Enhancement of acoustic absorption of a rigidly backed poroelastic plate with periodic elliptic inclusions

2019 ◽  
Vol 33 (30) ◽  
pp. 1950367
Author(s):  
Hongbo Zhang ◽  
Bilong Liu
Keyword(s):  
Material Properties ◽  
Composite Plate ◽  
Incidence Angle ◽  
Major Axis ◽  
Acoustic Energy ◽  
Absorption Peak ◽  
Acoustic Absorption ◽  
The Finite Element Method ◽  
Solid Materials ◽  
Low Frequencies

Perfect acoustic absorption is an important issue for a lot of applications. In this paper, a rigidly backed poroelastic plate with periodic elliptic inclusions is proposed to achieve perfect acoustic absorption at low frequencies by using the finite element method (FEM) with the porous material considered as fluid and solid materials. The absorption of the acoustic energy in such a composite plate resulting from viscous and thermal losses is enhanced by the resonances of the inclusions and energy trapping between the upper part of the poroelastic plate and the inclusion at low frequencies. The influence of the geometry, the incidence angle and the material properties on the absorption coefficient are investigated in detail. Our results show that increasing the major axis of the inclusion, the first absorption peak is pushed to lower frequencies and its value is first increased upto one and then it is decreased. The major axis is the most important parameter to tune the absorption peak, when the thickness is not changed. Once the major axis is determined, perfect acoustic absorption persists even if other parameters are changed. The reported results pave the way for the design of absorption devices which could be used to solve the major issue of noise control.

scholarly journals Propagation of a Crack in a Composite Plate

2018 ◽  
Vol 55 (2) ◽  
pp. 179-183
Author(s):  
Ionel Iacob ◽  
Ionel Chirica ◽  
Elena Felicia Beznea
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Material Properties ◽  
Composite Plate ◽  
Extended Finite Element Method ◽  
Fem Analysis ◽  
The Finite Element Method ◽  
Extended Finite Element ◽  
Time Step ◽  
Element Method

In this paper, a model of a composite plate with a central elliptical cut-out and with an initial fissure was subjected to a tension load in the finite element method (FEM) software Abaqus to observe the propagation of that crack during a certain amount of time that elapsed in the FEM analysis. Due to symmetry, only half of the plate was modeled, as a shell, and the extended finite element method (XFEM) was used for the crack. The material properties that were assigned to the plate were taken from the database of the Ansys Mechanical software. In the vicinity of the crack a finer mesh was applied to be able to better observe the evolution of the fissure and the changes of the Von Misses stress graphs for each time step of the analysis.

FEMLIB: An Object-Oriented Framework for Optimization and Simulation

1995 ◽  
Author(s):  
Michael M. Tiller ◽  
Jonathan A. Dantzig
Keyword(s):  
Material Properties ◽  
Object Oriented ◽  
The Finite Element Method ◽  
Simulation And Optimization ◽  
Gradient Based ◽  
Level Problem ◽  
Simulation Results ◽  
Optimization And Simulation ◽  
High Level ◽  
Simulation Parameters

Abstract In this paper we discuss the design of an object-oriented framework for simulation and optimization. Although oriented around high-level problem solving, the framework defines several classes of problems and includes concrete implementations of common algorithms for solving these problems. Simulations are run by combining these algorithms, as needed, for a particular problem. Included in this framework is the capability to compute the sensitivity of simulation results to the different simulation parameters (e.g. material properties, boundary conditions, etc). This sensitivity information is valuable in performing optimization because it allows the use of gradient-based optimization algorithms. Also included in the system are many useful abstractions and implementations related to the finite element method.

The natural neighbor radial point interpolation method in the Elasto-Static analysis of Honeycomb-Shaped foams

2021 ◽  
pp. 2150014
Author(s):  
N. A. Nascimento ◽  
J. Belinha ◽  
R. M. Natal Jorge ◽  
D. E. S. Rodrigues
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Interpolation Method ◽  
The Finite Element Method ◽  
Solid Materials ◽  
Cellular Solid ◽  
Natural Neighbor ◽  
Radial Point Interpolation ◽  
Point Interpolation Method ◽  
Point Interpolation

Cellular solid materials are progressively becoming more predominant in lightweight structural applications as more technologies realize these materials can be improved in terms of performance, quality control, repeatability and production costs, when allied with fast developing manufacturing technologies such as Additive Manufacturing. In parallel, the rapid advances in computational power and the use of new numerical methods, such as Meshless Methods, in addition to the Finite Element Method (FEM) are highly beneficial and allow for more accurate studies of a wide range of topologies associated with the architecture of cellular solid materials. Since these materials are commonly used as the cores of sandwich panels, in this work, two different topologies were designed — conventional honeycombs and re-entrant honeycombs — for 7 different values of relative density, and tested on the linear-elastic domain, in both in-plane directions, using the Natural Neighbor Radial Point Interpolation Method (NNRPIM), a newly developed meshless method, and the Finite Element Method (FEM) for comparison purposes.

Dynamic Instability of Delaminated Composite Plates under Parametric Excitation

2006 ◽  
Vol 326-328 ◽  
pp. 1765-1768 ◽  
Author(s):  
Meng Kao Yeh ◽  
Kuei Chang Tung
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Parametric Excitation ◽  
Composite Plate ◽  
Dynamic Instability ◽  
Composite Plates ◽  
Modal Parameters ◽  
The Finite Element Method ◽  
Electromagnetic Device ◽  
Instability Regions

The dynamic instability behavior of delaminated composite plates under transverse excitations was investigated experimentally and analytically. An electromagnetic device, acting like a spring with alternating stiffness, was used to parametrically excite the delaminated composite plates transversely. An analytical method, combined with the finite element method, was used to determine the instability regions of the delaminated composite plates based on the modal parameters of the composite plate and the position, the stiffness of the electromagnetic device. The delamination size and position of composite plates were varied to assess their effects on the excitation frequencies of simple and combination resonances in instability regions. The experimental results were found to agree with the analytical ones.

MEMS microphone intensity array for cabin noise measurements

2021 ◽  
Vol 263 (3) ◽  
pp. 3023-3034
Author(s):  
Carsten Spehr ◽  
Daniel Ernst ◽  
Hans-Georg Raumer
Keyword(s):  
Sound Intensity ◽  
Phase Match ◽  
Acoustic Energy ◽  
Low Frequencies ◽  
Cabin Noise ◽  
Noise Simulation ◽  
Mems Microphone ◽  
Noise Measurements ◽  
Mems Microphones ◽  
Absorbing Material

Aircraft cabin noise measurements in flight are used toto quantify the noise level, and to identify the entry point of acoustic energy into the cabin. Sound intensity probes are the state-of-the-art measurement technique for this task. During measurements, additional sound absorbing material is used to ease the rather harsh acoustic measurement environment inside the cabin. In order to decrease the expensive in-flight measurement time, an intensity array approach was chosen. This intensity probe consists of 512 MEMS-Microphones. Depending on the frequency, these microphones can be combined as an array of hundreds of 3D- intensity probes. The acoustic velocity is estimated using a high order 3D finite difference stencil. At low frequencies, a larger spacing is used to reduce the requirement of accurate phase match of the microphone sensors. Measurements were conducted in the ground-based Dornier 728 cabin noise simulation as well as in-flight.

scholarly journals Analysis and Optimization of a Piezoelectric Energy Harvester

2019 ◽  
Vol 112 ◽  
pp. 04001 ◽  
Author(s):  
Claudia Borzea ◽  
Daniel Comeagă
Keyword(s):  
Plate Theory ◽  
Beam Theory ◽  
Finite Element Method Simulation ◽  
Ease Of Use ◽  
The Finite Element Method ◽  
Low Frequencies ◽  
Operating Modes ◽  
Piezoelectric Energy ◽  
At Resonance ◽  
Static Regime

The paper aims to assess and improve the performances of a multilayer piezoelectric MEMS device for vibrations harnessing. Two operating modes are possible: at resonance and outside resonance. In some applications it is not possible to operate at resonance, functioning being mostly at low frequencies in a quasi-static regime. An Euler-Bernoulli classic beam theory mathematical model was studied for estimating the behaviour of multilayer piezoelectric generators, in terms of deflection and voltage, at functioning under resonance frequency. The analytical results were compared with the finite element method simulation in COMSOL Multiphysics. The main goal of this study is to obtain an accurate model for engineering design purposes, with simple analytical equations and ease of use, but with predictable errors. The study proved the usefulness of the derived model but also its limitations. It also proves the need to improve the model using plate theory, for sensors with high width/height ratio.

scholarly journals Numerical Investigation on the Sieving Performance of Elliptical Vibrating Screen

Processes ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1151
Author(s):  
Zhiquan Chen ◽  
Xin Tong ◽  
Zhanfu Li
Keyword(s):  
Major Axis ◽  
The Finite Element Method ◽  
Semi Major Axis ◽  
Vibration Direction ◽  
Maximum Deformation ◽  
Vibrating Screen ◽  
Performance Indexes ◽  
Screening Efficiency ◽  
Axis Length ◽  
Element Method

Screening techniques have been widely deployed in industrial production for the size-separation of granular materials such as coal. The elliptical vibrating screen has been regarded as an excellent screening apparatus in terms of its high screening efficiency and large processing capacity. However, its fundamental mechanisms and operational principles remain poorly understood. In this paper, the sieving process of an elliptical vibrating screen was numerically simulated based on the discrete element method (DEM), and an approach coupling the DEM and the finite element method (DEM–FEM) was introduced to further explore the collision impact of materials on the screen deck. The screening time, screening efficiency, maximum stress and maximum deformation were examined for the evaluation of sieving performance. The effects of six parameters—length of the semi-major axis, length ratio between two semi-axes, vibration frequency, inclination angle, vibration direction angle and vibration direction—on different sieving results were systematically investigated in univariate and multivariate experiments. Additionally, the relationships among the four performance indexes were discussed and the relational functions were obtained. The conclusions and methodologies presented in this work could be of great significance for the design and improvement of elliptical vibrating screens.

On the Use of the Finite Element Method on Some Acoustical Problems

1982 ◽  
Vol 104 (1) ◽  
pp. 108-112 ◽  
Author(s):  
L. Cederfeldt
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Analytical Methods ◽  
The Finite Element Method ◽  
Expansion Chamber ◽  
Low Frequencies ◽  
Angle Bend ◽  
Complicated Geometry ◽  
Sound Reduction ◽  
Element Method

In a project carried out in 1974-1975, financially supported by the National Swedish Council for Building Research, the finite element method was applied on some acoustical problems to illustrate the possibilities of the method. Calculations have been made for the following examples; sound attenuation of a lined right angle bend, a lined straight duct, and expansion chamber and the sound reduction of a resilient skin. The FEM has its power for small geometries particularly at low frequencies, that is, when analytical methods usually are weak. The more complicated geometry and boundary conditions of the studied problem may be the more powerful the FEM is compared to analytical methods.

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