Simulations of poroelastic materials in a complex acoustic system using frequency-dependent parameters in the mid-frequency range

2021 ◽  
Vol 263 (2) ◽  
pp. 4880-4888
Author(s):  
János Kun ◽  
Daniel Feszty ◽  
Dániel Feszty
Keyword(s):  
Steel Structure ◽  
Structural Damping ◽  
Acoustic Response ◽  
Frequency Range ◽  
Flat Plates ◽  
Frequency Dependent ◽  
Simulation Methodology ◽  
Poroelastic Materials ◽  
Fluid Damping ◽  
Simulation Results

Efficiency requirements prompt manufacturers to develop ever lighter acoustic packages in vehicles. Poroelastic materials are essential to achieve the desired interior noise level targets and thus the simulation of their effects is of utmost importance in NVH analyses. However, it is challenging to achieve good validation between finite element method (FEM) based simulation results and measurements in the mid-frequency range (400-1000 Hz). One possible reason could be the lack of using frequency-dependent Biot-paremeters describing the poroelastic materials (PEM) characteristics of trims. The present research aims to employ frequency-dependent Biot-parameters for the PEM materials to investigate the acoustic response of a scaled car-like steel structure composed of flat plates and U-section stiffeners enclosing an air cavity. Porous acoustic material is applied to the walls of the cavity. The focus of the study is to understand the effect of applying frequency-dependent Young's modulus and damping values for the PEM parameters in the 100-1000 Hz range. Simulation results obtained from ESI VPS FEM solver are compared with measurements, with particular focus on the interior sound pressure levels. The simulation methodology, including discretization techniques, structural damping and fluid damping applications are described in detail.

MINIMIZING THE EFFECTIVE AREA OF SCATTERING BY MEANS OF CHANGING THE RELATIVE MAGNETIC PERMEABILITY

2021 ◽  
pp. 85-88
Author(s):  
А.В. Володько ◽  
С.М. Фёдоров ◽  
Е.А. Ищенко ◽  
М.А. Сиваш ◽  
Л.В. Сопина ◽  
...  
Keyword(s):  
Magnetic Permeability ◽  
Dielectric Material ◽  
Threshold Value ◽  
Effective Area ◽  
Large Object ◽  
Frequency Dependent ◽  
Relative Magnetic Permeability ◽  
Effective Scattering Area ◽  
Maximum Value ◽  
Simulation Results

Исследуется зависимость эффективной площади рассеяния (ЭПР) от относительной магнитной проницаемости материала, из которого изготавливается структура. В качестве тела моделирования был выбран шар, который изготовлен из диэлектрического материала, у которого возможно выполнять изменение относительной магнитной проницаемости. По полученным результатам моделирования построены графики зависимости максимального значения моностатической ЭПР от частоты, а также от относительной магнитной проницаемости среды. Было показано, что с увеличением относительной магнитной проницаемости материала изготовления происходит увеличение значения ЭПР объекта, а также обнаружена зависимость эффективной площади рассеяния от соотношения размеров шара и длиной волны, так при превышении порогового значения, после которого шар становится крупным объектом, ЭПР резко возрастает. По результатам исследования был построен график зависимости эффективной площади рассеяния шара от относительной магнитной проницаемости материала изготовления. Доказана возможность применения материала с частотозависимой относительной магнитной проницаемостью в качестве стелс-покрытия. В статье содержится исследуемая модель, графики полученных результатов, по которым можно легко определить зависимость ЭПР от частоты и от относительной магнитной проницаемости материала изготовления The article investigates the dependence of the effective scattering area (ESA) on the relative magnetic permeability of the material from which the structure is made. We chose a sphere as the modeling body, which is made of a dielectric material, in which it is possible to change the relative magnetic permeability. Based on the obtained simulation results, graphs of the dependence of the maximum value of monostatic ESA on frequency, as well as on the relative magnetic permeability of the medium, were constructed. It was shown that with an increase in the relative magnetic permeability of the material of manufacture, an increase in the value of the ESA of the object occurs, and the dependence of the effective scattering area on the ratio of the size of the ball and the wavelength was found, so when the threshold value is exceeded, after which the ball becomes a large object, ESA rises sharply. Based on the results of the study, a graph of the dependence of the effective scattering area of the sphere on the relative magnetic permeability of the material of manufacture was built. The possibility of using a material with a frequency-dependent relative magnetic permeability as a stealth coating was proven. The article contains the investigated model, graphs of the results obtained, by which it is easy to determine the dependence of the ESA on the frequency and on the relative magnetic permeability of the material of manufacture

Frequency dependent resistance calculation of multiple conductors

2017 ◽  
Vol 36 (5) ◽  
pp. 1396-1410
Author(s):  
Tomislav Župan ◽  
Bojan Trkulja
Keyword(s):  
Design Methodology ◽  
Numerical Approach ◽  
Effective Resistance ◽  
Proximity Effects ◽  
The Finite Element Method ◽  
Frequency Range ◽  
Frequency Dependent ◽  
Content Type ◽  
Electromagnetic Devices ◽  
Practical Implications

Purpose The purpose of this paper is to present a method for calculating frequency-dependent resistance when multiple current-carrying conductors are present. Design/methodology/approach Analytical and numerical formulations are presented. Both skin- and proximity-effects are considered in the numerical approach, whereas only skin-effect can be taken into account in analytical equations. The calculation is done using a self-developed integral equation-based field solver. The results are benchmarked using professional software based on the finite element method (FEM). Findings Results from the numerical approach are in agreement with FEM-based software throughout the whole frequency range. Analytical formulations yield unsatisfactory results in higher frequency range. When multiple conductors are mutually relatively close, the proximity-effect has an impact on effective resistance and has to be taken into account. Research limitations/implications The methodology is presented using axially symmetrical conductors. However, the same procedure can be developed for straight conductors as well. Practical implications Presented fast and stable procedure can be used in most electromagnetic devices when frequency-dependent resistance needs to be precisely determined. Originality/value The value of the presented numerical methodology lies in its ability to take both skin- and proximity-effects into account. As conductors are densely packed in most electromagnetic devices, both effects influence the effective resistance. The method can be easily implemented using a self-developed solver and yields satisfactory results.

Flexural Bearing Capacity Research of Composite Beams with Edge Constraint Component

2013 ◽  
Vol 639-640 ◽  
pp. 807-811
Author(s):  
Yang Wang ◽  
Tian Li
Keyword(s):  
Bearing Capacity ◽  
Steel Structure ◽  
Composite Beams ◽  
Deformation And Failure ◽  
Finite Element Software ◽  
Composite Frame ◽  
Negative Moment ◽  
Flexural Bearing Capacity ◽  
Simulation Results ◽  
Current Code

To investigate the flexural bearing capacity in negative moment region of composite beams，we examined different ends constraint components. The modeling of the beam ends connected framework has been done by the finite element software ANSYS. The concrete thickness, slab reinforcement ratio and different component at the edge of the composite framework in the negative moment region are taken into account. The performance during the process of deformation and failure are got by nonlinear analysis. The flexural bearing capacity was reported, with the negative moment region of the composite frame beam, it revealed great differences when the beams are different component. Simulation results show that the concrete thickness take the biggest influence on bearing capacity. The results showed the behaviors of the composite frame beams are different with positive moment region, and calculation based on current code for design of steel structure (GB50017-2003) would be a big deviation.

Smoothed Finite Element Methods for Predicting the Mid to High Frequency Acoustic Response in the Cylinder-Head Chamber of a Diesel Engine

2019 ◽  
Vol 17 (09) ◽  
pp. 1950060
Author(s):  
Tengfei Dai ◽  
Xia Jin ◽  
Huaze Yang ◽  
Tianran Lin ◽  
Yuantong Gu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Diesel Engine ◽  
Modeling And Simulation ◽  
Finite Element Methods ◽  
High Frequency ◽  
Cylinder Head ◽  
High Frequency Range ◽  
Acoustic Response ◽  
Frequency Range

Modeling and simulation of the acoustic response in enclosed cavities of a diesel engine are of great significance for optimal design of an engine to achieve a better acoustic performance. Nevertheless, the use of the traditional finite element method (FEM) for the mid to high frequency acoustic prediction is limited by the well-known numerical dispersion errors and the tedious preprocessing of the model. Smoothed finite element methods (SFEMs) proposed originally for solid mechanics have been employed for the modeling of acoustic problems in the low to medium frequency ranges whilst acoustic modeling in the mid to high frequency range remains untouched. This paper comprehensively investigates into the performance of SFEMs in modeling and simulation of mid to high frequency acoustic problems. It is shown that the mass-redistributed edge-based smoothed finite element method (MR-ES-FEM) can yield an excellent prediction result in the mid to high frequency range in terms of accuracy, efficiency and robustness. The MR-ES-FEM is also used to simulate sound propagation in a cylinder head chamber of a four-cylinder diesel engine to prove its effectiveness. The findings presented in this paper offer an in-depth insight for engineers to select suitable numerical methods for solving mid to high frequency acoustic problems in the design of diesel engines.

Modeling of respiratory system impedances in dogs

1987 ◽  
Vol 62 (2) ◽  
pp. 414-420 ◽  
Author(s):  
A. C. Jackson ◽  
K. R. Lutchen
Keyword(s):  
Respiratory System ◽  
Element Model ◽  
Parameter Estimates ◽  
Frequency Range ◽  
Nonlinear Regression Analysis ◽  
Entire Frequency Range ◽  
Frequency Dependent ◽  
Impedance Data ◽  
Parameter Values ◽  
Gas Compressibility

Mechanical impedances between 4 and 64 Hz of the respiratory system in dogs have been reported (A.C. Jackson et al. J. Appl. Physiol. 57: 34–39, 1984) previously by this laboratory. It was observed that resistance (the real part of impedance) decreased slightly with frequency between 4 and 22 Hz then increased considerably with frequency above 22 Hz. In the current study, these impedance data were analyzed using nonlinear regression analysis incorporating several different lumped linear element models. The five-element model of Eyles and Pimmel (IEEE Trans. Biomed. Eng. 28: 313–317, 1981) could only fit data where resistance decreased with frequency. However, when the model was applied to these data the returned parameter estimates were not physiologically realistic. Over the entire frequency range, a significantly improved fit was obtained with the six-element model of DuBois et al. (J. Appl. Physiol. 8: 587–594, 1956), since it could follow the predominate frequency-dependent characteristic that was the increase in resistance. The resulting parameter estimates suggested that the shunt compliance represents alveolar gas compressibility, the central branch represents airways, and the peripheral branch represents lung and chest wall tissues. This six-element model could not fit, with the same set of parameter values, both the frequency-dependent decrease in Rrs and the frequency-dependent increase in resistance. A nine-element model recently proposed by Peslin et al. (J. Appl. Physiol. 39: 523–534, 1975) was capable of fitting both the frequency-dependent decrease and the frequency-dependent increase in resistance. However, the data only between 4 and 64 Hz was not sufficient to consistently determine unique values for all nine parameters.

scholarly journals Design and Development of a Wideband Planar Yagi Antenna Using Tightly Coupled Directive Element

Micromachines ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 975
Author(s):  
Muhammad A. Ashraf ◽  
Khalid Jamil ◽  
Ahmed Telba ◽  
Mohammed A. Alzabidi ◽  
Abdel Razik Sebak
Keyword(s):  
Reflection Coefficient ◽  
Wireless Communication ◽  
Radiation Pattern ◽  
Excellent Agreement ◽  
Frequency Range ◽  
Fractional Bandwidth ◽  
Yagi Antenna ◽  
Tightly Coupled ◽  
Simulation Results ◽  
Novel Concept

In this paper, a novel concept on the design of a broadband printed Yagi antenna for S-band wireless communication applications is presented. The proposed antenna exhibits a wide bandwidth (more than 48% fractional bandwidth) operating in the frequency range 2.6 GHz–4.3 GHz. This is achieved by employing an elliptically shaped coupled-directive element, which is wider compared with other elements. Compared with the conventional printed Yagi design, the tightly coupled directive element is placed very close (0.019λ to 0.0299λ) to the microstrip-fed dipole arms. The gain performance is enhanced by placing four additional elliptically shaped directive elements towards the electromagnetic field’s direction of propagation. The overall size of the proposed antenna is 60 mm × 140 mm × 1.6 mm. The proposed antenna is fabricated and its characteristics, such as reflection coefficient, radiation pattern, and gain, are compared with simulation results. Excellent agreement between measured and simulation results is observed.

Closed Loop Resonator Based Compact UWB Antenna with Single Notched Band Varying between WLAN and X-band for UWB Applications

Frequenz ◽  
2020 ◽  
Vol 74 (5-6) ◽  
pp. 201-209
Author(s):  
Mohammad Ahmad Salamin ◽  
Sudipta Das ◽  
Asmaa Zugari
Keyword(s):  
Closed Loop ◽  
Ground Plane ◽  
Frequency Range ◽  
Uwb Antenna ◽  
Notched Band ◽  
X Band ◽  
Compact Size ◽  
Simulation Results ◽  
Uwb Applications ◽  
Good Agreement

AbstractIn this paper, a novel compact UWB antenna with variable notched band characteristics for UWB applications is presented. The designed antenna primarily consists of an adjusted elliptical shaped metallic patch and a partial ground plane. The proposed antenna has a compact size of only 17 × 17 mm2. The suggested antenna covers the frequency range from 3.1 GHz to 12 GHz. A single notched band has been achieved at 7.4 GHz with the aid of integrating a novel closed loop resonator at the back plane of the antenna. This notched band can be utilized to alleviate the interference impact with the downlink X-band applications. Besides, a square slot was cut in the loop in order to obtain a variable notched band. With the absence and the existence of this slot, the notched band can be varied to mitigate interference of the upper WLAN band (5.72–5.82 GHz) and X-band (7.25–7.75 GHz) with UWB applications. A good agreement between measurement and simulation results was achieved, which affirms the appropriateness of this antenna for UWB applications.

A Theoretical Basis for the Active Control of a Boring Bar Operation

1975 ◽  
Vol 97 (2) ◽  
pp. 172-178 ◽  
Author(s):  
R. G. Klein ◽  
C. L. Nachtigal
Keyword(s):  
Active Control ◽  
Theoretical Basis ◽  
Controller Design ◽  
Experimental System ◽  
Practical Consideration ◽  
Structural Damping ◽  
Boring Bar ◽  
Low Stiffness ◽  
Simulation Results ◽  
Using Data

The properties of low stiffness and low structural damping in boring bars are widely known to be factors resulting in chatter and inaccurate machining. The application of active control offers a new alternative to improving the performance of a boring bar. This paper presents the theoretical basis for such an active control system. The analysis includes the practical consideration of principal modes in the boring bar model and discusses this influence on controller design. Simulation results using data from an experimental system illustrate some important factors of system design.

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