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Influence of Vulcanizing Agents on Fatigue Tear Characteristics of   a Type of Elastic Components 2013, 33(4): 1-4.  DOI: 10.3969/j.issn.1006-1335.2013.04.001 Abstract ( )   PDF (2552KB) ( )   The vulcanizing agent as an important part of the rubber ingredient has critical impact on the fatigue tear characteristics of rubber product. Previous studies mainly focused on test method, which needs long period and high cost. In this paper, the influences of vulcanizing agents on a certain type elastic component’s tear characteristics were studied using FEA. Therefore, several pieces of rubber material of different ingredients were obtained by adjusting the species and the amount of vulcanizing agents and the material constitutive models of different rubber were obtained firstly, and then the fatigue tear characteristics of the elastic component made of different pieces of rubber material were studied based on ANSYS. Finally, the influence of vulcanizing agents on the fatigue tear characteristics of a certain type elastic component is summarized and verified by experiments. Related Articles | Metrics

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Parameter Analysis of Dynamic Vibration Absorber  in Flywheel Vibration Control 2013, 33(4): 5-10.  DOI: 10.3969/j.issn.1006-1335.2013.04.002 Abstract ( )   PDF (1570KB) ( )   Dynamic vibration absorber for reduction of flywheel vibration was developed. Optimum tuning frequency and damping ratio of the absorber were derived by multi-variable multi-mutation adaptive genetic algorithm (MMAGA). Then mathematical formulae of the optimum parameters were obtained by regression analysis. The simulation conclusion showed that MMAGA are suitable to calculating optimum parameters of the absorber efficiently and the optimum absorber can reduce vibration response of flywheel obviously. Related Articles | Metrics

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Comparative Study on UNDEX Resistance of the Air-backed Stiffened Plate with Various Covering Layers 2013, 33(4): 11-15.  DOI: 10.3969/j.issn.1006-1335.2013.04.003 Abstract ( )   PDF (1171KB) ( )   In order to improve stealthy capacity of a submarine, acoustic covering layers are usually covered on hull surfaces of a submarine. Due to the special cavity structures in the acoustic covering layers, they will deform and absorb energy when they are subjected to UNDEX, which will greatly affect the submarine's anti-shock performance. In this paper，comparative study on UNDEX resistance of the air-backed stiffened plate with various covering layers is carried out. Through the peaks of acceleration and strain; the shock resistance is assessed. The results will provide a guideline to the design and study of acoustic covering layers against UNDEX. Related Articles | Metrics

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Influence of Foundation Vibration on Average   Centripetal Acceleration of Precise Centrifuges 2013, 33(4): 16-19.  DOI: 10.3969/j.issn.1006-1335.2013.04.004 Abstract ( )   PDF (911KB) ( )   The mathematical model is established from the angle of rigid body kinematics based on vibration characteristics, which describes the foundation vibration is how to affect the average centripetal acceleration. And then, the model-based theoretical analysis and numerical simulation is done. The method to reduce the effect of the foundation vibration is put forward. The influence of foundation vibration can be decreased by averaging, and the longer averaging time will make a good result. The influence of sinusoidal vibration caused by centrifuge rotation can be partly eliminated by averaging when time is an integer multiple of the centrifuge rotation period. However, a system error will be introduced to average centripetal acceleration if the frequency of sinusoidal vibration is the same with Centrifuge speed, which can not be eliminated or reduced by averaging, and the appropriate compensation method should be study further. Related Articles | Metrics

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Optimal Design of Acoustic Performance of a Composite Structure Combined by a Perforated Plate and a Sound Insulation Film Drape 2013, 33(4): 20-23.  DOI: 10.3969/j.issn.1006-1335.2013.04.005 Abstract ( )   PDF (838KB) ( )   Research on acoustic composite structure is now an acoustic Research hotspot. Based on the orthogonal experiment, we analyzed four influence factors, namely, the height of the drape, the perforation rate, the thickness of the perforated plate and the distance between the panel and the drape to study the absorption properties of the composite structure which is combined by the perforation plate and a sound insulation film drape. The result shows that the film drape structure can effectively improve the absorption properties of the perforation plate, and the highest Noise reduction coefficient (NRC) is 0.6. Along with the drape height, the distance between the drape and the panel and the Perforation diameter increase, the NRC is also improved. And along with the thickness of the panel increases, the NRC reduces. Among all these four influence factors, the most significant factor is the height of the drape, and the next is the thickness of the plate, the Perforation diameter, and the last one is the interaction factor of the height of the drape and the perforation diameter. Related Articles | Metrics

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Analysis of Seismic and Wind Induced Vibration Responses of the  Roof Machine Room of the Ship-lifter 2013, 33(4): 24-29.  DOI: 10.3969/j.issn.1006-1335.2013.04.006 Abstract ( )   PDF (1833KB) ( )   Related Articles | Metrics

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Shock Response Properties of Crane Slewing Bearing Under the Condition of Revolve Braking 2013, 33(4): 30-34.  DOI: 10.3969/j.issn.1006-1335.2013.04.007 Abstract ( )   PDF (1252KB) ( )   In order to figure out the origin of the gear failure of crane slewing bearing, this paper chose the outer race gear as research object, established an impact dynamics theory calculation model of the gear under the condition of revolve braking, analyzed the shock response properties of the gear in different rotary speed and discussed its general rule by using the explicit dynamics FEA analysis method. The result shows that the impulsive force is the main reason of gear surface pitting and brokenness; the shock response properties are more seriously while the rotary speed is increasing. Related Articles | Metrics

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Random Vibration Analysis of an Integrated Airborne Aid Unit on Ambulance Helicopter 2013, 33(4): 35-39.  DOI: 10.3969/j.issn.1006-1335.2013.04.008 Abstract ( )   PDF (1311KB) ( )   To realize the random vibration reponse characteristics of the integrated airborne aid unit on ambulance helicopter, according to the vibration characteristics of the ambulance helicopter airborne platform, random broadband superimposed sine vibration excitation spectrum was converted into pure random vibration spectrum, which can be used directly by ANSYS. The finite element model of the integrated airborne aid unit was built by using ANSYS software and the natural frequencies and modal shape of the unit was obtained by modal analysis. The converted vibration spectrum was exerted on this basis so that the dynamic response and the dangerous frequencies in different positions of the integrated airborne aid unit were received by the random vibration analysis, meanwhile, the dynamic strength was verified. The result of the analysis could provide a reference for the Anti-Vibration design of the integrated airborne aid unit. Related Articles | Metrics

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Topology Optimization for Free-damping Treatment Under Harmonic Excitation 2013, 33(4): 40-43.  DOI: 10.3969/j.issn.1006-1335.2013.04.009 Abstract ( )   PDF (879KB) ( )   Related Articles | Metrics

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Dynamic Response and Shock Resistance of Chiral Honeycomb Rubber Claddings Subjected to Underwater Explosion 2013, 33(4): 44-49.  DOI: 10.3969/j.issn.1006-1335.2013.04.010 Abstract ( )   PDF (1397KB) ( )   In this paper, dynamic response, shock resistance, mechanism of chiral honeycomb rubber claddings subjected to UNDEX were studied. Rubber test data were fitted with the hyperelastic models in ABAQUS finite-strain package. On the basis of the fitting results, the proper model was chosen. Furthermore, their dynamic characteristics, fluid-structure interaction (FSI) effect, transmitting and dissipation process of impact wave energy were analyzed. Finally, the influence of main design parameters including height and porosity on shock resistance was discussed. The results not only play an instructive role in understanding the protective mechanism and performance of claddings subjected to underwater explosion, but also provide a guideline to further optimal design. Related Articles | Metrics

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Analysis of Oil-retarding Property of Damping Rubber 2013, 33(4): 50-53.  DOI: 10.3969/j.issn.1006-1335.2013.04.011 Abstract ( )   PDF (1051KB) ( )   The damping rubber which was used in some places had some resorts that satisfied oil-retarding. In this paper, the physical properties of NBR/NR and Kd/Ks of isolator after them were soaked with different soaking time in IRM903 were explained. Through the comparison of properties of rubber and rubber isolator, it was obtained that decrease of 200% tensile strength made Kd/Ks increasing and vibration effect worse. Additionally, some other discussions were related about the standards of materials in Marine (mass change≤5%(23℃×70h)).It was found that mass change of rubber could not completely reflect the change of property of rubber. Related Articles | Metrics

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Effect Analysis of Water-lubricated Bearing on Dynamic Behavior of Air Compressor 2013, 33(4): 54-58.  DOI: 10.3969/j.issn.1006-1335.2013.04.012 Abstract ( )   PDF (1127KB) ( )   Water-lubricated sliding bearing is designed to support the centrifugal air compressor. Effect analysis of bearing stiffness and bearing location on critical speed of air compressor is important, which is a theoretic cause of adjusting water pressure or bearing location. It is found that critical speed is very sensitive in a certain range of bearing stiffness and will step increase with increased stiffness. It is also found that bearing location changed to increase the span of rotor will let lubrication system easier and critical speed lower. Related Articles | Metrics

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Oil Film Force Model of Tilting Pad Bearing and Its  Characteristic Analysis 2013, 33(4): 59-63.  DOI: 10.3969/j.issn.1006-1335.2013.04.013 Abstract ( )   PDF (1754KB) ( )   A method to model the fluid film force of tilting pad bearing and the torque of the pads were given. The difference of fluid film force of ordinary sliding bearing and tilting pad bearing was compared. Then the impact of pad preload, pad arc and pad motion were analysed with this model. Last, the vibration characteristic of tilting pad was studied combining the Jeffcott rotor by the Runge–Kutta method. The result shows this model is effective and gives the characteristic of tilting pad bearing. Related Articles | Metrics

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Study on the Fractal Feature of Cylinder-head Vibration Signal for Diesel Engines 2013, 33(4): 64-67.  DOI: 10.3969/j.issn.1006-1335.2013.04.014 Abstract ( )   PDF (1086KB) ( )   Wavelet transform and fractal theory is combined with applied to analyze the cylinder head vibration signal of the diesel engine, and to extract fault feature according to the nonlinear characteristics of the vibration signal. This is to diagnosis diesel engine abnormal valve clearance fault, calculated wavelet packet frequency band box dimension, wavelet transform module maximum and the multifractal spectrum of the vibration signal. The results show that fractal dimension and multifractal spectrum as system measure and fault characteristic parameter, make the diagnosis results simple and feasible. Related Articles | Metrics

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Review of FRF-based Substructure Method Using Experimental Data 2013, 33(4): 68-74.  DOI: 10.3969/j.issn.1006-1335.2013.04.015 Abstract ( )   PDF (1401KB) ( )   For dynamic modeling of complex isolation system in ships by using substructure method, the difficulty to represent the dynamics of substructures with adequate accuracy is a big obstacle, one possible solution is the FRF(Frequency response function)-based subtructuring method by employing experimental FRFs. In order to improve the accuracy of the tested FRF and the synthesized results, the literature reviews on FRF-based substructuring method by using experimentally measured component FRFs are summarized. The topics cover the developed FRF-based algorithms, the numerical techniques to eliminate the measurement errors, the influence and the test of rotational degrees of freedom, as well as common measurement noise and measurement related issues. The FRF-based substructure method by using experimental FFRs is applied to a practicle isolation system and good results are obtained. It is expected to provide some reference for practical application. Related Articles | Metrics

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Study on the Vibration Band-gap Characteristics of   Trigonal Chiral Structures 2013, 33(4): 75-78.  DOI: 10.3969/j.issn.1006-1335.2013.04.016 Abstract ( )   PDF (1215KB) ( )   In recent years, attention is devoted to the chiral structures due to its unique topology and property. The Bloch theorem is widely used in the analysis of the periodic structure. In this work, the bandgap property of trigonal chiral structure is studied. The finite element model is built to demonstrate that vibration transmission displays significant attenuation for the frequency located in the band gap, which exposes the efficiency and validity of the method. A parametric study is presented to investgate the dependence of unit cell geometry upon the distribution of the band structure, and the result shows the design flexibilty of the chiral lattice. Related Articles | Metrics

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Analysis of the Effect of Longitudinal Flutter of Single Wheelset 2013, 33(4): 79-83.  DOI: 10.3969/j.issn.1006-1335.2013.04.017 Abstract ( )   PDF (1347KB) ( )   Through establish a dynamic model of locomotive single wheelset,observe the longitudinal vibration resonance phenomenon of the single wheelset in some speed. Determine the frequency of wheel when the resonance occurs. Then analyse the resonance frequency, and offers a more close to the frequency criterion. Next,discuss the relationship between the longitudinal vibration resonance and the forward speed, adhesion utilization coefficient, and estimate longitudinal vibration resonance dangerous speed. On this basis, study the impact of longitudinal vibration resonance to the force in the wheel-rail contact area and relative sliding at the wheel-rail contact patch. Related Articles | Metrics

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Analysis of Acoustic Characteristics of Impinging Flame Noise and Pressure Fluctuations in an Entrained-flow Gasifier 2013, 33(4): 84-88.  DOI: 10.3969/j.issn.1006-1335.2013.04.018 Abstract ( )   PDF (1162KB) ( )   Characteristics of impinging flame noise and pressure fluctuations with two opposed burners are studied based on opposed multi-burner(OMB) entrained-flow bench-scale gasifier. Analysis on spectrum of noise signal and pressure signal of impinging flame is made through Hilbert-Huang transform. The results show that medium and high frequency pressure fluctuations are mainly caused by complex combustion status in impinging flame zone and generates flame noise from 50Hz to 100Hz. The amplitude and waveform of jet flow flame noise are influenced by low frequency pressure fluctuations and reverse flow from impinging zone. Monitoring on acoustic signal of impinging flame which has a corresponding relationship with combustion status could be a flame diagnostic method in a gasifier. Related Articles | Metrics

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Study on Ultimate Shock Load of GS2 Steel-string Vibration Isolator 2013, 33(4): 89-93.  DOI: 10.3969/j.issn.1006-1335.2013.04.019 Abstract ( )   PDF (1868KB) ( )   The ultimate shock load of GS2 steel-string vibration isolator is investigated with test. The ultimate load is gotten when sever deformation occurs on the isolator. Besides the test, the numerical simulation is also carried out to simulate the anti-shock performance of the isolator. Good agreement between the numerical results and experimental results prove the efficiency of the numerical method. The numerical method is a useful method to investigate the ultimate load and anti-shock performance of isolators. Related Articles | Metrics

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Simulation and Analysis of Absolute Stability of Aircraft’s Yaw-angle Control System 2013, 33(4): 94-98.  DOI: 10.3969/j.issn.1006-1335.2013.04.020 Abstract ( )   PDF (1404KB) ( )   The absolute stability of a aircraft yaw angle control system is studied based on Lyapunov direct method. The configuration and dynamic equation of control system are given. The Lyapunov function and derivation function are derived by superposition method. The absolute stable condition is also obtained. Using popov harmonic linearization the maximum value of nonlinear part is determined. Then popov stability criterion is introduced to simulate the absolute stability with variants of system parameter settings. Simulation results indicate that the absolute stable condition could guarantee the stability of the system. Related Articles | Metrics

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Vibration Research of an 9R-40 Rubbing and Breaking Machine 2013, 33(4): 99-102.  DOI: 10.3969/j.issn.1006-1335.2013.04.021 Abstract ( )   PDF (1310KB) ( )   Abstract: The rubbing and breaking machine is one of forage processing machines that vibrates drastically during working, which is bad for environment and worker’ health. .It gets the conclusion through the vibration test as follow: the main reason of machine vibration caused by rotor rotational imbalance; Secondly high speed rotating rotor drive the blade and hammer do periodic motion blow air particle can cause pulse impact pressure wave which can causes vibration on the machine shell. This paper revealed the relationship between vibration strength and main part, which provides reliable reference for optimizing and controlling noise and vibration of rub and breaking machine. Related Articles | Metrics

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Optimization Design of Flexible Rotor System ofSFD-sliding Bearings 2013, 33(4): 103-106.  DOI: 10.3969/j.issn.1006-1335.2013.04.022 Abstract ( )   PDF (854KB) ( )   The SFD can improve the stability of rotary mechanical system to a certain extent. Applying numerical simulation method, the paper researches on sensitivity of the rotor system and dynamic optimization. The study shows: SFD clearance, bearing clearance, shaft stiffness and oil viscosity have great effects on the first two critical speeds and the system is more sensitive to these parameters. Based on design variables offered by sensitivity analysis, this paper employs genetic algorithm to give an optimization analysis on critical speed, which aims to remove critical speed from working speed as much as possible. The critical speed ameliorates after the optimization which supplies theoretical basis as well as theoretical analysis towards the dynamic stability of high-speed rotor system and provides reference for the design of such rotor system. Related Articles | Metrics

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Comparison of Performances of Three Types ofActive Noise Control Algorithms 2013, 33(4): 107-113.  DOI: 10.3969/j.issn.1006-1335.2013.04.023 Abstract ( )   PDF (1799KB) ( )   In order to investigate how to choose active noise control algorithm in practical engineering, the performances of typical ANC algorithms are investigated in different conditions by simulations and experiments. The conditions of application of the algorithms are also studied. It is concluded that if the secondary path is linear and the requirement of the convergence speed is not strictly demanded，FxLMS algorithm is the best choice. If the noise to be actively controlled (i.e. the primary noise) is non-stationary or the requirement of convergence speed is strictly demanded, GSFxAP algorithm is a suitable choice. If the correlation between the primary noise and reference signal is poor, FsLMS algorithm is the choice. It provides a theoretical guide for the choice of active control algorithm in practical engineering. Related Articles | Metrics

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Experimental Study on the Mechanism of Spirant of Water-lubricated Rubber Stern-bearings 2013, 33(4): 114-117.  DOI: 10.3969/j.issn.1006-1335.2013.04.024 Abstract ( )   PDF (1164KB) ( )   Under the condition of low-speed, heavy-load and poor-lubrication, the water- lubricated rubber bearing would vibrate anomaly and occur spirant. This will seriously affect the hidden and viability of the underwater vehicle. Therefore, the further research of the mechanism of the spirant producing is of profound theoretical and practical application value. The research is mainly by theoretical analysis and simulation test bench, and use Pulse vibration analysis platform to do data acquisition and frequency analysis of the vibration of the stern bearing test bench, reveal the mechanism of the spirant and discuss the effects of load, linear velocity and the temperature on the law of the spirant. Related Articles | Metrics

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Analysis of Dynamic Characteristics of Track Vehicles Using ATV 2013, 33(4): 118-121.  DOI: 10.3969/j.issn.1006-1335.2013.04.025 Abstract ( )   PDF (1226KB) ( )   This paper had studied the dynamic characteristic change rule of track vehicle. Based on the character of track vehicle, and with the help of ATV, it used theoretical analysis and dynamic simulation to study the influences of ground topography, vehicle speed and initial track tension to the dynamic characteristic. Through the research, it had found the influence factors and the change rules of the track vehicle dynamic characteristic. As a result, it provided the basis for track vehicle design and optimization. Related Articles | Metrics

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Sound Insulation Property of the Composite Structure withMicro-perforated Panels and Honeycomb Core 2013, 33(4): 122-125.  DOI: 10.3969/j.issn.1006-1335.2013.04.026 Abstract ( )   PDF (1214KB) ( )   Abstract: The sandwich panels made up of aluminum honeycomb, micro perforated panel, GSGN film, and sawdust-board were prepared respectively. Their sound proof properties of different structural parameters of the honeycomb cores and microperforated panel were measured. The result showe that sound insulation index reached 58.41 dB and density only has 0.37 g/mm3. The experiment obtains the anticipanted results with low density. It’s expected that the noise of the traffic can be greatly reduced if these composite structure are applied, and the quality of comfort can be greatly improved. Related Articles | Metrics

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Acoustic Performance Analysis of Exhaust Muffler Using   Transfer Matrix Method 2013, 33(4): 126-130.  DOI: 10.3969/j.issn.1006-1335.2013.04.027 Abstract ( )   PDF (1094KB) ( )   A certain type of car exhaust muffler is taken as the object to research the acoustic performance. The muffler is divided into basic silencing units based on the transfer matrix method , and silencing units are analyzed to get muffler’s total transfer matrix , and its acoustic model is established. The frequency characteristic of transmission loss is calculated using Matlab software. Finite element simulation software , Sysnoise and Fluent are used for the simulation calculation to get the accurate frequency characteristic of transmission loss. The results obtained with both methods are compared to verify the accuracy of the acoustic model ,and the basis for improvement and optimization of the muffler is provide. Related Articles | Metrics

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Performance Research and Parameter Analysis of Resistance Mufflers of Mineral Trucks 2013, 33(4): 131-137.  DOI: 10.3969/j.issn.1006-1335.2013.04.028 Abstract ( )   PDF (1738KB) ( )   According to the different types of mine truck reserved different space for muffler, respectively discussed the different parameters：Length to diameter ratio、Expansion ratio、Perforation rate、Intubation length effect to resistance muffler selection. Under different parameters, transmission loss and the pressure loss was calculated by using SIDLAB software. It was showed that: the change of parameters have a great impact on the maximum amount of noise reduction, removal passing frequency, perforated tube muffler can achieve the most ideal silencing effect. When one interpolation is the half of expansion cavity length, the other interpolation 1/4 can achieve the best effect. For a 290T mine car muffler reserved space characteristics, through the pressure loss and transmission loss comparison, selected a suitable muffler. Related Articles | Metrics

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Simulation Analysis of Interior Noise and Optimization of an Ambulance Carriage 2013, 33(4): 138-144.  DOI: 10.3969/j.issn.1006-1335.2013.04.029 Abstract ( )   PDF (1893KB) ( )   Based on the theory of multi-body system dynamics and the analytical method of finite element and boundary element, the finite element model of vehicle body, the rigid-flexible coupled model of vehicle and the acoustic boundary element model of carriage were established by applying a variety of simulation softwares. Road roughness and engine vibration were simulated and the SPL of field points in carriage under these excitations were computed at the frequency range of 20-150Hz. Considering the size and the positive /negative nature of panels’ acoustic contribution at SPL peak of field points, damping treatments were taken on different combinations of panels to decrease multiple field points’ SPL peak and the optimal treatment was finally confirmed. The results show that the amplitude and frequency distribution of the field point SPL peak are related to the frequency distribution of the exciting force’s energy and structural modal. The frequency distribution of SPL will be changed by adhesiveing damping materials, which can reduce noise at the same time. The noise reduction measures can generally decrease the SPL peak around the Crew. Related Articles | Metrics

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Analysis of Low-frequency Interior Noise of Vehicles Based onATV and MATV Techniques 2013, 33(4): 145-148.  DOI: 10.3969/j.issn.1006-1335.2013.04.030 Abstract ( )   PDF (1464KB) ( )   Low-frequency interior noise is important contents for improving the NVH quality of vehicle .To predict the major sources of low-frequency noise and reduce it have important means for the noise control. The low-frequency interior noise is predicted by using the method of ATV ,We also obtain the frequency response function and contributions analysis for the field point；Modal contributions are obtained by using the method of MATV, the bodywork which has high contributions for the field point is predicted by the modal result. The interior low-frequency noise was reduced in some extent after improvement. Theoretical foundation is supplied to reduce the noise in the interior of vehicle. Related Articles | Metrics

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Step Analysis Based Car Noise Control Method 2013, 33(4): 149-152.  DOI: 10.3969/j.issn.1006-1335.2013.04.031 Abstract ( )   PDF (1631KB) ( )   A step analysis based noise control process is presented in the paper . According to the causes of noise sources, transmission paths and the result the process is divided into three levels, first level is analysis of the excitation source, and according to the excitation the corresponding transmission path come to the second level of analysis, then from the final result the third level of analysis is presented. The process has the character of clear and good operation. At last, with the method a car interior problem is solved, and from the result it can be known the method is efficient. Related Articles | Metrics

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Study on Calculation and Plotting of Dynamic Noise Contour of Single Flight Based on Equivalent Point Swing 2013, 33(4): 153-157.  DOI: 10.3969/j.issn.1006-1335.2013.04.032 Abstract ( )   PDF (949KB) ( )   The airport noise visualization plays an important role in airport range environmental evaluation, through the airport noise isoline map we can analyze the noise level in real-time and any place, and adjust flight plan and flight path to reduce noise intensity in the affected region. This paper study aircraft noise dynamic distribution based on the single flight event, use curve piecewise fitting noise value change rule and on the basis of real-time forecast the noise value. In order to avoid the multiple ergodic and complex contour computation in the conventional contour computing method, this paper proposes a method based on equivalent point rocking isoline grid queue algorithm, satisfy the dynamic draw on time complexity requirements. Related Articles | Metrics

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Design and Construction of Hemi-anechoic Room for  Pilot’s HRTF Measurement 2013, 33(4): 158-161.  DOI: 10.3969/j.issn.1006-1335.2013.04.033 Abstract ( )   PDF (936KB) ( )   The design indexes of hemi-anechoic room were proposed to achieve the acoustic environmental demand for measurement pilot’s head relation transfer function (HRTF), and designed with new compound panel absorber to build the hemi-anechoic room. Based on these designs, the ranges of free acoustic field have been maximized and the key acoustic indexes have been optimized within limited room. All of indexes are satisfied with correlative standard and some key indexes exceed the design indexes by NIM after hemi-anechoic room built. The hemi-anechoic room may furnish a free acoustic environment for HRTF measurement. Related Articles | Metrics

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Study on Application of Noise Mapping to Noise Environment Management 2013, 33(4): 162-166.  DOI: 10.3969/j.issn.1006-1335.2013.04.034 Abstract ( )   PDF (2049KB) ( )   The necessity of study on noise mapping is carried out in this paper. The composition and process of noise mapping are studied systematically. A noise management system is developed and tested based on the analysis of the relationship between Geographic Information System, acoustic model system, check system, display & management system, and then try to find a method of noise management based on this system. The study results may be helpful and referential for the construction of noise management platform. Related Articles | Metrics

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Applicability Analysis of Bornitz Model for Predicting Environmental Vibration Induced by Train Moving on Subgrade Cutting 2013, 33(4): 167-170.  DOI: 10.3969/j.issn.1006-1335.2013.04.035 Abstract ( )   PDF (814KB) ( )   In order to investigate the applicability of Bornitz model on predicting the environmental vibration induced by train moving on the subgrade of cutting, the environmental vibration was tested in Zhengzhou-xi’an high-speed railway. Use the measuring results to calculate the field attenuation coefficient of Bornitz prediction model. Analysis the prediction precision of Bornitz model on predicting environmental vibration based on attenuation coefficient’s discrete degree. The result shows that Bornitz model can present attenuation law of environmental vibration in general but it has low precision to predict the environmental vibration nearby vibration source, the prediction precision increase with the increasing distance away from vibration source. The prediction model is suitable for predicting the environmental vibration in the site far away from vibration source. Related Articles | Metrics

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Noise Control of Windmill Cooling System 2013, 33(4): 171-176.  DOI: 10.3969/j.issn.1006-1335.2013.04.036 Abstract ( )   PDF (1461KB) ( )   In this paper, a noise control of a typical wind turbine cooling system is solved. The noise control consists of measuring of noise sources, design of noise control, research of acoustic materials and devices, implementing and evaluation. The acoustic materials and devices include damping material, sound absorption material, sound barrier and silencer. In this project, the sound level at the key point decreases 22 dB, which effectively improve the wind turbine’s competitiveness in the overseas market. Related Articles | Metrics

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Vibration Analysis of Roof Space Structure above   the Parking Area  of Subways 2013, 33(4): 177-181.  DOI: 10.3969/j.issn.1006-1335.2013.04.037 Abstract ( )   PDF (1859KB) ( )   According to the new Exploitation of Roof Space above the Parking Area along Urban Rail Transit . Using finite element analysis software to make an analysis of the building frequency response and the transmission loss and using the situ experimental method to make a comparative can complete vibration Prediction. This method and conclusion of the research is helpful to the prediction and assessment of the vibration for the roof space above the parking area along Urban transit. Related Articles | Metrics

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Acoustic Design of Sound Barriers and Simulation of Their Noise Control Performance 2013, 33(4): 182-184.  DOI: 10.3969/j.issn.1006-1335.2013.04.038 Abstract ( )   PDF (1149KB) ( )   In order to analyze the sound barrier acoustic design process, survey analysis of traffic noise around one residential buildings in a avenue was conducted. And based on the data obtained, three preliminary designs of sound insulation reflective barriers with different structures at the top were designed for noise reduction requirements in this region. To verify the result, acoustic software of Virtual. Lab Acoustic was applied to simulate the noise performance of the three sound barriers. The simulation results show that the design of the vertical sound barrier can meet practical noise reduction requirements effectively. Related Articles | Metrics

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Review of Analysis Methods of Fault Pattern Recognition for  Rolling Bearings SU Tao 2013, 33(4): 185-189.  DOI: 10.3969/j.issn.1006-1335.2013.04.039 Abstract ( )   PDF (841KB) ( )   Abstract: After Extracting the rolling bearing fault features, how to design a reasonable classification of rolling element bearing fault pattern recognition is the key step of the fault diagnosis. The variable precision rough set of rough set pattern recognition and the least squares support vector machine of statistical pattern recognition, fuzzy means clustering algorithm of fuzzy pattern recognition were introduced. The basic principles, applications and features of the various methods are analyzed. The study has found that the integration of multiple fault pattern recognition method to use is the focus of future research direction. Related Articles | Metrics

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Artificial Fish Swarm Algorithm for Structural Damage Detection 2013, 33(4): 190-194.  DOI: 10.3969/j.issn.1006-1335.2013.04.040 Abstract ( )   PDF (1285KB) ( )   Structural damage detection in fact belongs to the system identification problem; its ultimate goal is to identify the change in physical parameters before and after structural damages. Measured structural modal parameters can be used to obtain the structural physical parameters. The identification procedure is often transformed into solving constrained optimization problems in mathematics. This paper tries to use artificial fish swarm algorithm (AFSA) to solve the kind of large civil engineering constraint optimization problem. First, the AFSA is introduced, its parameters are defined, its behavior and procedures described. The classical test functions are then adopted to test the performance of AFSA algorithm. Finally the objective function of the constrained optimization problem on structural damage identification is given and the effectiveness and robustness of the proposed AFSA method is evaluated by using a number of numerical simulations with noise polluted data. The illustrated results show that the AFSA method can effectively locate damage elements and quantity degree of damages with better noise immunity. It is promising to be applied to the field of structural damage detection in situ. Related Articles | Metrics

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Perturbation Method for Analyzing the Homoclinic Orbit ofa High-power Strongly Non-linear Self-excited Oscillator 2013, 33(4): 195-199.  DOI: 10.3969/j.issn.1006-1335.2013.04.041 Abstract ( )   PDF (850KB) ( )   Base on the previous studies on hyperbolic perturbation methods, the hyperbolic Lindstedt-Poincaré (L-P) method is extended for homoclinic solution and bifurcation analysis of quintic strongly nonlinear self-excited oscillator. By adopting the hyperbolic functions instead of traditional periodic functions in the L-P method, the perturbation procedure for high power strongly nonlinear system can be derived. In the present method, the homoclinic bifurcation value for limit cycle is expanded in power of perturbation parameter, the secular terms of perturbation homoclinic solutions are defined. The homoclinic bifurcation values can be determined by eliminating the secular terms. The homoclinic solutions which satisfy the homoclinic conditions is given. The general solution formula up to arbitrary perturbation order is also derived. The homoclinic bifurcation of a general Liénard oscillator is studied in detail. Phase portraits and bifurcation values of typical examples are obtained. Comparisons of results between the present method and the Runge-Kutta numerical method are made to illustrate the accuracy and efficiency of the present method. Related Articles | Metrics

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Method of Eliminating Ghost Images and Improving Reconstruction Precision in Acoustic-fields Reconstruction 2013, 33(4): 200-206.  DOI: 10.3969/j.issn.1006-1335.2013.04.042 Abstract ( )   PDF (1592KB) ( )   The ghost images easily exist in the reconstruction of acoustic fields by the use of beamforming algorithm, which leads to much difficulty for the accurate identification of reconstructed acoustic fields. After detailed deduction of the beamforming algorithm, the relation between the shape parameters of microphone array and the ghost images-existing and the method of eliminating ghost images were attained in the reconstruction of acoustic fields. After the elimination of ghost images, the reconstruction precision would be improved if the value of D/λwas increased by means of optimization design of the array shape. What’s more, some reconstruction of acoustic fields experiments of the pure sound and narrow-band noise were made, which verified the feasibility of the method. Related Articles | Metrics

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Improvement of Unknown Weak-signal Detection Method Based on Duffing Chaotic Oscillator 2013, 33(4): 207-211.  DOI: 10.3969/j.issn.1006-1335.2013.04.043 Abstract ( )   PDF (1461KB) ( )   It's very common that the Duffing chaotic oscillator system is widely used in detecting the weak signal of the noise background. The effect of the noise in the detection is often ignored because of the characteristics of sensitive to periodic signal and inert to noise. However, it's found that chaos system has low noise immunity for some different variance of noise after a large number of experiments, which makes mistake for the signal to be measured. In this paper, the affection of noise to weak signal detection is analyzed. The method of using cross-correlation detection system to process the signal is proposed, which can suppress noise. Also, the cyclic algorithm is introduced to the chaotic array which is universal poor and difficult to achieve with the application. This method is simple to operate and the simulation results have high accuracy. Related Articles | Metrics

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Influence of Signal-noise Ratio on Global DamageDetection of Offshore Platform 2013, 33(4): 212-218.  DOI: 10.3969/j.issn.1006-1335.2013.04.044 Abstract ( )   PDF (1505KB) ( )   Measurement noise is a crucial factor in health monitoring on structure in situ. In this paper, the influence of measurement noise on global damage detection to offshore platform is studied. And a new concept as Damage Element Modal Influence Index (DEMI) is also proposed. A scaled physical experimental model of an offshore jacket platform is employed and a series of damage scenarios are simulated. By means of mode strain energy method based on local measurement, the relationship between damage detection result and Signal-Noise Ratio (SNR) of impulse response and DEMI are obtained. The experiment result indicates that when DEMI is larger than 5, the damage location and damage severity can be identified correctly even with small SNR signals; when DEMI is smaller than 0.5, the damage identification cannot be realized even with largest SNR signals; when DEMI is in the critical value of 0.9-1.5, SNR becomes the key factor of damage identification, that is when SNR is larger than 20, the damage location can be identified correctly, as SNR decreases to a certain value 10, both of damage location and damage severity evaluation cannot be realized. Related Articles | Metrics

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Application of Short Time Fourier Transform and Hilbert-Huang Transform in Fault Diagnosis of Rolling Bearings of Windmill 2013, 33(4): 219-222.  DOI: 10.3969/j.issn.1006-1335.2013.04.045 Abstract ( )   PDF (1136KB) ( )   The acquisition of vibration signal on the abnormal operation wind turbines was completed by the vibration test system. Selection of a signal which acquisited when running in the rated wind speed. Then, extraction of fault signal by analysis of the signal in time domain and frequency domain and Short-Time Fourier Transform and Hilbert-Huang transform. The results showed that using of the Short-Time Fourier Transform to analyze non-balanced signal has many advantages such as high resolving power , it is better to extract fault signal. At the same time ,it is proved that Hilbert-Huang Transform is a good method for adaptive signal processing and it is very suitable for nonlinear and non-stationary signal analysis. The results showed that Hilbert-Huang Transform is effective in rolling element bearing fault diagnosis for wind turbines and it will make contribution to the developing of the fault diagnosis for wind turbines. Related Articles | Metrics

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Discussion of Measurement Technique for Cavity Noise 2013, 33(4): 223-226.  DOI: 10.3969/j.issn.1006-1335.2013.04.046 Abstract ( )   PDF (1181KB) ( )   Cavity flow phenomena often presents during the aircraft flight. The very high noise generated by this flow reduces life of surrounding structures and damages sensitivity of surrounding electronic components. Firstly, the paper introduces the generation mechanism of cavity noise, flow types and the noise distribution in the cavity. Because of the boundary condition differences among practical flight, computational simulation and wind tunnel test, the flight test is the unique method to measure the distribution characteristic of sound field and pressure field in cavity of aircraft in flight. The paper borrows measurement experiences from wind tunnel test inland and overseas, presents the measurement method and data processing method for cavity noise in flight test, and then proves the feasibility of this method by comparison test between fluctuating pressure transducer and surface microphone. Related Articles | Metrics

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Research of a Real-time Test System with PVDF Piezoelectric-film Sensors for Measurement of Dynamic Oil Film Pressure of Sliding Bearings 2013, 33(4): 227-231.  DOI: 10.3969/j.issn.1006-1335.2013.04.047 Abstract ( )   PDF (2182KB) ( )   A real-time dynamic oil film pressure measurement system of sliding bearing was designed by using PVDF sensor. The working principle of the PVDF piezoelectric-film sensor was analyzed and researched through experiments, then the method of its signal processing and signal software both were discussed. The experiment of real-time dynamic oil film pressure measurement system of sliding bearing had been conducted through installing PVDF Piezo-film sensors into the sliding bearing in Bently. The experiment indicated that PVDF Piezo-film sensor had good sensitivity, stability and repeatability, and could obtain accurately the dynamic oil film pressure signal, which could be used to real-time measure the dynamic oil film pressure of sliding bearing. Related Articles | Metrics

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Online Metrological Study on Key Parameters of Environmental Noise Monitoring Terminals 2013, 33(4): 232-236.  DOI: 10.3969/j.issn.1006-1335.2013.04.048 Abstract ( )   PDF (888KB) ( )   Firstly, metrological methods are put forward to solve the problem of lack of verification method for environmental noise monitoring terminal (ENMT). Frequency weighting, including using acoustic signal and electrical signal, is highlighted to introduce. Secondly, the parameters of the tube which is used to verify the ENMT online is calculated. Meanwhile, the estimated measurement uncertainty is also calculated to see if it meets the requirement of related standard for ENMT online metrology. Last but not the least, the feasibility of online metrological method is validated, by performing experiments and related measurement uncertainty assessment. Related Articles | Metrics

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Experimental Study on Parametric Resonance of Fluid Pipelines 2013, 33(4): 237-241.  DOI: 10.3969/j.issn.1006-1335.2013.04.049 Abstract ( )   PDF (1246KB) ( )   The technique of non-contact vibration measurement is applied on the experimental investigation of parametric resonance of clamped-clamped pipe conveying pulsating fluid. The experimental platform in this paper has a better function to control flow velocity, pulsation frequency and pulsation amplitude. A laser vibration measurement is used to obtain information of pipe’s vibration. Based on the results of many experiments, the regions of 1/2 sub-harmonic parametric resonance of the first mode shape are fitted, which are qualitatively consistent with the theoretical results. Related Articles | Metrics