Acoustic radiation mode shapes for control of plates and shells

An analysis based on the first kind of Lagranges equations was presented for investigating the vibration and acoustic radiation of underwater finite cylindrical shell with interior plate under multiple excitations. The strain energy and kinetic energy of cylinder and plate were gained by the theory of plates and shells, and the potential energy of excitation and fluid loading was found based on acoustic-vibration coupling, and the connection conditions of plate and cylinder were expressed by Lagrange multipliers, then the vibro-acoustic equations of finite cylinder with interior plate under shafting excitation were established. The influences of excitations and plates position to the vibro-acoustic characteristics were studied by the equations. The results show that the frequency components of plate-shell structure are more complex. For the double excitations on plate, the distance between excitations is larger, the average velocity and sound radiation power are lower, while the radiation efficiency is larger. The modeling and analytical methods adopted in this paper are also available for more complex composite structure.

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Acoustic radiation from rectangular panels coupled in an L shape

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1987.0023 ◽

1987 ◽

Vol 409 (1837) ◽

pp. 401-431

Keyword(s):

Radiation Resistance ◽

Small Amplitude ◽

Vibrational Energy ◽

Acoustic Radiation ◽

Mode Shapes ◽

Rectangular Plates ◽

Large Plate ◽

Transverse Vibrations ◽

Analytic Expressions ◽

Principal Contribution

Analytic expressions are given for the radiation resistance at high modal numbers, of an L junction of two finite rectangular plates. Initially, plates are taken to perform small-amplitude transverse vibrations with sinusoidal mode shapes. It is shown that the principal contribution to the radiation resistance can be derived from the solution of appropriate large plate problems. Consequently, account may be taken of more realistic modal profiles arising from the exchange of vibrational energy in structural subsystems.

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Effect of Orientation Angle on Acoustic Radiation Mode Amplitudes of Laminated Composite Plates

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.621.3 ◽

2014 ◽

Vol 621 ◽

pp. 3-6

Author(s):

Jin Wu Wu ◽

Hai Peng Yuan

Keyword(s):

Finite Element ◽

Acoustic Radiation ◽

Orientation Angle ◽

Laminated Composite ◽

Composite Plates ◽

Element Model ◽

Laminated Plate ◽

Laminated Composite Plates ◽

Radiation Mode ◽

Radiation Amplitude

In this paper, the acoustic radiation mode’s amplitudes of laminated composite plates are studied. The layer wise finite element model is imposed to determine velocity distributions of laminated composite plates. Based on the acoustic radiation mode, the effects of the panel orientation angle on the first three orders acoustic radiation mode’s amplitude of the laminated composite plates are then discussed. A twelve-layer laminated plate was used as an example, and the numerical simulations results show that the effects of the panel orientation angle on the acoustic radiation amplitude of the laminated composite plates are significant.

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Vibro-Acoustic Studies of Transmission Casing Structures

Volume 8: 1998 Power Transmission and Gearing Conference ◽

10.1115/detc98/ptg-5788 ◽

1998 ◽

Author(s):

D. Crimaldi ◽

R. Singh

Keyword(s):

Finite Element ◽

Free Boundary ◽

Boundary Conditions ◽

Material Properties ◽

Acoustic Radiation ◽

Real Life ◽

Cover Plate ◽

Mode Shapes ◽

Finite Element Models ◽

Free Boundary Conditions

Abstract Automotive transmission casing plates of irregular shape, with complex boundary conditions and non-uniform material properties, are experimentally and computationally studied to acquire a fundamental understanding of their dynamic and acoustic radiation characteristics. A modified flat cover is designed which simplifies the geometry while providing uniform thickness and material properties. Both covers (“real-life” and “laboratory”) are studied with free and bolted boundary conditions. In particular, the free boundary conditions are useful because they eliminate the cover-housing interaction allowing for a more detailed analysis of the cover plate. Finite element models for both covers under the free boundary conditions are developed and refined. Predicted natural frequencies and mode shapes are in excellent agreement with measured modal data. Then the finite element models are coupled with boundary element models to predict acoustic radiation properties. Predictions match well with measured acoustic directivity at resonant frequencies.

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Some Aspects of Acoustic Emissions during the Launch of a Space Rocket in Research of Earth by Satellites

10.5194/egusphere-egu21-15036 ◽

2021 ◽

Author(s):

Galyna Sokol ◽

Vladyslav Kotlov ◽

Victor Frolov ◽

Volodymyr Syrenko ◽

Volodymyr Dudnikov

Keyword(s):

Acoustic Radiation ◽

Acoustic Emissions ◽

Experimental Tests ◽

Acoustic Vibration ◽

Physical Models ◽

Acoustic Fields ◽

Acoustic Vibrations ◽

Secondary Sources ◽

Space Rocket ◽

Plates And Shells

Acoustic fields of various types of radiation and power arise during the rocket&#8217;s movement in the atmosphere after the launch. One of the most topical studies here is the analysis and assessment of the infrasonic radiation levels and their impact on the health of the nearby settlements population and the spaceport maintenance personnel. Therefore, it is necessary to identify the features and determine the directions of acoustic radiation research based on existing ideas about the generation, propagation, and impact of infrasound.The methodology for researching acoustic radiation during rocket movement includes identifying the primary sources of acoustic vibrations. That is vibrations from a working propulsion system, from the vibrating shell of the rocket case, turbulent vortices in the flow around the rocket case. And also the identification of acoustic vibrations secondary sources arising from the primary vibrations reflection from collisions with obstacles, for example, the launch pad surface type.It is necessary to develop physical models of acoustic fields, the nature of which depends primarily on the type of acoustic sources.These are the following models:<ul><li>point radiation (monopoles);</li> <li>analysis of acoustic fields generated in the environment by force acting on a rigid surface and characterized by the Lamb potential;</li> <li>acoustic radiation and fields during vibrations of plates and shells of various shapes, lengths, and areas;</li> <li>acoustic radiation during the movable environment and solid bodies interaction;</li> <li>acoustic radiation at the jets outflow from nozzles;</li> <li>excitation and propagation of acoustic vibrations inside gas and liquid cavities, taking into account the peculiarities of the shells&#8217; structural schemes, the resonances identification;</li> <li>monochromatic and pulsed radiation.</li> </ul>The next step is the creation of mathematical models designed to calculate the acoustic field characteristics (analytical methods, the use of Taylor and Fourier series, numerical programming methods). Mathematical dependences will make it possible to analyze the relationship between the acoustic radiation sources energy characteristics and the characteristics of their acoustic fields. It is important to calculate the acoustic radiation amplitude-frequency characteristics.Experimental tests, the development of programs, and methods for measuring the acoustic vibration characteristics are important. At the same time, a list of equipment necessary for measuring acoustic characteristics (instruments, circuits, equipment) is created.As a result of physical and mathematical analysis of acoustic vibrations sources, it is possible to develop active and passive methods of damping them. As well as giving recommendations for damping acoustic vibrations.

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Acoustic Radiation of Axially Stepped-Thickness Piezoelectric Cylindrical Shells

Volume 3: Biomedical and Biotechnology Engineering ◽

10.1115/imece2018-86306 ◽

2018 ◽

Cited By ~ 1

Author(s):

Ata Meshkinzar ◽

Ahmed M. Al-Jumaily

Keyword(s):

Piezoelectric Transducer ◽

Acoustic Radiation ◽

Design Method ◽

Input Power ◽

Mode Shapes ◽

Uniform Thickness ◽

Radiation Characteristics ◽

Cylindrical Piezoelectric Transducer ◽

Thickness Variations ◽

Thickness Shell

In this work, a new design method is proposed to intensify the focused acoustic field generated inside a circular cylindrical piezoelectric transducer. The proposed design incorporates a stepped-thickness piezoelectric transducer which has thickness variations along the length. The location of these steps are identified based on the mode shape analysis of a uniform-thickness tube. Once the step locations are identified, two cases are considered with internal and external steps. Acoustic radiation characteristics and mode shapes are compared with the uniform-thickness shell. All the investigations are performed using ANSYS. An increase in the sound pressure level is obtained utilizing the stepped-thickness tube at the same input power.

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Buckling Analysis of Mindlin Plates Under the Green–Lagrange Strain Hypothesis

International Journal of Structural Stability and Dynamics ◽

10.1142/s0219455414500795 ◽

2015 ◽

Vol 15 (06) ◽

pp. 1450079 ◽

Cited By ~ 6

Author(s):

Eugenio Ruocco ◽

Vincenzo Minutolo

Keyword(s):

Solution Method ◽

Plate Theory ◽

Mode Shapes ◽

Governing Equations ◽

Nonlinear Strain ◽

Out Of Plane ◽

Plates And Shells ◽

Moderately Thick Plates ◽

Lagrange Strain ◽

Plane Displacement

In the present paper, the influence of Green–Lagrange nonlinear strain-displacement terms, usually considered negligible under the von Kármán hypothesis, on the buckling of isotropic, moderately thick plates and shells, is investigated. The first order shear deformation plate theory is applied and the governing equations, containing nonlinear terms related to both in-plane displacement and out-of-plane rotations usually ignored in the literature, are derived using the principle of minimum of the strain energy. The general Levy type solution method is employed, and exact buckling loads and mode shapes are derived. To verify the accuracy of the solution obtained, comparisons with existing data are first made. Then, through graphics and tables, the effect of the nonlinear strain-displacement terms for a range of boundary and load conditions, variations of aspect ratio, thickness ratio and changes in geometry is presented. The results obtained show that the von Kármán's model can sensibly overestimate the critical load for structures characterized by the modes involving comparable in-plane and out-of-plane displacements.

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ANALYSIS OF DYNAMIC AND ACOUSTIC RADIATION CHARACTERS FOR A FLAT PLATE UNDER THERMAL ENVIRONMENTS

International Journal of Applied Mechanics ◽

10.1142/s1758825112500287 ◽

2012 ◽

Vol 04 (03) ◽

pp. 1250028 ◽

Cited By ~ 41

Author(s):

QIAN GENG ◽

YUEMING LI

Keyword(s):

Stress State ◽

Thermal Stresses ◽

Natural Frequencies ◽

Acoustic Radiation ◽

Mode Shapes ◽

Thermal Loads ◽

Frequency Range ◽

Uniform Temperature ◽

Thermal Environments ◽

Element Method

A study on vibration and acoustic radiation characters of an isotropic rectangular thin plate under thermal environments is presented in this paper. It is assumed that thermal loads caused by thermal environments just change the structure stress state. Thermal stresses induced by uniform temperature rise of the plate are determined with the thermo-elastic theory. Then the stress state is used in the following dynamic analysis as a pre-stressed factor. It is observed that thermal loads influence the natural frequencies evidently, especially the fundamental natural frequency. The order of mode shapes stays the same. Dynamic response peaks float to lower frequency range with the increment of structure temperature. Acoustic radiation efficiency of the plate subjected to thermal loads decreases in the mid-frequency band. For validation, numerical simulations are also carried out. It can be found that the combined approach of finite element method (FEM) and boundary element method (BEM) is more appropriate for radiation problems.

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