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2022 Vol. 41, No. 19
Published: 2022-10-15
 
1 Measurement method of structural dynamic displacement based on machine vision and UAV
HAN Yitian1, FENG Dongming1,2, WU Gang1,2
Here, aiming at limitations of vision-based structural displacement measurement method, such as, insufficient resolution of camera or difficulty in selecting location of measurement base station, a structural dynamic displacement measurement method combining machine vision and unmanned aerial vehicle (UAV) was proposed. Taking laser spot projected by static laser lamp on structure surface as a reference, an algorithm was designed to automatically detect target measurement point and laser spot position, calculate and update scale factor frame by frame, estimate and eliminate motion of UAV itself, and then calculate absolute displacement of target measurement point. In order to verify the accuracy of the proposed method, a small frame model test was designed, and then this method was applied in large-scale earthquake simulation shaking table tests. The results showed that displacement responses obtained using the proposed method agree well with the reference data measured using laser displacement meter and accelerometer; the proposed method can better be applied in structural dynamic displacement measurement and modal parametric identification.
2022 Vol. 41 (19): 1-7 [Abstract] ( 258 ) HTML (1 KB)  PDF (1855 KB)  ( 73 )
8 Influence mechanisms of different bridge spans on vertical coupled vibration of low and medium speed maglev train-simply supported beam system
LI Xiaozhen1, WANG Yuwen1, HU Qikai1, WANG Dangxiong2
In order to research the influences of different spans on the vertical dynamic interaction of low-to-medium speed(LMS) maglev train-simply supported beam system. The vertical coupling vibration analysis model for LMS maglev train-simply supported beam system was established. Taking the three typical concrete simply supported beams with different spans of 25m, 30m and 35m as the research object, the vertical vibration characteristics of low-to-medium speed maglev train-simply supported beam system were analyzed. It was shown that the numerical model of coupling vibration is reliable; with the increase of simply supported beam span, the vertical deflection of the bridge decreases, while the vertical acceleration decreases; the vertical dynamic displacement and acceleration of the vehicle body and suspension frame increase with the increase of simply supported beam span, the dominant frequency bands of the vertical acceleration of the suspension frame are concentrated in 0-30Hz and 50-80Hz, the whole car body exhibits low frequency vibration (0-15Hz); the fluctuation range of the suspension gap and levitation force increases with the increase of simply supported beam span; the different spans can change the spectrum distribution characteristics of vertical acceleration of bridge; according to the need, the maglev line can flexibly choose the span of the simply supported beam on the premise of meeting the static safety service, so as to save the project cost to the maximum extent.
Keywords: Low-to-medium-speed maglev train; simply supported beam; different bridge span; coupling vibration; model verification
2022 Vol. 41 (19): 8-15 [Abstract] ( 85 ) HTML (1 KB)  PDF (3199 KB)  ( 15 )
16 Dynamic bending of gun barrel during tank moving under multi-source excitation
CHEN Yu1, YANG Guolai2, LIU Jinfeng1, ZHOU Honggen1
Dynamic bending of tank barrel under multi-source excitation such as random road excitation and projectile-barrel contact force is the key factor that restricts the firing accuracy of the moving tank at present. Based on the harmonic superposition method and the improved L-N contact algorithm, the influence of the road random excitation and projectile-barrel coupling were described. A dynamic co-simulation methodology was used to establish the dynamic model of the moving tank considering the barrel’s flexibility. The dynamic bending of the tank barrel during the projectile in-bore motion under multi-source excitation was calculated and analyzed. The research results show that the dynamic bending of the barrel is less affected by the projectile-barrel coupling effect, and it is mainly a comprehensive performance under the effect of dead weight and road excitation. When revising the firing accuracy error of the high mobility tank, the influence caused by the barrel dynamic bending should be considered comprehensively.
Keywords: tank gun; road excitation; projectile-barrel coupling; barrel bending; muzzle vibration
2022 Vol. 41 (19): 16-21 [Abstract] ( 104 ) HTML (1 KB)  PDF (1846 KB)  ( 27 )
22 Analysis of mixed-lubrication characteristics and structural optimization of marine composite liner stern bearing with inclined journal
L Fangrui1,2, RAO Zhushi2, WANG Jue1
The marine stern tube bearing supports the propeller shaft stretching outside the ship. Due to the gravity of the propeller, the center line of the journal is no longer parallel to that of the bearing hole, but misaligned in the vertical direction. The journal misalignment makes the bearing film thickness and pressure no longer evenly distributed along the axial direction, significantly reduces the bearing capacity, and makes the bearing in mixed-lubrication regime. It is easy to cause problems such as collision, serious wear and even burnt out, which seriously endangers the service safety of the shafting. In order to improve the lubrication performance of misalignment water-lubricated bearing, especially improve the pressure distribution, a bearing design method using composite liner is proposed in this paper. The polymer material is used as the bearing surface, and a rubber layer is between the polymer layer and the metal shell. The thickness of the rubber layer can be uniform or non-uniform. On this basis, the mixed-lubrication model of composite liner water lubricated bearing is established, and the performances of the bearings with single liner structure, with uniform thickness composite liner structure and with non-uniform thickness composite liner structure are analyzed. The results show that for the water-lubricated bearing in mixed-lubrication regime, the composite liner can improve the pressure distribution, reduce the friction coefficient and the speed when the mixed lubrication regime transitions to the hydrodynamic lubrication regime, and the non-uniform thickness composite liner can significantly improve the lubrication characteristics. The fitting formula of the optimal rubber layer thickness is summarized, and the application range of the formula is given. The form of the formula is simple and convenient for bearing design and calculation.
Key words: Marine stern tube bearing; journal misalignment; mixed-lubrication; structural optimization
2022 Vol. 41 (19): 22-29 [Abstract] ( 87 ) HTML (1 KB)  PDF (2345 KB)  ( 17 )
30 Non-Gaussian wind pressure extreme value estimation method for long-span roof structure considering bandwidth modification
YAN Bowen1, WEI Min1, LIU Min1, LIU Kun2, LI Zhengliang1, ZHOU Xuhong1,3
This study proposed a Translation Process Method (TPM) with modified bandwidth for the broad-band wind pressure and the extreme value estimate method. Based on the wind tunnel experiments, the peak factors of wind pressures on the large-scale roof structure were systematically studied with the proposed TPM and available extreme value estimate methods. The results show that the peak factor of wind pressures estimated by the extreme value distribution of Gaussian process significantly deviated from those obtained by the estimate methods for non-Gaussian process; the Hermite moment method neglecting the bandwidth parameter overestimated the peak factor of non-Gaussian wind pressures; as compared with the Hermite moment method and the target probability method with modified bandwidth parameter, the Sadek-Simiu method and TPM with modified bandwidth estimated the peak factors of wind pressures on the large-scale roof structure more accurately, which were in better correspondence with the observed extreme values from the experiments; meanwhile, the discrepancies and skewness of the estimated peak factors by the method proposed in this study were the smallest; therefore, the proposed TPM with modified bandwidth could efficiently and reasonably estimate the extreme values of non-Gaussian wind pressures on the large-scale roof structure.
Key words: Large-scale roof structure; non-Gaussian wind pressure; peak factor; wind tunnel test; bandwidth parameter
2022 Vol. 41 (19): 30-36 [Abstract] ( 92 ) HTML (1 KB)  PDF (2343 KB)  ( 20 )
37 Effects of spatial difference of ground motion on seismic response of asphalt concrete core wall rockfill dam-overburden foundation system
LI Chuang1, SONG Zhiqiang1, WANG Fei1, LIU Yunhe1, ZHANG Cunhui2
The spatial variation of ground motion often has a significant impact on the response of structure-foundation system. Based on the physical mechanism of the formation of ground motion variation, the incident P-wave and SV wave time histories are determined based on the two-dimensional design ground motion. The combined effect of ground motion is introduced to construct the spatial non-uniform seismic field, and the wave input model of spatial differential ground motion was established. The seismic response of earth-rock dam-overburden foundation system with asphalt concrete core wall is further studied with the input model. The results show that the non-uniform seismic input model of the surface free field displacement horizontal and vertical component of the control points are in good agreement with the design ground motion, and to consider the ground motion spatial correlation based on the simulation of seismic wave propagation time lag, the amplitude and the schedule change shape differences, spatial characteristics. Compared with the consistent input, the variance of horizontal and vertical acceleration distribution of overburden foundation plane increases by 341% and 50% respectively under the non-consistent input. The vertical stress and shear stress of the core wall may be increased by 198% and 51.9% respectively due to the spatial difference of ground motion. The mean values of the acceleration and permanent deformation of the dam crest increase, and the maximum results increase by 25.53% and 13.06%, respectively. The traditional uniform wave input method may underestimate the seismic response of the structure, so it is necessary to consider the spatial difference of seismic response of the earth-rock dam-overlay foundation system with asphalt concrete core wall 
Key words: spatial variation of motion; combination of seismic waves; non-uniform seismic input; asphalt concrete core wall rockfill dam; seismic response of dam
2022 Vol. 41 (19): 37-47 [Abstract] ( 79 ) HTML (1 KB)  PDF (3509 KB)  ( 39 )
48 Vertical-torsional coupled vibration characteristics of strip mill under additional dynamic bending moment of universal joint shaft
HOU Dongxiao1, CHEN Shanping1, FANG Cheng1, SHI Peiming2, WANG Xingang1
Considering the effect of the Angle of universal joint on the additional dynamic bending moment, the vertical torsional coupling vibration model of the lower strip mill affected by the Angle of universal joint was established. The main common amplitude-frequency equation of the rolling mill coupling system is obtained by multi-scale method. The bifurcation characteristics of the coupled vibration system are analyzed by singularity theory, and the transition set of the system and the conditions of different bifurcation forms are obtained. Finally, the actual parameters of 1780 rolling mill were used to analyze the influences of joint Angle, rolling force parameters, joint torsional stiffness and external disturbance force on the main common amplitude and frequency characteristics of the vertical and torsional directions of the rolling mill, so as to provide theoretical reference for further suppressing the vibration of the rolling mill.
Key words: joint angle;Strip rolling mill; additional dynamic moment; vertical-torsional coupled; primary resonance
2022 Vol. 41 (19): 48-54 [Abstract] ( 70 ) HTML (1 KB)  PDF (1751 KB)  ( 35 )
55 Application of CMRDE in bearing fault diagnosis
CHEN Yan, ZHENG Jinde, PAN Haiyang, TONG Jinyu
The vibration signals are often nonlinear and non-stationary when the fault occurs. Reverse dispersion entropy (RDE) can effectively extract nonlinear dynamic fault features from vibration signals. However, the RDE value at a single scale cannot fully reflect the complexity and nonlinear characteristics of vibration signals. Inspired by multi-scale entropy (MSE) and aiming at the problem of coarse-graining in MSE, composite multi-scale reverse dispersion entropy (CMRDE) was proposed. CMRDE is compared with multi-scale reverse dispersion entropy (MRDE) and RDE through simulation signal analysis and the results show that it can reflect the difference of signal complexity at different scales and its varying trend is much smoother and the fluctuation is much smaller. Based on this, CMRDE was applied to the fault feature extraction of rolling bearings and a new rolling bearing fault diagnosis method was proposed based on CMRDE, ensemble empirical mode decomposition and cuckoo search support vector machine. The proposed fault diagnosis method was applied to analyze experimental data of rolling bearing with comparing with the existing methods and the analysis results indicate that the proposed method can effectively identify the fault location of rolling bearing and the errors of extracted fault feature is smaller and the fault recognition rate is higher than the compared methods.
Key words: reverse dispersion entropy; composite multi-scale reverse dispersion entropy; rolling bearing; fault diagnosis
2022 Vol. 41 (19): 55-63 [Abstract] ( 90 ) HTML (1 KB)  PDF (3083 KB)  ( 54 )
64 Applicability of bridge vibration energy harvester based on nonlinear energy sink
YANG Xingsen1, LI Zhaoyu2, WANG Shaohua2, DOU Yinling1,3, ZHAN Yulin1, ZHAO Renda1
As a classical vibration control technology, nonlinear energy sink (NES) has been innovatively combined with approaches to harvest vibration energy in recent years, and a series of research efforts had been made. For health monitoring system of bridges, energy supplying of the sensors has always been a problem needed improving. Exploring the applicability of vibration energy harvester based on nonlinear energy sink to bridges, which is of great theoretical and practical significance. Taking a simply supported railway girder bridge as example, this work investigates the applicability of vibration energy harvester based on the nonlinear energy sink to the bridge. Firstly, mechanical properties and parameters of the NES are characterized. Subsequently, dynamic responses and energy harvesting effect of the NES under different initial excitation conditions are evaluated using the vertical coupling dynamics theory of vehicle-track-bridge and the finite element method. The results show that the NES with weak linear stiffness and strong nonlinear stiffness installed on the bridge is sensitive to initial displacement, and targeted energy transfer (TET) is excited only if initial displacement reaches a certain threshold. Moreover, TET cannot be excited when initial energy input cannot surpass the critical threshold, so the energy harvesting efficiency is poor. Based on the results of numerical analysis, the proposed NES can take full advantage of nonlinear characteristics under appropriate vibration excitation of the bridge, so as to obtain excellent energy harvesting efficiency.
Keywords: bridge vibration; nonlinear energy sink; piezoelectric vibration energy harvesting; targeted energy transfer
2022 Vol. 41 (19): 64-70 [Abstract] ( 95 ) HTML (1 KB)  PDF (2426 KB)  ( 25 )
71 Near-fault pulse-like ground motion identification method based on non-causal filtering and zero- point method
FENG Jun, ZHAO Boming, ZHAO Tianci
An algorithm for extracting the velocity pulse signal was proposed based on the Butterworth non-causal low-pass filter and the zero-point method, and the cut-off frequency of the filter is determined by the number of extreme points in the pulse signal. 666 records with peak ground velocities above 30 cm/s were utilized as training data. The identification criteria of single-pulse-like and double-pulse-like records based on the relative energy and amplitude of pulse signals were proposed. The pulse period was calculated by the duration of the most effective pulse. The comparison with the reference methods shows that the proposed pulse extraction method has a high fitting effect and can be used to extract asymmetric pulse signal and double-pulse signal; The proposed quantitative identification criteria can effectively identify single-pulse-like and double-pulse-like ground motions; The proposed pulse period calculation method can calculate the pulse periods of s single-pulse-like and double-pulse-like records.
Key words: near-fault ground motion; pulse-like ground motion; velocity pulse; pulse period; quantitative identification
2022 Vol. 41 (19): 71-79 [Abstract] ( 81 ) HTML (1 KB)  PDF (2984 KB)  ( 34 )
80 Modeling and nonlinear vibration response of antisymmetric cross-ply bistable shallow shell in humid and hot environment
ZHANG Boyu, ZHANG Wei
Firstly, the nonlinear dynamic modeling of antisymmetric cross-ply bistable shallow shell in hot and humid environment is carried out. Based on the classical shell theory and considering the effects of temperature and humidity, the thermal expansion coefficient and wet expansion coefficient are added to the constitutive equation. Secondly, the compatible equation and the dynamic equilibrium equation are combined to establish a nonlinear dynamic model for the antisymmetric cross-ply laminated bistable shell. Finally, Galerkin discretization is conducted on the vibration partial differential equation to obtain the three-degree-of-freedom nonlinear ordinary differential equation. The averaged equation under the polar coordinate system and the averaged equation under the rectangular coordinate system is used to study the non-linear dynamics in the antisymmetric bistable shallow shell. The influence law of the external excitation parameters on the system is explored and the system’s non-linear dynamic behavior characteristics are explored when the main resonance   is close to   and the internal resonance is 1: 2: 2.
Keywords: Antisymmetric cross-ply; Bistable shell; Galerkin discretization; Nonlinear dynamics
2022 Vol. 41 (19): 80-89 [Abstract] ( 57 ) HTML (1 KB)  PDF (1959 KB)  ( 28 )
90 Sensitivity of vibration measuring point location to cavitation of centrifugal pump
ZHANG Yuhang1, DONG Liang1, SONG Liwei2
Vibration signals are often used to detect cavitation in centrifugal pumps. In order to more accurately capture the development state of cavitation and explore the influence of cavitation on the vibration signals of the centrifugal pump at different positions, a single-stage centrifugal pump was used to study the vibration signals at different cavitation stages. The sensitivity of the vibration signal of each measuring point to cavitation is analyzed by calculating the total vibration level change rate of each measuring point at the incipient cavitation and when the head of the centrifugal pump drops by 3%. The vibration signal is divided into multiple frequency bands through the 1/3 octave spectrum, and the sensitivity of vibration signals in different frequency bands to cavitation is analyzed. The results show that the vibration signals of the casing tongue and the inlet flange Y shows a high sensitivity to the inception cavitation and severe cavitation in the centrifugal pump. These two measuring points are suitable for the study of cavitation in the centrifugal pump. The bearing seat Z measuring point and the inlet flange Z measuring point have the lowest sensitivity to cavitation and is not suitable for the study of cavitation.
Key words: centrifugal pump; cavitation; vibration analysis
2022 Vol. 41 (19): 90-97 [Abstract] ( 122 ) HTML (1 KB)  PDF (4124 KB)  ( 37 )
98 Anti-penetration performance of honeycomb aluminum sandwich panel
YUAN Hao1,2, REN Kai1,2, REN Xiaopeng3, YANG Li3, ZHANG Yin3, FU Jianping1,2, CHEN Zhigang1,2
In order to explore the anti-penetration performance of the honeycomb aluminum sandwich panel, an experimental study was carried out on the penetration of the Ø6mm tungsten ball into the honeycomb aluminum sandwich panel, and the ballistic limit speed was 169m/s;In order to further compare the anti penetration law of penetrating honeycomb aluminum sandwich panel, LS-DYNA is used for numerical simulation to analyze and compare the penetration of fragments with different shapes into honeycomb aluminum sandwich plate and spacer aluminum target,and the equivalent target thickness of 2A12 is analyzed by numerical simulation and improved de Marre formula,The results show that the penetration resistance of spherical fragments is the worst, and the sandwich layer can increase the strength of the target by about 18%;The equivalent 2A12 aluminum target thickness of numerical simulation is 1.3mm, and the theoretical calculation is 1.33mm. The relative error is less than 5%, which can meet the requirements of engineering calculation.The research results can provide some reference for the design of anti satellite and anti space target warhead.
Keywords:Honeycomb aluminum sandwich panel;Limit penetration velocity;Numerical Simulation;De Marre formula;equivalent targrt;
2022 Vol. 41 (19): 98-103 [Abstract] ( 74 ) HTML (1 KB)  PDF (2034 KB)  ( 27 )
104 Bridge modal deflection prediction method based on additional mass block
QI Xingjun1, SUN Xufa1, WANG Shanshan2, CAO Sanpeng1
Taking the 16m span hollow slab single beam as the research object, the method of mass normalization based on additional masses and the modal flexibility method are studied to test the accuracy and engineering feasibility of bridge modal deflection prediction. Based on the environmental excitation test of the modal parameters of the 16m single beam before and after the mass block is applied, a normalized calculation method for the modal mass including the relative frequency change square term is proposed to predict the modal of the single beam under multi-level vertical static loads. Deflection, compare the modal deflection with the measured static deflection, study the test prediction accuracy of the single beam modal deflection under 8 additional mass conditions, analyze the influence of the proportion of additional mass and the number of masses on the prediction accuracy, and analyze the number of sensors Influence on the accuracy of modal deflection prediction. The results show that under environmental excitation, the prediction accuracy of the modal deflection of the 5 sensors and the 8 sensors is basically the same, which meets the engineering accuracy requirements; the modal deflection predicted based on the additional mass can replace the measured elastostatic deflection to evaluate the actual stiffness of the bridge Status; when the mass of the additional mass accounts for about 10% of the total weight of the beam, the relative error of the modal deflection prediction is within 8%, and the prediction accuracy is high. In practical engineering applications, it can be applied to other span bridges; When the proportion of blocks is the same, the prediction accuracy of multiple small-mass and fast modal deflection is better than that of large-mass blocks; only the first two vertical modes of a single beam can be used to obtain more accurate modal deflection.
Key words: Bridge structure; additional mass; flexibility matrix; mode mass normalization; modal deflection
2022 Vol. 41 (19): 104-113 [Abstract] ( 70 ) HTML (1 KB)  PDF (3537 KB)  ( 15 )
114 CEEMD-LSTM-based diagnosis method for off-design working conditions of centrifugal pump
LIU Rongwei1, HE Weiting2, WANG Linlin1, YANG Shuai1, WU Peng1, WU Dazhuan1
Centrifugal pumps are widely used in various industries and consume power heavily. When centrifugal pump operates under partial working conditions, the internal flow tends to be chaotic, resulting in a decline in efficiency and an increase in energy consumption. In this paper, according to weak variation and strong interference of vibration signals in off-working condition of centrifugal pump, two-channel information fusion and complementary set empirical mode decomposition(CEEMD) were adopted to extract the time-series features of vibration signals. Combined with the intelligent recognition of long-short time memory(LSTM) model, a diagnostic model was established for off-working condition of centrifugal pump. The simulation signals are compared with different preprocessing methods to highlight the feature extraction ability of CEEMD. The correlation is verified between working conditions and low-frequency vibration signals. The superiority of the model is further verified through comparative analysis of experimental data, and the test accuracy rate reaches 98.5%. This method can monitor the running condition of centrifugal pump and ensure the running efficiency.
Key words: Partial conditions; Empirical mode of complementary set; Long and short time memory model
2022 Vol. 41 (19): 114-121 [Abstract] ( 76 ) HTML (1 KB)  PDF (2476 KB)  ( 34 )
122 Low frequency line spectrum reconstruction tests of ship vibration based on hysteretic nonlinear base structure
WU Guoxun1,2, JIA Xingguang2, ZHANG Yu1,2, WANG Jiarui2, YAO Xiongliang2
Aiming at problems of low frequency (below 100Hz) line spectrum reconstruction of ship vibration and noise, a hysteretic nonlinear base structure with semi-active actuator (Magnetorheological Damper) and a method of low frequency line spectrum reconstruction based on current regulation of MRD was proposed. Based on Bouc-Wen hysteretic nonlinear model, the motion equation of the new base structure was established and the numerical simulation analysis was carried out. The results show that the introduction of MRD makes the base vibration appear bifurcation and chaos characteristics, which lays a theoretical foundation for the reconstruction of ship vibration line spectrum. In order to further verify effects of line spectrum reconstruction, a scaled model test platform was built and the line spectrum reconstruction experiment was carried out. The results show that the average reduction effect of line spectrum amplitude is 49.8%, and the maximum is 90.7% in 40 groups of working conditions.
Key words: hysteresis nonlinearity; Low frequency line spectrum; base; line spectrum reconstruction; Experimental study
2022 Vol. 41 (19): 122-128 [Abstract] ( 74 ) HTML (1 KB)  PDF (2399 KB)  ( 21 )
129 Frequency estimation of combined complex signals with phase difference method
LUO Jiufei, ZHENG Mingxuan, LI Jing
In the traditional time-shifting based phase difference method, the anti-noise performance of the algorithm can be improved by increasing the translation coefficient. However, the estimation accuracy of traditional method is limited due to the phase-wrapping problem probably caused by the random noise, the location of spectral bins and the large translation coefficient. In this paper, the main factors leading to phase wrapping are investigated and their effects on the frequency estimation are analyzed. In order to improve the accuracy of frequency estimation, an estimator based on the phase difference of combined complex signals is proposed. Simulation results show that the proposed algorithm still works and has a better noise immunity than the traditional methods when the translation coefficient exceeds one.
Key words: phase difference method; phase wrapping; frequency estimation; translation coefficient
2022 Vol. 41 (19): 129-135 [Abstract] ( 89 ) HTML (1 KB)  PDF (1513 KB)  ( 14 )
136 FDEM simulation of dynamic failure mechanism of coal rock under impact
CHENG Shufan1, GAO Rui1, ZENG Yawu1, ZHANG Jiafan2, CHEN Shiguan3
In order to study the dynamic failure law of coal, the impact failure experiment of coal was carried out by using the Φ 50mm split Hopkinson pressure bar (SHPB) device. A finite discrete element (FDEM) model of coal was established based on zero-thickness cohesive element and the relative model parameters were calibrated. Finally, the SHPB impact test is simulated on the LS-DYNA software platform, and the applicability of FDEM in dynamic failure simulating is discussed, and the failure process of coal is analyzed. The results show that: (1) the dynamic compressive strength and strain rate of coal and rock meet the empirical relationship. When the strain rate is 98.05s-1, 119.22s-1 and 135.85s-1, its dynamic strength factor (DIF) is 1.92, 2.08 and 2.23, respectively. (2) Under impact loading, the elastic deformation stage of coal is short, the plastic deformation ability is strong, and the strain rate dependence of dynamic elastic modulus is not significant. (3) FDEM model can simulate brittle failure of rock materials by failure of zero thickness cohesive force element. When the grid size is reasonable, the model parameters calibrated by quasi-static test are also suitable for impact failure simulation due to inertia effect. (4) The fracture degree of coal under impact is positively related to the impact velocity, and its failure forms are the local shear failure caused by compression wave loading and the entire tension failure caused by Poisson effect.
Key words: impact failure; strain rate dependence; split Hopkinson pressure bar (SHPB); hybrid finite-discrete element method (FDEM); cohesive model
2022 Vol. 41 (19): 136-143 [Abstract] ( 120 ) HTML (1 KB)  PDF (2763 KB)  ( 43 )
144 Fault diagnosis method of rotating machinery based on sparse filtering and long-short term memory network
LI Yibing1,2, CAO Rui1, JIANG Li1,2
Aiming at the problem that the original vibration signal inevitably contains redundant noises, a rotating machinery fault diagnosis model based on Sparse Filtering (SF) and Long and Short-Term Memory network (LSTM) is proposed in this paper. In this model, the original time-domain signals are converted into frequency domain signals by Fast Fourier Transform(FFT), and then the low-dimensional fault features are extracted by SF, which are input into the LSTM stack classifier to identify the fault condition of rotating machinery. The vibration signals of bearings and gears are taken as examples to carry out experimental verification, and compared with Softmax, Deep Neural Networks (DNN), Support Vector Machine (SVM), Denoising Autoencoder (DAE) and other methods. The results show that the proposed method not only has higher accuracy and robustness in noise environment, but also can achieve more than 98% accuracy in the diagnosis of unbalanced data sets.
Key words: rotating machinery; feature extraction; sparse filtering; long and short-term memory network; fault diagnosis
2022 Vol. 41 (19): 144-151 [Abstract] ( 64 ) HTML (1 KB)  PDF (3249 KB)  ( 23 )
152 Frequency estimation algorithm of multi-frequency real signals with noise based on Subtraction Strategy
CHEN Peng1,2, LIU Chunhua2, SHEN Ting’ao3, YUE Kaibai2
to suppress the spectrum leakage influence on frequency estimation for multi-tone real values sinusoid signal, a novel frequency estimation algorithm is proposed. Firstly, the FFT algorithm and a subtraction strategy are used to preprocess the sampled signal, and the spectrum index of maximum spectrum of each frequency component is obtained gradually, and coarse values of spectrum offset and complex amplitude of all frequency components are calculated subsequently. Secondly, the reference signal containing all non-estimated frequency components is constructed, and the reference signal is subtracted from the sampled signal by a subtraction strategy to obtain the estimated single-tone complex value signal, and it’s more accurate estimation values of spectrum offset and complex amplitude are calculated by two points interpolation for the spectrum of estimated signal. Then, the more accurate estimation values of frequency offset and complex amplitude of all frequency components are obtained subsequently by means of reference signal construction, subtraction strategy and spectrum analysis. Finally, the precision frequencies of all components are obtained by an iterative procedure. Meanwhile, the precision amplitudes and initial phases of all components are also obtained. The simulation experiments of frequency estimation are carried on different conditions such as without noise and in different frequency interval, and the simulation results indicate that the proposed algorithm can effectively suppress the spectrum leakage influence and improve the frequency estimation accuracy of multi-tone real values sinusoid. In addition, the mean square errors of frequency estimation results are closer to the Cramer-Rao low Bound than those of other excellent algorithms.
Key words: frequency estimation; subtraction strategy; spectrum leakage; multi-tone real values sinusoid
2022 Vol. 41 (19): 152-156 [Abstract] ( 73 ) HTML (1 KB)  PDF (1030 KB)  ( 30 )
157 Seismic damage model and tests of CFST latticed columns under repeated load
HUANG Zhi1,2, CHEN Xiangwen1, JIANG Lizhong3, ZHOU Wangbao3, XIONG Luzeng1, QI Jingjing1
To enable a better understanding of the damage and aseismic performance of these concrete filled steel tubular (CFST) laced columns, four CFST laced columns consisting of 4 main steel-concrete tubes were tested under cyclic loading. Failure modes and damage characteristics were studied based on the results from the lateral cyclic loading tests. Based on the analysis of experiments, the traditional Park-Ang damage was revised. And calculating formulas of damage index and energy dissipation factor, which is suitable for concrete filled steel tubular laced columns in a giant composite structure system, is established. According to the experimental phenomenon and the characteristics of each stage of the specimen through loading to failure, the calculation results among Park-Ang damage model, the energy-based damage model and the revised Park-Ang damage model were compared. The results shows that the damage degree of the concrete-filled steel tube lattice columns can be better evaluated by the improved Park-Ang model, and the damage value could be divided into repairable, unrepairable but undamaged, and unrepairable. The damage value of 0.4 is suggested as the critical value of whether the specimen can be repaired or not.
Key words: mega-composite structure; concrete filled steel tube; experimental study; damage model; laced columns
2022 Vol. 41 (19): 157-163 [Abstract] ( 81 ) HTML (1 KB)  PDF (1747 KB)  ( 24 )
164 Free vibration analysis of variable cross-section beam with internal discontinuities
GU Yeqing, CHANG Tingting, BAO Siyuan, SHEN Feng
Aiming at solving the free vibration of an Euler-Bernoulli beam with variable cross-section and internal spring subjected to axial compression load under arbitrary boundary conditions, a strategy based on the improved Fourier series and Garlerkin method is proposed to study the vibrational characteristics of beams. In order to simulate arbitrary boundaries, the transverse displacement spring and rotational spring are set at both ends of the beam. By assigning different values to the stiffness coefficient of the spring, the internal discontinuity condition is simulated. First, the displacement admissible function of the vibration displacement is established, in which the auxiliary polynomial is derived from the value of the end function or derivative. Then, the Garlerkin method is used to deal with the governing differential equation for free vibration of beams, thus the vibration problem is transformed into matrix eigenvalue problem. Finally, the numerical simulation is carried out by using the numerical calculation software. When the boundary conditions and mid-span discontinuity are changed, the mass matrix and stiffness matrix of the system can be determined by changing the spring stiffness coefficient, and the corresponding vibrational characteristics can be obtained. Numerical results show that the proposed method is simple, reasonable and of good practical significance.
Keywords: Euler-Bernoulli beam; internal discontinuity; the improved Fourier series; free vibration
2022 Vol. 41 (19): 164-171 [Abstract] ( 77 ) HTML (1 KB)  PDF (1049 KB)  ( 38 )
172 Contrastive analysis for performances of dynamic pressure gas thrust bearings with different configurations of spiral groove bottom
LI Yunlong, DONG Zhiqiang
Based on the bearing principle of spiral groove dynamic pressure gas thrust bearing, in order to further optimize the bearing characteristics and increase the bearing capacity and support stiffness by using the principle of step flow, this paper improved two convex and groove structures and compared them with the flat-bottomed spiral groove dynamic pressure gas thrust bearing, and numerically simulated the calculation area by CFD software, using ideal air as the test gas. The gas film pressure, radial velocity, tangential force of gas film, bearing capacity, friction resistance and friction power consumption of three kinds of gas bearings with different groove bottoms are compared. The results show that the bearing capacity of convex groove bottoms increases more than the other two groove types with the increase of rotating speed, and the friction force, friction coefficient and friction power consumption are much larger than the other two groove types.
Key words: Trough type; Gas film; Pressure; Radial velocity; Bearing capacity; Frictional force; Friction power consumption
2022 Vol. 41 (19): 172-178 [Abstract] ( 93 ) HTML (1 KB)  PDF (2494 KB)  ( 41 )
179 An intelligent bearing fault diagnosis method based on fusion of bidirectional LSTM structure and MSC structure
OUYANG Li, HE Shuilong, ZHU Liangyu, HU Chaofan, JIANG Zhansi
Bearings, as one of the most wearable core basic components in rotating machinery, are the key monitoring objects of mechanical equipment. Aiming at the problems of one-sided data mining and low utilization of existing bearing intelligent fault diagnosis models, this paper constructs a deep learning network model based on the fusion of bidirectional long short-term memory structure and multi-scale convolution structure. First of all, in order to enhance the classification performance of the model and improve the fit of the model to the actual engineering environment, the data volume of various types of fault data in the data set is non-equal. Then, the data set is used to obtain symmetrical data features through a bidirectional LSTM structure. In this way, the model’s memory of the fault information before and after the fault is reduced, and the information utilization rate is enhanced. Then, the data features are understood and communicated from multiple angles through the multi-scale convolution structure to prevent the feature extraction from one-sidedness. Simultaneously, it can also enhance the anti-noise performance of the model. Finally, intelligent classification is realized through a fully connected network. The proposed model is used to process and analyze the fault data of deep groove ball bearings and cylindrical roller bearings. The results indicate that the intelligent model has high accuracy and practicability.
Key words: bidirectional long-short-term memory structure; multi-scale convolution structure; deep learning; intelligent fault diagnosis of bearing
2022 Vol. 41 (19): 179-187 [Abstract] ( 52 ) HTML (1 KB)  PDF (2722 KB)  ( 18 )
188 Anti-impact performance of plain woven composite patching structure based on multi-scale analysis
PI Xiaofan, TIE Ying, HU Minghao
Since the plain woven composite repaired structure has a multi-scale effect on the response of impact loading, a numerical model was built using a multi-scale approach to compare the differences of impact response between plain woven composite repaired structure and unidirectional composite repaired structure. And the damage evolution at different impact energies and the effect of patch shape on the impact resistance were also studied. At first, the microscale model of fiber yarn and the representative volume element (RVE) were developed to predict the mesoscale material properties. Then the effective macroscale cross-ply laminate (ECPL) model of the plain woven composite structure was further obtained by using local homogenization method, ECPL). And then a multi-scale model was established to analysis the damage evolution of the plain woven composite repaired structure. The damage evolution of the repaired structure during the impact was analyzed by using the continuous damage mechanics model and the 3D Hashin criterion, and the accuracy of the numerical model was verified by the force-energy curves obtained from the drop hammer impact test. The numerical and the experimental results show that the plain woven repaired structure had better impact resistance than the unidirectional repaired structure; the impact damage of plain woven repaired structure was mainly distributed along 0/90 direction, and the main load-bearing part was transferred from the patch to the parent plate with the increase of the impact energy; the cohesive layer started to fail at the impact energy of 12 J; the plain woven composite structure repaired by the circle patch showed better impact resistance performance than others.
Key words: plain woven composite; external repair; damage evolution; patch shape; impact resistance
2022 Vol. 41 (19): 188-197 [Abstract] ( 78 ) HTML (1 KB)  PDF (3754 KB)  ( 46 )
198 Gear crack fault diagnosis of convergent planetary rowbased on 1-D depth residual shrinkage network
TIAN Qinwen1, FENG Fuzhou2, LI Ming2, CHEN Xiaoming2, ZHU Junzhen2, HU Hao2, SONG Chao2
When cracks appear in the catchment star row of armored vehicles, there is a lot of interference on the surface of the box, and there is a certain deviation in the common fault diagnosis methods. For this reason, a crack diagnosis model of confluence planetary gear based on one-dimensional depth residual shrinkage network is proposed. Its characteristic is that it combines the attention mechanism with soft threshold to enhance the useful information, restrain the redundant information, and introduce it into the residual neural network to significantly improve the ability of model feature extraction. In order to verify the feasibility of the model, the vibration signals of four kinds of planetary gear cracks are collected as samples for fault diagnosis. The results show that this method can achieve higher accuracy in a shorter time for the vibration signal of the confluence planetary gear box, and can achieve better classification results than other methods.
Key words: Deep Learning; Convergent Planetary Bar; Crack Fault Diagnosis
2022 Vol. 41 (19): 198-206 [Abstract] ( 97 ) HTML (1 KB)  PDF (2192 KB)  ( 31 )
216 End crushing tests of composite laminates
HUANG Chenghang1, SHEN Yuping1, LI Xiangqian2, WANG Yonggang1, PAN Diankun1, WU Zhangming1
In this research, a series of end crush experiments was carried out on T800 composite laminates. The effects of different lengths, thicknesses, stacking sequences, trigger angles and cementation pressures on the compressive properties of composite materials were studied. The failure mechanism was revealed by analyzing the load-displacement curve of the composite laminates in the process of end crush and observing the end failure morphology of the test sample. The results show that the end crushing process of composite laminates is unstable brittle fracture mode, while the end crushing process of composite laminates with 45° trigger angle is beam bending failure mode; In the end crushing test, the compressive strength of composite laminates increases with the increase of thickness, while the increase of length decreases the compressive strength. At the same time, [45/90/-45/0]3s laminates has better axial bearing capacity than [45/0/-45/0]3s laminates; The addition of trigger angle will change the failure mode and greatly reduce the compressive strength of the specimen during crushing, which is the key factor affecting the energy absorption capacity of composite structure; Finally, it is found that the mechanical properties of composite laminates under different cementation pressures increase gradually with cementation pressures, but the mechanical properties decrease when the cementation pressures increase to a certain value.
Keywords: Composite laminates; Macroscopic failure mode; End crushing; Trigger angle; Cementation pressure
2022 Vol. 41 (19): 216-222 [Abstract] ( 90 ) HTML (1 KB)  PDF (1988 KB)  ( 40 )
223 Application of lifting wavelet fractal strategy in feature extraction of motor bearing electrolytic corrosion fault
CHEN Binqiang1, QING Tao1, CAO Xincheng1, HE Wangpeng2, ZENG Nianyin1
Electrolytic corrosion is a common physical phenomenon in service duration of roller bearing in an induction motor, which makes the surfaces of the bearing more vulnerable to localized mechanical damage. In order to enhance effectiveness of fault detection based on vibration measurement, a novel fractal lifting scheme (FLS) is proposed for signal decomposition. Implicit wavelet packets, generated by combination of neighboring wavelet packets, can address the problem of insufficient detection ability of classic dyadic discrete wavelet transform in transition band feature extraction, thus enhance the effectiveness of nonstationary transient component extraction. Mathematically we show that sets composed of implicit wavelet packets can be used to construct fractal geometry in the frequency-scale plane. A novel fault feature extraction method is proposed based on the combination of FLS and kurtosis. This method is applied to vibration signal analysis of a roller bearing in a high power induction motor installed on a leveling machine. Periodic impulses, induced by mechanical damage on the bearing, were successfully extracted in an ensemble wavelet packet generated by the fractal lifting scheme. Thus the electrolytic fault causing the mechanical damage was identified in a shutdown maintenance. The processing results by the proposed method are compared with some other mainstream methods to show its enhanced performance in fault feature isolation.
Key words: Induction motor; rolling bearing; electrolytic corrosion; lifting scheme; ensemble wavelet packet
2022 Vol. 41 (19): 223-230 [Abstract] ( 78 ) HTML (1 KB)  PDF (3102 KB)  ( 23 )
231 Dynamic compression characteristics of aluminium powder
DENG Yongxing1, LU Xiaoxia1, LI Lei1, XU Songlin2, MIAO Chunhe2
In order to obtain the mechanical behavior of ductile powder under dynamic compression, dynamic compression experiments of micron aluminum powder under different loading conditions were carried out by using split Hopkinson pressure bar (SHPB). A high-speed camera and an infrared temperature measurement system (ITMS) were used to record the development of the speckle field and the surface temperature of the aluminum powder samples, respectively. In the strain rate range from 10-4 s-1 to 3600 s-1, aluminum powder has obvious strain rate effect. The results of digital image correlation (DIC) show that the deformation of the specimen is not uniform, and the compaction of the specimen is dominated by particle translational motion in the early stage of compression, but by particle rotation and sliding in the later stage. ITMS results show that the radiation temperature of aluminum powder samples still rises after loading, which is different from that of solid materials. In the aluminum powder sample, due to a large number of pores, the particles accelerate under the drive of stress wave, and the impact energy is transformed into kinetic energy of particles. After further compression of the sample, the pores reduce and the particle movement is restricted, and the kinetic energy is transformed into internal energy of particles, and the temperature of the sample increases.
Key words: aluminium powder; Split Hopkinson pressure bar; Digital image correlation method; Infrared temperature measurement
 
2022 Vol. 41 (19): 231-236 [Abstract] ( 63 ) HTML (1 KB)  PDF (1936 KB)  ( 16 )
237 Model tests for effect of fill reinforcement on seismic response of cantilever retaining wall
WEI Ming1,2, LUO Qiang1,2, JIANG Liangwei1,2, WANG Tengfei1,2, ZHANG Liang1,2, LIAN Jifeng3
In order to investigate the effect of backfill reinforcement on the seismic performance of cantilever retaining wall, shaking table tests on a 1/4 scale model of backfill reinforced and unreinforced behind cantilever retaining wall were conducted. The model structures were excited by simple harmonics of 0.11g for minor earthquake, 0.24g for moderate earthquake and 0.39g for major earthquake, and the responses such as acceleration, displacement and earth pressure were obtained. The influence of soil reinforcement on the natural frequency and damping ratio of the model is analyzed. The differences of seismic responses such as acceleration amplification factor, vibration displacement and wall-soil interaction are compared, and the characteristics of seismic mitigation effect of backfill reinforcement with loading amplitude are discussed. The results show that the backfill reinforcement can enhance the integrity of the wall-soil system and reduce the vibration damage, and the variation range of natural frequency and damping ratio after vibration are smaller than that of the unreinforced model; Backfill reinforcement measures can cause obvious phase misalignment between inertia force and seismic earth pressure on the wall under minor and moderate earthquakes, and greatly reduce the seismic earth pressure on the wall in the state of unfavorable displacement. However, the horizontal displacement of the wall is less than that of backfill under major earthquake, and the backfill chases and squeezes the wall significantly, and the seismic mitigation effect is not fully exerted.
Key words: cantilever retaining wall; shaking table test; backfill reinforcement; seismic response; seismic mitigation effect
2022 Vol. 41 (19): 237-247 [Abstract] ( 107 ) HTML (1 KB)  PDF (3825 KB)  ( 17 )
248 Optimization design and analysis of broadband sound absorption for honeycomb micro-perforated structure
YAN Shanlin, WU Jinwu, XIONG Yin, CHEN Jie, LI Heming
The single-layer microperforated plate structure has the disadvantages of narrow sound absorption frequency band and inferior sound absorption performance. In order to improve the noise reduction performance of single-layer microperforated plate structure, a single-layer honeycomb micro-perforated structure with highly efficient broadband sound absorption performance was designed and analyzed from three perspectives of theoretical model, simulation calculation and experimental test. It was based on the characteristics that the resonant frequency of the structure could move with the the change of cavity depth. The principle of electroacoustic analogy and particle swarm optimization algorithm were used in combination. The principle of using unequal cavity depth to improve the sound absorption performance of the structure was analyzed from the real and imaginary parts of the relative acoustic impedance of the structure. The results show that the sound absorption coefficient of the structure is above 0.9 in the range of 1140-3000 Hz. The feasibility of using particle swarm optimization algorithm to design the broadband sound absorber is verified.
Key words: Honeycomb Micro-perforated plate; Cavity depth; Particle swarm; Optimization algorithm; Broadband sound absorber
2022 Vol. 41 (19): 248-253 [Abstract] ( 87 ) HTML (1 KB)  PDF (1607 KB)  ( 23 )
254 Vibration characteristics analysis of coaxial contra-rotating gear train with tooth surface spalling defects
DU Zhengzhu1, XU Lixin1,2, NIU Kun3
Aiming at the design of a coaxial counter-rotating main reduction gearbox for a certain type of unmanned helicopter, a 25-degree-of-freedom dynamic model of the multi-stage helical gear transmission system in the gearbox was established by using the lumped parameter method. The effects of time-varying meshing stiffness, bearing support stiffness, torsional stiffness of the transmission shaft, and meshing error were considered. The influence laws of the input speed and the size and position of tooth surface spalling defect located at the high speed stage gear on the dynamic characteristics of the system was analyzed. The results showed that the dynamic meshing force of the upper and lower rotor shaft gear pairs fluctuate greatly and the degree of dynamic meshing force fluctuation of the upper rotor shaft gear pair is 1.7 times that of the lower rotor gear pair. As the speed raise, the amplitude of the double input stage meshing frequency in the dynamic response of the gear pairs at all levels have the most significant increased. When the high-speed gear tooth surface has a spalling defect, the sidebands will appear near the meshing frequency, and the vibration impact will increase with the increase of the defect size. Among the different defect positions, it is located at the junction of the double-tooth meshing area and the three-tooth meshing area where the vibration shock peak value is the largest. The conclusions provide theoretical references for the vibration reduction and noise reduction of the unmanned helicopter coaxial contra-rotating main reduction gearbox and the fault diagnosis.
Key words: coaxial contra-rotating; gear transmission; lumped parameter method; spalling defect; dynamics
2022 Vol. 41 (19): 254-265 [Abstract] ( 75 ) HTML (1 KB)  PDF (2586 KB)  ( 15 )
266 Prediction and tests for vibration and noise of exhaust valve plate of rotary vane compressor based on fluid-structure interaction
LUO Shengxi1, HE Zeyin1,2, TAO Ping’an2, LIU Hongmei2, HU Lizhi2, SUN Shizheng1
In order to reveal the vibration characteristics of the reed valve plate of rotary vane compressor, a single-particle model of the valve plate was established, and the relationship between the exhaust condition, geometric parameters and the vibration displacement of the valve plate was studied; Then, the fluid structure interaction model of the improved valve plate exhaust structure is established to study the flow characteristics of the valve plate; Then, based on the turbulence parameters of the flow field, the broadband noise model of the reed valve is established, and the noise distribution law of the improved valve is studied. The results show that: by improving the valve parameters, the flat sticking time is effectively increased, and the peak to peak vibration velocity of the valve is reduced; There is a negative pressure area in the flow field of the degassing slot when the valve is working, and there is a backflow phenomenon in the flow field of the exhaust hole when the valve is closed; The aerodynamic noise sources of the exhaust structure are mainly concentrated on the surface where the valve plate collides with the valve seat and near the degassing groove; After the improvement, the noise reduction of the compressor in the frequency domain is obviously reduced, and the maximum noise amplitude of the rear field point is reduced by 6%.
Key words: rotary vane compressor; reed valve; single-particle model; fluid structure interaction; exhaust noise
2022 Vol. 41 (19): 266-273 [Abstract] ( 63 ) HTML (1 KB)  PDF (2272 KB)  ( 25 )
274 Cluster identification of acoustic emission parameters for bending-tensile damage of rock-concrete composite beams
CHEN Xudong1, GUO Yuzhu1, HU Liangpeng1, BAI Yin2, NING Yingjie3
In order to study the bending damage characteristics of the surrounding rock-concrete lining structure, four rock-concrete composite beams were prepared by selecting two types of rock (granite and black sandstone) and two types of concrete (fiber and fiberless). The composite beams were tested in four-point bending using MTS testing machine, and the bending damage process of the composite beams was monitored using acoustic emission (AE) technique. The damage localization results of acoustic emission showed that the main damage processes of the rock-concrete composite beams can be divided into four stages: concrete damage section, interface damage section, rock damage section and residual bearing section. To identify the damage types at each stage of flexural damage of composite beams, a Gaussian mixture model was used to cluster the acoustic emission parameters and compared with the conventional RA-AF analysis method. Compared with the conventional RA-AF analysis method, the Gaussian mixture model does not require artificially selected empirical parameters, and the identification of damage is more scientific and reasonable. In addition, the results of the Gaussian hybrid model analysis show that the rock-concrete composite beam mainly occurs in tensile damage (accounting for more than 87.9%), and only a small amount of shear damage is generated (accounting for less than 12.1%).
Key words: surrounding rock; concrete; acoustic emission; Gaussian mixture model; damage
2022 Vol. 41 (19): 274-281 [Abstract] ( 87 ) HTML (1 KB)  PDF (4057 KB)  ( 64 )
282 Transient cavitation pressure fluctuation characteristics in regulating valve
LIU Xiumei1, XIE Yongwei1, LI Beibei1, HE Jie2, CHEN Jinsong1
The unsteady flow in a hydraulic regulating valve was numerically studied based on a computational fluid dynamics (CFD) method. Spectral analysis was conducted for pressure signals, and the correlation between the unsteady cavity behaviors and the pressure fluctuations was discussed. The results showed that a typical quasi-periodic process of cloud cavitation development is characterized by the process of attached cavity growth, attached cavity shedding, and the growth and collapse of cloud cavities. The periodic frequency of cavitation is 565Hz. The pressure gradient at the end of the attached cavity near the wall is the main cause of the reverse jet, and then the vortex is formed to make the attached cavity shedding. At the same time, the development of shedding also affects the pressure pulsation in the flow passage. The average pressure variation in different sections of the valve has the same dominant frequency, and the frequency is basically consistent with the unsteady quasi-periodic breaking and shedding frequency of the shedding.
Key words  regulating valve; unsteady cavitation flow; re-entrant jet; pressure fluctuation;  numerical simulation
2022 Vol. 41 (19): 282-288 [Abstract] ( 75 ) HTML (1 KB)  PDF (2119 KB)  ( 9 )
289 Fault diagnosis of reciprocating compressor air valve based on VMD-MSE and SSA-SVM
BIE Fengfeng1,2, ZHU Hongfei1,2, PENG Jian1,2, ZHANG Ying1,2
The fault vibration signal of reciprocating compressor gas valve contains strong nonlinearity and non-stationarity. In order to extract fault features from the vibration signal of the reciprocating compressor valve for fault diagnosis, a fault feature extraction method based on Variational Mode Decomposition(VMD) and Multiscale Sample Entropy(MSE) was proposed, and the model of Support Vector Machine(SVM) optimized by Sparrow Search Algorithm(SSA) was studied for reciprocating compressor valve fault mode recognition. Through the VMD decomposition, the appropriate Intrinsic Mode Function (IMF) component of the vibration signal from the reciprocating compressor valve was selected for signal reconstruction, from which the MSE entropy value was obtained to form a feature vector set. Finally it was input into SSA-SVM for training and mode identification. Experimental study showed that the fault diagnosis model based on VMD-MSE and SSA-VMD can effectively and accurately identified the fault of the reciprocating compressor valve.
Keywords: reciprocating compressor; Variational Modal Decomposition; Multiscale Sample Entropy; Support Vector Machine; mode recognition
2022 Vol. 41 (19): 289-295 [Abstract] ( 100 ) HTML (1 KB)  PDF (2052 KB)  ( 20 )
296 Design and analysis of elevator vertical low frequency vibration isolator
SONG Danlong1, SHI Pu1, DU Chunhua1, LIU Kai1, XIAO Yongheng2
In order to solve low frequency vibration of traction elevator, a novel low frequency vibration isolator which consists of buckling steel plate and cylindrical rubber was analyzed and developed by theoretical modeling and finite element analysis based on the principle of quasi-zero stiffness. A series of static and dynamic experiments were conducted for buckling steel plate, cylindrical rubber and low frequency vibration isolator at the same time. The results show that the average stiffness of the new low-frequency vibration isolator at the equilibrium position was below 20 N/mm. The natural frequency of the elevator car was reduced to 1 Hz, and the initial frequency of vibration isolation was reduced by 81.80%. The size and buckling of the spring plate and the size and hardness of the cylindrical rubber were the key parameters which affected the performance of the low-frequency vibration isolator. The novel low frequency vibration isolator not only ensures the static stability, but also realizes low frequency vibration isolation for the elevator car, and improves the riding comfort of the elevator.
Key words: Elevator; low frequency vibration; quasi-zero stiffness; vibration isolation; transmissibility
2022 Vol. 41 (19): 296-302 [Abstract] ( 90 ) HTML (1 KB)  PDF (2221 KB)  ( 16 )
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