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2019 Vol. 38, No. 12
Published: 2019-06-15
1
Design and analysis of an aeroelastic model forthe 1 000 kV Sutong long span transmission tower-line system
ZHAO Shuang1,YAN Zhitao1,2,LI Zhengliang1,DONG Jianyao3,NIE Xiaochun1
The Sutong long-span transmission tower-line system was of tall and long span, and the concrete in the steel tube may be invalidated by pull force in strong wind.These reasons made the design and analysis of its aeroelastic model difficult.Based on the data from the boundary layer wind tunnel test of a rigid model, the influences of loosening Froude number similarity criterion of transmission tower, changing the elastic stiffness of transmission line and two variable ratio transmission line models on the wind-induced responses were analyzed respectively by using the finite element model.Further, its aeroelastic model was designed.The influences of the material nonlinearity of concrete-filled steel tube and gradient wind height on the wind-induced responses were analyzed through the finite element model.The results show that by increasing the elastic stiffness of transmission lines and using the accurate line length similarity ratio, an aeroelastic model of Sutong long span can be designed reasonably; the influence of considering the material nonlinearity of concrete-filled steel tube on the wind-induced responses is small under designed wind speed, and the wind-induced responses decreases with the height of gradient wind.
2019 Vol. 38 (12): 1-8 [
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280
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A study on the life prediction of time-varying vehicle-bridge coupling vibrationof reinforced concrete (RC) bridge structures in Salt Lake Area
LI Shuangying1,2,ZHAO Jianchang1
The time-dependent vehicle-bridge coupling vibration of reinforced concrete (RC) bridge structures corroded by chloride attack is a complex multi-factor and seriously non-linear process in Salt Lake regions.The characteristic is gradually enhanced with wind speed and train speed, which results in higher requirement prediction model for life prediction assessment of RC bridge structures.A vehicle-bridge vertical coupled vibration model of RC bridge was established based on the secondary active suspension system.Based on the pseudo-excitation method, the vertical vibration displacement of the train at different running speed was solved, and the influence factors of load f(δ) were determined by the displacement and the energy conservation law.Based on the theory of the Fick second diffusion law, the time dependence of chloride diffusivity of concrete, the influence of track irregularity excitation and the running speed of high-speed train on the vertical vibration of RC railway bridge members were fully considered.Therefore, a modified model for the chloride diffusion of RC bridge was established, which considers both the influence factor of load f(δ) and the chloride binding capacity.The simulation results show that compared with the traditional chloride diffusion model without considering the influence factors of train running speed, the modified chloride diffusion model of the RC railway bridge is more reasonable.It is more practical for predicting structural service life of existing RC bridges in the Saline Lake regions.
2019 Vol. 38 (12): 9-16 [
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218
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17
Vibration control in a reciprocating compressor piping system using a radial-exhaust surge tank
MA Quyang,YANG Guoan,LI Mengjun
Vibration of a reciprocating compressor piping system is caused mainly by the pressure pulsation.To further improve the performance of suppressing pressure pulsations in the whole piping system by using a surge tank, the characteristics of pulsation suppression using the radial-exhaust surge tank was studied.The transfer matrix was developed, and the distribution of pressure pulsation was predicted.The results showed that the relative suppression ratio in the piping system with a radial-exhaust surge tank is increased by 10% compared with an axial-exhaust surge tank.The validity of the theoretical model was verified by experiments and three-dimensional transient simulations.The optimization of the geometrical parameters, such as the distance between the inlet and outlet pipes and the ratio of length to diameter, was performed.The maximum peak-to-peak pressure pulsation in the piping system is decreased by 8% when the distance was shortened and the ratio was decreased.This work may provide guidance for vibration control in the industry.
2019 Vol. 38 (12): 17-24 [
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291
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Modification of a dynamic constitutive model-HJC model forroller-compacted concrete and numerical verification
ZHANG Sherong1,2 SONG Ran1,2 WANG Chao1,2 SHANG Chao1,2 WEI Peiyong1,2
It is necessary to understand the dynamic mechanical behaviors and constitutive relations of dam materials in studying the dynamic response of hydraulic roller-compacted concrete (RCC) dam withstand high strain rate loads of impact and explosion.Referring to the mix proportion and the construction method of practical hydraulic concrete dam, RCC specimens were prepared and static compression test and split Hopkinson pressure bar (SHPB) test were conducted to explore the dynamic mechanics of RCC.The HJC model which has been widely used to describe the mechanical behavior of concrete under high strain rate was modified including strength surface, strain rate strengthening effect and failure criterion based on the static and dynamic mechanical test results of RCC.Then SHPB experiment was simulated via the finite element method to verify the effectiveness of modified HJC model.The results demonstrate that the dynamic mechanical properties of RCC under high strain rate impact loading show obvious strain rate effect, the dynamic compressive strength increases with strain rate and is related to the specimen size.The reconstructed stress-strain curve obtained by the numerical simulation matches the SHPB test and the maximum principal strain failure criterion can describe the damage process of RCC specimen during SHPB tests well, so that the improved HJC model basing on test data can predict the dynamic mechanical behavior of RCC under high strain rate loading.The research findings can be used in the anti-impact and explosion design of RCC structures.
2019 Vol. 38 (12): 25-31 [
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263
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32
Innovative nonlinear-linear structural control methods for seismic response reduction
WANG Jingjing, LIU Zhibin, HAO Wenming
Tuned mass dampers (TMDs) are an effective structural control method with weak robustness against frequency changes.Nonlinear energy sinks (NESs) are frequency-robust but dependent on the input energy level for optimal control capacity.Two types of nonlinear-linear combined structural control methods including single-mass dampers and dual-mass dampers were proposed.Numerical models of a two-degree-of-freedom primary structure with different control devices attached respectively were constructed based on their equations of motion.The single-mass damper and dual-mass damper were optimized under impulsive excitations.The results show that the two combined methods exhibit similar effectiveness as an optimized TMD and NES and are able to maintain a relatively high robustness against the changes of frequency and energy level.Furthermore, the single-mass and dual-mass dampers can better reduce the structural responses under the earthquakes than both linear and nonlinear methods considering the uncertainty in input energy level and the frequency change in the primary structure.
2019 Vol. 38 (12): 32-38 [
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243
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39
An experimental study on water impact of large amphibious aircrafts
SUN Feng1, 2, WEI Fei1, 2,WU Bin1, 2, ZHANG Jiaxu1, 2,CHU Lintang1, 3
The traditional seaplane water load test basically adopts the rigid ratio model, which does not take into account the influence of elastic deformation and scale ratio on load.A large amphibious aircraft cabin section was used to carry out a water load test and a test plan was designed for large test pieces.Different weight states and water-entry speeds were tested.Changes of acceleration peaks, the history and distribution of pressure characteristics were analyzed.The theoretical and experimental values of accelerations at different half widths of wetting were compared.The results show that the secondary peak phenomenon appears in the partial pressure curve; the acceleration peak increases nonlinearly with the weight and the water-entry velocity; as the weight increases, the half width of wetting corresponding to the acceleration peak increases, and the velocity influences it mildly; The Von-Karman theory is closer to the experimental result than the Wagner theory; the smaller the water-entry velocity, the greater the influence of gravity on the water entry of the structure.
2019 Vol. 38 (12): 39-43 [
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199
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44
Synchronization behaviors and vibration synchronization transmission of the dual-vibratory-rotor system under superresonant conditions
CHEN Bang1, XIA Xiaoou1, WANG Xiaobo2
In order to reveal the synchronization characteristics of the system with two rotors mounted on two coupled bodies, a simplified physical model of the dual-vibratory-rotor system was proposed.The coupling mechanism between two rotors was analyzed by the integral method and the Lyapunov principle.The synchronization condition, stability of the system, and vibration synchronization transmission condition were summarized.Taking the maximum vibration torque as the breakthrough point, the influence of the coupling spring stiffness on the synchronous performance was investigated.By introducing the concept of system characteristic frequency, the strong coupling mechanism of the system was expounded.Theoretical research shows that as the coupling frequency is close to the coupling characteristic frequency, the vibration torque is large and coupling performance can be strong.When coupling effects between rotors are weak, self-synchronization can be obtained by adjusting the coupling spring.Synchronization characteristics of the system can be the theoretical basis for designing high-stability and high-tolerance vibration systems.Vibrations of the dual-vibratory-rotor system with different parameters were simulated respectively, and the results are in good agreement with the theoretical analysis.
2019 Vol. 38 (12): 44-52 [
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249
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53
Stochastic resonance characteristic analysis ofthe new potential function under Levy noise and bearing fault detection
HE Lifang 12 ZHOU Xicheng 1 2 ZHANG Gang1 2 ZHANG Tianqi1 2
Based on the output saturation of classical bistable stochastic resonance, a new type of piecewise nonlinear bistable potential stochastic resonance (PNBSR) system was constructed.Firstly, the PNBSR system was compared with the CBSR systems in theory.Then, the mean signal-to-noise ratio gain was treated as an index to measure the stochastic resonance phenomenon.The quantum particle swarm algorithm was used to seek optimal parameters.The laws for the resonant output of piecewise nonlinear bistable system governed by l , c, a, b, and D of Levy noise were explored under different characteristic index α and symmetry parameter β of Levy noise.The results show that the output of the PNBSR system has increased 4dB compared with the output signal-to-noise ratio of a classical bistable stochastic resonance(CBSR) system.And the stochastic resonance phenomenon can be induced by adjusting the piecewise nonlinear system's parameters under any α or β of Levy noise and D of Levy noise, and the best interval does not change with α or β.At last, the piecewise nonlinear bistable stochastic resonance system was applied to detect bearing fault signals, which achieves better performance compared with the classical bistable stochastic resonance system.
2019 Vol. 38 (12): 53-62 [
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196
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63
Memory alloy drive unlocking mechanism for a periscopic laser communication terminal
MENG Lingchen1,3,MENG Lixin1,2,ZHANG Lizhong1,2,ZHAO Honggang1,3,ZHANG Yiqun1,3
In order to meet the locking requirements of a servo-rotation system for a periscopic laser communication terminal, this paper proposed an unlocking mechanism based on shape memory alloy (SMA) wire.The laser communication terminal was ensured stably locked during satellite launch.Firstly, the mechanism used the spring component to realize the locking, and the heating memory alloy wire output the return stress to drive to unlock; then, the unlocking mechanism was optimized, and the locking force and the locking displacement were optimized by the lever principle; The balance between the locking force and the unlocking force of the unlocking mechanism was analyzed.In addition, the relationship between the unlocking time and the supply voltage and current was analyzed experimentally.Finally, the prototype was developed and the ground test of the aerospace environment such as high temperature and vibration shock was carried out.The experimental results show that the mechanism can provide 1 000 N locking force, stable and reliable locking under 90 °C, and the unlocking time can be stabilized within 3 s.The function and stability of the mechanism meet the launch requirements of spaceborne laser communication terminals.
2019 Vol. 38 (12): 63-68 [
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133
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69
Dynamic deformation monitoring of bridge structures based on GPS-RTK and accelerometers
XIONG Chunbao1, LU Huali1, ZHU Jinsong1, YU Jiayong2
The real-time dynamic monitoring technology of the global positioning system GPS-RTK (Real-Time Kinematic) and accelerometers were used to monitor the dynamic deformation of Fumin Bridge in Tianjin.The sampling frequency of the RTK receiver was internally upgraded from 1Hz to 20 Hz.A joint monitoring device of RTK and an accelerometer was designed.In order to reduce the influence of multipath errors and random noise in RTK monitoring data, the AFEC hybrid filter (Autocorrelation Function based EEMD and Chebyshev) which was a combination of an autocorrelation function-based ensemble empirical mode decomposition (EEMD) filter and a Chebyshev filter was proposed.By filtering the data collected by RTK, the dynamic displacement of the bridge can be identified and compared with the displacement sequence obtained by integrating the acceleration data, and the results were basically consistent.It was shown that the AFEC filter can effectively weaken the multipath error and random noise in the RTK monitoring data.
2019 Vol. 38 (12): 69-73 [
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159
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74
Study on the sound quality of unsteady exhaust noise based on RNR-WVD calculation and GA-wavelet network
ZENG Falin1,SUN Sumin2
The GA-BP acoustic quality prediction model based on the psychoacoustical objective parameters can accurately predict the sound quality of the steady state exhaust noise.For the research on unsteady state noise, RNR (regularization non-stationary regression technique) was applied to compute the WVD distribution (RNR-WVD), and a new parameter SQP-RW was built to replace the objective parameters that have less correlation with the satisfaction degree.Meanwhile, a WNN (Wavelet Neural Network, WNN) was constructed by using the Morlet wave basis function which was used as the transfer function of the hidden layer.And GA was used to optimize the weights and thresholds of the WNN layers, the GA-WNN was constructed and used to predict the acoustic quality of the unsteady exhaust noise.The results show that the GA-WNN is more accurate in predicting the sound quality of unsteady exhaust noise than the GA-BP neural network.With the introduction of SQP-RW, the model has higher accuracy and it can reflect the characteristics of unsteady signals and the sound quality characteristics.
2019 Vol. 38 (12): 74-80 [
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181
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81
A study on vibration control strategy for a parallel driven electro-hydraulic system
SHEN Gang1，RUI Guangchao2，ZHANG Mingfei1，LI Ge1，TANG Yu1
In order to suppress internal force coupling of a parallel driven electro-hydraulic system, a dynamic model of the vibration system was established and the causes of coupling disturbance were analyzed.Then, the degree-of-freedom decomposition was applied to realize independent control of eight exciters, an internal force decoupling controller was applied to eliminate the coupling internal force in the process of operation.On this basis, a three-variable controller was applied to realize acceleration closed-loop control of the electro-hydraulic system and improve dynamic characteristics of the vibration system, and a feedforward inverse controller was applied to expand the system bandwidth.Performances of the proposed control strategy were validated through experiments using a parallel driven electro-hydraulic testing rig, and the experimental results demonstrate that the proposed control strategy can improve vibration accuracy.
2019 Vol. 38 (12): 81-89 [
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160
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90
Rotation speed extraction from vibration signals in the dehydration stage of a washing machine based on AMDF and DTS
CHANG Yu1,GAO Cuiyun1,TONG Huaijun2
To meet the national standard GB/T4288—2018, the sensors are required to be installed on the shell of washing machines for vibration parameters detection, and the measurement for rotation speed requires the sensor to be installed outside the wash basket, which is less efficient.Therefore, it was proposed to use an acceleration sensor on the shell of a washing machine to extract the dehydration rotation speed, and it is supposed to detect the rotation speed and the vibration parameters simultaneously without disassembling the machine.The difference between the rising control curve and the free descending section of the washing machine dehydration stage were analyzed, a novel method combining average amplitude difference function (AMDF) and differential threshold segmentation (DTS) was proposed to extract the rotation speed from the vibration signal in the dehydration stage of the washing machine.The relevant rotation speed curve of the vibration signal part with too low SNR and energy at the descending section was found and cut, and a few outliers in the whole speed curve were corrected.The method was tested by using a certain type of a pulsator washing machine under three kinds of modes with different dehydration time.The experiment results show that the errors between tested rotation speed curve and theoretical rotation speed curve of steady stages and setting goal stages meet the error requirements of the national standard.
2019 Vol. 38 (12): 90-97 [
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144
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98
POD-based dimension reduction simulation of stochastic wave force field
LIU Zhangjun1,2,LIU Lei2,WANG Feng2
Due to the theory of multivariate stationary stochastic process, the proper orthogonal decomposition (POD) formula based on the orthogonal random variables was derived.On the basis of this, by defining the random function form of the orthogonal random variable set in the POD formula, a POD-random function approach was suggested for simulating the multivariate stationary stochastic process.Note that the proposed approach and the conventional approach based on the random phase angles are both the special cases of the POD approach based on the orthogonal random variables.However, the proposed approach can accurately represent the multivariate stationary stochastic process with just two elementary random variables.The power spectrum density matrix involved in the multivariate stationary stochastic process of wave force was derived according to the linearized Morison formula.Then by means of the proposed approach, effective dimension reduction simulation for the multivariate stationary stochastic process of wave force could thus be realized.Finally, combined with the P-M wave spectrum, the power spectrum density matrix involved in the multivariate stochastic process of the horizontal wave force was derived.And the numerical simulation analysis of the horizontal stochastic wave force field was carried out.The example shows that the proposed approach requires the least number of the elementary random variables and a small number of representative samples which constitute a complete set of probabilities.It has significant advantages in terms of simulation accuracy.
2019 Vol. 38 (12): 98-104 [
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160
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105
Grüneisen equation of state of warhead charge under impact loading
CAI Xuanming1，ZHANG Wei2，XU Peng1，GAO Yubo1，FAN Zhiqiang1
Aiming at the application problem of PBX explosive in weapon warhead, the effects of plane positive shock wave to the state equation of PBX explosive were studied.Based on the planar shock wave equation and the Hugoniot curve, using symmetric collision experiments, the state equation of different densities of PBX explosive under different shock wave loading were studied through the relationship of the application of shock wave velocity and particle velocity.In the research results, the impact factors and sound velocity of different densities PBX explosive were obtained.The relevant parameters of the Gruneisen state equation were obtained, which provided an important basis for predicting the internal pressure, density and energy state of the PBX explosive in the face of the larger shock wave array.And the result reveals that the relationship between Gruneisen coefficient Γ and body strain ξ is highly linear.
2019 Vol. 38 (12): 105-111 [
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187
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112
Effectiveness of an inerter-spring-damper device in the seismic response control of a isolated structure under extreme earthquakes
CHONG Cholap1,KOHJU Ikago2,ZHANG Yongshan1
This paper considers the use of an inerter-spring-damper (ISD) device to suppress excessive seismic responses of seismic isolated structures subjected to extreme earthquakes.The ISD consists of an inerter, a device that exerts forces proportional to the relative acceleration of its two ends, coupled with a series springs and dampers.The ISD is a device that can utilize amplified apparent mass and tuning effects.Based on the fixed-points theory, we derived closed-form expressions for optimal ISD tuning parameters for harmonically excited single-degree-of-freedom primary systems.The performance of the ISD was compared to the linear viscous damper (LVD) located at the isolation story, a 6 story seismic isolated structure was presented as an example, and the design of ISD optimum parameters was determined by optimum tuning formulae.The performance of the isolated structure containing an ISD and LVD device subjected to extreme earthquakes were investigated.The results show that utilizing the optimum ISD can result in an improvement in the seismic performance in comparison to the LVD.
2019 Vol. 38 (12): 112-117 [
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258
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118
Reynolds number effects on aerodynamic forces of a streamlined closed-box girder during vortex-induced vibrations
HU Chuanxin1,ZHAO Lin1,CHEN Haixing2,ZHOU Zhiyong1,GE Yaojun1
Aiming at a traditional streamlined closed-box girder of long-span bridges, wind tunnel tests of synchronal measurement of pressures and displacement responses of a spring-suspended sectional model with scales of 1∶70 and 1∶20 were conducted, with Reynolds number of 6.08×103-2.28×104 and 1.06×104-1.40×105 respectively, and then effects of Reynolds number on wind-induced vibration (VIV) as well as time-frequency characteristics of the aerodynamic forces on the surface of the girder were revealed.It was found that there were obvious VIV phenomena both at low and high Reynolds number.Compared with VIV performance at low Reynolds number, lock-in regions were lower and maximum amplitudes were smaller at high Reynolds number, indicating that VIV performance at low Reynolds number was more unfavorable.Then time-frequency characteristics of the aerodynamic forces were investigated.It was found that the spatial distribution characteristics of mean pressure coefficients, RMS of pressure coefficients and phase lags between vortex-excited forces (VEF) and distributed aerodynamic forces were obviously different at different Reynolds numbers, which indicated that there were significant Reynolds number effects.The distributed aerodynamic forces in downstream and middle-upper reaches of the upper surface, as well as the lower surface contributed mostly to the VEF at high Reynolds number.The aerodynamic forces in downstream of the upper surface as well as lower surface had enhancement effects on the VEFs, while those in other regions had suppression effects on the VEFs.However, aerodynamic forces in middle-upper of the upper surface contributed little to the VEFs at low Reynolds number，and the contribution of aerodynamic forces in the downstream of the upper surface were very close to that at high Reynolds number .The negative contribution of aerodynamic forces to VEF in lower surface and windward inclined web were far smaller at low Reynolds number than that at high Reynolds number, while that in corner region of lower surface and tail wind fairing were far higher at low Reynolds number than that at high Reynolds number, which was responsible for the fact that VIV responses at high Reynolds number were higher than that at low Reynolds number.
2019 Vol. 38 (12): 118-125 [
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196
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126
A study on the lateral vibration of saturated soil-pipe pile-rigid platform
LIU Linchao,YAN Qifang
Based on the theory of saturated porous media, a system model of saturated soil-pipe pile-rigid platform coupling system was established, and the dynamic properties of saturated soil-pipe pile-rigid platform coupling system under horizontal harmonic load was studied.The soil around the pipe pile and pile core soil were regarded as saturated soil, and the equations of motion of saturated soil were given based on the theory of porous media, the motion equations of platform were established by regarding the platform as rigid body.The solution of horizontal vibration of saturated soil around the pile and pile core saturated soil were obtained through the method of separation of variables by considering boundary conditions of the soil and the continuity conditions of pile-soil.The solution of the lateral vibration of the pipe pile was obtained by considering the boundary condition of pipe pile ends with the initial parameter method, and we also obtained the analytical solution in frequency domain of the horizontal displacement of the rigid platform by the transfer matrix method considering the continuity conditions of the pipe pile-rigid platform.Numerical examples show that the saturated soil-pipe pile-rigid platform coupling system has obvious resonance under horizontal harmonic load, it is easy to cause resonance when the pipe pile wall is too thin, and the existence of pile core soil can improve the seismic performance of the saturated soil-pipe pile-rigid platform system, and increasing the buried depth of the pipe pile can significantly reduce the horizontal displacement amplitude of the rigid platform, reducing the height and the mass of the platform is helpful to provide the seismic performance of the system.
2019 Vol. 38 (12): 126-132 [
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192
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133
Experimental study on near-ground wind profile characteristics of typhoon in Coastal Hilly Geomorphology of Southern Zhejiang Province
ZHU Yunhui1, SUN Fuxue2，JIANG Shuo2， SHI Wenhai2,3，ZHANG Chuanxiong1, LI Zhengnong4，ZHAO Zhefei3
Based on the geomorphological anemometer tower (100 m) in the coastal hills of Cangnan, Zhejiang Province, the data of wind speed and direction at different heights in the landing process of Typhoon Morakot were obtained.The characteristic parameters of wind profile, such as average wind speed and wind direction angle, turbulence degree, gust factor, coherence coefficient, turbulence integral scale and power spectral density, were further studied.The results showed that the changes of 10 min mean wind speed and wind direction angle at different heights are very synchronous under the action of typhoon, and the exponential law can well reflect the distribution of wind speed along the measured height range in the coastal hilly landform of southern Zhejiang where the wind tower is located.With the increase of height, the turbulence degree and gust factor decrease gradually, and the mean value of turbulence integral scale increases gradually, the turbulence degree is quite different from the national norms, which tend to be conservative.There is a linear relationship between turbulence and gust factor.with the increase of turbulence, the gust factor increases accordingly, and with the increase of height, the dispersion of linear relationship decreases gradually.The median profile of downwind turbulence integral scale is close to that of Japanese code; the power spectral density of fluctuating wind speed is well fitted with Von Karman spectrum in downwind direction, especially at 100 m, but varies greatly in crosswind direction; with the increase of anemometer spacing,the correlation becomes weaker rapidly, and the correlation at the high level is better than that at the low level at the same distance.
2019 Vol. 38 (12): 133-139 [
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209
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140
Properties of guided waves propagating in honeycomb sandwich plates and the detection of disbonding damage using ultrasonic waves
PENG Bo,SHUI Guoshuang,WANG Yuesheng
Properties of guided waves propagation in honeycomb sandwich plates were studied based on a finite element model, and a experimental study on detection of disbonding damage within the honeycomb sandwich structure was conducted by using ultrasonic waves.A finite element model was employed based on an actual honeycomb sandwich plate structure, and the propagations of guided waves both in perfect and damaged structure were simulated using the commercial software COMSOL Multiphysics.In the experimental study, piezoelectric wafers were used to excite the guided waves, and the waves were acquired using a Polytec Scanning Vibrometer.It was shown that the guided waves possess the features of dispersion and multi-modes; A0 mode is sensitive to the disbonding damage in the honeycomb sandwich structure, and the experimental result agrees well with the simulation.Furthermore, disbonding damage was located based on wavelet transform and damage probability imaging.
2019 Vol. 38 (12): 140-147 [
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197
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148
Modeling of a micro vibration energy harvester considering size effect
LI Chuangye1,2,HUO Rui1,2,WANG Weike1,2,ZHAO Chen3
Young’s modulus changes in micro world with size effect.Considering this, a micro piezoelectric cantilever beam was analyzed by ANSYS.A vibration characteristics experimental platform was established.Considering size effect, the dynamic equation of the micro beam was studied.Results show that it is accurate.The dynamic model of micro vibration energy harvester was improved based on that.A T-type micro vibration energy harvester was designed and fabricated.Resonant frequency, tip displacement and output voltage of the harvester were obtained.Comparing with the macroscopic model of vibration harvester, the improved model reduces errors by 13%，35%, and 22%.
2019 Vol. 38 (12): 148-152 [
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109
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153
Design and intelligent collaboration optimization for testing parameters of a new shock response spectrum generator
LIU Chengwu,WEN Jingjing,WU Bin,CHEN Jie,XU Feng
In order to expand the function of a vertical impact testing machine, a new type of shock response spectrum (SRS) generator was designed in this paper.Combined with the Mindlin plate theory and the finite element simulation, the relationship among the inherent characteristics of a simply supported plate, the excitation load, and SRS was analyzed.An intelligent collaboration optimization scheme was proposed, which contains the orthogonal test, support vector machine (SVM), and the multi-population genetic algorithm (MPGA).First, we established a database of simulated SRSs by emulating orthogonal tests with Nastran software.Then, we used SVM to establish the surrogate model for predicting the root mean square error (RMSE) of simulated SRSs and the standard ones.Lastly, the optimal parameters of the resonant plate size (length a, width b, thickness h) and excitation load (peak A, width D) were obtained from the surrogate model by MPGA.The optimized results are that the size of the resonant plate is a=398 m, b=387 mm, h=32 mm and the excitation load is A=4.628 kN, D0=0.8 ms, and the RMSE is 27.7.Meanwhile these optimized results were verified and validated with simulation and experiments.The results show that both the simulated SRS and the experimental SRS meet the requirement of test standard.The simulated RMSE is 39.6 and the experimental RMSE is 33.4.This study provides a new way for impact test.
2019 Vol. 38 (12): 153-161 [
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209
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162
Complex variable function solution of vibration isolation for two-dimension foundation wave impeding block
ZHOU Fengxi1,2,ZHENG Qi1
Theoretical analysis of a two-dimensional elastic foundation wave impeding block (WIB) seismic isolation system was conducted.First, based on the theory of elastic mechanics, the governing equation of the rectangular wave impeding block in the two-dimensional elastic foundation was established.Then, based on the incident of plane SH wave and the continuity condition between wave impeding block and half-space interface, the analytic solution of vibration isolation performance for the two-dimensional foundation wave impeding block was obtained by the wave function expansion method.In the end, according to the variation of amplitude attenuation coefficient, the influence of the shear modulus of wave impeding block, the depth of wave impeding block and the incident angle of elastic wave on the vibration isolation effect was analyzed.The results show that, the vibration isolation performance is improved obviously with the increase of shear modulus of wave impeding block; the vibration isolation effect for surface displacement increases gradually with the depth of wave impeding block; the smaller the incidence angle of elastic wave is, the more obvious the vibration isolation effect is.
Key words:wave impeding block; complex variable function; conformal mapping; SH wave; vibration isolation effect
2019 Vol. 38 (12): 162-167 [
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Inverse analysis of concrete dam thermal parameters based on an improved particle swarm optimization method
WANG Feng 1,2 ZHOU Yihong1,2 ZHAO Chunju1,2 WANG Fang1,2
A swarm intelligence optimization algorithm-particle swarm optimization (PSO) model was constructed for thermal parameter identification based on temperature observation data.Therefore, thermal characteristics of concrete in real pouring environment can be obtained in real time.In order to solve this problem that traditional PSO is easy to fall into the local extreme point prematurely, an improved particle swarm optimization (IPSO) was proposed, which combines particle swarm optimization and concave function weight decreasing strategy.Effectiveness of IPSO was illustrated by the algorithm performance comparison analysis.Considering the influence of cooling water and outside temperature change, IPSO was applied to inverse analysis of thermal parameters of an arch dam during hot season construction.The inversion parameters were validated by comparison of measured temperature and calculated temperature.The numerical example shows that IPSO has advantages of converging quickly and identifying accurately.
2019 Vol. 38 (12): 168-174 [
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148
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175
Simplified Design Method of Viscous Damping Frame Structure Based on Preset Damping Distribution Mode
LIU Shuai1,PAN Chao2,ZHOU Zhiguang3
A design method based on performance requirements and conceptual optimization for viscous damping frame structures was proposed to simplify the design process of damping parameters of such damping structures.In order to make energy dissipation of the damper more effectively, it was assumed conceptually that the distribution of damping parameters along the floor is positively correlated with the story drift angle, and the distribution expression of damping parameters was given.Under this preset damping distribution model, the relationship between the equivalent additional damping ratio of multi-story damping structure and the additional damping parameters of each layer was derived.Combined with the performance-based design concept, it was proposed that the damping ratio is taken as the damping design goal, and the required additional damping ratio of the damping structure can be determined according to the relationship between the damping ratio and the damping attenuation of the seismic design response spectrum.Combined with the distribution expression of preset damping parameters, the required damping parameters of each layer can be calculated quickly.The damping design and seismic performance checking calculation of a frame structure with viscous dampers were carried out.It was shown by the design example that the method has clear design goal, simple calculation process and reasonable parameter configuration.
2019 Vol. 38 (12): 175-181 [
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186
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182
Vibration response analysis of an unsaturated soil foundation
LI Weihua1,WANG Wenqiang2
The development of the wave theory of unsaturated porous media makes the dynamic analysis of unsaturated soil foundation possible.In this paper, an explicit finite element method for the existing dynamic formulation of unsaturated porous media was proposed.The decoupling-technique was used in the explicit finite element method.Based on the method, the computational program was written and verified by comparing with the analytical solution after degeneration.The method was applied to analyze the dynamic responses of a strip rigid and flexible foundation in an unsaturated porous medium separately, and the influence of saturation on the dynamic responses of unsaturated soil foundation was discussed.The computational results indicate that, the dynamic response of the rigid foundation is larger than that of flexible foundation under the same conditions.For both kinds of foundations, the dynamic response for Sr=1 is smaller than that for Sr<1.For the rigid foundation, the vertical displacement of each point decreases and the horizontal displacement increases with saturation level when Sr<1.For the flexible foundation, saturation has limited influence on the dynamic response of unsaturated soil foundations.
2019 Vol. 38 (12): 182-190 [
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201
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191
Influence of different pitch control on floating characteristics of offshore wind turbine
Yu Wan1, Ding Qinwei1, Li Chun1, 2, Hao Wenxing1, Zhou Hongjie1, Zhu Haitian1, Han Zhiwei1
The pitch operation of offshore wind turbine blades affects the dynamic response of the supporting platform, namely the floating stability of the offshore wind turbine.However, the floating stability of the offshore wind turbine is an important factor in its ability to exploit wind energy in the deep sea.Therefore, disturbance accommodating control (DAC) was established in the open source software FAST and the Matlab / Simulink co-simulation platform, and compared with the original control strategy of FAST to study the influence of different controllers on the floating characteristics of offshore wind turbines.The result show that: Compared with the FAST control strategy, DAC has better control effect on offshore wind turbines, which aggravate the dynamic response of offshore wind turbines.The influence of different control strategies on the floating characteristics of offshore wind turbines mainly lies in the direction of surge and pitch.In the design of pitch control strategy of offshore wind turbine, the natural frequency in pitch direction should be avoided firstly to improve the floating stability of offshore wind turbine.The results provide a theoretical basis for designing a pitch controller that is more suitable for offshore wind turbines.
2019 Vol. 38 (12): 191-198 [
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150
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199
An experimental study on tbe rheological perturbation effect and a constitutive model of water-rich soft rock
YU Yongjiang1,LIU Feng1,2,ZHANG Wei1,ZHANG Guoning1
Deep water-rich soft rock roadway under dynamic disturbance has the characteristics of large rheological deformation and rapid deformation rate, which is the main reason for the difficulty of roadway support and the creep-induced rock bursts.In order to study the creep failure characteristics and a constitutive model of water-rich soft rock under dynamic disturbance, the stage-loading creep test of soft rock with different moisture content was conducted by a self-developed rock disturbance creep experiment system.The results show that: The deformation of the soft rock increases suddenly when the disturbance is applied, and then the deformation rebounds from different degrees.Finally, the deformation continues developing on this basis.The disturbance deformation rate increases slowly with disturbance energy under less stress level and low moisture content.On the contrary, the perturbation deformation rate increases rapidly with perturbation energy under high stress level and high moisture content, which lead to failure of rock specimens.The constitutive model of rheological perturbation effect of water-rich soft rock was established based on the perturbation state equation of perturbation energy and model parameters were identified.The model fitting curves agree well with the experimental curves, which verified that the model can be described correctly in rich water soft rock creep properties under dynamic disturbance.
2019 Vol. 38 (12): 199-205 [
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135
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An experiment and numerical modeling method of gelatin bird striking on force sensors
FENG Zhenyu1,2,HUO Yujia1,2,PEI Hui1,2,XIE Jiang1,2,MOU Haolei1,2,LIU Xiaochuan3,GUO Jun3
In order to study the numerical modeling methods of gelatin bird under different quality and different velocities, the gelatin bird impact force sensor experiment were conducted.It was shown that two kinds of failure modes of the gelatin bird that fluid-like failure and remaining part rebound after the front end breaks.In numerical modeling, the SPH method of discretization and the equation of state constitutive were used to model the gelatin bird in the case of fluid-like failure; the Lagrange method of discretization and elastic-plastic with damage constitutive were used to model the gelatin bird in the case of remaining part rebound after the front end breaks.According to the experiment results, the constitutive parameters were inverted respectively; the numerical result is in good agreement with the test results.It shows that the modeling method is reasonable.The verification of applicability of constitutive parameters was performed, under the premise of gelatin bird quality and impact velocity range in this paper, it also shows that different quality gelatin bird need different constitutive parameters to model for the elastic-plastic with damage constitutive; gelatin bird of different quality and different velocity need different constitutive parameters to model for the equation of state constitutive.
2019 Vol. 38 (12): 206-212 [
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236
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213
Sound absorption performance analysis of anechoic coatings under oblique incidence condition based on COMSOL
YE Hanfeng,TAO Meng,LI Junjie
Based on the oblique incidence theory of plane wave, a simulation model of the anechoic coating with double plates has been established using the FEM software COMSOL.The influence of structural and material parameters under oblique incidence condition on sound absorption performance has been studied.Firstly, the accuracy of this model has been validated via the comparison between the FEM and the theoretical results.Then, the influence of incidence angles, hole structures, perforating rates, and thickness on sound absorption performance of anechoic coatings has been studied.The results show: If incidence angles increase, the frequency space between the peak and trough of sound absorption coefficient curves and the associated numerical values will increase.The frequency values at peaks and troughs of sound absorption coefficient curves are higher and the curves will shift to left as the perforating rate and the thickness increase.
2019 Vol. 38 (12): 213-218 [
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205
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219
Reliability analysis of human-ground friction coefficient for vehicle-pedestrian traffic accident
ZHANG Xiaoyun1 YANG Xiaobo1 ZHANG Dongming1 HOU Xinyi2
Traditionally, friction coefficient between human and ground, combining with various other parameters is considered as a constant to predict the pre-impact velocity of a car.It is impossible to accurately determine all these parameters used for simulation since there are uncertain factors at the accident scene.A method of constructing the relationship between calculation result and human-ground friction coefficient was proposed in this paper.By using the site measurement data and numerical simulation, we built a reliability analysis model related to the human-ground friction coefficient.Quantitatively analysis on the effect of reconstruction result and human-ground friction coefficient was conducted based on the above model.A 0.95 confidence interval of pre-impact velocity of car was also presented at last.Our analysis indicates that the friction coefficient between human and ground is of great significance for the estimation of the pre-impact velocity.That also reminds us reducing the error of friction coefficient measurement can help with obtaining a much more reliable result in vehicle-pedestrian contact collision accident reconstruction.
2019 Vol. 38 (12): 219-224 [
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176
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225
A study on complexity feature extraction of ship radiated signals based on a multi-scale permutation entropy method
CHEN Zhe, LI Yaan
In order to solve the problem of feature extraction of ship radiated signals in complex ocean environment, a multi-scale permutation entropy method based the complexity feature extraction method for ship radiated signals was proposed.Firstly, the center frequency of intrinsic mode function with the highest energy, the energy difference between high and low frequency, permutation entropy and multi-scale permutation entropy were respectively used to extracted features of five types of ship radiated signals.Then the extracted ship features by four kinds of methods were respectively sent into a probability neural network for identification.The study discovers that multi-scale permutation entropy is a powerful nonlinear characteristic because it has good consistency and stability and is able to describe a signal over multiple scales.The results indicate that the multi-scale permutation entropy method has a good separability.The identification accuracy is obvious higher than other ship radiated noise feature extraction methods when using multi-scale permutation entropy as the feature.
2019 Vol. 38 (12): 225-230 [
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247
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231
An experimental study on the failure characteristics of magnetite ore based on dynamic load
LI Zhanjin1, HAO Jiawang1, 2, GAN Deqing1, LIU Zhiyi1
The impact experiments of magnetite ore under different strain rates were carried out by a splitting Hopkinson pressure bar (SHPB) equipment.The mechanical properties and the crack propagation of the magnetite ore under dynamic load were analyzed to evaluate the distribution pattern of the fragmentation of the magnetite ore.Experiment results indicate that the strain rate effect of the dynamic elastic modulus and strength of the magnetite ore is obvious.The unloading rates and unloading modes in the post-peak of stress-strain curve are different under different strain rates.With strain rate increasing, the softening factor (K) of the magnetite ore decreases and the softening degree increases.Both the relations between the strength scale factor (λ) of the magnetite ore and ε?1/3, and the specific energy absorption of the magnetite ore and ε? are linear distribution.The broken form of the magnetite ore is of distinct self-similarity that the mean fragment size of the magnetite ore decreases, fractal dimension increases and the magnetite ore is broken strongly with strain rate.The fractal dimension increases linearly both with the strain rate and the specific energy absorption of the magnetite ore.The distribution pattern of the fragmentation of the magnetite ore, which is clearly revealed by means of the total logarithmic curve of the cumulative particle size, combined with the block distribution coefficient (C), the reasonable range of the strain rate of the magnetite ore crushing is obtained.The study results provide significant references for the analysis of the crushing mechanism of magnetite ore under dynamic load, the distribution of the fragmentation and the energy consumption.
2019 Vol. 38 (12): 231-238 [
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169
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239
A VHCF test method based on three-point bending for composite
CHEN Chao1,CHEN Xuan1,CHENG Li1,2
In order to solve the problem of composite`s very high cycle fatigue (VHCF), a method of three-point bending test based on ultrasonic fatigue testing device was proposed; the necessity of composite VHCF test was discussed; the modal of the horn, the connecting rod and the specimen was analyzed by ABAQUS, and the resonant frequency of the designed device as well as the specimen was satisfied.Aiming at the phenomenon of temperature rise in the experiment process, a combined cooling system of liquid nitrogen with compressed air was put forward.The results indicate that the method greatly shortens the test period, improves the test efficiency, eliminates the thermal effect of the specimen during the high frequency loading period, and ensures the validity of the experimental results.
2019 Vol. 38 (12): 239-245 [
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180
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246
Structure strength analysis and parameter optimization of rubber spring
DING Zhiping1, ZENG Jiaxing1,2, LIN Sheng2, HUANG Youjian2
The influence of the structural parameters of conical rubber spring on the stiffness, and the maximum principal strain range was studied, by using the Mooney-Rivlin hyperelastic constitutive model, and the structural parameters of the conical spring were optimized.Based on the orthogonal test method, the structure parameters of large radius R , groove depth h, surface angle θ and small radius r for structural strength factors, were carried out simulation test for conical spring.The experimental results show that the factor θ has greatest impact on the stiffness and the maximum principal strain range of the rubber spring, the influence degree of each factor on the stiffness is θ>r>R=h, the influence degree on the maximum principal strain range is θ>h>r>R.Based on a second-order response surface model and the Optimal Latin hypercube design method , the arc radius R, groove depth h, surface angle θ and small radius r as design variables, the spring stiffness as constraints, the maximum principal strain range as the objective function, the optimization mathematical model was established.The Multi-Island Genetic Algorithm(MIGA) was used to optimize the structure parameters of conical rubber spring, and the optimization results are substituted into the simulation model to verify.The error between the stiffness and the maximum principal strain range of test results and the optimal solution results were 1.75%, 3.57%, compared with the original structure, the maximum principal strain range was reduced 19.9%, which has a better optimization effect; the error between the test stiffness value and the optimal stiffness value was 4.71%, which meets the technical requirements.
2019 Vol. 38 (12): 246-251 [
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264
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252
Modal experiment for a spherical hinged space truss structure
WANG Guilun1,2, JIANG Dong1,3, ZHOU Lizhenhui1,2, FEI Qingguo1,2
The accurate dynamics characteristics of a flexible and joint-dominated space truss structure is difficult to obtain in the ground test.The ground modal test of truss structure is susceptible to test conditions.The experimental modal analysis of a spherical hinged space truss was conducted using the hammer method.The modal parameters were obtained based on the experiment results.The MAC (Modal Assurance Criterion) was utilized to verify the reliability of the results.Combined with different cases in the test, the influence of suspension condition and response point position on the modal experimental results of the truss structure was analyzed.The modal analysis of the truss structure under free boundary condition was carried out using FEM.The results obtained through the experiment method and FEM were compared.The results show that lower added stiffness of suspension can avoid modal coupling.distributing suspension points uniformly and symmetrically improves the repeatability of the modal experiment.placing accelerometer near the center of the structure reduces the energy loss of the excitation, which can ensure the completeness of the modal results.increasing length of suspension can reduce the influence of suspension effect on low order modes.
2019 Vol. 38 (12): 252-257 [
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171
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258
A decoupling method of powertrain mounting systems and vibration characteristics analysis of complex flexible foundations
SUN Qi, LIU Shan, NIU Ning, HOU Liwen, SUN Lingling
A dynamic model of a powertrain mounting system was derived to explore multi-dimensional coupling vibration of the powertrain.Then six degree-of-freedom natural frequencies were calculated and decoupling conditions of the most important vibration modal were confirmed.A powertrain mounting system of heavy truck was designed and verified.FEM and the power flow theory were combined to explore flexible vibration of complex foundations in engineering.Modal information of complex foundations can be obtained from FEM and taken into vibration power functions.Then vibration power transmitted in the vibration isolation system with complex flexible foundations can be obtained.The results show that obvious and dense peaks of vibration power appear because of foundation flexibility, isolation effect has deteriorated at middle and high frequencies.Foundation flexibility is essential to vibration transmission in the whole system.The increase of foundation rigidity is beneficial to vibration isolation.The new method is practically significant to explore flexible vibration isolation systems with complex foundations in engineering.
2019 Vol. 38 (12): 258-263 [
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230
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Extraction of Runyang bridge vibration information based on a fusion method of wavelet threshold denoising and EMD decomposition
YU Teng1, HU Wusheng2, WU Jie1, LI Haifeng3, QIAO Yan1
The data of dynamic vibration monitoring of the Runyang bridge, a large-span bridge, are large and complex, In order to better filter out noise and obtain real vibration information, a method of wavelet denoising and EMD decomposition was proposed.At first the signal was decomposed with the wavelet method, and then noise was filtered out with an improved threshold function.The signal was decomposed after the wavelet threshold de-noising using the EMD method.Finally the signal was refactored.Example analysis shows that the method can filter out noise more effectively and extract the bridge vibration information.
2019 Vol. 38 (12): 264-270 [
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229
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