Genetic Algorithms for the Vibroacoustic Optimization of the Thin Parts of I.C. Engine

2003 ◽  
Author(s):  
Xiaolong Deng ◽  
Zongjie Zhang ◽  
Chunpeng Sun ◽  
Shaohe Li
Keyword(s):  
Noise Level ◽  
Numerical Optimization ◽  
Acoustic Power ◽  
Single Frequency ◽  
Acoustic Response ◽  
Promising Tool ◽  
Specific Frequency ◽  
Radiated Sound ◽  
Noise Vibration ◽  
Radiated Sound Power

The Noise Vibration Harshness (NVH) behavior of engines is one of the predominant factors for market acceptance of vehicles. To reach this goal it is necessary to reduce the absolute noise level and also the noise level in specific frequency ranges. The design of radiating structures for minimal sound radiation is a multidisciplinary problem that involves complex objective functions and expensive computations. In this paper, genetic algorithm is used as a promising tool for numerical optimization of such problems. The objective of the study is to determine effective, general design methods for determining the optimal design of thin parts of I.C. engine that minimizes the total radiated acoustic power. Variable attached discrete masses are considered. Acoustic response is minimized either at a single frequency or first five natural frequencies. Radiated sound power is calculated using a boundary element method, in conjunction with a finite element solver ANSYS for the solution of the structural acoustical problem.

Vibroacoustic Optimization of Mechanical Structures: A Controlled Random Search Approach

2012 ◽  
Vol 622-623 ◽  
pp. 158-161 ◽  
Author(s):  
Mostafa Ranjbar ◽  
Steffen Marburg
Keyword(s):  
Random Search ◽  
Power Level ◽  
Search Method ◽  
Frequency Range ◽  
Controlled Random Search ◽  
Sound Power Level ◽  
Specific Frequency ◽  
Radiated Sound ◽  
Search Approach ◽  
Radiated Sound Power

A combination of controlled random search method and geometry modification concept is used to minimize the root mean square level of structure borne sound for a model. The structure is a rectangular plate made of steel. A specific frequency range for this porpuse is considered. The results show that this approach could produce significant reduction in the value of radiated sound power level of the structure within a limited time.

Weak Radiator Design Using Dimples

2010 ◽  
Author(s):  
Wen Nan Cheng ◽  
Chih Chun Cheng ◽  
Gary H. Koopmann
Keyword(s):  
Vibration Mode ◽  
Design Method ◽  
Vibration Modes ◽  
The Finite Element Method ◽  
Key Issues ◽  
Beam Surface ◽  
Specific Frequency ◽  
Radiated Sound ◽  
Radiated Sound Power ◽  
Do So

A design method for achieving minimum sound radiation from a beam is presented. The strategy is to form a series of cylindrical dimples on the beam surface in order to make one or more vibration modes of this dimpled beam have the same shape as the weak modes. Consequently, the dimpled beam behaves as a weak radiator when one or more vibration modes are excited. Instead of minimizing the radiated sound power at a specific frequency or in a bandwidth, the objective is to maximize the modal assurance coefficient (MAC) which quantifies resemblance between the vibration mode of a dimpled beam and a weak mode. To perform this strategy, two key issues are addressed in this paper. The first is to determine the so-called weak mode of a beam. And the second is how to determine the required dimple size and the dimple location on this beam so that the dimpled beam may have vibration modes resembled to the weak modes. A methodology to do so based on the finite element method and the mode assurance criteria is proposed. Results show that the radiation efficiency of the dimpled beam after optimization using MAC as the objective is generally lower than the uniform beam. However, the effectiveness of this strategy depends on how close in shape between the vibration mode of the dimpled beam and the designated weak mode.

Quieting Plate Modes With Optimally Sized Point Masses: A Volume Velocity Approach

1995 ◽  
Author(s):  
Hans-Walter Wodtke ◽  
Gary H. Koopmann
Keyword(s):  
Acoustic Radiation ◽  
Sound Intensity ◽  
Structural Vibration ◽  
Acoustic Response ◽  
Radiation Problem ◽  
Volume Velocity ◽  
Intensity Measurements ◽  
Radiated Sound ◽  
The Masses ◽  
Radiated Sound Power

Abstract The radiated sound power of the second symmetric mode of a clamped square plate is minimized by attaching optimally sized point masses to the plate. The plate is driven by a point force at its center and the positions of the masses are prescribed. The structural vibration problem is solved using a simple Rayleigh-Ritz approach. Solving the acoustic radiation problem is simplified by making a low-ka-assumption, i.e., the point masses are determined so as to minimize the surface volume velocity of the plate. The predicted results are verified experimentally by means of sound intensity measurements. It is shown that a structural resonance can be deleted from the acoustic response by exploiting volume velocity cancellation. The effects involved are illustrated in detail.

Application of the Helmholtz Integral in Acoustics

1986 ◽  
Vol 108 (4) ◽  
pp. 447-453 ◽  
Author(s):  
M. A. Latcha ◽  
A. Akay
Keyword(s):  
Acoustic Radiation ◽  
Surface Element ◽  
Sound Power ◽  
Acoustic Response ◽  
Element Size ◽  
Radiated Sound ◽  
Radiated Sound Power ◽  
Helmholtz Integral

The solution of an isoparametric, overdetermined formulation of the Helmholtz Integral is presented and demonstrated in three examples of acoustic radiation from spherical sources. The placement of the interior, overdetermining points is discussed and guidelines concerning surface element size are developed and tested. The total radiated sound power and transient acoustic response of a dilating sphere are computed.

Optimum Stiffener Design to Reduce Broadband Vibration and Sound Radiation

2001 ◽  
Author(s):  
Dongjai Lee ◽  
Ashok D. Belegundu ◽  
Gary H. Koopmann
Keyword(s):  
Finite Elements ◽  
Design Method ◽  
Acoustic Power ◽  
Vibration Energy ◽  
Pattern Design ◽  
Design Variables ◽  
Proper Design ◽  
Radiated Sound ◽  
Vibration And Sound Radiation ◽  
Radiated Sound Power

Abstract This paper presents a rib-stiffener pattern design method for reducing vibration energy and/or radiated acoustic power from a vibrating structure. Structural dynamics, acoustics and optimization are programmed in a unified code. To avoid difficulties in defining proper design variables such as the location, the number and the size of stiffeners to be attached on a structure, this paper adopts the idea of “topology optimization”, based on finite elements. This approach enables one to find an optimal rib-stiffener pattern by using a simple design variable, e.g., the density of finite elements. To illustrate this method, a rectangular plate with clamped edges is optimized to reduce the radiated sound power/kinetic energy and the results are compared to that the same plate but without rib-stiffeners.

Structural-Acoustic Optimization of Sandwich Panels

2006 ◽  
Vol 129 (3) ◽  
pp. 330-340 ◽  
Author(s):  
Francesco Franco ◽  
Kenneth A. Cunefare ◽  
Massimo Ruzzene
Keyword(s):  
Composite Structures ◽  
Sandwich Panels ◽  
Structural Elements ◽  
Acoustic Response ◽  
Truss Core ◽  
Design Flexibility ◽  
Radiated Sound ◽  
Optimal Configurations ◽  
Selection Of ◽  
Radiated Sound Power

Sandwich panels comprising face sheets enclosing a core are increasingly common structural elements in a variety of applications, including aircraft fuselages, flight surfaces, vehicle panels, lightweight enclosures, and bulkheads. This paper presents the optimization of various innovative sandwich configurations for minimization of their structural-acoustic response. Laminated face sheets and core geometries comprising honeycomb and trusslike structures are considered. The design flexibility associated with the class of considered composite structures and with truss-core configurations provides the opportunity of tailoring the structure to the load and dynamic response requirements of a particular application. The results demonstrate how the proper selection of selected key parameters can achieve effective reduction of the radiated sound power and how the identified optimal configurations can achieve noise reduction over different frequency ranges and for various source configurations.

A New Design Strategy for Minimizing Sound Radiation of Vibrating Beam Using Dimples

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
W. N. Cheng ◽  
C. C. Cheng ◽  
G. H. Koopmann
Keyword(s):  
Vibration Mode ◽  
Sound Radiation ◽  
Design Strategy ◽  
Vibration Modes ◽  
The Finite Element Method ◽  
Optimization Scheme ◽  
Modal Assurance Criterion ◽  
Specific Frequency ◽  
Radiated Sound ◽  
Radiated Sound Power

A method is proposed for minimizing the sound radiation of a vibrating beam by patterning the beam with a series of cylindrical dimples such that one or more of the vibration modes have the same shape as the corresponding weak modes. In implementing the proposed approach, the objective is to minimize the shape difference between the vibration mode(s) and the designated weak mode(s) rather than to minimize the radiated sound power at a specific frequency or over a certain bandwidth. The design objective is achieved by calculating the weak modes of the beam using the finite element method and then applying an optimization scheme with the modal assurance criterion (MAC) as the objective function. The optimization results, which cause the vibration mode(s) of the dimpled beam to approach the corresponding weak modes(s), determine the dimple angle and dimple depth. The numerical results show that the radiation efficiency of the optimized dimpled beam using MAC as the objective is generally lower than that of a uniform beam. However, the effectiveness of the proposed design strategy depends on the degree of closeness between the shape of the vibration mode(s) of the dimpled beam and that of the designated weak mode(s).

scholarly journals Supersonic Windtunnel Noise Attenuation

2021 ◽  
Author(s):  
William Wai Lim Wong
Keyword(s):  
Wind Tunnel ◽  
Sound Pressure Level ◽  
Noise Level ◽  
Sound Pressure ◽  
Power Level ◽  
Mesh Size ◽  
Acoustic Power ◽  
Pressure Level ◽  
Supersonic Wind Tunnel ◽  
Acoustic Treatment

The aerodynamic generated noise in the supersonic wind tunnel during operation at Ryerson University has exceeded the threshold of hearing damage. An acoustic silencer was to be designed and added to the wind tunnel to reduce the noise level. The main sources of noise generated from the wind tunnel with the silencer were identified to be located at the convergent divergent nozzle and the turbulent region downstream of the shock wave at the diffuser with the maximum acoustic power level of the entire wind tunnel at 161.09 dB. The designed silencer provided an overall sound pressure level reduction of 21.41 db which was considered as acceptable. Refinement to the mesh size and changes to the geometry of the mixing chamber was suggested for a more accurate result in noise output as well as flow conditions would match up to the physical flow. Additional acoustic treatment should be applied to the wind tunnel to further reduce sound pressure level since the noise level still exceeded the threshold of hearing loss.

Influences of the Noise of Woodworking Wide Belt Sander on Human’s Psychological Load

2010 ◽  
Vol 29-32 ◽  
pp. 2008-2012
Author(s):  
Qiu Yun Mo ◽  
Hao Li
Keyword(s):  
Heart Rate ◽  
Human Body ◽  
Noise Level ◽  
The Other ◽  
Single Frequency ◽  
Frequency Noise

The acousic comfort of woodworking wide belt sander has been evaluation by impacts of on-the-spot noise and the main single frequency noise of woodworking machine-sander on workers’ physiological and psychological load from the aspect of the noise influencing heart rate．Experimental noises are abstracted from the noise of the woodworking sander under the usual processing, as the noise source．The heart rate experiments are done under two states, namely the noise and the quiet in the laboratory．Finally, the change of human load is analyzed on the basis of the heart rate．The method of heart rate instead of traditional noise level puts more emphasis on the workers’ psychological load than traditional methods．The noise influence on human body is discussed from the aspects of both psychology and physiology. The results show that the influence of the 67 Hz noise on human body’s load is the greater than the other noises in the noise-exposed period and that of the 1422 Hz noise is the greatest and most difficult to recover in the experimental recovery course.

A Study on Relevance between Distortion of Distributed Mode Loudspeaker and Characteristic of Sound Panel

2011 ◽  
Vol 291-294 ◽  
pp. 2105-2110
Author(s):  
Liang Jin Luo
Keyword(s):  
Vibration Frequency ◽  
Sandwich Panel ◽  
Flexural Vibration ◽  
Sound Power ◽  
Impedance Matrix ◽  
Cell Ratio ◽  
Radiated Sound ◽  
Sound Sensitivity ◽  
The Relationship ◽  
Radiated Sound Power

From flat-plate flexural vibration and radiated sound power discussed the inherent relationship between panel vibration frequency of distributed mode loudspeaker and geometric parameters, impedance matrix of soundboard and studied the relationship between soundboard structure of polyester foam sandwich panel and distortion of loudspeaker. Experimental results showed that distortion increases as the cell size and compress modulus, cell ratio, cell open ratio and thickness increases, but the sound sensitivity decreases as the compress modulus increases.

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