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2022 Vol. 41, No. 6
Published: 2022-03-28
 
1 Robust rolling bearing fault feature extraction method based on cyclic spectrum analysis
YAN Yunhai，GUO Yu，WU Xing
Cyclic stationary analysis is one of the important methods for rolling bearing fault feature extraction. However, the bearing fault feature cannot be effectively extracted for the excessive irrelevant interference component. A robust rolling bearing fault feature extraction method based on cyclic spectrum analysis has been proposed to solve the problem in this paper. The random component of signal can be extracted by discrete random separation (DRS), and then the vibration energy sequence will be calculated by Teager energy operator (TEO) though the random component. With the fast spectral correlation analysis, the energy intensity of each cycle frequency (order) slice can be characterized by energy difference coefficient based on energy entropy. The influence of irrelevant interference component can be reduced by entropy weighting. Then, the fault feature of rolling bearing can be effectively extracted. It verified the advantage of this method in the application of rolling bearing fault diagnosis by experimental comparison of fast spectral kurtosis, fast spectral correlation and fast spectral correlation based on total variation de-noising.
2022 Vol. 41 (6): 1-7 [Abstract] ( 337 ) HTML (1 KB)  PDF (1998 KB)  ( 155 )
8 Magnetic circuit simulation and optimization of a permanent magnet eddy current recoil brake
SHEN Yanping，LIU Ning，XIE Zihao，LIANG Yuxia，SUN Mingliang，WANG Nannan
Based on the permanent magnet eddy current damping technology, a brand-new design of the recoil brake is carried out. The principle experiment verifies that the scheme of the same-pole relative permanent magnet array exhibites good performance for buffer braking. A simulation model of the permanent magnet eddy current recoil brake is established. The recoil resistance characteristics of the recoil brake under the influence of different magnetic yoke, air gap, conductor tube and magnetic tube thickness parameters are analyzed for the recoil process under strong impact load. A multi-objective recoil resistance optimization model is established, and based on the modern optimization calculation method under BP(back propagation) neural network and genetic algorithm, the optimal solution of the saddle-shaped characteristics of the recoil resistance curve under the influence of demagnetization is found in the Pareto solution set. The results show that the impulse response experiment of eddy current damper verifies the feasibility of the magnetic circuit scheme and the correctness of simulation results. The thickness of yoke and conductor barrel, two parameters of eddy current recoil brake, greatly influences recoil resistance and demagnetization degree. The saddle-shaped characteristics of the recoil resistance curve are weakened after optimization, and the curve fullness is increased from 79.51% to 88.05%, which verifies the feasibility of the optimization strategy.
2022 Vol. 41 (6): 8-14 [Abstract] ( 210 ) HTML (1 KB)  PDF (1678 KB)  ( 104 )
15 Optimization of the alignments of turnout guide curves based on multi-body dynamics
ZHOU Junzhao1,2，LUO Yanyun1,2，LIAO Bo1,2
In order to improve the passing through branch lines performance of the turnout, combined with the structural characteristics of the turnout, it is proposed to reduce the guide curve of the inner rail of the side strands to achieve the purpose of setting the superelevation in the turnout. Taking the 1:42 turnout as an example, two new line types: the cubic curve & cubic curve and the 7th curve & 7th curve, were designed to establish vehicle-turnout dynamics. Learn the coupling model and compare the derailment coefficient and wheel-rail lateral force under different working conditions. It is found that setting the superelevation and using the higher-order curve in the guide curve is effective, which can improve the safety and speed of the vehicle compared with the existing type. The extreme value of the derailment coefficient of the new alignments is reduced by 14.4%-20% compared with the existing, and the extreme value of the wheel-rail lateral force is reduced by 14.5%-26.4%.
2022 Vol. 41 (6): 15-20 [Abstract] ( 223 ) HTML (1 KB)  PDF (1419 KB)  ( 63 )
21 Cross-domain fault diagnosis of rolling element bearings using DCGAN and DANN
HU Ruohui1，ZHANG Min1,2，XU Wenxin1
A large amount of label data is needed to realize intelligent fault diagnosis of rolling element bearings. However, in practice, sufficient vibration signals cannot be collected in advance due to bearing faults, which makes it difficult to determine the bearing fault mode under variable conditions. To solve this problem, a domain adaptive transfer learning model using a small amount of sample data is proposed. Firstly, a small amount of vibration signals are extended by the Deep Convolutional Generative Adversarial Networks. The generated signals retain the complete high and low frequency characteristics of the real signals. Secondly, the features of source domain and target domain are projected into the same feature space through the Domain-Adversarial Neural Networks to achieve multi-domain feature extraction and adaptation. Finally, the health status of unknown label rolling bearing is identified by transfer learning network. The experimental results show that the proposed method can accurately and effectively realize the cross-domain fault diagnosis of rolling bearings when the available samples are relatively small. The accuracy is better than other transfer learning comparison models.
2022 Vol. 41 (6): 21-29 [Abstract] ( 292 ) HTML (1 KB)  PDF (1697 KB)  ( 175 )
30 Reliability of peak ground acceleration in the seismic response analysis on stratified soil
LIANG Shijun，JIANG Bei
Aiming at the reliability problem of ground peak acceleration under the uncertain influence of the randomness of earthquake and site conditions, based on the probability distribution of equivalent site shear wave velocity, the expression of the analytical solution of ground peak acceleration in seismic response of horizontally layered foundations was derived at the same time with the probability density distribution function of the ground peak acceleration of the site, through the collected 100 actual soil measurements from a site in a science and technology city in Zhejiang, Flac3D was used to simulate and analyze the numerical solution of the ground peak acceleration, and the probability density distribution function of the ground peak acceleration of the site was fitted. On this basis, the confidence interval equation of the ground peak acceleration of the site at any reliability level was given. The results show that the seismic response ground peak acceleration of the horizontal layered foundation site obtained by analytical or numerical analysis conforms to the normal distribution, and the maximum allowable deviation of the confidence interval of the seismic response ground peak acceleration obtained by the analytical analysis is more than that obtained by the numerical analysis. The maximum allowable deviation is less, and the peak ground acceleration obtained by numerical analysis is more discrete than the distribution of peak ground acceleration obtained by analytical analysis.
2022 Vol. 41 (6): 30-36 [Abstract] ( 201 ) HTML (1 KB)  PDF (2352 KB)  ( 77 )
37 Vortex-induced vibrations of a free spanning pipeline with slug flow
LI Xiaomin，LI Sheng，GU Honglu，GUO Haiyan
Numerical investigation was conducted for the dynamic analysis of the submarine suspended pipeline under the coupling effect of slug flow and vortex-induced vibration (VIV). Considering the internal slug flow, the VIV analysis model of the submarine suspension pipeline is established based on the vector form intrinsic finite element method (VFIFE) and the wake oscillator model. The transverse vibration laws under different Taylor bubble or slug translation velocities (VT=3-5m/s) and different slug lengths (LS=15-45D) were investigated. The analysis results showed that the lock-in region of VIV of the submarine suspended pipeline tends to extend backward due to slug flow. The increase of Taylor bubble translation velocity and the decrease of the slug length significantly increase the lock-in interval. Moreover, the increase of slug length aggravates the vibration amplitude.
2022 Vol. 41 (6): 37-43 [Abstract] ( 172 ) HTML (1 KB)  PDF (2073 KB)  ( 82 )
44 Remaining useful life prediction based on BiLSTM and attention mechanism
ZHAO Zhihong1,2，LI Qing1，YANG Shaopu2，LI Lehao1
Remaining useful life (RUL) prediction occupies an important position in modern industry, and in recent years improving the accuracy of RUL prediction has become a widely researched topic. The traditional RUL prediction methods generally use model-based prediction methods wherein features are manually extracted. Furthermore, these traditional methods cannot learn feature information automatically, and obtains the complex mapping relationship between the original data and the RUL. In this study, a RUL prediction model based on bidirectional long short term memory (BiLSTM) and an attention mechanism is proposed. In contrast to traditional prediction models, the proposed model directly inputs the obtained original time series into the BiLSTM neural network, and the device status is automatically extracted. Then, the attention mechanism is used to assign different weights to the features, so that the health status information of a device or machine can be extracted more accurately. We carry out various RUL prediction experiments on engines and bearings, and compare the results with the long short-term memory(LSTM) and BiLSTM RUL prediction models. The experimental results show that the proposed BiLSTM integrated with an attention mechanism can predict the RUL more accurately and can be used in real-world settings.
2022 Vol. 41 (6): 44-50 [Abstract] ( 345 ) HTML (1 KB)  PDF (1586 KB)  ( 488 )
51 Novel early fault detection and diagnosis for rolling element bearings in graph spectrum domain
CHEN Zixu1,2,3，ZHU Zhenjie1,2,3，LU Guoliang1,2,3
Health status online diagnosis is an important way to ensure the reliable operation of rolling element bearings(REB). As a self-adaptive decomposition method, local mean decomposition(LMD) can describe the non-stationary signal into multi-scale. However, the decomposed component signal always has a large scale and is hard to extract weak fault features. To solve these problems, a novel early fault detection and diagnosis method for rolling element bearings in graph spectrum domain is proposed. We first decompose the vibration signal into multi-scale by LMD. Based on the generated component signal, the graph theory is used for dynamically modeling of rolling element bearings. Then a quantitative index of dynamic characteristics can be established by calculating the similarity between adjacent models, pauta criterion is employed to make early fault detection. Finally, the pattern recognition method is used to make fault diagnosis. The experiment on XJTU-SY and Case Western Reserve University(CWRU) data sets demonstrate the effectiveness of our method.
2022 Vol. 41 (6): 51-59 [Abstract] ( 216 ) HTML (1 KB)  PDF (1359 KB)  ( 120 )
60 Damage assessment of a buried CFRP petroleum pipeline subjected to blast loading
CUI Ying1,2，ZHAO Junhai3，QU Zhan1,2，FANG Jun1,2
With buried explosion experiment, the anti-explosion performance of buried steel petroleum pipeline with Carbon Fibre Reinforced Polymer (CFRP) reinforcement was researched thoroughly. Furthermore, with the experimental data and numerical simulation, the damage assessment criterion of buried steel petroleum pipeline with CFRP reinforcement was established. The results show that under the condition of scale distance of 0.19m/kg1/3 and shallow buried blast loading exerted on, there were obvious dent deformations on the surface facing the explosive of the normal buried pipeline and the CFRP buried pipeline both, and the dent deformation values of the CFRP pipeline decreased 38.2% compared with the normal buried pipeline. And, it was venerable to have damage on the buried pipeline surface facing explosive and joint ends of the two specimens. As to the overpressure of buried pipeline surface facing explosive, the values of the normal buried pipeline was higher than that of the CFRP pipeline, which also proved that the CFRP sheets could decrease the value of overpressure of buried pipeline surface facing explosive effectively. As to the lasting time of positive pressure, it was similar between the normal buried pipeline and the CFRP buried pipeline, which also proved that the CFRP sheets had little effect on the lasting time of positive pressure of the two experimental specimens. Finally, considering the dent depth and dent length of the buried steel pipeline with CFRP reinforcement surface simultaneously, with the fixed end constraints, the damage assessment formula based on a new critical ratio between the dent depth and dent length was established according to pressure and impulse (P-I) damage assessment theory.
2022 Vol. 41 (6): 60-69 [Abstract] ( 185 ) HTML (1 KB)  PDF (3205 KB)  ( 206 )
70 3D dynamic analysis and test verification of the string-bridge structure of a Guzheng
DENG Xiaowei1，YU Zhengyue1，YAO Weiping1，ZHOU Li2
The Guzheng string-bridge structure is an important component of Guzheng vocal system, and also, the primary issue of sound mechanism research. The 3-D dynamic model of Guzheng string-bridge has been establish with the Guzheng Bridge be considered as rigid double code feet and the string vibration be considered as bounded string vibration. Then the change rule of normal faces of the two code feet in different plucking angles have been analyzed by using the Matlab numerical calculation. Finally, the calculated results have been verified using the experimental measurement. The results show that the 3-D dynamic model of Guzheng string-bridge is effectively and reliable. When plucking the string in 00, the minimum value of the dynamic force of left code foot is very closed to zero, which is easy to cause bridge hopping; When plucking the string in 900, the phase dynamic forces of two code feet are same, and the resultant force of two code feet is largest; When plucking the string in 450 and 1350, the bridge dynamic forces of two angles are dissymmetry, and the phase dynamic forces of two code feet are opposite in this two angles. The work of this paper optimizes the dynamic model of Guzheng string-bridge structure. And it summarized the change rule of normal faces of the two code feet in different plucking angles, and will provide more or less support and guidance for improvement of future Guzheng.
2022 Vol. 41 (6): 70-75 [Abstract] ( 158 ) HTML (1 KB)  PDF (1183 KB)  ( 202 )
76 Distortion correction and fractal characteristics of vibration signals of a tunnel blasting
FU Xiaoqiang1,2,3，YU Jin2，LIU Jifeng1，YANG Renshu4，DAI Liangyu3
Affected by the test environment, the monitoring vibration signals of tunnel blasting generally contain noise and trend interference components. To eliminate the interference items, the distorted blasting signals detected in typical tunnel were selected as the analysis objects. Baseline estimation and denoising with sparsity (BEADS) was used to extract noise and trend item, to obtain the calibrated signal that reflecting the true information. The chaotic fractal characteristics of three components are captured by multi-fractal detrended fluctuation analyses（MF-DFA）, and the time-frequency domain correlation between them and the original signal is accurately characterized according to the wavelet correlation aggregation spectrum. The chaotic fractal characteristics of high frequency noise, low frequency trend item and calibrated signal of tunnel blasting are significantly different. The trajectory of the calibrated signal attractor is characterized by a fractal spectrum with persistent and anti- persistent periodic fluctuation and its recursion graph has periodic pattern; The attractors of the low-frequency trend item have the shape of approximate straight line and the persistent fractal spectrum characteristic, and the recursion graph has the mutation pattern of diagonal distribution; The attractor of high frequency noise is characterized by random fluctuation and anti-persistent fractal spectrum, and its recursion graph has drift pattern. In the range of wavelet influence cone with confidence of 95%, the calibrated signal, trend item and noise have the characteristics of persistent positive correlation, local negative correlation, and no correlation with the original signal, respectively. The effective separation of three components and the extraction of chaotic fractal features provide objective characterization and quantization indexes for the identification and classification of blasting signal components.
2022 Vol. 41 (6): 76-85 [Abstract] ( 189 ) HTML (1 KB)  PDF (2157 KB)  ( 167 )
86 Numerical investigation on the dynamic responses of rockfall impact onto a sand cushion
WANG Haisheng1，ZHANG Jinhua2，CHEN Li2，ZHANG Yadong2，LI Qiaosheng1
Aiming at the dynamic response of rockfall impact sand cushion, the diffusion angle, attenuation coefficient and transfer coefficient of compression wave in sand were studied. A conical bar model of compression wave propagation in sand was proposed. The propagation process and interaction mechanism of compression waves in sand were investigated. Firstly, according to the mechanical properties of sand, the Soil and Foam model was selected, and the parameter calculation method was given. The numerical calculation was carried out with ANSYS / LS-DYNA software, and compared with the existing test results. Secondly, the impact effect of rockfall and the propagation law of compression wave were investigated by numerical research method. The fitting formula between attenuation coefficient and sand depth is obtained. Finally, a conical bar model was proposed to investigate the propagation, attenuation and interaction mechanism of compression wave in sand. The research results lay a foundation for further analysis of the dynamic response of rockfall prevention structure under rockfall impact load.
2022 Vol. 41 (6): 86-96 [Abstract] ( 240 ) HTML (1 KB)  PDF (2984 KB)  ( 213 )
97 Complex mode superposition response spectrum approach for isolated structure analysis
YANG Kui1,2，TAN Ping1,2，CHEN Huating1,2，LI Xiaolei1,2
Seismically isolate structures exhibit non-proportional large damping characteristics, which makes the research on the complex mode decomposition response spectrum approach more and more important. In this paper, the coupling effect of the non-proportional damping matrix is considered through the equation of motion of the isolated structure, and the complex mode decomposition response spectrum method is proposed based on the complex mode and stationary random process theory. Four different overall non-proportional damping matrices are assembled according to three methods of Rayleigh damping, mode superposition damping coefficient and damping ratio conversion damping coefficient. The applicability of damping matrix is analyzed according to the characteristics of isolated structure ,Under the natural wave response spectrum of the far field and the near field, the effects of the equivalent period and equivalent damping ratio of the seismic isolation layer under different damping matrix assembly methods on the calculation accuracy of the Complete Quadratic Combination (CQC) and Complex Complete Quadratic Combination (CCQC) methods are analyzed. Finally, based on the design response spectrum CQC and the design response spectrum CCQC response spectrum method, the effect of different equivalent periods and equivalent damping ratios of the isolation layer on the floor displacement, floor shear and floor overturning moment error of the isolation structure is analyzed. The analysis results show that the damping coefficient method is more suitable for the construction of non-classical damping matrix. The CQC response spectrum method cannot accurately reflect the actual response under near-field earthquakes, and its application range is more limited, while the CCQC response spectrum method can well reflect the seismic response of the isolation results.
2022 Vol. 41 (6): 97-105 [Abstract] ( 271 ) HTML (1 KB)  PDF (2180 KB)  ( 363 )
106 Simulation of vehicle flow development and analysis of vehicle bridge coupling vibration in mass fog environment
LIU Huanju，LIU Ning
The coexistence and dynamic development of multi-state traffic flow in mass fog bridge area lead to drastic change of vertical action density and dynamic application of longitudinal force. In order to analyze the structure effect in the fog environment, two key problems need to be solved, which are the development of the simulation vehicle flow under the mass fog and the improvement of the vehicle bridge coupling mechanical relationship. Firstly, the fog boundary was vertical, and the actual mass fog was abstracted as the mass fog box. According to the popular characteristics of mass fog vehicles, the mass fog bridge area was continuously divided, and the calculation method of vehicle flow characteristic parameters of each bridge section was deduced and determined, forming the development model of vehicle flow under the condition of mass fog, solved the establishment of multi-stage speed change points in the traffic flow model with the method of group mass fog identification. The simulation program was compiled and connected. Secondly, The state of motion in which a vehicle decelerates first, then moves at a constant speed and finally accelerates in mass fog, it broke through the general rule of once constant speed change of macro traffic flow and need to match the mechanical model of vehicle transmission and integrate into the vehicle bridge coupling system to construct the response analysis platform of vehicle bridge system under the condition of mass fog. Finally, Taking a typical cable-stayed bridge as the background, the influence factors and analysis indexes of the bridge response to the mass fog were calculated and determined, and the parameter analysis of the influence of the fog range and location factors on the bridge response was carried out. The results show that the displacement along the bridge and the vertical displacement of the bridge under the condition of mass fog exceed the condition of the same ownership and the standard traffic flow, the maximum value appears as the mass fog in the middle of the span, the uneven distribution of vehicle load and the longitudinal force caused by mass fog on the bridge cannot be ignored; as the mass fog range is constant, with the mass fog moving to both ends of the bridge, the influence of the mass fog on the longitudinal and vertical displacement response of the bridge decreases gradually; as the mass fog center is fixed in the middle of the bridge, with the mass fog range increasing, the displacement of the beam along the bridge increases first and then decreases, and the vertical displacement decreases gradually and approaches to 1.
2022 Vol. 41 (6): 106-114 [Abstract] ( 169 ) HTML (1 KB)  PDF (1484 KB)  ( 332 )
115 Coupling analysis and model verification of anti aircraft impact on a nuclear power plant structure considering the soil-structure interaction
WANG Yougang1，SUN Yunlun1，LI Jianbo2,3，LI Xiaohong1，CHEN Yan1，MEI Runyu2,3，NIU Yanru2,3，LIN Gao2,3
The interaction is an important factor of the dynamic response of the structure - soil system under the impact load, especially under the condition of non - rock foundation site, the rigidity constraint of the structure is weakened. The effective and reasonable simulation of the foundation and other factors is the key premise to ensure the reliability of the conclusion. In this paper, combined with the analysis of dynamic characteristics of HTGR demonstration project under the condition of aircraft impact, a coupling dynamic analysis method of detailed simulation is proposed. Based on the factors such as aircraft load curve and wall impact deformation, the grid density closely related to the analysis scale is analyzed. A perfect matching layer (PML) is set up at the boundary to simulate the radiation damping effect of infinite foundation. The different soft and hard site conditions and different positions of aircraft impact are compared and analyzed, and the influencing factors of superstructure vibration response are obtained. The sensitivity analysis of the model parameters can provide the basis for the standardized modeling of the refined model, and the numerical results show that the soil structure interaction has a significant impact on the overall dynamic response of the nuclear power plant against aircraft impact in the condition of non - rock foundation site, especially the floor spectrum.
2022 Vol. 41 (6): 115-122 [Abstract] ( 229 ) HTML (1 KB)  PDF (1938 KB)  ( 86 )
123 Experimental study of a tubular K-joint with preloaded axial tension on its chord under lateral impact loading
QU Hui1，WANG Qingfan1，LI Wei1，CHEN Qi1，XU Jie2
As the support member of steel tubular structure, the tubular joint may be damaged under impact and explosion, even causing the collapse of the entire structure. To study the effect of initial stress and ratio of diameter to thickness, two groups of 6 tubular K-joints were tested by drop hammer testing machine. In each group of 3 specimens, the initial force states are that the chord and the brace were not loaded the initial axial force, the chord was loaded the axial tension and the two braces were loaded the axial pressure at the same time, and the chord was loaded the axial tension and two braces were loaded tension and pressure force respectively. Based on the results obtained from the test, the calculating methods on the impact bearing capacity of the relevant codes at home and abroad is compared. The results show that the failure mode of all joints is the dent failure of top surface of chord at the impact zone. When the initial stress state is the same, the local dent deformation and transverse deformation of the larger diameter-thickness ratio increase by 19% and 3% respectively, the peak value of impact force decreases by 8%, and the impact duration increases by 11%; When the diameter-thickness ratio is the same and the chord and brace are not applied the initial axial force, the local dent deformation is the smallest, the impact force is the largest and the impact duration is the shortest; the platform value of the impact force time history curve is suitable to be taken as the impact bearing capacity.
2022 Vol. 41 (6): 123-129 [Abstract] ( 143 ) HTML (1 KB)  PDF (1947 KB)  ( 186 )
130 Concise and closed solution of the seismic responses of viscoelastic energy dissipation structures under Kanai-Tajimi spectrum excitation
ZOU Wanjie，JIANG Yan，ZHANG Mengdan，GE Xinguang
Frequency domain method is widely used in the calculation of random response of linear system, but its significant disadvantages are as follows: (1) There is no closed solution to calculate the power spectrum of random response of multi degree of freedom dynamic system; (2)Numerical integration is needed to obtain the variance and spectral moment of structural response, and the analysis accuracy and efficiency are greatly affected by the integration step and integration interval. Based on the above problems, the analytical solution of the steady response of six parameter viscoelastic energy dissipation multi-degree-of-freedom structure under Kanai-Tajimi spectrum earthquake is studied. A 5-story building structure is analyzed by using this method, and the concise closed form solutions of series response variance and 0-2 order spectral moment of linear multi degree of freedom energy dissipation structure are obtained, which are compared with the virtual excitation method. The results show that the simplified closed form method is a very effective method to calculate the stochastic steady state response of linear multi degree of freedom system.
2022 Vol. 41 (6): 130-138 [Abstract] ( 134 ) HTML (1 KB)  PDF (1680 KB)  ( 38 )
139 Diesel engine fault diagnosis based on an improved convolutional neural network
ZHANG Junhong1,2，SUN Shiyue1，ZHU Xiaolong1，ZHOU Qidi1，DAI Huwei1，LIN Jiewei1
Aiming at the problems of slow model convergence and low diagnosis accuracy when processing small sample data based on the existing Convolutional Neural Network (CNN) diesel engine fault diagnosis method, a diesel engine fault diagnosis method based on improved CNN is proposed. In the convolutional neural network architecture, Exponential Linear Units (ELU) are used as the activation function and the small batch training method accelerates the model convergence, and the global average pooling replaces the fully connected layer to reduce the risk of overfitting. Experimental data analysis shows that the accuracy of the method proposed for diesel engine typical fault diagnosis reaches 99.18%; compared with the unimproved model and the existing CNN-based diesel engine fault diagnosis algorithm, this method still maintains the highest accuracy when dealing with small sample data sets.
2022 Vol. 41 (6): 139-146 [Abstract] ( 293 ) HTML (1 KB)  PDF (1977 KB)  ( 83 )
147 Path perception synchronization trigger method for mechanical vibration wireless sensor cluster networks
FU Hao,TANG Baoping,HUNG Yi,DENG Lei,HE Hao
Aiming at the problem that mechanical vibration wireless sensor networks rely on clock synchronization, beacon synchronization, communication between nodes synchronization and low accuracy, a path sensing synchronization trigger method in cluster network is proposed. Firstly, the dual-mode multiplexing method is used to design the node architecture, and the adjoint networking method is proposed to construct the network topology under the cluster network. Next, the path sensing time measurement method with the auxiliary device measurement as the core is proposed to the dependence on beacon and improve the synchronization trigger accuracy. Finally, the maximum time difference compensation and time first synchronous trigger measurement method are proposed to solve the problem time delay compensation and system instruction interruption. The experimental results show that the maximum error of path sensing synchronization trigger is between 50 and 60μs, and the minimum error is between 10 and 16μs.
2022 Vol. 41 (6): 147-152 [Abstract] ( 145 ) HTML (1 KB)  PDF (1702 KB)  ( 153 )
153 Reasonable lateral seismic system of a long-span cable stayed bridge
LI Lifeng,YIN Huina,TANG Jiahao,HU Rui
In order to explore the reasonable lateral seismic system of cable-stayed bridge under earthquake, taking a long-span cable-stayed bridge as an example, three kinds of lateral seismic system arrangement are proposed, namely, the lateral full limit system, the lateral sliding system and the lateral seismic isolation system with steel dampers. The nonlinear dynamic finite element model is established, and the lateral seismic response of these three seismic systems is analyzed by nonlinear time history method. The results show that the lateral vibration reduction and isolation system of long-span cable-stayed bridge can well control the lateral internal force and deformation of the structure, and the effect of seismic reduction and isolation is good. On this basis, three kinds of layout schemes of steel damper including setting at the main tower, at the main tower and transition pier, at the main tower and transition pier and auxiliary pier are selected, and the corresponding lateral seismic response is compared. Furthermore, the parameters of the optimal layout are analyzed. The results show that the transverse seismic performance of long-span cable-stayed bridge is the best when steel dampers are set at the main tower and transition pier, sliding bearing is set at the auxiliary pier, and the yield strength ratio of steel damper at the main tower and transition pier is generally 0.6~1.2. The research methods and ideas of transverse seismic design in this paper can provide reference for the design of transverse seismic system of cable-stayed bridges in practical projects.
2022 Vol. 41 (6): 153-159 [Abstract] ( 170 ) HTML (1 KB)  PDF (2086 KB)  ( 180 )
160 Effects of mass ratio on the vortex-induced vibration of two types of tandem circular cylinders
DU Xiaoqing1,TANG Chenxin1,ZHAO Yan2,WU Gefei1,YANG Xiao1
To clarify the effects of mass ratio and the vibration conditions of the upstream cylinder (a fixed or a vibrated upstream cylinder) on vortex-induced vibration of two tandem circular cylinders, numerical simulations were carried out at a Reynolds number of 100 with an intermediate pitch ratio of P/D = 4, where P is the distance between the centers of two cylinders and D is the diameter of the cylinder. The effects of the mass ratio (m* = 2, 10 and 20) and the vibration conditions of the upstream cylinder on vibration characteristics and flow patterns of two tandem circular cylinders were analyzed as well as their mechanisms. Results show that the vibration amplitudes of the downstream cylinders decrease with the increase of mass ratio. Compared with a fixed upstream cylinder, a vibrated upstream cylinder would induce a larger transverse vibration amplitude of the downstream cylinder of the same mass ratio. For a vibrated upstream cylinder, apparent “lock-in” regions are observed for both cylinders at three mass ratios. Note that a “soft lock-in” phenomenon arises for both cylinders at the mass ratio of 2. For a fixed upstream cylinder, the “lock-in” region is not detected. Three identical wake flow modes, i.e., “2S” mode, irregular mode and parallel vortex street mode, are observed in the wake region of two tandem cylinders for all three mass ratios. Two flow generation mechanisms, namely, vortex impingement and vortex fusion, arise in the wake of two tandem cylinders for two types of upstream cylinders.
2022 Vol. 41 (6): 160-168 [Abstract] ( 154 ) HTML (1 KB)  PDF (2938 KB)  ( 248 )
169 Experimental and numerical study on the incident pulse similarity law and pulse shaping technique in SHPB test
WANG Jiangbo, LI Wenfeng, REN Wenke,WANG Xiaodong,LI Jiliang, GAO Guangfa
Based on the dimensional analysis theory, whether the incident pulse of split Hopkinson pressure bar(SHPB) test with pulse shaper satisfied the geometric similarity law is studied. The results are verified by experiments and numerical simulation. The effects of pulse shaper and impact bar parameters on the two important inflection points of incident pulse are analyzed by the SHPB device with a diameter of 14.5mm. Moreover, the dimensionless expressions of incident pulse at T1 and T2 inflection points are obtained. The results show when the pulse shaper and striker bar diameter are enlarged or shrunk with the impact bar velocity remains constant, the SHPB device pulse-shaped conforms to the geometric similarity law. The inflexion point T1 is mainly related to the pulse shaper diameter and its thickness and the striker bar velocity, while the inflection point T2 is mainly affected by the pulse shaper thickness and the striker bar velocity. The striker bar length only effects the incident pulse duration, but has no effect on the rise edge stage of the incident pulse.
2022 Vol. 41 (6): 169-176 [Abstract] ( 146 ) HTML (1 KB)  PDF (1975 KB)  ( 54 )
177 Water hammer protection effect of gasbag-type pneumatic tank based on the analysis using the Bentley Hammer software
WANG Shunsheng,GUO Xinyuan
Water hammer is inevitable in pressurized pipeline water delivery projects. Gasbag-type pneumatic tanks are more reliable and economical than other water hammer protection measures in the high-lift water delivery projects with medium-and-small flow. Based on the actual project, the commercial software Bentley Hammer was applied to analyze the hydraulic transient process of the water delivery pipeline. The water hammer protection result was studied when the combination of the gasbag-type pneumatic tank, multi-function water pump control valve and air valve was used, and the impact of the volume and preset pressure of the tank on the result of water hammer protection was explored. Numerical simulation models for three cases were constructed through the Bentley Hammer software, where no protective measures were used, the combination of multi-function pump control valve and air valve was used, and the combination of multi-function pump control valve, air valve and gasbag-type pneumatic tank was adopted respectively. Hydraulic transient process analysis was performed when the three pumps stopped simultaneously. The research results showed that the installation of gasbag-type pneumatic tank in high-lift water delivery project with medium-and-small flow can achieve good water hammer protection result. For the overall water delivery pipeline system, the water hammer protection ability of the gasbag-type pneumatic tank increases with the increase of the volume and the preset pressure of the tank. Appropriate volume and preset pressure of the pneumatic tank can effectively control the maximum positive and negative pressure of water hammer in the pipeline and help to achieve the optimal social and economic benefits.
2022 Vol. 41 (6): 177-182 [Abstract] ( 196 ) HTML (1 KB)  PDF (1877 KB)  ( 62 )
183 Transverse free vibration characteristics of a tapered pile in the three-parameter Pasternak viscoelastic foundation
ZHANG Jinlun,ZHANG Axiang,GE Renyu,SUN Junwei
Based on a three-parameter Pasternak viscoelastic foundation model, the transverse free vibration characteristics of tapered pile of circular section subjected to initial axial pressure were investigated. The pile was simplified into a vertical linear elastic Timoshenko tapered beam-column, and the effects of pile-soil interface friction and the longitudinal variation of foundation parameters around the pile were considered, and then the dynamic governing equations for the tapered pile-soil system were derived. The solution of the equations was transformed into the first order eigenvalue problem of general linear algebraic equations with variable coefficients by means of variable separation, dimensionless and numerical simulation of the differential quadrature method. Then, the eigenvalues and eigenvectors of each order were solved by QR method. The effects of cone angle of pile, axial load on pile head, length-diameter ratio, lateral friction, soil foundation parameters around pile and their linear variation on the fundamental frequencies and attenuation coefficients of the tapered pile were discussed under corresponding boundary conditions. The results show that the natural frequencies and corresponding attenuation coefficients of tapered pile decrease with the increase of cone angle, and the critical damping decreases with the increase of cone angle, and then the coupling effect between cone angle and foundation damping is obvious. The influence of the lateral friction and the non-uniform distribution of foundation parameters along the longitudinal direction of the pile on the fundamental frequency cannot be ignored.
2022 Vol. 41 (6): 183-196 [Abstract] ( 124 ) HTML (1 KB)  PDF (2948 KB)  ( 61 )
197 Instantaneous frequency identification of time-varying structures using variational mode decomposition and synchroextracting transform
TANG Lei,HUANG Tianli,WAN Xi
Aiming at the problem that synchroextrcting transform (SET) cannot separate multi-component signals whose frequency components are close to each other, a method combining variational mode decomposition (VMD) and synchroextrcting transform is proposed to identify the instantaneous frequency of time-varying structures. Firstly, the number of preset modes is determined by Fourier transform, and the multi-component signal is decomposed by using VMD to obtain multiple mode components; Then, SET is used to analyze each modal component to obtain the instantaneous frequency; Finally, the time-frequency representation of each modal component is superimposed to obtain a complete time-frequency representation of multi-component signal. The results of instantaneous frequency identification for multi-component time-varying signals and two degree of freedom time-varying structural free vibration response signals verify the effectiveness and correctness of the method based on VMD and SET. The results show that the method has strong noise robustness and energy aggregation, it circumvents the problem that SET process multi-component signals with close frequency components, and can effectively identify the instantaneous frequency of time-varying structure with close frequency components. The applicability of the method is verified by the experiment of identifying the instantaneous frequency of the cable when the cable force changes linearly and sinusoidally.
2022 Vol. 41 (6): 197-205 [Abstract] ( 226 ) HTML (1 KB)  PDF (2595 KB)  ( 98 )
206 Centrifugal pump fault diagnosis based on the multi-physical field signals correlation analysis and support vector machine
SUN Yuanli1,2,SONG Zhihao2
In order to solve the problem of traditional centrifugal pump fault diagnosis using only a single vibration signal and unable to comprehensively utilize the correlation information of multi-physics, this paper proposes a fault diagnosis based on the combination of multi-physical field signals correlation analysis and support vector machine (SVM) method. First, normalize the collected multi-physics signals of the centrifugal pump in different states; secondly, calculate the correlation of any two normalized multi-physics signals and form the correlation matrix; and finally, Using the correlation matrix as a feature to use SVM for diagnosis. In order to verify the effectiveness of the method proposed in this paper, the failure data of g centrifugal pump is used to verify the proposed method. The results show that: compared with the fault diagnosis method that only uses a single signal, the method proposed in this paper can fully extract the multi-physics correlation information of the centrifugal pump, feature extraction is more sufficient, and effectively improve the fault diagnosis rate of the centrifugal pump.
2022 Vol. 41 (6): 206-212 [Abstract] ( 163 ) HTML (1 KB)  PDF (1961 KB)  ( 114 )
213 Control of the complex vibration of a class of double-side capacitive microresonator via the delayed position feedback
SHANG Huilin,LIU Hai,DONG Zhanghui,LIU Zhiqun
A type of electrostatic double-side capacitive micro resonator is considered, and time-delayed position feedback on the DC voltage of its driven circuit is applied to control the complex dynamic behaviors of the microstructure, such as chaos and pull-in instability. Firstly, based on the theory of global bifurcation, the necessary conditions for homoclinic bifurcation and heteroclinic one in a time-delay position feedback control system are discussed; thus, the control mechanism of the chaotic motion and pull-in instability is analyzed. Then the validity of theoretical prediction is verified by the agreement between numerical results and theoretical ones. It follows that when the coefficient of the gain is positive, the delayed position feedback can be applied to effectively suppress the two complex dynamic phenomena i.e. chaos and pull-in instability which can be attributed to the global bifurcation but with totally different mechanism. This paper has some potential value of application in ensuring the dynamic integrity of the micro-resonator vibration systems and the design of the microstructures.
2022 Vol. 41 (6): 213-221 [Abstract] ( 167 ) HTML (1 KB)  PDF (1623 KB)  ( 67 )
222 Vibration characteristics analysis of the metro tunnel subarea blasting based on wavelet packet technique
CHEN Jihui1,QIU Wenge1,ZHAO Xuwei1,WANG Hailiang2
Wavelet packet analysis is widely used in the amplitude frequency characteristics of blasting vibration signals. It is helpful to analyze the propagation law and control of blasting vibration. Based on the divisional blasting vibration test of Qingdao Metro overlapping tunnel, the monitoring data of blasting vibration are obtained. The frequency and energy distribution characteristics of tunnel blasting vibration signals are studied by using wavelet packet technology. The results show that the differences of blasting vibration characteristics are caused by the number of free surfaces and excavated area. The main frequency of blasting vibration in cutting area is smaller than that in auxiliary area. With the increase of horizontal distance, the main frequency band in front of the blasting face (i.e. the tunnel not excavated section) generally moves to high frequency, and the proportion of high frequency energy increases. At the back of the working face, the main frequency band moves to low frequency with the increase of horizontal distance, and the proportion of low frequency energy increases. The variation trend of blasting vibration energy with distance in auxiliary area and cutting area is basically the same, but the attenuation rate of energy with distance is different. Combined with the frequency and energy factors, this paper puts forward constructive suggestions on the safety protection of the existing tunnel, so as to ensure the safety and stability of the tunnel.
2022 Vol. 41 (6): 222-228 [Abstract] ( 158 ) HTML (1 KB)  PDF (2419 KB)  ( 263 )
229 Parameter design of bulk material machining system with variable delay feedback
CHEN Ning， ZHANG Hongbing， LI Wanxiang， LI Xiongbing
A parameter design method for variable time-delay vibration system was proposed to ensure the stability of bulk machining system. In this system the materials accumulation affects production speed and processing unit weight, the material impacts the processing unit after free falling, the settlement displacement signal of the processing unit is used to complete the negative feedback regulation of the material supply speed and a variable time delay feedback link is formed. Firstly, the static equilibrium and stability of the system was studied according to the dynamic differential equation of the system. Then, the parameters range of stiffness coefficient and damping coefficient which can ensure the stability of the system was solved by using the condition of Hopf bifurcation. Finally, the theoretical analysis was verified with Simulink simulation, and the selected parameters make the system have certain anti-interference ability. Using the eigenvalue characteristics of bifurcation points to determine the selectable range of parameters could provide a reference method for the parameter design of variable time-delay systems.
2022 Vol. 41 (6): 229-235 [Abstract] ( 127 ) HTML (1 KB)  PDF (1484 KB)  ( 156 )
236 Extraction method of rolling bearing fault characteristics based on FVMD
ZHANG Shuang1,2, WANG Xiaodong1,2, LI Xiang1,2, YANG Chuangyan1,2
Since the mode number K and penalty factor α of variational mode decomposition (VMD) cannot be determined adaptively, a method of rolling bearing fault feature extraction based on fast VMD(FVMD) is proposed. Firstly, the spectrum trend segmentation method is used to determine the spectrum trend segmentation boundary, and then the decomposition mode number K, penalty factor α and initial central frequency ω of VMD are adaptively determined. Secondly, the adaptive decomposition of the original vibration signal is completed based on the parameters K, α and ω, and the kurtosis criterion of effective weight is established to extract the effective intrinsic mode function (IMF) components. Finally, the effective IMF component is calculated by Hilbert envelope demodulation, and the envelope spectrum of the reconstructed signal is obtained to extract the fault features of rolling bearing. Simulation signals, Case Western Reserve University (CWRU) and National Aeronautics and Space Administration (NASA) of rolling bearing data are used to complete the comparative experiments between the proposed method and the traditional VMD method. Experimental results show the effectiveness and feasibility of the proposed method.
2022 Vol. 41 (6): 236-244 [Abstract] ( 226 ) HTML (1 KB)  PDF (2421 KB)  ( 118 )
245 Shock amplification mechanism based on multi-body dynamics
YAN Ming, GU Xiping, JIN Yingli, KONG Xiangxi
To study the shock amplification method, combined classical collision theory with dynamic contact theory, created kinematic model of double mass shock amplifier, derived the calculation formula of acceleration and acceleration magnification factor. Studied the effects of collision duration ratio, mass ratio (between the amplifier and the drop-off stage), waveform generator stiffness ratio on acceleration amplification factor. Finally, the theory of two body collision is verified by experiments. The results show that the acceleration magnification ratio decreases with the increase of mass ratio and increases with the increase of waveform generator stiffness ratio and collision duration ratio.
2022 Vol. 41 (6): 245-249 [Abstract] ( 221 ) HTML (1 KB)  PDF (997 KB)  ( 81 )
250 Fast deconvolution algorithm based on compressed focus grid points
WANG Yue1， YANG Chao1， WANG Yansong1， HU Dingyu2
In order to improve the computational efficiency of the deconvolution algorithm, a fast deconvolution algorithm was proposed to compress focus grid points. Based on the output of functional beamforming, the algorithm compressed the number of focus grid points participating in the deconvolution algorithm loop according to the set sound source recognition threshold. The algorithm combines the advantages of functional beamforming and CLEAN-SC（CLEAN based on spatial source coherence）, which can further improve the spatial resolution of multi-source location and effectively reduce the calculation time of the algorithm. Simulations and experiments show that the proposed algorithm has a good recognition effect for incoherent multiple sound sources below the Rayleigh limit. In the experiment, the computational efficiency of the proposed algorithm is about 3.90 times higher than that of CLEAN-SC.
2022 Vol. 41 (6): 250-255 [Abstract] ( 161 ) HTML (1 KB)  PDF (1073 KB)  ( 45 )
256 Response analysis of a submerged floating tunnel under the combined effect of underwater explosion and wave
LUO Gang1, GUO Zhengru1, ZHANG Yulong1, REN Yi2, PAN Shaokang3
In order to study the response of the submerged floating tunnel under the combined effect of underwater explosion and wave, the third-order Stokes wave equation and Morison equation were used to calculate the wave force, the differential equation of motion was established based on the D'Alembert principle and the Galerkin method and Runge Kutta method were used to solve it. The load model and joint model were verified.Finally,the influence factors such as different load -forms,wave parameters,and explosion parameters were compared and analyzed. The results show that the combined effect of underwater explosion and wave has a significant impact on the dynamic response of the submerged floating tunnel system. Based on the numerical calculation results,as the wave height and inertia force coefficient CM increase, the mid-span maximum displacement of the structure increases. With the increase of the period, embedded depth and Drag force coefficient CD,the mid-span maximum displacement of the structure decreases. The relationship between the scaled distance and the mid-span maximum displacement of the structure is power exponential, the larger the scaled distance, the smaller the mid-span displacement of the structure. Furthermore, the peak pressure Pm of the explosion shock wave is also affected by the similarity coefficients K0 and α in the Cole formula. Through the study of the similarity coefficients K0 and α, it is found that the similarity coefficient K0 has little influence on the system displacement response, and α has a significant influence on the system displacement response. As α increases, the system response tends to stabilize.
2022 Vol. 41 (6): 256-264 [Abstract] ( 166 ) HTML (1 KB)  PDF (1823 KB)  ( 48 )
265 Sound absorption characteristics of acoustic tiles with local resonance cavity structure under oblique incidence
WANG Jiabei, ZHOU Hao
The sound absorption characteristics of the Anechoic tiles have an important effect on the acoustic stealth performance of underwater vehicles. Considering the structure of the cavity covering layer and the low frequency sound absorption performance of the local resonance film material, the finite element model of the sound absorption tile with the local resonance cavity structure has been established by COMSOL. The sound absorption performance in the frequency band of 10-2000Hz has been studied. The sound absorption mechanism has been revealed by the vibration displacement nephogram. The influences of incident angle on sound absorption performance have been analyzed by displacement vector diagram and kinetic energy density diagram. The results show:(1) The sound absorption coefficient increases with the increase of frequency and oblique incidence angle; (2) The sound absorption mechanism is as follows: the contraction and expansion of the upper and lower cavities cause the transformation of p-wave to s-wave with large loss factor. The anti-resonance of the local resonance structure consumes sound energy. The two work together to improve the sound absorption performance of the anechoic tiles; (3) Oblique incident acoustic waves increase the transverse displacement, increasing the shear waves’ conversion; The larger the oblique incidence angle is, the higher the kinetic energy density is. The more sound energy is consumed, so the sound absorption performance is enhanced. The research results can provide theoretical guidance for the design of low frequency sound absorption characteristics of anechoic tiles.
2022 Vol. 41 (6): 265-270 [Abstract] ( 152 ) HTML (1 KB)  PDF (1353 KB)  ( 67 )
271 On the axial vibration and the failure of outer-rotor fans
LIU Haitao, CHEN Jun, HUANG Di, TANG Xionghui, LIU Yongjiang, LI Hua, PENG Xuanlin, ZENG Yaping, XIA Liang
In order to systematically study and solve the short-term failure of the outer-rotor fans which are used for the auxiliary converters of the first low-speed maglev train in China, a dynamical model of a two-degree-freedom system on a flexible base was built to simulate the axial vibration of the fans. According to the analytical solutions of the displacement of the model, the vibration tests on the running lines, the variable frequency vibration test of the fans as well as the FRF tests both on trains and test-rig in the lab, it can be verified that it is the coupling between the fourth order electromagnetic force as well as the current harmonic excitations and the axial vibration mode of the fans that causes the excessive vibration of the rotor shaft, which leads to the friction between the bearing and the belleville spring. Based on the analysis results, a method and the corresponding load spectrum to locate and reproduce the failure of the bearings were proposed, which was conducted on a shake table successfully. At last, the effect of the parameters of the fans such as the resilience of the base as well as the stiffness and damping of the stator and rotor of the fan were analyzed systematically in order to improve the reliability and optimize the structural design.
2022 Vol. 41 (6): 271-280 [Abstract] ( 252 ) HTML (1 KB)  PDF (2507 KB)  ( 80 )
281 Analysis on fractal characteristics of the ballastless track irregularities of high-speed railways
LI Zaiwei1, WU Pengfei1, LIU Xiaozhou2, HE Yuelei1
Ballastless track irregularities, as a direct indicator of the line's service status, have always been the core of high-speed railway inspection and maintenance operations. In order to deeply and effectively grasp the temporal and spatial distribution characteristics of ballastless track irregularities, starting from the basic physical meaning of fractal geometry, analyzing the fractal characteristics of track irregularities, comparing and selecting the calculation methods of the fractal dimension of track irregularities, by analyzing typical high-speed railways Accumulated inspection data of ballastless track irregularities, discuss the feasibility and rationality of fractal dimension for track section quality management. The results show that track irregularities have typical fractal characteristics of self-similarity and scale invariance; the results of track irregularity calculations by various fractal dimension methods have significant differences, and the calculation accuracy and robustness of the variation method are better. It is suitable for calculating the fractal dimension of track irregularity; the fractal dimension can effectively characterize the trend of deteriorating service status of the track, and it is less disturbed by the line operation and maintenance. It is suggested to further study the characteristics of the fractal dimension of track irregularities under different track conditions based on the specific maintenance conditions of the track.
2022 Vol. 41 (6): 281-288 [Abstract] ( 176 ) HTML (1 KB)  PDF (1980 KB)  ( 133 )
289 Influence of thickness distribution on the vibration characteristics of thin plates with variable thickness
XU Fengxiang1, 2, DONG Zhuang1, 2, SU Jianjun3
Based on the theoretical model of the variable-thickness thin plate and the method of solving vibration characteristics, the vibration characteristics of different types of variable-thickness thin plates are simulated and analyzed, and the change rule with the thickness change is summarized. Through the modeling and simulation of linear and non-linear variable thickness thin plates, the accuracy of the variable thickness thin plate modeling process and simulation results is verified; based on the same modeling method, the thin plate is given different thickness variation rules, including unidirectional linear, single There are four kinds of nonlinear thickness, bidirectional linear and bidirectional nonlinear variable thickness thin plates. The vibration characteristics of the thin plates with equal thickness and equal thickness under the classic boundary conditions and their own changes with the thickness change parameters are changed. Finally, A new type of variable-thickness thin plate is proposed, and it is found and verified that it can effectively improve the low-order natural frequency of the thin plate under the classical boundary conditions compared to the previous four variable-thickness thin plates.
2022 Vol. 41 (6): 289-297 [Abstract] ( 166 ) HTML (1 KB)  PDF (2368 KB)  ( 72 )
298 Numerical simulation on the protective effect of the wind barrier on a flat steel box girder
HU Bo1, XIANG Huoyue1,2, LI Yongle1,2
In order to study the protective effect of the wind barrier on the flat steel box girder, based on the verification of the accuracy of the numerical model, the influence of the wind barrier on the wind field distribution of the bridge deck was studied. The surrogate model of wind speed reduction factor of wind barrier is established by using neural network model, the influence of height and porosity of wind barrier on its wind protection effect is analyzed, and the contour of wind speed reduction factor with height and porosity of wind barrier is provided. The results show that: when the height of the wind barrier is increased to a certain extent, increasing the height of the wind barrier does not significantly improve the wind protection effect; with the increase of the porosity of the wind barrier, the wind speed reduction factor presents different curves at the positions of the windward side lane and the leeward side lane; when the porosity of wind barrier is greater than 20% and the height is less than 3.5m, the wind speed reduction factor on the upstream lane is greater than that on the downstream lane. The neural network model of wind speed reduction factor can be used to predict and evaluate the wind protection effect of wind barrier, and the research results can be used as a reference for the selection of wind barrier parameters.
2022 Vol. 41 (6): 298-306 [Abstract] ( 178 ) HTML (1 KB)  PDF (2735 KB)  ( 325 )
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