Inter-Modal Couplings between Two Sea Subsystems with an Arbitrary Interface

2011 ◽  
Vol 130-134 ◽  
pp. 824-828
Author(s):  
Lin Ji ◽  
Zhen Yu Huang
Keyword(s):  
Energy Analysis ◽  
Simple Technique ◽  
Dynamic Stiffness ◽  
Statistical Energy Analysis ◽  
Coupling Loss ◽  
Simple Manner ◽  
Modal Density ◽  
Modal Coupling ◽  
Coupling Stiffness ◽  
High Modal Density

A simple technique is introduced to estimate the inter-modal coupling relations of two Statistical Energy Analysis (SEA) subsystems connected via an arbitrary interface. Based on a subsystem modal approach, the dynamic stiffness matrix of a generic built-up system is derived analytically. The coupling stiffness terms between any pair of subsystem modes can then be determined in explicit expressions. Under the proper SEA conditions, e.g. each subsystem has a high modal density and the couplings between SEA subsystems are sufficiently weak, these inter-modal coupling stiffness expressions can be greatly simplified. The results can then be easily accommodated within the standard SEA modeling procedure to predict the SEA response of generic built-up systems in a simple manner. Theoretical applications are made to estimate the SEA coupling loss factors between two subsystems connected by two rigid points.

Power Flow and Energy Sharing between an Oscillator and a Continuous Receiver Structure

2011 ◽  
Vol 189-193 ◽  
pp. 1914-1917
Author(s):  
Lin Ji
Keyword(s):  
High Frequency ◽  
Power Flow ◽  
Energy Analysis ◽  
Statistical Energy Analysis ◽  
Coupled Subsystems ◽  
Modal Density ◽  
Vibration Problems ◽  
Energy Sharing ◽  
High Modal Density ◽  
Vibration Modeling

A key assumption of conventional Statistical Energy Analysis (SEA) theory is that, for two coupled subsystems, the transmitted power from one to another is proportional to the energy differences between the mode pairs of the two subsystems. Previous research has shown that such an assumption remains valid if each individual subsystem is of high modal density. This thus limits the successful applications of SEA theory mostly to the regime of high frequency vibration modeling. This paper argues that, under certain coupling conditions, conventional SEA can be extended to solve the mid-frequency vibration problems where systems may consist of both mode-dense and mode-spare subsystems, e.g. ribbed-plates.

scholarly journals A Simple Estimation of Coupling Loss Factors for Two Flexible Subsystems Connected via Discrete Interfaces

2016 ◽  
Vol 2016 ◽  
pp. 1-10
Author(s):  
Jun Zhang ◽  
Lin Ji ◽  
Zhenyu Huang ◽  
Pingping Zhang ◽  
Wei Wang
Keyword(s):  
Dynamic Properties ◽  
Coupling Loss ◽  
Dynamic Interactions ◽  
Coupling Region ◽  
Modal Density ◽  
Present Technique ◽  
Coupling Stiffness ◽  
Simple Estimation ◽  
High Modal Density ◽  
Loss Factors

A simple formula is proposed to estimate the Statistical Energy Analysis (SEA) coupling loss factors (CLFs) for two flexible subsystems connected via discrete interfaces. First, the dynamic interactions between two discretely connected subsystems are described as a set of intermodal coupling stiffness terms. It is then found that if both subsystems are of high modal density and meanwhile the interface points all act independently, the intermodal dynamic couplings become dominated by only those between different subsystem mode sets. If ensemble- and frequency-averaged, the intermodal coupling stiffness terms can simply reduce to a function of the characteristic dynamic properties of each subsystem and the subsystem mass, as well as the number of interface points. The results can thus be accommodated within the theoretical frame of conventional SEA theory to yield a simple CLF formula. Meanwhile, the approach allows the weak coupling region between the two SEA subsystems to be distinguished simply and explicitly. The consistency and difference of the present technique with and from the traditional wave-based SEA solutions are discussed. Finally, numerical examples are given to illustrate the good performance of the present technique.

Vibration Transient Response Using Statistical Energy Analysis

2011 ◽  
Vol 55-57 ◽  
pp. 941-944
Author(s):  
He Li ◽  
Quan Feng Liu ◽  
Bang Chun Wen
Keyword(s):  
Transient Response ◽  
Rise Time ◽  
Loss Factor ◽  
Energy Analysis ◽  
Statistical Energy Analysis ◽  
Coupling Loss ◽  
Mathematical Expressions ◽  
Internal Loss ◽  
Peak Energy ◽  
Coupling Stiffness

Transient Statistic Energy Analysis (T. S. E. A.) for transient response of a vibration system is investigated in this paper. Mathematical expressions of the rise time and the peak energy were derived. Numerical modeling of the system was also made. It showed that the peak energy decrease as the internal loss factor and the coupling stiffness decrease, the rise time decease as the internal loss factor and the coupling loss factor increase. It was found that the results of TSEA and the traditional methods are identical.

Statistical Energy Analysis of Subway Wheel/Track Noise

2013 ◽  
Vol 423-426 ◽  
pp. 1563-1566
Author(s):  
Xiao Feng Zhang ◽  
You Gang Xiao ◽  
Yu Shi ◽  
Wu Yang Zeng
Keyword(s):  
Energy Analysis ◽  
Control Measures ◽  
Statistical Energy Analysis ◽  
Coupling Loss ◽  
Factors Affecting ◽  
Track System ◽  
Total Noise ◽  
Modal Density ◽  
Wheel Track ◽  
Loss Factors

Dividing wheel-track system of subway into a series of sub-systems, the statistical energy analysis (SEA) model of wheel/track system is established. The factors affecting the wheel/track noise, such as modal density, damping loss factors, coupling loss factors, are gotten by theoretical analysis combined with experiments. The calculated results show that the track noise is about 4.5 dB(A) higher than the wheel noise at 160 km/h, and the wheel noise is reduced by 2.8 dB(A) at 160 km/h and by 2.3 dB(A) at 90 km/h by attaching damped layer plates to the wheels, but the total reduction is only 0.9 dB(A) at 160 km/h and 0.4 dB(A) at 90 km/h, so the attempts to reduce the total noise should exert noise control measures on the track, not on the wheel.

The Effect of Direct Field Component on a Statistical Energy Analysis (SEA) Model

2013 ◽  
Vol 471 ◽  
pp. 279-284 ◽  
Author(s):  
Azma Putra ◽  
Al Munawir ◽  
W.M.F.W. Mohamad ◽  
J.I. Mohammad
Keyword(s):  
Field Component ◽  
Energy Analysis ◽  
Complex Structure ◽  
Sound Field ◽  
Injection Technique ◽  
Statistical Energy Analysis ◽  
Coupling Loss ◽  
Model Assumption ◽  
Power Injection ◽  
Acoustic Space

Statistical Energy Analysis (SEA) is a well-known method to analyze the flow of acoustic and vibration energy in a complex structure. The structure is divided into subsystems where the energy in each of the subsystem is assumed to be reverberant. This study investigates the application of SEA model in a 'damped' acoustic space where the direct field component from the sound source dominates the total sound field rather than a diffuse field in a reverberant space which the SEA model assumption is based on. A measurement was conducted in a scaled room divided into two acoustic spaces separated by a partition with an opening. Absorbent materials were installed on the room walls and the power injection technique was implemented to obtain the coupling loss factor (CLF) of the system. It is found that correction of the direct field component from the subsystem energy improves the prediction of the CLF of the system.

Prediction of Transient Vibration Envelopes Using Statistical Energy Analysis Techniques

1990 ◽  
Vol 112 (1) ◽  
pp. 127-137 ◽  
Author(s):  
M. L. Lai ◽  
A. Soom
Keyword(s):  
Loss Factor ◽  
Energy Analysis ◽  
A Priori ◽  
Coupled Systems ◽  
Time Varying ◽  
Statistical Energy Analysis ◽  
Coupling Loss ◽  
Transient Vibration ◽  
Coupled Plates ◽  
Coupling Loss Factor

The prediction, by the statistical energy analysis (SEA) method, of transient vibration envelopes for coupled systems is investigated. The relation between the time-varying energy transferred between two coupled subsystems and time-varying energies of the subsystems is studied numerically and experimentally. These studies indicate that time-varying energy transmitted between two subsystems is related to the subsystem energies by an apparent time-varying coupling loss factor. It is shown that the apparent coupling loss factor approaches the asymptotic (or steady-state) coupling loss factor as response energies and transferred energies are integrated over progressively larger times. Both the apparent time-varying coupling loss factor and the asymptotic coupling loss factor, determined experimentally, are used in energy balance equations to predict the time-varying vibration envelopes of a system of two point-coupled plates and the results are compared. Although overall response predictions are similar, considerable differences are noted in individual frequency bands. However, no general method for a priori determination of the apparent time-varying coupling loss factor is suggested.

Formulation of SEA parameters using mobility functions

1994 ◽  
Vol 346 (1681) ◽  
pp. 477-488 ◽  
Keyword(s):  
Dynamic Systems ◽  
Energy Analysis ◽  
Statistical Energy Analysis ◽  
Coupling Loss ◽  
Coupled Subsystems ◽  
Power Inputs ◽  
Complex Structural ◽  
General Mobility ◽  
Power And Energy ◽  
Loss Factors

Statistical energy analysis SEA formulates the dynamic response of a system in terms of power and energy variables. The SEA parameters include power inputs; damping loss factors; which control the power dissipated within the system; and coupling loss factors, which control the power transmitted between coupled subsystems. One of the great difficulties in using SEA is the calculation of these parameters. In this paper sea parameters are formulated using general mobility functions. Simplifications that result from averaging the parameters either over frequency or over an ensemble of dynamic systems are presented. These simplifications make it possible to apply SEA to very complex structural-acoustic systems.

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