measured with a laser vibrometer.The measurement results agreed well with theoretical analysis ones.Finally, a test platform for measuring the motor’s output characteristics was constructed and torque-speed characteristics of the motor under different voltages were measured.The results showed that the resonance frequency of the stator working mode is 73.3 kHz; when applied voltage amplitude is 100 V with frequency of 74 kHz, the motor’s no-load speed is 45 r/min, and its blocking torque reaches 0.41 N-m; compared to other ultrasonic motors with the same sizes, the proposed motor has a larger blocking torque.
2020 Vol. 39 (5): 57-62 [
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166
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63
Nonlinear seismic responses of a hydropower house under near-fault ground motions oblique input
WANG Fei1, SONG Zhiqiang1, LU Tao2
Compared with remote ground motions, near-fault ground motions perhaps have larger velocity and displacement pulse effect.As the buried depth of seismic fault is shallow, the assumption of vertical surface incidence of seismic waves is generally no longer applicable.Until now, the aseismic study on hydropower house has not considered influences of near-fault pulse-type ground motion oblique input.Here, 5 near-fault pulse-type ground motion records and 5 near-fault non-pulse type ground motion ones were chosen to meet site conditions of a certain hydropower house and taken as inputs.According to the wave theory, the viscoelastic dynamic artificial boundary method was used to derive calculation formulas of equivalent node forces of artificial boundary under SV wave 3-D oblique incidence.These formulas were verified with examples.A finite element analysis model for 3-D plastic damage of hydropower house was established to analyze its nonlinear seismic responses under vertical and oblique incidences of near-fault pulse-type and non-pulse type ground motions.The results showed that near-fault pulse-type ground motions oblique input can excite high-order modal shapes of a hydropower house structure, cause its lower structure’s larger damage, displacement and stress responses, and have the strongest destructive effect on it.
2020 Vol. 39 (5): 63-73 [
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201
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74
Tests for crack propagation characteristics of three-point bending beam with circular hole defect
MEI Bi
Effects of circular hole defect with different diameters and positions on crack propagation characteristics was tested and studied for a 3-point bending beam with this hole defect made of PMMA material subjected to impact load using a dynamic caustic line test system.The results showed that before propagating crack interacts with circular hole defect, crack propagation reveals I type tensile fracture, and propagation path is straight; after propagating crack interacts with circular hole defect, penetrated initiating secondary crack continues to propagate in a straight line, and unpenetrated crack propagates in offset; in process of crack propagation penetrating circular hole defect, crack propagation velocity and dynamic stress intensity factor (DSIF) drops rapidly to zero, crack propagation is suppressed, the larger the hole diameter and the nearer the distance to hole, the more significant the suppression action; both initial speed and initial fracture toughness of penetrated initiating secondary crack increase with increase in circular hole defect diameter; in process of interaction between propagating crack and offset circular hole defect, the larger the hole diameter and the smaller the offset distance, the shorter the initial offset distance of crack and the larger the maximum offset, and DSIF and propagation velocity of crack propagation increase a little bit locally; the study results provide a reference for analyzing dynamic crack propagation features and material failure mode.
2020 Vol. 39 (5): 74-80 [
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191
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81
An improved DDTFA method and its application in gearboxes’ fault diagnosis
TIAN Lili, LI Rong, CHEN Lin, LIU Jian
Aiming at initial phase function selection of the data-driven time-frequency analysis (DDTFA) method, an improved DDTFA method was proposed to optimize initial phase function accurately, quickly and adaptively.Introducing the idea of solving extreme values of a function in mathematics, a signal’s initial phase function selection problem was converted into a continuous optimization of an initial solution set.Through simplifying Gauss-Newton iterative algorithm in DDTFA, the slope variation of initial phase function in an initial solution set before and after first iteration was taken as the derivative to obtain the continuous derivative set of the initial solution set, and further get local extreme values.Then the energy of signal components corresponding to local extreme values being the maximum was taken as the criterion to optimally choose initial phase function of a signal, and further complete signal decomposition.Simulation analysis and actual examples of gearboxes’ fault diagnosis showed that the proposed method can correctly, rapidly and adaptively optimize initial phase function, and effectively extract fault features; it has a certain anti-noise ability.
2020 Vol. 39 (5): 81-88 [
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177
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89
Rolling bearing fault diagnosis based on DBN algorithm improved with PSO
LI Yibing1,2,WANG Lei1,2, JIANG Li1,2
Aiming at the problem of debugging network layer structure being time-consuming during deep belief network (DBN) being applied in bearing fault diagnosis, the DBN algorithm improved with particle swarm optimization (PSO) and the bearing fault diagnosis model based on the DBN algorithm improved with PSO were proposed.In the proposed model, PSO algorithm was used to optimize DBN network structure, and the adaptive time instant estimation algorithm was used to finely tune the model parameters.Then, the DBN model with the optimal structure was used to extract low-dimensional fault features in the original vibration signals.The extracted fault features were input into a Soft-max classifier to identify bearing fault modes.The results using the proposed model were compared with those using SVM, BP neutral network, DBN and stacked de-noising auto-encoders, respectively.The comparison results showed that the DBN algorithm improved with PSO has higher accuracy and better robustness.
2020 Vol. 39 (5): 89-96 [
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222
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97
Rolling bearing fault diagnosis of launch vehicle based on adaptive deep CNN
CAO Jiping1, WANG Sai1,2, YUE Xiaodan2, LEI Ning1
As key components of launching vehicle, rolling bearings’ working conditions usually are very complex to make their fault diagnosis be difficult.Here, in order to effectively perform rolling bearing fault diagnosis, a novel method called the adaptive deep convolutional neural network (CNN) was proposed.Aiming at problems of lower calculation efficiency and parametric adjusting needing manual experience existing in the traditional CNN diagnosis method, PSO algorithm was used to determine structure and parameters of a CNN model.The principal component analysis (PCA) method was used to visualize its fault diagnosis feature learning process, and evaluate its feature learning ability.The diagnosis results with several diagnosis methods, respectively under 10 different bearing working conditions showed that compared with standard CNN, SVM and ANN diagnosis methods, the proposed method has higher diagnosis accuracy and better robustness.
2020 Vol. 39 (5): 97-104 [
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322
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105
Extreme value response statistics of a vehicle-bridge system based on SS/S method
XIANG Huoyue1, TANG Ping1, WANG Tao2, LI Yongle1
Failure of vehicle-bridge systems is a small probabilistic event.Here, the subset simulation with splitting (SS/S) method was used to calculate responses of a vehicle-bridge system.Firstly, the analysis code for vehicle-bridge systems was programed with the software MATLAB, and verified with numerical examples.Secondly, the basic principle of the SS/S method was reviewed, the autoregressive (AR) model was used to do the conditional simulation for track irregularity to give the SS/S statistical analysis framework for the response of vehicle-bridge system, and this framework was verified with numerical examples.Finally, for a vehicle-bridge system, the SS/S method was used to calculate exceedance probabilities of vehicle body’s vertical and lateral accelerations, and the results were compared with those using Monte Carlo statistics (MCS).The results showed that compared to the direct MCS, the SS/S method can greatly reduce number of required samples used to estimate exceedance probabilities of extreme value responses of a vehicle-bridge system, and significantly improve the calculation efficiency.
2020 Vol. 39 (5): 105-111 [
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119
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112
Working mode design and tests for hydraulically interconnected energy-feeding suspension
WANG Ruochen, SUN Dong, DING Renkai, MENG Xiangpeng, YU Feng
Aiming at the problem of a hydraulically interconnected suspension being not able to realize vehicle’s global working condition optimal under a single integrated mode, a hydraulically interconnected energy-feeding suspension with three modes of comfort, safety and energy-feeding was designed to feedback vibration energy when improving vehicle ride comfort and handling stability.Road excitation frequencies were taken as the suspension’s mode switching thresholds.A multi-mode control system was designed based on the constant current control method, and the optimal current value under each mode was calculated.Taking a sinusoidal road surface and a random one as examples, the suspension performance under designed three working modes was simulated and analyzed, respectively.The results showed that compared with single integrated mode, vehicle body’s acceleration decreases by 10.77% under suspension’s comfort mode; vehicle tire’s dynamic load under suspension’s safety mode drops by 17.43%; theoretical energy-feeding power under suspension’s energy-feeding mode increases by 19.48%.To verify the effectiveness of simulation, a suspension principle prototype was fabricated for bench scale tests.The test results showed that the proposed suspension’s 3 working modes can balance vehicle’s ride comfort, handling stability and energy-feeding characteristics.
2020 Vol. 39 (5): 112-117 [
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161
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118
Elastic dynamic modeling and analysis for a 3-CPaRR decoupled parallel mechanism with joint clearance
WANG Jian1,3, DONG Hu1,3, WANG Zhaodong1,3, LIU Junchen1,3, CAO Yi1,2,3
In order to study effects of joint clearance on output kinematic characteristics of a parallel mechanism under flexible condition, a 3-CPaRR parallel mechanism was taken as the study object.Firstly, according to this mechanism’s spatial position relations, its kinematic laws were studied.It was shown that this mechanism’s driving cylindrical pair can equivalently be decomposed into a driving moving pair and a passive rotating one.Then, based on this mechanism’s spatial position vector model, the kinematic models of rotating joint with clearance in radial direction and axial one were established.Furthermore, various branched rotating joints with clearance’ kinematic models were also established.Secondly, based on Lankarani-Nikravesh contact force model and Coulomb friction model, various branched rotating pairs with clearance’ dynamic models in normal direction and tangential one were established.Then, forces produced due to clearance at passive joints were transferred to ones at driving joints to establish the elastic dynamic model for a 3-CPaRR parallel mechanism with joint clearance.Finally, effects of different joint clearances on this parallel mechanism’s kinematic responses were analyzed with actual examples.The results showed that flexible branches with joint clearance significantly affect output kinematic characteristics of a parallel mechanism; the study results provide a theoretical basis for elastic dynamic modeling of other multi-body systems with joint clearance.
2020 Vol. 39 (5): 118-130 [
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159
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131
Growth law analysis for strain and deflection of steel circular plates subjected to multiple underwater explosions
LI Xudong1,2, YIN Jianping1, DU Zhipeng2, ZHAO Pengduo2, ZHANG Chunhui2, LI YING2,3, ZHANG Fei1,2
In sea wars, surface ships and submarines may be attacked by multiple missiles or torpedoes.Cumulative damages produced affect sustained combat capability and vitality of surface ships and submarines.Here, continuous underwater explosion loading tests were conducted for an air back liner steel circular plate with diameter of 390 mm and thickness of 5 mm under 50 g of explosive.The plate center strain, deflection and thickness reduction rate were measured.The test results showed that when the first explosion loading happens, the plate’s strain produced due to local cavitation is one time of that due to shock wave loading; after the steel plate is blown and bent, the second loading phenomenon due to the second blast and local cavitation is not obvious; bubble pulsation and bubble jet cause the steel plate to have obvious elastic deformation, its strain value is 10% of that caused by initial shock wave.The data analysis for plate center deflection and thickness reduction rate showed that the steel plate’s thickness reduction rate increases linearly with increase in center deflection; the study results provide a certain test support for evaluating warships’ sustained combat ability and vitality.
2020 Vol. 39 (5): 131-136 [
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169
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137
An improved method for near-fault strong ground motion records’ baseline correction
ZHANG Bin, YU Yanxiang, XIAO Liang
Based on the principle of Iwan et al.’ two-stage correction method, the parameter of time shift slope ratio ki was introduced to determine starting time of strong seismic stage offset t1, and the maximum flatness of corrected displacement f was introduced to determine starting time of ending stage offset t2.The parameter of root mean square deviation RMSD was introduced to choose order number of fitted function at the end of displacement, and the improved method of baseline correction for near-fault strong ground motion records was proposed.Then this improved method was used to do baseline correction for strong seismic motion records of 8 near-fault stations of Wenchuan earthquake and Lushan one to get permanent displacements.The results showed that permanent displacements obtained agree well with the same seismic displacements measured at GPS stations close to near-fault ones, ratios of permanent displacements to GPS measured results are within the range of 0.57-1.72 and the average value is 0.99, the uncertainty brought by subjective experience to baseline correction results can be reduced to a certain extent.Meanwhile, effects of 7 baseline correction methods on peak ground motion parameters and permanent displacements were analyzed contrastively.It was shown that effects of different baseline correction methods on PGA and PGV are smaller, while those on PGD and permanent displacements are much larger.
2020 Vol. 39 (5): 137-142 [
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143
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143
Structural damage identification using ABC combined with improved PMC sampling
FANG Sheng’en1,2, CHEN Shan1
In order to avoid sampling being immersed in low-probability areas and to raise sampling efficiency, the population Monte Carlo (PMC) sampling algorithm was improved and then combined with the approximate Bayesian calculation (ABC) and stochastic response surface (SRS) to propose a probabilistic damage identification method.Firstly, PMC algorithm was embedded in ABC, and sample variance in each iteration step was used to perturb a particle swarm, and obtain adaptive weight coefficients.An error function was constructed to measure the similarity between simulated and measured samples, and replace the likelihood function.Then the explicit expression for structural stochastic response was established using SRS to greatly improve the calculation efficiency of response statistical features.Finally, obtained statistical values of parametric posterior probability distribution were taken as damage indexes.According to indexes’ changes before and after damage, damage locations and degrees were judged.Damages of a test reinforced concrete beam under a single working condition and multiple working conditions were identified, respectively.It was shown that the proposed method can be used to effectively improve the calculation efficiency of Bayesian inference process under the condition of ensuring parametric posterior distribution’s estimation accuracy.
2020 Vol. 39 (5): 143-149 [
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180
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150
Sensitivity of sequence seismic effects of double-layer reticulated domes
ZHANG Yingnan1,2, ZHI Xudong1,2, FAN Feng1,2
To study whether or not structural responses of double-layer reticulated domes was sensitive to sequence earthquake to avoid structure collapse under aftershocks, a structure’s finite element model was established based on the finite element software ABAQUS.Data of main shock and aftershock responses to sequence earthquake in database of the pacific earthquake engineering research center (PEER) were selected to collect 342 groups of main shock and aftershock acceleration response time histories data.The dynamic time history analysis method in full load domain was adopted to obtain variation laws of structural characteristic responses with changes of acceleration amplitude under various sequence earthquakes.4 effect levels on reticulated shell structures’ multiple seismic responses were classified and defined.Then, statistic analysis was done for a lot of example results to obtain the relation between reticulated shells’ characteristic responses of maximum nodal displacement, proportion of yield members and structural damage factor when main shock was over and structures’ anti-aftershock ability.Finally, the proportion of yield members was taken as the index to measure double-layer reticulated domes’ anti-aftershock ability, and sensitive limit values of proportion of yield members for double-layer reticulated domes with different spans were given.The study results provided a reference for aseismic design and aseismic performance evaluation of reticulated shell structures.
2020 Vol. 39 (5): 150-156 [
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155
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157
Bolt looseness nonlinearity detection and location based on 3/2-D spectrum
WU Jin, QU Wenzhong, XIAO Li
A method for bolt loosening nonlinearity detection and location based on 3/2-D spectral analysis was proposed.The multi-scale method was used to analyze the mechanism of nonlinear phase coupling produced by bolt looseness, study the signal-processing process with 3/2-D spectral analysis and analyze the principle of its identifying nonlinear second harmonics.A bolt structure on an aluminum plate were taken as the test object, piezoelectric actuator/sensor elements bonded on the aluminum plate were used to perform tests, and 3/2-D spectral analysis was done for structural response signals to effectively judge the bolt’s connection state.In order to realize loose bolt’s positioning, the nonlinear index for bolt loosening was defined, and the radial basis interpolating function was introduced.The nonlinear index for response signals of the piezoelectric array bonded on the aluminum plate was obtained with tests, and the radial basis interpolating function was used to fit the damage location image.The test results showed that the proposed method can effectively detect bolt loosening nonlinearity and realize loose bolt’s positioning.
2020 Vol. 39 (5): 157-163 [
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156
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164
Numerical simulation for Mach reflection in air explosion near ground
LIAO Zhen, TANG Degao, LI Zhizhong, SHAO Luzhong
In order to study variation law of Mach wave’s parameters and effects of charge type and charge shape on triple-point trajectory, the finite element analysis software AUTODYN was adopted here to establish a finite element model of TNT charge in air explosion near ground.The calculated results were compared with test ones, and the former agreed well with the latter.Then, numerical simulations were performed for near-ground air explosions with different charge shapes and charge types.The results showed that impulse on Mach wave front surface decreases slowly with increase in height, overpressure peak value firstly decreases slowly with increase in height and then decreases rapidly; Mach wave is approximately perpendicular to ground, overpressure peak value at its top is only 67.6%-80.3% of that at its bottom, and impulse at its top is 91.3%-99.0% of that at its bottom; triple-point trajectory of spherical charge and that of column one with a length to diameter ratio of 1 are almost identical; the larger the length to diameter ratio of column charge, the smaller the height of Mach wave; Mach wave height formed with C4 explosive is slightly larger than that with B explosive, but they are relatively close to each other; Mach wave height formed with TNT is obviously smaller than those with C4 and B explosives
2020 Vol. 39 (5): 164-169 [
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307
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170
Unbalanced fault feature extraction for wind power gearbox based on improved VMD
ZHOU Fucheng1, TANG Guiji2, HE Yuling2
Variational mode decomposition (VMD) is a new modal decomposition method different from recursive one, and has a good frequency partition characteristics.However, it is seriously affected by number of components in signal processing, so it is difficult to set up its parameters rationally with subjective experience.Here, to solve this problem, the singular value decomposition (SVD) with clear signal-to-noise resolution ability was used to automatically search component number of VMD according to the optimal effective rank order of singular value, and propose an improved VMD method for unbalanced fault feature extraction of a wind power gearbox.Simulated signals and shaft unbalance test ones were used to verify the proposed method.The proposed method was applied in field fault diagnosis of a wind power gearbox under stable working condition to successfully extract weak fault feature frequency information, and realize effective judgement for wind power gearbox’s unbalanced fault with certain reliability.
2020 Vol. 39 (5): 170-176 [
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257
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177
Time response characteristics of a single-cylinder dual-channel MR damper
HOU Baolin,ZHENG Jie,ZHENG Pengfei
All real-time control applications require fast response time.In order to make a magnetorheological (MR) damper meet the requirements of real-time control, dynamic response time study becomes particularly important.Here, a new type dual-channel MR damper was taken as the study object, various links affecting the response time of the damper were studied.The simulation results were combined with theoretical analysis to establish the damper’s electromagnetic response model, and the finite difference method was used to establish the mathematic model for rheological effect process of a MR fluid, obtain the change process of flow field and damping force in the channel from power outage to power on, and further achieve the dynamic response time of the damper.The actual response time of the damper was obtained with tests and compared with the theoretical calculation results to verify the creditability of the proposed calculation method.
2020 Vol. 39 (5): 177-182 [
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191
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183
Dynamic characteristics of an airbag-marine rotating machinery system with displacement restrictor under shock excitation
LI Pengchao, LI Ming
Dynamic characteristics of an airbag-marine rotating machinery system with displacement restrictor under shock excitation were studied.Firstly, the nonlinear dynamic model of the airbag-rotating machinery system under shock excitation was established considering nonlinear oil film force of bearings and unbalance force of rotor.Then, the numerical simulation method was used to analyze effects of displacement restrictor on dynamic characteristics of the system under shock excitation, and discuss dynamic responses of the system under variation of displacement restrictor’s parameters including stiffness ratio, installation clearance and damping ratio.The results showed that displacement restrictor’s stiffness ratio and installation clearance have larger effects on the system’s maximum relative displacement and absolute acceleration under shock excitation, while effects of damping ratio decrease with increase in stiffness ratio.
2020 Vol. 39 (5): 183-187 [
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162
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188
Probabilistic distribution of Von Mises stress and strength evaluation of structures under static-random vibration combined condition
HAO Yu, FENG Jiaquan, HU Jie
Aiming at linear structures under combined action of static-Gaussian random loads, probabilistic distribution of structure’s Von Mises stress process was examined.Then the central Chi-squared distribution was used to approximately study Von Mises stress calculation under a certain cumulative probability level of 99.73%.Further, a strength evaluation method was proposed under static-random vibration combined condition.Based on a numerical example, the simulation results and calculation efficiency using the proposed method were compared with those using Monte Carlo method.The results showed that the proposed method has higher accuracy and calculation efficiency.Finally, two commonly used engineering approximation methods were examined to mathematically prove engineering approximation methods being always conservative, and provide a theoretical basis for existing methods.
2020 Vol. 39 (5): 188-193 [
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251
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194
Model tests for safety of stick-slip fault tunnel in strong earthquake area using rigid-flexible combined anti-shock absorption technology
CUI Guangyao1, LI Pengyu1, WANG Mingnian2,3, ZHU Chang’an4
In order to study using rigid-flexible combined anti-shock absorption technology for safety of stick-slip fault tunnel in strong earthquake area, a model was fabricated based on F8 stick-slip fault segment in Longxi tunnel of Duwen super highway in Sichuan Province, static stick-slip dislocation tests and large 3-direction 6-DOF strong shock tests were conducted for the model.The test data was analyzed and used to study longitudinal strain, contact pressure and internal force of upper and lower tunnel structure.The test results showed that after setting shock absorption gap, increase multiple of longitudinal strain and contact pressure along longitudinal tunnel structure varies from severely to more uniformly; effect of taking tunnel structure-strengthening measures is limited for resisting stick-slip dislocation and strong earthquake shock; effect of setting shock absorption gap is obvious for resisting stick-slip dislocation and strong earthquake shock; anti-shock absorption effect of tunnel structure’s longitudinal strain is more than 97%, the anti-shock absorption effect of contact pressure is more than 86% and the minimum value of safety factor is increased more than 5-fold; using rigid-flexible combined anti-shock absorption technology for a stick-slip fault tunnel in strong earthquake area can greatly improve its safety, the minimum value of its safety factor can be increased more than 8-fold; the study results can provide a reference for the shock absorption fortification design of stick-slip fault tunnels in strong earthquake area.
2020 Vol. 39 (5): 194-200 [
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155
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201
Shaking table tests for design and performance of a new type laminar shear model box
AN Junhai1,2, TAO Lianjin2
Shaking table model test is an important means to study soil-underground structure dynamic interaction under earthquake.The property of soil filled model box directly affects the correctness of test results.Here, based on the basic principle of structural dynamics, a laminar shear model box with adjustable spring and damping was designed, and its effectiveness was verified with shaking table tests.Meanwhile, the dynamic performance of the model box was analyzed with the software ANSYS.The test and analysis results showed that the designed laminar shear model box with adjustable spring and damping has a good effect to simulate actual site with infinite boundary condition, and reflect a soil-underground structure interaction system’s dynamic response feature of being controlled by speed and displacement; the performance of model box can be adjusted according to type of model soil to meet test’s requirement of reducing model box boundary effect; the developed laminar shear box can provide a new idea for selection of test box in other geotechnical seismic engineering problems.
2020 Vol. 39 (5): 201-207 [
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181
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208
Vector bonding graph method for simulation of double-crank series crank slider press mechanism
WANG Zhongshuang, GAO Mengqi, YIN Jiuzheng
To improve the efficiency and reliability of dynamic modeling and simulation for a double-crank series crank slider press mechanism, the vector bonding graph method was proposed.According to kinematic constraint relations among mechanism components, vector bonding graph models for mechanism moving components, revolute joints and translational ones were combined to establish the whole mechanism’s vector bonding graph model.Using the effective augmented method, the differential causality in the mechanism vector bonding graph model was eliminated to overcome the algebraic difficulty brought by it to mechanism automatic modeling, and realize the mechanism’s automatic modeling and simulation.Effects of working resistance in form of pulse on the mechanism dynamic performance were analyzed, and the effectiveness of the proposed method was presented.
2020 Vol. 39 (5): 208-213 [
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153
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214
Basic characteristics of differential quadrature method for dynamic response of structures
MEI Yuchen, LI Hongjing, SUN Guangjun
Based on basic numerical mode of the differential quadrature (DQ) method for dynamic response of structures, the numerical stability and numerical dissipation of DQ method were investigated when time point distributions were uniform distribution, Chebyshev one and Chebyshev-Gauss-Lobatto (CGL) one, respectively within a time step.The algebraic accuracy order number of DQ method was strictly deduced with the equivalent first-order model.The study showed that the method’s numerical stability is closely related to time point distributions within a time step, non-uniform modes are obviously better than uniform ones, but the system damping ratio has large influence on the method’s stability; the method’s algebraic accuracy depends on number of discrete time points, higher numerical accuracy can be realized generally; DQ methods with time points’ two non-uniform distribution modes of Chebyshev distribution and CGL one, respectively have excellent numerical dissipation.
2020 Vol. 39 (5): 214-221 [
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189
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222
Design and analysis of a new type vibration isolator
LI Xinyi1, WENG Xuetao2, CHAI Kai2
Aiming at defects of poor suppression of low frequency vibration for traditional passive vibration isolators, a new type electromagnetic-rubber active-passive integrated vibration isolator was designed.Its vibration reduction performance was evaluated through studying its output force characteristics.Firstly, the equivalent magnetic circuit analysis method was used to design and simulate its magnetic circuit structure, perform its dynamic analysis, and obtain its electromagnetic force calculation formula.Furthermore, based on the software COMSOL, dynamic simulation and analysis were done for the output force of the actuator to clarify effects of current and its frequency on output force characteristics.Finally, the characteristics test results were compared with simulation ones.
2020 Vol. 39 (5): 222-226 [
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222
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227
Measurement and calculation for sound insulation performance of automobile body sheet metal reinforcing rib
YUAN Zhongxiang1, Subhash Rakheja1, XIAO Yi1, XIE Xinxing2, SHANGGUAN Wenbin1， ZHU Gang3
Measurement and calculation for sound insulation performance of automobile body sheet metal reinforcing rib were studied here.The calculation model for sound transmission loss (STL) of a thin plate was established with SEA and FE-SEA hybrid modeling methods.Its calculation results were compared with test ones for verification.Automobile body sheet metal reinforcing rib’s height, width, hole and arrangement density were taken as variables to design and fabricate different schemes of automobile body sheet metal reinforcing rib.These schemes’ STLs were measured in a reverberation-complete elimination room.The test results showed that with increase in width of sheet metal reinforcing rib, its STL increases within full frequency range; if a hole is opened on a rib, its STL drops; with increase in arrangement density of ribs, peaks and valleys of sound insulation curve increase.Based on contrastive results of tests and calculation, factors affecting STL calculation of automobile body sheet metal reinforcing rib were analyzed.
2020 Vol. 39 (5): 227-234 [
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185
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235
Chatter suppression at end of a manipulator for grinding wind turbine blade based on incremental coupling predictive control
DAI Shijie1,2, CHENG Jun1,2, ZHANG Huibo1,2, WANG Xiaojun1,2
Aiming at the problem of end-actuator tangential chatter caused by rigid contact between end-actuator and blade surface in process of grinding wind turbine blade, an incremental coupling predictive control method for the end-actuator based on the composite structure of force feedback and acceleration feedforward was proposed.On the basis of mathematical modeling for flexible driving unit of the end-effector, the composite PID control strategy was improved based on incremental coupling dynamic matrix predictive control algorithm.The uncontrollable but predictable input acceleration was taken as a part of prediction sequence of grinding axial force.Meanwhile, the control target was optimized by rolling in finite time domain with minimizing quadratic performance index to ensure flexible contact between end-actuator and wind turbine blade.Simulation and test results showed that the proposed method can quickly realize the end-effector’s tangential chatter suppression, and minimize errors brought by control time delay, environmental time-varying and model mismatch, etc.
2020 Vol. 39 (5): 235-243 [
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164
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244
Steady-state features of a power function type single-well system driven by color-associated multiplicative and additive noise
WU Shaoxiang, LUO Yang, CHEN Jian
Steady-state problems of a power function type single-well system under action of color-associated multiplicative and additive noise were studied.Firstly, the uniform colored noise approximate method was used to deduce the steady-state probability density function.Then, effects of color-associated multiplicative and additive noise on the steady-state probability density were analyzed.Finally, structural parameters of a potential well were used to analyze effects of the well structure on the steady-state probability density.The results showed that under the condition of the parameter b=1, cross-correlation intensity, self-correlation time and structure parameters a, b of the potential well can induce non-equilibrium phase transitions.
2020 Vol. 39 (5): 244-249 [
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142
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250
Vibration characteristics analysis and numerical simulation for stiffened plates with damping core composite
LU Qinghe,LIANG Sen, ZHOU Yunfa, ZHENG Changsheng
Based on the first-order shear deformation theory (FSDT), expressions of strain energy and kinetic energy of a stiffened plate with damping core composite and stiffeners were derived, and its governing dynamic differential equations were established using Hamilton principle.According to the relevant boundary conditions, the equations were solved using Fourier series.The finite element model for this damping core composite stiffened plate was established using the software ANSYS considering combination mode of damping material and fiber prepreg in this plate.Dynamic characteristics of the plate were studied with the finite element numerical simulation method of modal strain energy.Through comparing the numerical simulation results with the theoretical solutions, the rationality and effectiveness of the finite element model were verified.Effects of different rib sizes, number of ribs and distribution of ribs on dynamic characteristics of this plate were discussed to obtain variation laws of its first-order modal frequency and loss factor versus varying curves of different parameters.The study results provided a reference for optimization design of stiffened plates with damping core composite.
2020 Vol. 39 (5): 250-261 [
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151
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262
Clearance parametric identification and test method for a control actuator system based on Hilbert transformation
SHI Xiaoming1, DOU Yibin1, MEI Xinglei1, XU Quan1, TAO Jian2
To identify clearance parameters of a control actuator system, a test device with adjustable clearance was designed to simulate clearance of a control actuator system’s transmission mechanism.Static load was exerted on it and sudden unloading made it have free vibration.The free vibration analysis method based on Hilbert transformation was used to obtain its double-fold line elastic force curve, and its clearance parameters were identified.This method was applied in clearance identification of control actuator system of an actual aero-craft.It was shown that vibration data acquired with the proposed test method have good signal-to-noise ratio; the proposed method’s engineering evaluation results are more secure; it has a good applicability for small control actuator systems.
2020 Vol. 39 (5): 262-266 [
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183
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267
Impact toughness of thick steel plates
YE Bing1, LI Rui1, LUO Shiting2, HU Xianqun2, LI Xiaozhang1
At present, steel products are widely applied in long-span bridge engineering of our country, thickness of steel plate day-to-day increases.Increase in steel plate’s thickness causes change of its stress-strain state and serious central segregation phenomena to more easily reduce toughness in steel plate’s thickness direction, this phenomenon is particularly prominent under low-temperature environment.The current code lacks provisions for impact tests of thick steel plates.Here, according to test data of low-temperature impact toughness of thick steel plates, effects of steel plate’s thickness variation on its impact toughness were explored.Boltzmann function was used to fit test results.The study results provided a reference for choosing impact toughness value of thick steel plates in engineering.
2020 Vol. 39 (5): 267-271 [
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190
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272
Fundamental frequency analysis method for medium-low frequency concentrated mass cantilever reed instrument
HUI Anmin1, YAN Ming1, FENG Linhan2,JIANG Lijie1, LIU Haochao1
Reed instrument is a measuring device for medium-low frequency impact response spectra.It can be simplified as a cantilever beam with concentrated mass at its free end during its design.There is a transcendental function in its vibration mode shape equation.For a reed instrument with uniform cross-section, this equation can be solved with the bisection method, but the numerical computation is time-consuming.This method is not suitable for fundamental frequency design of reed instruments with complex cross-section.Here, firstly, the deflection formula for a cantilever beam subjected to a concentrated force at its free end was used to derive the equivalent stiffness of a single-DOF spring-mass system equivalent to the beam.The relevant natural frequency formula of this single-DOF spring-mass system was proposed to solve the fundamental frequency problem for a uniform cross-section cantilever beam with a concentrated mass.Comparing the beam’s fundamental frequency calculated using the proposed method with that using the vibration mode shape equation, it was found that within the medium-low frequency range of less than 10 Hz, the fundamental frequency accuracy of the cantilever beam with uniform cross-section can be well kept; within the medium frequency range of larger than 10 Hz, error rapidly increases with increase in frequency; Mohr integral method was used to deduce the maximum deflection at free end of a uniform strength concentrated mass cantilever beam, and give the design formula of its fundamental frequency.Comparing its fundamental frequency data calculated with the proposed method to test data, it was found that the error has the same trend as that of the cantilever beam with uniform cross-section; Rayleigh energy method is used to modify mass parameters in the design formula, and the error between the modified data and test ones is about 5%.Through theoretical calculation and test verification, it was shown that the proposed design method for a reed instrument’s fundamental frequency is simple and feasible, and the computation results are believable.
2020 Vol. 39 (5): 272-277 [
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127
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