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2020 Vol. 39, No. 15
Published: 2020-08-15
 
1 Tests for relationship between cavity evolution and motion characteristics of cavity wall during a cylinder entry into water
XIA Weixue, WANG Cong, CAO Wei, LI Jiachuan
The present study aims to address the water entry cavity evolution of cylinder with lower Froude number. For this purpose, an experiment on water entry cavity of a cylinder with different inclined angles and horizontal velocities is conducted by utilizing a high-speed video camera. The cavity flow phenomena induced by the complex movement cylinder is obtained from the video, and the relationship between cavity evolution and the motion characteristic of cavity wall is analyzed by contrast. The phases of impact water entry cavity are divided according to its motion characteristic. The experimental results demonstrate that, the motion characteristic of cavity wall is closely related to the cavity evolution, so the phases of cavity evolution can be quantitatively divided through the motion characteristic of cavity wall. The cavity evolution is affected seriously by its closure type. There are four phases for the cases that the surface seal occurs, namely, open-cavity, expand-volume cavity, stretch-cavity, and closed-collapsing cavity respectively, and the corresponding boundary time is T=2.8, T=5.4, and T=6.9. When the cases only occur deep seal, the evolution process includes three phases, open-cavity, closed-cavity, and collapsing-cavity respectively. The boundary time for those cases is T=2.8 and T=8.4. The overlapped part doesn’t exist in each cavity evolution phases by the divided way of the motion characteristic of cavity wall.
2020 Vol. 39 (15): 1-7 [Abstract] ( 159 ) HTML (1 KB)  PDF (1980 KB)  ( 75 )
8 Shaking table tests for a small-scale single-layer latticed cylindrical shell and its dynamic response probability model
ZHANG Ming1,2， XIE Changlin3,4，ZHI Xudong3,4
In this paper a small single-layer latticed cylindrical shell model was fabricated for shaking table test in order to reduce the cost of the whole experiment process, and the dynamic response probability model considering the variability of ground motion was studied based on the shaking table test. Firstly, a small single-layer latticed cylindrical shell model was fabricated referring the existing method for fabricating the single-layer reticulated dome. Afterwards, a series of shaking table tests on the shell model, including dynamic response tests in the elastic phase and dynamic collapse test in the elastic-plastic phase, were conducted under the action of TAFT wave, artificial seismic wave and simple harmonic wave. Then, the dynamic response characteristics and collapse mode of the shell model were analyzed combining the field test data and the numerical simulation analysis results using the finite-element package ABAQUS. Finally, the effect of ground motion variability on the dynamic response of the shell model was studied based on the field test data of 40 tests followed by the preliminary fitting curve of the dynamic response probability and the variability of ground motion. This paper could provide an important reference for conducting a series of shaking table tests of the shell models and improving seismic design theories of spatial grid structures.
2020 Vol. 39 (15): 8-17 [Abstract] ( 199 ) HTML (1 KB)  PDF (3168 KB)  ( 64 )
18 TMD limited position strategy for vibration suppression of floating offshore wind turbines
YANG Jiajia, HE Erming, YAO Wenxu, XIONG Bo
The tuned mass damper (TMD) could effectively reduce the vibration responses of floating offshore wind turbines. In wind-wave loads, the TMD would appear a large amplitude and collide with wind turbines, which perhaps affect the safety of the wind turbine structure. Therefore, a TMD limiter should be designed to solve these problems. A TMD was installed in the nacelle of the barge floating wind turbine, and three kinds of TMD limited position strategies, which are the damping limited position, stiffness limited position and joint limited position, were presented. Considering the TMD stroke constraint, a three-degree-of-freedom coupled model of the wind turbine and TMD was established using the Lagrange’s equations. Subsequently, the vibration suppression effects of the nacelle TMD were studied in different limited position strategies. The results show that the joint limited position strategy could avoid the defects of the other strategies, the maximum TMD stroke is 7.85m; the suppression rates of the standard deviation for the tower top longitudinal displacement and platform pitch angle are 40.01% and 61.78%, respectively.
2020 Vol. 39 (15): 18-24 [Abstract] ( 185 ) HTML (1 KB)  PDF (905 KB)  ( 69 )
25 Bearing fault diagnosis method based on deep metric learning
LI Xiaojuan1,2, XU Zengbing1,2, XIONG Wen3, WANG Zhigang1,2, TAN Junjie1,2
As the intra-class scatter and inter-class similarity are big in bearing fault data, which constrains the diagnostic accuracy, a new method of deep metric learning for fault diagnosis is proposed. The deep neural network (DNN) is used to adaptively extract the fault features, and the marginal Fisher analysis method based on Euclidean distance is used to optimize the features, then, the BPNN classifier is added to the top-level feature output layer of the constructed deep metric network (DMN) to fine tune the parameters and realize fault classification and recognition.  Finally, diagnostic analysis on bearing fault experimental data of different fault types and different fault severity verified that the method can effectively diagnose bearing faults with high precision and the effect is better than traditional deep belief network (DBN) fault diagnosis method as well as the common time-domain statistical features combined with support vector machine (SVM) classification fault diagnosis method.
2020 Vol. 39 (15): 25-31 [Abstract] ( 206 ) HTML (1 KB)  PDF (2013 KB)  ( 109 )
32 Effects of stress state on penetration performance of cement mortar
CHEN Lina，SHAN Junfang，ZHOU Lijiang，WANG Pengfei，XU Songlin
An experimental technique for concrete penetration under triaxial confinement is developed in our lab. The hydraulic servo control system is employed to apply independent-controlled triaxial confinement on cubic specimens, and high-pressure gas is employed to drive bullets to penetrate the specimens along a hollow square bar. Responses of the cube specimen are recorded by strain gauges on six bars attached to the specimen, Taking M10 cement mortar as an example, the penetration behaviors of cement mortar under different stress states are investigated, and the corresponding data processing methods are established. The penetration differences of cubic specimens under unconfined, unidirectional confinement and bidirectional confinement are compared and analyzed, and the effect of stress state on penetration performance is discussed in details. It might be helpful for the development of new concept defense construction.
2020 Vol. 39 (15): 32-40 [Abstract] ( 151 ) HTML (1 KB)  PDF (3348 KB)  ( 52 )
41 Wind-induced internal pressure response of low-rise buildings with leeward wall opening
HUANG Peng, CHEN Sheng, HUANG Shunjie
In wind disasters, the closed structures will become open structures after being destroyed, and the internal pressure of the structures will suddenly increase, which has greater damages to the structures. At present, the researches on wind-induced internal pressure mainly focus on the structure with opening on windward wall, but ignore the situation of leeward wall with opening. Firstly, the calculation method of wind-induced response of structure with opening on leeward wall was deduced theoretically. Then the natural frequencies of the internal pressure system and the internal pressure responses obtained from the field measurement and the theoretical calculation method were compared to verify the accuracy of the theoretical method. After that, a rational method about the opening area on the leeward walls was explored and established, which was demonstrated to have obvious effects on improving the load conditions of roofs under strong wind.
2020 Vol. 39 (15): 41-47 [Abstract] ( 162 ) HTML (1 KB)  PDF (1292 KB)  ( 973 )
48 DOA estimation of vector sensor arrays based on sparse signal power iterative compensation
WANG Weidong1, ZHANG Qunfei1, SHI Wentao1, TAN Weijie1, WANG Xuhu2
Aim to low resolution probability and estimation accuracy for close space targets of the existing sparse signal power iteration algorithms, a sparse signal power iteration compensation method is proposed to estimate direction of arrival (DOA) via vector sensor arrays. Firstly, based on the principle of sparse signal compensation and the fitting criterion weighted covariance matrix, the objective function including sparse signal power and compensation weight is constructed. Secondly, the closed-form solution of sparse signal power iteration renewal expression is derived. Finally, DOA estimation is obtained by searching the spectral peaks of sparse signal power. The theoretical analysis shows that the proposed algorithm improves the resolution probability and estimation accuracy for close space targets by compensating the signal power at discrete grid points. Simulation results show that, compared with the classical subspace algorithm and the existing sparse power iteration algorithm, the proposed algorithm improves the resolution probability and estimation accuracy for close space targets.
2020 Vol. 39 (15): 48-57 [Abstract] ( 162 ) HTML (1 KB)  PDF (1205 KB)  ( 51 )
58 Dynamic analysis for vibration and impact of liquid film sealing
XU Lushuai1，HAO Muming2，YUAN Xiaoyang1，WANG Yunlei1，JIN Yingze1，LI Yongfan2
The instantaneous change of operating conditions, system vibration and insufficient lubrication easily cause rub-impact of sealing surface, which has serious effect on the service life of liquid film seals. Dynamic model of sealing system considering face contact was established. Then the equations of motion, Reynolds equation considering mass conservation cavitation boundary condition and asperity contact equation were solved simultaneously at each time step. Furthermore, the effects of liquid film cavitation, axial disturbance and transient operating conditions on seal stability and impact characteristics were investigated. Results show that cavitation dramatically improves the anti-disturbance ability of sealing system. The vibration frequency of liquid film is significantly larger than that of full film lubricated regime when contact occurs. The impact force and shock frequency are continuously enhanced with increase of speed and pressure. There is an obvious change of velocity direction at the instant of face impact.
2020 Vol. 39 (15): 58-65 [Abstract] ( 178 ) HTML (1 KB)  PDF (1231 KB)  ( 73 )
66 Early fault diagnosis for rolling bearing based on noise-assisted signal feature enhancement
ZHOU Yiwen1, CHEN Jinhai1, WANG Heng1, JIANG Jie2
An early fault diagnosis method for rolling bearing based on the feature enhancement of noise-assisted signal was proposed, aiming at the fault feature of rolling bearing vibration signal, some useful signals are filtered out while filtering out the interference noise, which causes the loss of characteristic signal. The generalized multi-scale permutation entropy screening criterion was used to screen the vibration signal, and the parameters of the Duffing vibration subsystem were optimized by the particle swarm optimization algorithm to achieve the optimal matching among the Duffing vibration subsystem and the input signal and noise, thereby improving the stochastic resonance effect. Part of the background noise energy is transferred to the early weak fault signal feature of the rolling bearing, which enhances the feature of the early weak fault signal. The proposed method was applied to the early fault diagnosis of rolling bearing life state, and compared with the adaptive morphology method based on variational mode decomposition. The results show the effectiveness and feasibility of the proposed method.
2020 Vol. 39 (15): 66-73 [Abstract] ( 216 ) HTML (1 KB)  PDF (1244 KB)  ( 92 )
74 Shaking table tests for seismic isolation of structures with pure new  type steel roller supports and those with combined supports
HUANG Xiangyun， ZHANG Lei， LIU Yanhui， TAN Ping， JIN Jianmin
Aimed to research the performance of a new type of steel roller isolation bearing, a group of steel roller isolation bearings and a group of friction pendulum isolation bearings are designed and manufactured. The shaking table tests of a two-story steel frame with fixed support, steel roller isolation, combination system of steel roller isolation and MR damper, friction pendulum isolation have been implemented. The test results show the isolation effect of the new steel roller isolation bearing is better than that of the friction pendulum isolation support, and the pure roller isolation model and the hybrid isolation model of the roller and MR dampers can reduce the acceleration response of the structure by 56.1% ~ 80.8%.The reasonable optimization of the damping value of the hybrid damping isolation system can make the isolation effect better. At the same time, the hybrid isolation model with MR dampers can reduce the displacement response of the isolation layer by 58.7% ~ 87.4%, and the control effect is better with the increase of damping value. Therefore, it is effective and feasible to combine the new steel roller isolation support with the damping device, which can not only give full play to the isolation effect of the roller isolation support, but also avoid the problem of excessive displacement of the structure isolation layer.
2020 Vol. 39 (15): 74-81 [Abstract] ( 143 ) HTML (1 KB)  PDF (3104 KB)  ( 56 )
82 Tests for effects of airbag on underwater implosion of photomultiplier tube
WU Tianzheng1，2, ZHENG Peng1, DU Zhipeng2, ZHANG Lei2, HE Miao3
The underwater implosion test of photomultiplier tube with air bag was carried out in pressurized sealed tank. The experimental process data were recorded by high-speed camera and pressure sensor. The experimental results are compared with the data of photomultiplier tube underwater implosion without balloon. The feasibility of using balloon to protect photomultiplier tube underwater implosion is explored, which provides a new idea for the protection of photomultiplier tube underwater implosion.
2020 Vol. 39 (15): 82-87 [Abstract] ( 110 ) HTML (1 KB)  PDF (1017 KB)  ( 34 )
88 Tests for unbalance superposition effect of a single-sided vertical balancing machine
WANG Qiuxiao, LI Haoyue, GUO Yongcai, GUO Sicen
When using the single-sided vertical dynamic balancing machine to measure the unbalance of rotors of different sizes and different masses, it is found that there is an extra unbalance that does not match the theoretical value. The traditional method is difficult to give a reasonable explanation, analysis shows it ignores the variation of the synthesis centroid of the rotor and the swing frame system, the unbalance superposition effect will affect the accuracy of the measurement. The centroid equation of motion caused by the eccentricity of the rotor and the swing frame system was analyzed, and the position of vibration center was obtained. The concept of unbalance superposition effect and extra unbalance is proposed. Superimposed unbalance formula of the synthesis system was deduced. Effect of rotor mass and rotor mounting height on the extra unbalance was analyzed. Comparative error analysis was performed based on the experimental data. The relationship between the additional unbalance and rotor mass and rotor mounting height is verified. The source of the extra unbalance was clarified.
2020 Vol. 39 (15): 88-94 [Abstract] ( 118 ) HTML (1 KB)  PDF (1106 KB)  ( 42 )
95 Seismic residual deformation control for RC frame structures based on a novel self-centering friction damping brace
BI Zhongjun, HU Zhiqiang, WANG Qi, HU Xiaobin
Utilizing the Cu-Al-Be alloy wires, a novel self-centering friction damping brace was developed in this paper. The hysteresis performance of the brace was studied experimentally and the corresponding numerical analysis model was established on the OpenSEES platform. Finally, the brace was applied to control the residual deformation of reinforced concrete (RC) frame structures under seismic excitations. The results show that, as the friction force increases, the brace achieves a better energy dissipation capacity while having larger residual displacement. The hysteresis curves computed using the OpenSEES analysis model agree well with the test ones, indicating that the established analysis model has a fairly good accuracy. In addition, it can cost-effectively mitigate the residual displacements of the RC frame structure under seismic excitations on the whole by installing the proposed braces at the storeys where the residual displacements are relatively larger.
2020 Vol. 39 (15): 95-102 [Abstract] ( 137 ) HTML (1 KB)  PDF (2011 KB)  ( 81 )
103 Optimal parametric design of a new aeroelastic model forhigher-order vertical modalvortex-induced vibration tests
WEN Qing1,2, HUA Xugang2, CHEN Zhengqing2, WANG Xiuyong1
Elastically multi-supported aeroelastic model is a new model to investigate the high-order vertical mode vertox-induced vibration of large-span bridge. To make the frequencies, modal masses and mode shapes of this model match with that of the original structures, in this paper, a model parameters optimization method based on matrix equation of dynamic system is proposed. First, the optimal objective function on the frequencies, modal masses and mode shapes of this model is established by using the matrix equation of dynamic system. Then, the optimal designs of the stiffness of beam and springs and the additional mass are found out by the least square method. The proposed method has been validated by numerical simulation. The feasibility of this method on real bridges are investigated by taking two different types of suspension bridges as examples. The results indicate that: the model designed by this method can well match with the original structure.
2020 Vol. 39 (15): 103-108 [Abstract] ( 144 ) HTML (1 KB)  PDF (1020 KB)  ( 65 )
109 Vibration characteristics analysis for an axially loaded beam with elastic boundary restraints
ZHAO Yuhao, DU Jingtao, XU Deshui
In this paper, an improved Fourier series expansion is employed to establish the vibration analysis model of an axially loaded beam with elastic boundary restraints. Through the introduction of translational and rotational restraining springs at both ends, any types of classical boundary condition and their combination can be simulated by setting the stiffness coefficients accordingly. The vibrational displacement of beam structure is expanded as the superposition of Fourier series and boundary smoothed terms. According to the energy principle, the total kinetic energy, total potential energy and external force of the whole system are formulated, and the system characteristic matrix is obtained in combination with Rayleigh-Ritz procedure. Numerical examples are then given to verify the correctness and reliability of the proposed model for the vibration characteristics analysis of beam structure under different boundary conditions and axial loads. Based on this, the influence of system parameters, including boundary restraining stiffness, axial load and force excitation, on the vibration characteristics of beam structure is investigated. The proposed model has the advantages of high efficiency and precision, which can provide an effective analytical tool for studying the vibration behavior of axially loaded beam with complex boundary conditions.
2020 Vol. 39 (15): 109-117 [Abstract] ( 173 ) HTML (1 KB)  PDF (3141 KB)  ( 120 )
118 Check valve fault diagnosis based on VMD parametric optimization and enhanced multi-scale permutation entropy
PAN Zhen1,2， HUANG Guoyong1,2， WU Man1,2
Aiming at the complex mechanical structure of the high-pressure diaphragm pump, the fault characteristic information of the check valve is distributed on multiple scales, and it is difficult to extract the feature comprehensively at a single scale. A fault diagnosis method for check valve based on parameter optimization variational mode decomposition (VMD) and enhanced multi-scale permutation entropy (EMPE) was proposed. Firstly, the vibration signals of check valve were decomposed by VMD, and the parameters of VMD were optimized with the minimum envelope entropy principle to obtain several intrinsic mode functions (IMFs). Then, the enhanced multi-scale permutation of the IMFs was extracted to construct the fault characteristics vector; Finally, variable predictive model based class discriminate (VPMCD) was used to train and identify the fault feature vector, and then the fault diagnosis of the check valve was realized. The simulation signal and engineering experiment analysis show that the method can accurately identify the fault type of the check valve, and has certain reliability and engineering application value.
2020 Vol. 39 (15): 118-125 [Abstract] ( 226 ) HTML (1 KB)  PDF (1420 KB)  ( 82 )
126 Hybrid simulation for aseismic performance of subway station with its RC central column as test specimen
YANG Chengyu1, CAI Xuesong2, YUAN Yong1，2
The issue of scale ratio still exists in the seismic performance test of underground structures. Hybrid simulation is adopted to study the seismic performance of structure of a subway station under earthquake excitation. The central column is selected as the full-scale specimen of experimental substructure, the remaining parts of the structure and soil surrounding the station are taken as numerical substructure. In terms of the test results, as the Peak Base Acceleration (PBA) increases, the specimen reaches the plastic working state and its lateral stiffness decreases. When the input motion is Shanghai artificial wave (bedrock wave), the shear force and displacement of analytical model match well with results of hybrid simulation in the elastic working state. The results show that hybrid simulation system based on OpenSee, OpenFresco, and MTS has good stability and accuracy when applied in underground structures seismic issues.
 
2020 Vol. 39 (15): 126-132 [Abstract] ( 134 ) HTML (1 KB)  PDF (1984 KB)  ( 69 )
133 Guided wave monitoring method based on over-determined independent component analysisunder temperature variation conditions
XIAO Hang, XIAO Li,QU Wenzhong
Ultrasonic guided wave based structural health monitoring technology will be affected by changing environment and operating conditions in practical engineering applications. Because of the limitations of independent component analysis methods for processing a large number of monitoring guided waves, and the lack of research on different degrees of damage characterization, a guided wave monitoring method based on over-determined independent component analysis is proposed and the damage index based on k-means clustering is improved. The temperature, which has a large influence on the monitoring signal and is widely exist, is taken as an environmental variable. The principal component analysis (PCA) is used to analyze the observation matrix composed of a large number of guided wave signals to determine the number of independent components, and independent component analysis (ICA) is used to decompose the processed guided wave signals into independent components. The influence of damage and that of environmental and operational conditions are separated into different independent components. The guided wave monitoring experiment was carried out on aluminum plates subjected to long-term changes in ambient temperature. The results show that the method can effectively reduce the number of independent components and eliminate the interference from the ambient temperature in a large number of guided signals to identify the damage. Furthermore, the damage identification experiment was carried out on the aluminum plate with intact and different damage degree under the temperature change condition. The effect of the method on charactering the damage degree while eliminating the environmental temperature interference was studied.
2020 Vol. 39 (15): 133-141 [Abstract] ( 108 ) HTML (1 KB)  PDF (2058 KB)  ( 37 )
142 Tests for effects of lateral tenon and mortise tightness on aseismic performance of step through tenon joints
SU Haihong1,2, GAO Yonglin2,3, TAO Zhong3, SU Hexian3, ZHANG Qing3
Through controlling constant width mortise,and change width tenon of step through tenon node model,make three models,which are loose nodetight node,moderate node, tight node loose node. Research on lateral closeness between mortise and tenon of joints effects on the seismic performance by low-cyclic reversed loading tests.At the same time, through use of the simple moire technique (5mm x 5mm grid), the phenomenon and process of insertion of tenon during tests are observed. The results show: The lateral closeness has great influence on node energy consumption, ultimate bearing capacity, initial stiffness and ductility, and the closer of mortise-tenon, the more obvious of the brittle character. Ultimate bearing capacity relationships: Tight node model > Moderate node model > Loose node model; Initial stiffness size relationships: Tight node model > Moderate node model > Loose node model; Equivalent viscous damping coefficient size relationships: Moderate node model > Tight node model > Loose node model；Tight node model ductility is bad, brittleness is obvious, the positive limit angle was only 0.08rad and the reverse limit was 0.06rad, and the minimum limit angle of both loose and moderate node models reached 0.12rad .easy ductility is good.
2020 Vol. 39 (15): 142-149 [Abstract] ( 166 ) HTML (1 KB)  PDF (2406 KB)  ( 34 )
150 Tests for transmission error and tooth root stress of spiral bevel gears under quasi-static condition
WANG Cheng1, WAN Bowen2, CHEN Yanyan3, MAO Feihong1, GUO Jing1, CHEN Juan1
开展弧齿锥齿轮的试验研究可为理论设计、制造和装配等提供基础数据，提高弧齿锥齿轮的啮合质量和使用性能。以弧齿锥齿轮为研究对象，采用功率封闭试验系统，在准静态条件下开展试验研究。对不同转速和扭矩工况的传递误差和齿根应力开展测试，并从时域和频域角度进行了对比分析。结果表明：弧齿锥齿轮的传递误差呈正弦或余弦形式波动，并以转频对应幅值为主；随着扭矩的增加，弧齿锥齿轮传递误差峰峰值呈现递增的趋势，且传递误差转频对应幅值近似呈线性比例增加；转速对传递误差峰峰值影响较小，但对传递误差转频对应幅值影响较大。随着扭矩的增加，齿根应力峰峰值呈线性比例递增；转速对齿根应力峰峰值的影响较小；从小端到大端，齿根应力的变化很大且呈现增大的趋势；齿轮啮合过程中，轮齿进入啮合时，齿根应力为拉伸方向且应力逐渐增加达到峰值，随后轮齿逐渐退出啮合，齿根应力逐渐减小直至压缩方向并达到最小值；从频域角度齿根应力以转频及其倍频为主。
2020 Vol. 39 (15): 150-155 [Abstract] ( 169 ) HTML (1 KB)  PDF (1548 KB)  ( 161 )
156 Acoustic absorption characteristics of a flexible micro-perforated panel cavity with a flexible back one
HOU Jiuxiao1,2， ZHU Haichao1,2， YUAN Suwei1,2
The influence of the vibration of micro-perforated panel and back cavity panel, made of lightweight materials, on absorption coefficient must be taken into account. Based on the mode superposition method, the theoretical model of flexible micro-perforated panel cavity with flexible back panel (FMPPCFBP) is established. Then, the effects of stiffness, surface density, tension and damping on the sound absorption coefficient of the FMPPCFBP are studied, and the comparison made between the sound absorption coefficient under different boundary condition. Experimental data and finite element methods are used to verify the theory prediction. The result shows that, at the mode frequencies of the flexible micro-perforated panel (FMPP) and the flexible back panel (FBP), the absorption coefficient is improved. The absorption bandwidth can also be broadened, by configuring the parameters of FMPP and FBP properly.
2020 Vol. 39 (15): 156-162 [Abstract] ( 142 ) HTML (1 KB)  PDF (1610 KB)  ( 57 )
163 Stiffness nonlinearity and control of multi-DOF micro-gyroscope under time-delay displacement feedback
HAO Shuying1,2, SONG Yuhao1,2, LI Weixiong1,2, ZHANG Qichang3, FENG Jingjing1,2, HAN Jianxin4
To reveal influence of displacement feedback term on the dynamic characteristics of a multi-DOF micro-gyroscope nonlinear system and explore control methods for nonlinearity, a class of 4-DOF electrostatically driven micromachined gyroscopes is researched, then the dynamic characteristics of micro-gyroscope controlled system in frequency domain and time domain are analyzed by multi-scale method. The research found that feedback gain can effectively adjust the resonant frequency of the system when the time delay is the whole period or half period; feedback gain mainly affects the amplitude and the resonant frequency remains basically the same when the time delay is one quarter or three quarters of the period; When the feedback control parameters are selected properly, multistable solutions caused by nonlinearity can be eliminated ,then sensitivity stability of the gyroscope is increased, however, improper selection will lead to complex almost periodic motion of the system, which will destroy the sensitivity stability.
2020 Vol. 39 (15): 163-169 [Abstract] ( 128 ) HTML (1 KB)  PDF (2251 KB)  ( 43 )
170 Simplified dynamic modeling and model parametric identification for bolted flange connection structures
JIANG Guoqing, HONG Rong, CHEN Wanhua
Abundant nonlinear factors included in bolted flange joint, like contact and gap, make dynamic analysis more complex and lower inefficient, constructing simplified dynamic model is one of the main means to improve computational efficiency. By treating the bolted flange joint as a black box, and cutting out a part of the vertical section from the bolted flange joint structure, a “local joint structure” is formed. After obtaining the contact characteristic of junction surface, a single bolted joint is simplified by using some spring-damping elements whose tension rigidity and compression rigidity is different, then a simplified dynamic model of the local joint structure is built. The simplified dynamic model’s parameters are identified by using the force state mapping method. Dynamic test data shows that the prediction errors of the simplified dynamic model of the bolted flange joint are not more than 20%.
 
2020 Vol. 39 (15): 170-175 [Abstract] ( 210 ) HTML (1 KB)  PDF (1635 KB)  ( 59 )
176 Fault localization for rolling bearing based on AE
LIU Xiaoqin, TANG Linjiang, HOU Kaize, WU Xing, WANG Zhihai
The fault characteristic frequencies of low-speed rolling element bearing is low, and is greatly affected by the speed variation. It is difficult to identify the fault in those bearings by spectrum analysis. In this paper, a fault localization method for bearing damage based on the time difference of arrival (TDOA) of acoustic emission is proposed, which does not rely on the speed of acoustic emission signal. The optimal time difference can be obtained by minimize the variation of TDOA on each band of wavelet package decomposition. The pencil-lead break experiments on the ring of the bearing show that high localization accuracy can be achieved. The experiments carried out on the bearing test bench also demonstrates that the damage locations can be found with minor errors. This localization method does not depend on the rotating speed and frequency analysis, which has great advantage for the fault diagnosis and location of variable speed and large bearings.
2020 Vol. 39 (15): 176-182 [Abstract] ( 185 ) HTML (1 KB)  PDF (2371 KB)  ( 62 )
183 Construction and selection of nonconformal near-field acoustic holography wave function based on wave superposition method
XIANG Yu1， SHI Ziyu1,2， LU Jing1,2， WU Wenjun1,2
In traditional wave superposition method for near-field acoustic holography,its integral kernel function usually adopts the single-layer potential wave function or double-layer potential wave function. When the holographic plane and the equivalent source plane are non-conformal, this kind of wave function can easily lead to the enhancement of the linear correlation and the aggravation of the ill-conditioned state of the system matrix.Most studies focused on the regularization of ill-conditioned matrices to obtain better results.Firstly, the reason of ill-conditioned system caused by traditional single-layer potential wave function or double-layer potential wave function was analyzed theoretically. Then, a series of ray wave functions with strong directivity were constructed by calculating derivatives of the Green's function.By replacing the single-layer potential or double-layer potential wave function used in the traditional wave superposition method with the ray wave functions, the resulting system matrix can be principal diagonal dominant and approximate symmetrical form, so the results can be more accurate and stable without using the regularization method.In this paper, the numerical simulation of the conventional pulsating sphere and swing sphere source and the general ball source which can be superimposed as the external sound field of any sound source is carried out. The results show that the superposition method of high order wave function proposed in this paper can significantly reduce the condition number of system matrix and make the system matrix tend to be well-formed under the condition that the system matrix of traditional wave superposition method is ill-conditioned and cannot obtain satisfactory results without Tikhonov regularization.Therefore, in this sense, this method is also a regularization means to improve the stability of reconstruction.It was also found that, weather the traditional single-layer potential wave function and double-layer potential wave function, or the ray wave function constructed in this paper, each had itsapplication scope, advantages and disadvantages. Therefore, different wave functions should be selected according to different situations to improve the computational stability and efficiency.
2020 Vol. 39 (15): 183-192 [Abstract] ( 134 ) HTML (1 KB)  PDF (2928 KB)  ( 86 )
193 Nonlinear dynamic characteristics of two-stage planetary gear transmission system in wind turbinegearbox
XIANG Ling, LIU Suixian, ZHANG Junhua
Based on the time-varying meshing stiffness, meshing error and backlash of the two-stage planetary gear train of the wind turbine gearbox, the dynamics model of the two-stage planetary gear transmission system in generalized coordinates is established. The variable step gill integral method is used to solve the model. Using the bifurcation diagram, phase diagram, FFT spectrogram, poincaré maps and the maximum Lyapunov exponent diagram comprehensively, the influence of excitation frequency and meshing damping ratio on the system vibration response and bifurcation characteristics was analyzed. The results show that the system exhibits rich nonlinear dynamic behavior under the coupling of various nonlinear factors. With the increase of excitation frequency, the system switches between multi-periodic motion, quasi-periodic motion and chaotic motion. And the way to exit chaos is backward bifurcation. In addition, under the premise of ensuring the system transmission efficiency, properly increasing the meshing damping ratio of the system can significantly suppress the chaotic motion of the system, reduce the vibration amplitude, and improve the stability of the system.
2020 Vol. 39 (15): 193-199 [Abstract] ( 204 ) HTML (1 KB)  PDF (1873 KB)  ( 50 )
200 Hierarchical control strategy for active suspension system of automobile powertrain
CHEN Zheming, WANG Heng, CHEN Yong, FU Lijuan
Aiming at the structural characteristics of the active mounting system of the vehicle powertrain and considering the influence of the dynamic characteristics of the actuator on the control accuracy of the system, a hierarchical control method is proposed. Based on the analysis of the three-degree-of-freedom (DOF) 1/4 vehicle active mounting system, the mathematical model of the mounting system and the electromagnetic actuator control circuit is derived. The upper and lower controllers are designed for the mount part and the actuator circuit part by using the layered control strategy. The upper mount controller adopts LQR control with better comprehensive performance and uses genetic algorithm to optimize its performance index weight coefficient. The lower actuator circuit adopts simple and practical PID control, besides, optimizes its parameters using particle swarm optimization algorithm. Finally, the simulation is verified by setting two typical operating conditions for the designed active mounting system. The results show that compared with traditional control, the active mounting system designed according to the hierarchical control strategy can implement more precise control for different working conditions of the vehicle, and has strong robustness and force tracking.
2020 Vol. 39 (15): 200-206 [Abstract] ( 143 ) HTML (1 KB)  PDF (2322 KB)  ( 57 )
207 3-D acceleration measurement of traction passenger elevator based on magnetic levitation technology
JIANG Dong, CHEN Cai, ZHAO Yanchao, WANG Deyu
In order to achieve three-dimensional acceleration measurement of traction passenger elevator an inertial acceleration measurement model using magnetic levitation technology was designed. The motion equation of the vibrator was established in the vertical direction and the horizontal direction. A three-dimensional acceleration measurement simulation model of magnetic levitation was designed. The vertical and horizontal acceleration were simulated respectively, and the method was verified by experiments. The vertical and horizontal acceleration of the traction passenger elevator were measured. As the vibrator of the magnetic suspension acceleration measurement system is suspended that its sensitivity is higher, its measurable frequency is lower and resolution is higher. Thus, it is easy to achieve absolute multi-dimensional acceleration measurement. Experiments show that it is suitable for elevator acceleration and vibration measurements, and it is ease of installation and debugging and so on.
2020 Vol. 39 (15): 207-213 [Abstract] ( 118 ) HTML (1 KB)  PDF (1539 KB)  ( 13 )
214 Probabilistic model of cumulative plastic strain of coarse-grained soil fill based on large-scale dynamic triaxial tests
LENG Wuming1,2, ZHAI Bin1, XU Fang1,2, ZHANG Qishu1, AI Xi1, HAN Xu1
The cumulative plastic deformation of subgrade soils under long-term cyclic dynamic loads is discrete. Firstly, a series of large-scale dynamic triaxial tests of a coarse-grained soil filling were conducted to investigate the development trend and variation law of cumulative plastic strain with confining pressure, dynamic stress and water content. The results show that the cumulative plastic strain and its stable value increase with the increase of dynamic stress and decrease with the increase of confining pressure, indicating that the increase of confining pressure can effectively inhibit the cumulative plastic deformation of the soil. The dynamic stability of the soil increases with the decrease of water content. Secondly, based on the semi-logarithmic prediction model, the relevance theory of grey systems is adopted to explore the correlation between the model parameters and water content and dynamic-static stress ratio, and a normality test is performed to demonstrate that the model parameter controlling the growth rate of the cumulative plastic strain of the coarse-grained soil obeys a normal distribution. Finally, based on the probability failure theory, a probabilistic model for predicting the cumulative plastic strain of coarse-grained soil fillings is proposed, which can predict the cumulative plastic strain development range of coarse-grained soil fillings under cyclic dynamic loadings.
 
2020 Vol. 39 (15): 214-220 [Abstract] ( 133 ) HTML (1 KB)  PDF (1820 KB)  ( 36 )
221 Tests for cavitation and motion characteristics of double-ball parallel water entry
WANG Xu，L Xujian
The water entry problems receive extensive attention in recent years. Compared with single water entry, water entry side-by-side has a stronger application background in in military applications such as multiple aerial torpedo and multiple projectiles entering into water side-by-side, which can significantly improve the damage effect of underwater moving target. To explore the hydrodynamic characteristics of twin bodies during water entry, the twin spheres synchronous water entry of different lateral distances are experimentally investigated using the high-speed camera. It is found that the contact lines are obliquely pinned on the surface of twin spheres and showing a very good symmetry. The inclination angle of the pinned line reduces with the increase of the lateral distance between the twin spheres. When the lateral distance is small (≤2.5D), a molar-shaped cavity is formed by the overlapping of inner-side cavity wall. We found the collapse wake of twin cavities interweaves into cloud-shaped and horseshoe-shaped wake when the lateral distance is 1.5D and 3.5D, respectively. In addition, top separation of the water column which induced by surface seal is observed when the lateral distance is less than 3.5D. Furthermore, the influence of adjacent bodies on the cavity evolution is gradually weakened with the increase of lateral distance, therefore, the length, the diameter and the splashing were similar to that of single water entry.
2020 Vol. 39 (15): 221-229 [Abstract] ( 149 ) HTML (1 KB)  PDF (3144 KB)  ( 37 )
230 In-plane random vibration of stay cable system under Poisson white noise excitation
LIU Jingrui1, CHEN Lincong1,2, ZHAO Yaobing1
The nonlinear random vibration of stay cables has been studied extensively so far, but it appeared to be limited to Gaussian white noise excited cases. However, the random disturbances in reality are non-Gaussian excitations. There will be large errors if Gaussian excitations are replaced by non-Gaussian excitations. In this paper, the stay cable system is supposed to be excited by Poisson white noise, and the in-plane random vibration of stay cable system under non-Gaussian stochastic excitation is studied. First, the stochastic differential equation of the in-plane vibration of stay cable system under Poisson white noise excitation is formulated, and the corresponding reduced generalized Fokker-Plank-Kolmogorov (FPK) equation governing the probability density function (PDF) of stationary response is established. Then, the iterative method of weighted residuals is proposed to solve the fourth-order generalized FPK equation to yield the approximate stationary PDF of system. Finally, the effects of sag ratio, damped coefficient and pulse arrival rate on the in-plane stochastic vibration of cable are examined. The results show that the asymmetric appearance of response is becoming much obvious while the sag ratio increases; the response is then suppressed obviously as the coefficient of damping increases; the response of stay cable system increases rapidly with the increase of pulse arrival rate, and is getting closer to the Gaussian white noise excited case. Besides, the feasibility of the method is compared with the Monte Carlo simulation. The results show that the analytical solutions are in good agreement with Monte Carlo simulation data.
2020 Vol. 39 (15): 230-236 [Abstract] ( 194 ) HTML (1 KB)  PDF (1383 KB)  ( 50 )
237 Aseismic system of medium-span cable-stayed bridge in strong earthquake area
HUANG Yongfu, MA Jian, XIA Zhixian
In high earthquake intensity areas, selecting a reasonable seismic constraint system has good effects on optimizing seismic performance of medium-span cable-stayed bridges. Cable-stayed bridge with a span of 100m+240m+100m is used as engineering case, and modal analysis and nonlinear time-history analysis of four different transverse constraint systems are carried out, then the effects of three constraint schemes of the transition pier on overall seismic performance of bridge are also compared. The results show that the structural seismic response is greatly reduced when elastic-plastic constraint device is installed in the transverse direction of bridge. In addition, the sensitivity analysis of mechanical parameters Fy ,K1 and K2 of elastoplastic constraints is carried out, trend of structural seismic response is obtained and suggestions for parameter design are given. Based on the theoretical analysis, the design idea of three anti-seismic defense lines is proposed for the engineering application of elastoplastic constraint devices under different seismic levels, which provides a reference for the selection of seismic systems for medium-span cable-stayed bridges.
2020 Vol. 39 (15): 237-242 [Abstract] ( 129 ) HTML (1 KB)  PDF (1686 KB)  ( 52 )
243 Robust optimization design for vehicle SEM based on 6 method
ZHANG Ziwei1, ZHENG Ling1,2, XUE Wanying1, WU Xing1, LIAO Guangliang1
Dynamic performances of a kind of vehicle engine’s SEM with a controllable orifice in dual model operations are studied. The lumped parameter model is set up to reveal its characteristics. In this paper, GA method is used to solve the mount’s deterministic optimization problem that the minimization of the force transmission rate between two modes is taken as optimization objective, and the optimization variables are selected by sensitivity analysis. Considering the manufacturing errors, the semi-active mount’s performance is variable. In order to enhance the reliability and robustness of product, the semi-active mount is further optimized based on Six Sigma method after analyzing the result of robustness of deterministic optimization by means of Monte Carlo simulation. The results which calculated by robust optimization based on 6σ method show that the mount becomes much more reliable, compared with deterministic optimization’s results.
2020 Vol. 39 (15): 243-249 [Abstract] ( 146 ) HTML (1 KB)  PDF (1976 KB)  ( 88 )
250 Nonlinear chaos control parametric perturbation and orbital deviation of a gear-bearing system
LIN He1, WANG Sanmin2, RTSCH Matthias3, XU Guangshen1
In order to investigate the chaotic vibration control problems of gear-bearing system, nonlinear dynamic model with multiple clearances was performed, the nonlinear excitations, such as backlash, bearing radial clearances were contained. Jacobi matrix and sensitivity vectors were computed based on system state model and variational transformation, then associated with differential manifold theorem and OGY (Ott-Grebogi-Yorke) chaos control method, the dominating conditions for controlling chaotic attractors to higher periodic orbits when unstable dimension variability happens were improved. The P8 and P10 unstable periodic saddle points which embedded in the interior of chaotic attractors were calculated by means of Newton-Raphson numerical algorithm, and both of which were verified containing critical complex conjugate eigenvalues with modulus 1 inside Jacobi matrix eigenvalue spectra, consequently, the target periodic orbits of P8 and P10 were revealed to be non-hyperbolic. Taking bearing preload as nominal controlling excitation, chaotic transient oscillation takes place nearby the location of trajectory switching point according to the analysis of multi-stage controlling of P1, P2, P4, P8 and P10, for higher periodic orbits controlling, the accuracy decreases with high trajectory deviations, finally, the parameter excitation evolves and complies with the controlled periodic orbital state after stabilization.
2020 Vol. 39 (15): 250-256 [Abstract] ( 210 ) HTML (1 KB)  PDF (1540 KB)  ( 59 )
257 Typhoon-induced response characteristics and yaw effects of large wind turbine based on multi-body dynamics method
BAO Wenyi, WANG Hao, KE Shitang
For the study of the effects of aerodynamic load distribution and dynamic response of the large wind turbine caused by violent typhoon under different yaws. This paper investigates the 5mw wind turbine of NREL, based on the multi-body dynamics and mixed multibody system modeling method, established the rigid-flexible multibody dynamics model, using the ADAMS/Vibration to analyze the dynamic characteristics and the validation. of the model. At the same time, the three-dimensional stochastic wind field in the typhoon eyewall at the strongly interferential stage is simulated based on the spectral decomposition, and the aerodynamic load of the turbine are simulated numerically based on the yin-momentum theory in 7 working environment where the angle of yaws is different. And the influence of yaws on the aerodynamic load of the whole wind turbine is analyzed. Finally, the time history analysis of turbine with different angle of yaws is performed based on the multi-body dynamics model and the effecting law of wind-induced response with different angle of yaws is extracted. The results show that: The supercell method can accurately describe the dynamic characteristics of the wind turbine with less freedom. The results show that the typhoon-induced wind load and wind-vibration response of the structure increase significantly at the yaw angle of 30° and 120°, which is a typical unfavorable condition and should be avoided. The main conclusions can provide a scientific basis for the wind-resistant design of large wind turbines under extreme conditions.
2020 Vol. 39 (15): 257-265 [Abstract] ( 196 ) HTML (1 KB)  PDF (3085 KB)  ( 41 )
266 Active vibration control of time-varying mechanical systems based on an adaptive algorithm with model real-time identification
ZHENG Hongbo1, YANG Dequan1, HUANG Zhiwei2, ZHANG Zhiyi1
Phenomena of time-varying parameters widely exist in mechanical systems.If a system’s parameters change greatly with time, effects of time-varying parameters on control algorithm should be considered in active vibration control schemes.Here, an adaptive algorithm with model real-time identification was proposed for suppressing vibration of time-varying mechanical systems with larger variation of dynamic characteristics.The proposed algorithm combined the traditional filtered adaptive algorithm and the recursive prediction error method, the latter with gradient change was used to estimate the control channel model in real time.A time-domain model for longitudinal vibration of a non-uniform cross-section beam with spring-mass supports was established.The spring stiffness in the model changes with time to cause larger variation of the model’s dynamic characteristics.Numerical simulation for vibration control was performed for the established beam model using the proposed adaptive algorithm with model real-time identification.Simulation results showed that the proposed control algorithm can effectively suppress the time-varying system’s narrowband and broadband vibration; compared to the existing adaptive algorithms, the proposed algorithm can have a better control performance.Finally, the proposed control algorithm was applied in vibration control tests of a time-varying swing system.It was shown that test results verify the feasibility and effectiveness of the proposed control algorithm.
2020 Vol. 39 (15): 266-270 [Abstract] ( 134 ) HTML (1 KB)  PDF (1438 KB)  ( 85 )
271 Simulation and tests for lateral vibration transmission suppression of  a propulsion shafting system based on active stern support
XIE Xiling1,2, REN Mingke1,2, HUANG Xiuchang1,2, ZHANG Zhiyi1,2
An active control method is proposed to suppress the lateral vibration transmission in a shaft-hull coupled system of underwater vehicles subject to the excitation of propeller forces. The active stern support, which uses a Stewart structure to replace the traditional surface support in the stern bearing, is employed to suppress vibration transmission from the shaft to the hull structure. The dynamic model of the shaft-hull system embedded with the active stern support is established. The characteristics of vibration transmission in the system and the feasibility of active control are analyzed and the attenuation of vibration induced by the lateral excitation of propeller forces is also calculated. An experimental system was built to verify the effectiveness of the control method. Numerical and experimental results have shown that the active stern support is able to suppress the lateral vibration transmission under the excitation of propeller forces, and the attenuation of the normal vibration of the hull structure can be achieved.
2020 Vol. 39 (15): 271-276 [Abstract] ( 138 ) HTML (1 KB)  PDF (1841 KB)  ( 30 )
277 Dynamic response monitoring of flexible structures based on microwave sensing
XIONG Yuyong, LI Songxu, PENG Zhike
The health monitoring of flexible structures represented by long-span bridges and elevated roads in the service process has received much attention. The structural dynamic testing is one of the important ways for structural health monitoring. In this paper, the application of dynamic monitoring of flexible structures is investigated by using the new non-contact vibration measurement technology based on microwave sensing. Firstly, the composition of microwave vibration measurement systems, the basic theory and method of vibration measurement based on single-frequency continuous wave (CW) and frequency-modulated continuous wave (FMCW) microwave radars are illustrated. Then, according to the requirement and characteristic of dynamic testing of flexible structures for practical applications, the mode selection and optimal parameter setting criteria of microwave vibration measurement systems are proposed and established. Finally, based on the built microwave vibration measurement system, the dynamic testing experiments of the elevated road structure under the excitation of subway trains are carried out and the dynamic characteristics of the structure under different load conditions are analyzed. The results indicate that the vibration measurement technology based on microwave sensing can effectively monitor the deflection and vibration response of flexible structures, which provides a new vibration measurement technology and method for the health monitoring of flexible structures.
2020 Vol. 39 (15): 277-282 [Abstract] ( 219 ) HTML (1 KB)  PDF (1955 KB)  ( 181 )
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