Optimization of Noise Transmission Through Sandwich Structures

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Mohamed Guerich ◽  
Samir Assaf
Keyword(s):  
Sandwich Plate ◽  
Transmission Loss ◽  
Sandwich Structures ◽  
Acoustic Medium ◽  
Element Formulation ◽  
Sound Power ◽  
Surface Mass ◽  
Various Boundary Conditions ◽  
Design Variables ◽  
Noise Transmission

An optimization methodology to increase the noise transmission loss (TL) of damped sandwich structures is presented. The prediction of the TL uses a numerical tool based on a finite element formulation for the sandwich plate coupled to a boundary element method for the acoustic medium. This tool can be used for arbitrarily shaped three-layer sandwich plates with various boundary conditions and it is well adapted to parametric and optimization studies. First, a parametric study was conducted to choose the objective function, the constraints, and the pertinent design variables to use in the optimization problem which consist in reducing the sound power transmitted by a viscoelastically damped sandwich plate. Next, by constraining the acoustical behavior of the sandwich panel, the surface mass of the sandwich structure was minimized. It is shown that a significant reduction in the transmitted sound power can be achieved by selecting the appropriate geometric configuration and damping layer material.

Advances in Sandwich Structural Optimization for Noise Transmission Reduction

2006 ◽  
Author(s):  
H. Denli ◽  
Jian-Qiao Sun
Keyword(s):  
Sandwich Structures ◽  
Acoustic Radiation ◽  
Structural Parameters ◽  
Weight Ratio ◽  
Sound Transmission ◽  
Acoustic Medium ◽  
Design Parameters ◽  
Noise Transmission ◽  
Out Of Plane ◽  
Transmission Reduction

The sandwich structures in aerospace industry experience high noise transmissions since they are often stiff and light, and have low damping. Optimization studies of sandwich structures for noise transmission are relatively fewer. Most optimization studies in composite sandwich community seek for high stiffness with minimal weight. Advanced sandwiches must meet not only stiffness to weight ratio demands, but also have improved acoustic transmission performance. This paper presents recent advances in optimization of sandwich structures for minimum sound transmission. The finite element models of sandwich beams and plates are presented in this paper. The acoustic radiation of the structure is computed by using the Rayleigh integral. Sensitivity plays an important role in optimization studies. Analytical expressions of sensitivity can improve computational efficiency dramatically and accuracy at the same time. The explicit sensitivity functions of power and natural frequencies with respect to design parameters are derived in this work. In the optimization studies, we have considered structural parameters that can influence the transverse propagation of sound from the sandwich to the acoustic medium. These parameters include core topology and coupling stiffiness between in- and out-of-plane strains. We also study the optimization of the structure with respect to the structural boundary conditions to minimize the sound transmission. Numerical examples of single tone and broadband applications are presented in the paper. The results show that significant reduction of sound transmission across sandwich structures can be obtained. Finally, it should be noted that the novel optimized sandwich structures can meet not only stiffness to weight ratio demands, but also have significantly improved acoustic performance.

Free Vibration and Instability Analysis of Sandwich Plates with Carbon Nanotubes-Reinforced Composite Faces and Honeycomb Core

2021 ◽  
Author(s):  
Sushila Chowdhary ◽  
Mesfin Kebede Kassa ◽  
Yitbarek Gashaw Tadesse ◽  
Ananda Babu Arumugam ◽  
Rajeshkumar Selvaraj
Keyword(s):  
Finite Element ◽  
Glass Fiber ◽  
Sandwich Plate ◽  
Natural Frequencies ◽  
Element Formulation ◽  
The Core ◽  
Glass Fiber Reinforced ◽  
End Conditions ◽  
Honeycomb Sandwich ◽  
Instability Regions

In this study, the instability regions of a honeycomb sandwich plate are investigated for different end conditions under periodic in-plane loading. The core layer of the sandwich plate is made of carbon nanotube (CNT)/glass fiber-reinforced honeycomb and the face layers of CNT/glass fiber- reinforced laminated composite. The governing equations are derived using classical laminated plate theory (CLPT) and solved numerically by using finite element formulation. The effectiveness of the developed finite element formulation is demonstrated by comparing the results in terms of natural frequencies with those available in the literature. The effects of CNT wt.% on the core material, CNT wt.% on the skin material, ply orientation and various end conditions on the variation of natural frequencies, loss factors and instability regions are studied. Finally, some inferences for the effects of CNT reinforcement on the honeycomb sandwich plate subjected to the periodic in-plane loads are discussed.

Mode Interactions and Sound Power Transmission Loss of Expansion Chambers

2006 ◽  
Vol 129 (2) ◽  
pp. 141-147 ◽  
Author(s):  
C. K. Lau ◽  
S. K. Tang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Plane Wave ◽  
Industrial Application ◽  
Power Transmission ◽  
Transmission Loss ◽  
Wave Power ◽  
Sound Power ◽  
The Finite Element Method ◽  
Mode Interactions

The mode interactions and the sound transmission loss across the expansion chambers with and without tapered sections are studied by the finite element method in the present investigation. Results from chambers with symmetrical inlet and outlet suggest lower sound power transmission loss at frequencies below that of the first symmetrical transverse chamber mode when the tapered section angle is reduced. Weak sound power transmission loss is also observed for this chamber type at frequency higher than that of the first symmetrical duct mode. Numerous high and low sound power transmission loss regions are observed between these two eigenfrequencies. Higher plane wave power transmission loss can be found at smaller tapered section angle only if one of the chamber endings is not tapered. Such chamber bears important industrial application.

A Comprehensive Analysis on the Structural–Acoustic Aspects of Various Functionally Graded Plates

2015 ◽  
Vol 07 (05) ◽  
pp. 1550072 ◽  
Author(s):  
N. Chandra ◽  
S. Raja ◽  
K. V. N. Gopal
Keyword(s):  
Power Law ◽  
Volume Fraction ◽  
Transmission Loss ◽  
Sound Radiation ◽  
Functionally Graded ◽  
Radiation Efficiency ◽  
Sound Power ◽  
Acoustic Behavior ◽  
Acoustic Response ◽  
Plate Velocity

The vibration, sound radiation and transmission characteristics of plates with various functionally graded materials (FGM) are explored and a detailed investigation is presented on the influence of specific material properties on structural–acoustic behavior. An improved model based on a simplified first order shear deformation theory along with a near-field elemental radiator approach is used to predict the radiated acoustic field associated with a given vibration and acoustic excitation. Various ceramic materials suitable for engineering applications are considered with aluminum as the base metal. A power law is used for the volume fraction distribution of the two constitutive materials and the effective modulus is obtained using the Mori–Tanaka homogenization scheme. The structural–acoustic response of these FGM plates is presented in terms of the plate velocity, radiated sound power, sound radiation efficiency for point and uniformly distributed load cases. Increase in both vibration and acoustic response with increase in power law index is observed for the lower order modes. The vibro–acoustic metrics such as root-mean-squared plate velocity, overall sound power, frequency averaged radiation efficiency and transmission loss, are used to rank these materials for vibro–acoustically efficient combination. Detailed analysis has been made on the factors influencing the structural–acoustic behavior of various FGM plates and relative ranking of particular ceramic/metal combinations.

Sound Radiation Characteristics of Lightweight Roof Constructions Excited by Rain

1994 ◽  
Vol 1 (4) ◽  
pp. 249-270 ◽  
Author(s):  
Hiromi Suga ◽  
Hideki Tachibana
Keyword(s):  
Transmission Loss ◽  
Power Level ◽  
Sound Radiation ◽  
Sound Intensity ◽  
Sound Power ◽  
Radiation Characteristics ◽  
Natural Rainfall ◽  
Artificial Rainfall ◽  
Sound Power Level ◽  
Measurement Results

In order to investigate the sound radiation characteristics of lightweight roof constructions when excited by rainfall, an artificial rainfall apparatus was constructed to simulate natural rainfall conditions. From the measurement results, it can be seen that the facility developed is practically applicable for the examination of the sound radiation characteristics of rain noise. It was therefore used in the measurement of sound power of 20 lightweight roofs. In addition, the relationship between sound power level and sound transmission loss measured by the sound intensity method was investigated statistically. As a result, it has been shown that a linear relationship exists between them and there is a possibility of estimating the sound power level from the transmission loss.

Turbulent Boundary Layers With Mass Transfer by the Dorodnitsyn Finite Element Method

1987 ◽  
Vol 54 (1) ◽  
pp. 197-202 ◽  
Author(s):  
C. A. J. Fletcher ◽  
R. W. Fleet
Keyword(s):  
Mass Transfer ◽  
Finite Element ◽  
Boundary Layers ◽  
Adverse Pressure Gradient ◽  
Skin Friction Coefficient ◽  
Turbulent Boundary Layers ◽  
Element Formulation ◽  
Surface Mass ◽  
Surface Mass Transfer ◽  
Good Agreement

The Dorodnitsyn finite element formulation is extended to cover incompressible, two-dimensional turbulent boundary layers with surface mass transfer in the normal direction. The method is shown to give accurate and economical answers with only eleven points spanning the boundary layer. Good agreement is obtained when the computational solutions are compared with the experimental results of McQuaid [13] for skin friction coefficient, displacement and momentum thickness and velocity profiles. Zero and adverse pressure gradient and discontinuous injection cases have been considered.

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