Increase of Wave Velocity in Precast Pile along with Time and Its Analysis

Low strain dynamic testing on actual pile was conducted to investigate if the wave velocity is varied in the installed pre-cast pile.It was found that the wave velocity of the pile is raised along with time.The analysis has been carried out through with one dimension and three dimension stress wave propagation theories.Among various factors influencing the rise of wave velocity,the factor of the side soil contribution is the chief one.The soil around the pile works jointly with the pile,as if to enlarge the section size of the pile.Both the increase of wave velocity and the bearing capacity of pile are consistent.So the time effect of wave velocity can be used to study the time effect of bearing capacity of the pile and to determine the bearing capacity of piles.     

Analysis of Low frequency Noise of Bridge Considering the Vibration of Bridge Deck

Under the dynamic load of vehicle, the bridge will vibrate and radiate low frequency noise which is harmful to human health. A method for predicting the low frequency noise is proposed based on the analysis of vibration of bridge deck. The prediction includes the analysis of vehicle bridge coupling vibration considering the bridge deck and the analysis of sound radiation and propagation in the air. By taking a bridge with low frequency noise as example, the vibration and sound radiation of the bridge are analyzed respectively by the current method and the previous method based on the grillage model. The results show that the prediction based on the vibration of bridge deck is more accurate. Furthermore, the measures to reduce the noise of bridge are explored, and the results indicate that a smoother road surface leads to lower noise. But when the condition of road surface is up to the extremely good standard defined by ISO, the effect of reducing the roughness of surface is not significant. Also, strengthening the crossbeam in the bridgehead is a simple and effective way to reduce the low frequency noise of bridge.     

A Study on Vibration Isolation for the Machine on Flexible Foundations

The problem of vibration isolation for the multi supporting machine installed on flexible foundations was studied by power flow and four end parameters methods.The general model of machine,isolator and flexible foundations was founded,and the transmission characteristic of the vibration system is analyzed.The expressions of power flow of the system with wave propagation effect being concerned was also presented.Finally,the effect of foundation flexibility and wave propagation on isolation was analyzed in detail.     

Analysis on stress wave effect during the process ofrock breaking by pulsed jet

A mathematical model of rock breaking under pulsed jet is established by introducing the Johnson-Holmquist-Concrete constitutive relation and the smoothed particle hydrodynamics method. Based on this model, the formation, propagation and attenuation of stress wave during rock breaking by pulsed jet are simulated. The relations between pressure and time at different points on rock surface and the curve of peak stress wave versus distance to action spot are obtained. Destruction behaviors of rock under pulsed jet and effects on stress wave effect from jet velocity and lithology are studied according to the above calculation results, analysis results show that stress wave effect of pulsed jet acts locally and the peak stress wave shrinks sharply as the acting distance increases. The rock breaking mechanism of stress wave is tensile failure during the high speed process of load-unload. Power and effect range of stress wave is in high direct proportion with jet velocity. There is a threshold velocity before the macroscopic failure. Rocks of different lithologies have different destruction types under pulsed stress wave of pulsed jet. Destruction type of low strength rock like sandstone is crack propagation under the tensile stress during the high speed process of load-unload, while the destruction type of high strength brittle rocks like granite and limestone is vertical failure of stress concentration.     

Stress wave effect in numerical simulation on rock breaking under high pressure water jet

The evolvement of rock damage struck by a high pressure water jet is characterized by nonlinear properties, thus making it a complicated dynamic problem. Based on a nonlinear finite element and elastic plasticity theory, a computational model was established. The dynamic load striking the rock by a high pressure water jet was simulated by the dynamic contact method. Furthermore, the propagation of a stress wave in the same rock was simulated at different impact velocities. The results show that the propagation velocity of a stress wave is proportional to the impact velocity of the high pressure water jet. The effects of a stress wave in sandstone and coal impacted by high pressure water jets of the same velocity were simulated.The effect of a stress wave in coal was stronger than in sandstone, while the region of propagation of stress wave in coal was smaller.     

A POWER FLOW IN INFINITE VISCOELASTIC CYLINDRICAL SHELLS

In this paper, a solution of propagation wave in an. unconstrained damping viscoelastic cylindrical shells of infinte length under forced vibration is derived by Fourier integral transform techniques. The power flow transmitted along it is analysed. The power flow in an elastic cylindrical shell and that in a viscoelastic shell are compared. The effects of vibration reduction in two viscoelastic shells with different thickness are compared. The results provide a reference for designer in structural vibration reduction.     

Development of Automobile Noise and Vibration Analysing System with Object Otiented Technology

With the developing of the automobile industry, how to control the noise and vibration level of the products come to urgently for the auto factories during their developing and producing period. Finding out the main noise source and vibration source quickly, analyzing the noise and vibration signal effectively, contriving a noise descending algorithm reasonable and economical become the first and most important job for auto corporations. At the mean time it complicate the developing guide line of the noise and vibration testing system. With object oriented technology, we can develop the noise and vibration testing system in a short time and with a low cost. The object oriented technology emphasizes the circulation, exoteric and expandable of the codes. It enables us developing the system follow a flexible, integrable and economical procedure..     

切割片减振降噪的优化设计

为了研究切割片在工作过程中的振动及噪声问题,基于有限元方法,借助于ANSYS APDL有限元软件建立了切割片有限元模型;采用反转法施加载荷,简化模型及分析过程,在振动特性分析中,得出调整切割片结构参数可以降低切割片振动幅度的结论;基于振动能量与速度的平方关系,以测试点的速度平方和为目标函数,设计了优化程序对切割片模型进行调整优化,获得了一组最优调整数据,为实际生产提供了参考依据。     

Study of Quality Management and Inspection Technology of Anchorage System

Sonoprobe method has been applied in non-destructive inspection of anchorage project. Its fundament is to cause anchor bar's elastic vibration by dynamic transient excitation and the flaws of anchor bar can be estimated or deduced by determining the transient response. The numeric solution!of hyperbolic equation by FEA indicates that the deductions should comply with the acoustic parameters such as sound velocity, vibration range, wave shape etc., when inspecting the interior flaws in grouting of anchor bar. As a non-linear dynamic system,"the artificial neural networks dealing with quality inspection of gray system have been proved efficient.     

Junction stiffness analysis and vibration noise prediction of wind power speed-increase gearbox

In order to study the vibration characteristics and radiation noise of wind power speed-increase gearbox, a torsional vibration model of wind power speed-increase gearbox is established based on the analysis of supporting stiffness of bearing and contact stiffness of gear pairs. By solving the vibration differential equation with the help of Matlab, the frequency and corresponding vibration mode are obtained. With taking stiffness excitation, error exaction and meshing impact exaction into account, the dynamic finite element model of speed-increase gearbox is set up, and the dynamic response simulation is carried out. Regarding vibration displacement of the nodes on gearbox surface as boundary condition, an acoustic boundary element model of speed-increase gearbox is built. The surface acoustic pressure of gearbox and the radiation noise of field points are solved by the direct boundary element method. The results show that there is a great difference between torsion frequency and excitation frequency of wind power speed-increase gearbox, and so the resonance doesn't occur. The maximum structural noise and radiation noise mainly appear near the double octave of the gears meshing frequency of high-speed grade.     

Analysis on new gyratory fixed spindle cycloid drive

The current cycloid reducer drive has the shortage of needing special output mechanism, large volume and high vibration. To solve this problem, a new gyratory fixed spindle cycloid drive is designed. The drive principle of the reducer is introduced. Formula for calculating the basic parameters and tooth profile equation of cycloid gear are derived. On the basis of discussion of the mechanism and the principles of gear connection, a prototype is designed and manufactured. The results of the prototype test on the gear test rig indicate that the transmission efficiency of the new drive may reach 91.9% at rated operating conditions, the biggest vibration velocity effective value is 3.09 mm/s, and the biggest structure noise is 101.6 dB.     

Vibration & Noise Analysis on Double-ring Gear Reducer

Double-ring gear reducer with Central inputting shaft is studied. The basic structure of reducer as well as testing equipment, probe spot and testing method of Structure-borne noise and air-borne noise is presented. Based on frequency spectrum of each point, amplitude spectrum of structure-borne noise and testing results of air-borne noise, the authors analyze the vibration characters and latent faults of double-ring gear reducer, coming to the value and the cause of the noise, providing theoretical basis for proper design of the double-ring gear reducer and method of reducing its vibration and noise.     

Seismic Effect Analysis of Cutting Blasting Digging in High Way

A seismic effect is main harm in engineering blasting. By analyzing Seismic velocity and frequency of the main control factors of them, according to the data measured on the spot, the relation formula among Seismic velocity and dynamite and the distance between blasting fountain are obtained. Effects on buildings produced by vibration frequency and differences between blasting earthquake and natively seismic are analyzed. The calculation of blasting safety distance and selecting standard of breakage judge are studied and validated. The results of experiment and research indicate that we should attach importance to blasting seismic rules and effects on different buildings in order that basting techniques bring much economy benefits and reduce harm of blasting vibration as possible as much.     

New Development of Transmission Researches about Optical Solitons in Optical Fiber Telecommunication Systems

This paper prieseuts comprehensively new development of transmission researches about the optical solitons in optical fiber tele communication systems abroad,including:1.N soliton interaction in optical fiber;2.pulse propagation in the fiber;3.the femtosecond soliton soliton interaction in dispersion shifted fiber;4.strongly coupled nonlinear parametric solitary waves;5.higher order effects in bandwidth limited soliton propagation in optical fibers;6.suppression of noise accumulation in band width limited soliton transmission by means of nonlinear loop mirrors.     

Upstream Transmission Way in a HFC Network

In the HFC network, the funnelling effect of noise is the main restrict matter of raising the rate in the up stream channel. The requirements for the wide band services in a up stream channel are fist studied, and used as the criteria to compare the transfer ways each other used in up stream channel. Then, the ways in DOCSIS are analyzed, which were used to resist the noise, and the effect is showed by an example. The raised ability of resisting noise in the CDMA is obtained by reducing the transfer rate. Although it has a little better performance in resisting noise, but the rate is low and can not meet the requirements of wide band services. A kind of network structure is given, in which the users are connected in serial way, the noise funnelling is eliminated and have a high rate in the up stream channel. It is suitable for the wide band services, but the technology realizing the network structure needs perfecting.     

Analysis and test on vibration and acousticnoise of GWC6066 marine gearbox

The mesh stiffness of gear tooth is simulated by spring elements, the connected bolt between various housings are simplified as bar elements, and the sliding bearing and rolling bearing are simplified as spring dumping elements. Based on them, the gear-shaft-bearing-housing coupled finite element model and boundary element model of GWC6066 marine gearbox are established. Finally, the dynamic response under internal dynamic excitation is analyzed and the vibration severity, structural-borne noise and air-borne noise of the gear system are forecasted. Through the experimental modal analysis of gear system, and the test of vibration response and air pressure, the natural frequencies, vibration severity, structural-borne noise and air-borne noise are obtained. Compared with numerical results, two results show good agreement.     

Vibration control of active constrained layer damping structure

A finite element dynamic model for plates with active constrained layer damping (ACLD) treatments is derived based on the constitutive equations of elastic, viscoelastic and piezoelectric materials by application of Hamilton principle. The closed loop control system considering displacement and velocity feedback of self sensing voltage from sensor layer is developed. The dynamic behaviors of active constrained layer damping (ACLD) plates including nature frequencies, loss factors and responses in frequency domain are investigated. The influence of control gains on vibration suppression is discussed. Numerical examples demonstrate the validity of the finite element model and the control strategy approach. The proposed control strategy can be widely used to structure vibration control with ACLD patches due to its simple scheme and easy implementation.     

The optical isolation method of suppressing electromagnetic interference of automotive ignition system

Electromagnetic radiation, which is caused by the engine ignition system, is the most powerful electromagnetic interference (EMI) source in the vehicles, as well as the main reason of most electronic control unit (ECU) malfunction. In order to reduce interference from ignition noise on ECU, we use optical isolation technology to isolate electrical connections between the interference source and the control circuit. The formation mechanism of the ignition system EMI is analyzed. The possibility of suppressing ignition system EMI with optical isolation technology is discussed. Then, as a result we design an experimental platform of suppressing ignition system EMI. The experimental results show that the effect of suppressing ignition noise, in 20~100 MHz frequency band, is obvious after applying optical isolation circuit. It can address the issue of automotive EMC.     

EXPERIMENTAL INVESTIGATION ON VIBRATION AND NOISE BY C6132 LATHE

This paper presents the principle of high-pass-absolute-value demodulation tcchnigue which is applied with spectrum analysis to investigate the vibration and noise produced by the C61 32 Lathe. The main noise sourse is found out and some reliable data are provided to decrease the noise and vibration and to improve the dynamic performence of the c6132 Lathe.     

The frequency detection model with anti-noise in the autonomous chaotic system

A method of detecting the signal frequency which is disturbed by the noise based on the autonomous chaotic system is proposed. A signal with noise was added to an autonomous chaotic system, and then a negative feedback was imposed to it. The feedback gain was appropriately adjusted, so as to let the noisy system orbit be a limit cycle. The number of times that the orbit went directly through a plane was calculated by loop phase technology, and the vibration frequency was found according to it. The frequency of system is determined by the frequency of the test signal, yet free from noise, so the frequency of the test signal is the vibration frequency of the system. Simulation results further demonstrate the effectiveness of the method.