scholarly journals Investigation of the Broadband Microwave Absorption of Citric Acid Coated Fe3O4/PVDF Composite Using Finite Element Method

2019 ◽  
Vol 9 (18) ◽  
pp. 3877 ◽  
Author(s):  
Lawal Lanre Adebayo ◽  
Hassan Soleimani ◽  
Noorhana Yahya ◽  
Zulkifly Abbas ◽  
Ayinla Tobi Ridwan ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Citric Acid ◽  
Microwave Absorption ◽  
Fe3o4 Nanoparticles ◽  
Electromagnetic Properties ◽  
Frequency Range ◽  
Band Frequency ◽  
Enhanced Absorption ◽  
Element Method

Magnetite (Fe3O4) have been thoroughly investigated as microwave absorbing material due to its excellent electromagnetic properties (permittivity and permeability) and favorable saturation magnetization. However, large density and impedance mismatch are some of the limiting factors that hinder its microwave absorption performance (MAP). Herein, Fe3O4 nanoparticles prepared by facile co-precipitation method have been coated with citric acid and embedded in a polyvinylidene fluoride (PVDF) matrix. The coated Fe3O4 nanoparticles were characterized by X-ray diffraction spectrometer (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), and vibrating sample magnetometer (VSM). COMSOL Multiphysics based on the finite element method was used to simulate the rectangular waveguide at X-band and Ku-band frequency range in three-dimensional geometry. The citric acid coated Fe3O4/PVDF composite with 40 wt.% filler loading displayed good microwave absorption ability over the studied frequency range (8.2–18 GHz). A minimum reflection loss of −47.3 dB occurs at 17.9 GHz with 2.5 mm absorber thickness. The composite of citric acid coated Fe3O4 and PVDF was thus verified as a potential absorptive material with improved MAP. These enhanced absorption coefficients can be ascribed to favorable impedance match and moderate attenuation.

scholarly journals Effect of Material Thickness on Attenuation (dB) of PTFE Using Finite Element Method at X-Band Frequency

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Abubakar Yakubu ◽  
Zulkifly Abbas ◽  
Mansor Hashim
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Electric Field ◽  
Rectangular Waveguide ◽  
Electric Field Intensity ◽  
Reflection Coefficients ◽  
Band Frequency ◽  
Ptfe Sample ◽  
X Band ◽  
Element Method

PTFE samples were prepared with different thicknesses. Their electric field intensity and distribution of the PTFE samples placed inside a rectangular waveguide were simulated using finite element method. The calculation of transmission/reflection coefficients for all samples thickness was achieved via FEM. Amongst other observable features, result from calculation using FEM showed that the attenuation for the 15 mm PTFE sample is −3.32 dB; the 30 mm thick PTFE sample has an attenuation of 0.64 dB, while the 50 mm thick PTFE sample has an attenuation of 1.97 dB. It then suffices to say that, as the thickness of the PTFE sample increases, the attenuation of the samples at the corresponding thicknesses increases.

A Hybrid Finite Element Method for Calculating the Vibration of Co-Linear Beams in the Mid-Frequency Range

1999 ◽  
Author(s):  
Xi Zhao ◽  
Nickolas Vlahopoulos
Keyword(s):  
Finite Element Method ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Theoretical Development ◽  
Frequency Range ◽  
Element Analysis ◽  
Hybrid Finite Element Method ◽  
Hybrid Finite Element ◽  
New Formulation ◽  
Element Method

Abstract The theoretical development of a hybrid finite element method is presented. It combines conventional Finite Element Analysis (FEA) with Energy Finite Element Analysis (EFEA) in order to achieve a numerical solution to mid-frequency vibrations. In the mid-frequency range a system is comprised by some members that contain several wavelengths and some members that contain a small number of wavelengths. The former are considered long members and they are modeled by the EFEA. The latter are considered short and they are modeled by the FEA. The new formulation is based on deriving appropriate interface conditions at the joints between sections modeled by the EFEA and the FEA methods. Since the work presented in this paper constitutes a fundamental step in the development of a hybrid method for mid-frequency analysis, the formulation for one flexural degree of freedom in co-linear beams is presented. The excitation is considered to be applied on a long member and the response of the entire system is computed. Uncertainty effects are imposed only on the long members of the system. Validation cases for several configurations are presented.

A HYBRID FINITE ELEMENT CALCULATION OF COMPLEX ELECTROMAGNETIC FIELDS

2008 ◽  
Vol 22 (04) ◽  
pp. 269-274 ◽  
Author(s):  
NIAN LIU ◽  
CHI XIE
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Electromagnetic Fields ◽  
Electromagnetic Properties ◽  
Specific Work ◽  
Hybrid Finite Element Method ◽  
Hybrid Finite Element ◽  
Electromagnetic Device ◽  
Modern Physics ◽  
Element Method

In order to increase to a greater extent the calculation accuracy for complex electromagnetic fields in the modern physics, a hybrid finite element method (HFEM) is presented for analysis and simulation of complex electromagnetic fields. In the paper, the hybrid finite element method (HFEM) with high accuracy is introduced, and the complex electromagnetic field in an electromagnetic device has been calculated successfully by the hybrid finite element method (HFEM) and the electromagnetic properties of the electromagnetic device under the specific work condition is evaluated. It is shown that the method can provide a much more accurate calculation and good agreement between the computed values and the experimental values.

NEW FINITE ELEMENT METHOD OF ELECTROMAGNETIC CALCULATION FOR COMPLEX ELECTROMAGNETIC FIELDS

2007 ◽  
Vol 21 (11) ◽  
pp. 655-662 ◽  
Author(s):  
NIAN LIU ◽  
CHI XIE ◽  
YING LIU ◽  
LU LIU ◽  
KE-XUN JIANG
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Electromagnetic Fields ◽  
Electromagnetic Properties ◽  
Specific Work ◽  
Electromagnetic Device ◽  
Modern Physics ◽  
Experimental Values ◽  
Computation Speed ◽  
Element Method

In order to increase greatly the calculation accuracy and the computation speed for complex electromagnetic fields in modern physics, a new finite element method, which has the high computation accuracy, fast computation speed and less computer storage requirements, is presented in this paper. The new method with a high-order finite element without internal nodes is introduced to compute and analyze some complex electromagnetic fields in the electron accelerators. In this paper, the complex electromagnetic field in an electromagnetic device has been calculated successfully by the finite elements, and the electromagnetic properties of the electromagnetic device under the specific work condition is analyzed and evaluated. Good agreement is found between the computed values and the experimental values.

Investigation on Vibration Behaviour of Cantilever Type Glass/Carbon Hybrid Composite Beams at Higher Frequency Range Using Finite Element Method

2014 ◽  
Vol 984-985 ◽  
pp. 257-265 ◽  
Author(s):  
R. Murugan ◽  
Rajagopal Ramesh ◽  
K. Padmanabhan
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Modal Analysis ◽  
Elastic Constants ◽  
Hybrid Composite ◽  
Composite Beams ◽  
Woven Fabric ◽  
Frequency Range ◽  
Glass Carbon ◽  
Element Method

Woven fabric composites are now being increasingly used in aircraft and automobile structures due to balanced properties in the fabric plane. In the present work, woven fabric glass beam is modified and strengthened by interplying high modulus carbon fabric plies for improving the strength to weight ratio and thereby to achieve better performance in various dynamic conditions. The objective of the present work is to investigate the vibration behavior of cantilever type glass/carbon hybrid composite beams subjected to higher frequency of operation using finite element method. Unit plied woven fabric glass, carbon and hybrid of glass/carbon laminates were fabricated using hand layup technique. Experimental modal analysis of unit plied composite beams was carried out by impulse excitation technique under fixed free boundary condition. Theoretical modal analysis was done by finite element method using elastic constants derived from rule of mixture equations. The experimental and theoretical frequency results were compared and analyzed for finding the degree of deviation using regression analysis. The coefficients of regression analysis were used to find effective elastic constants of composite laminates. Further these effective elastic constants were applied for modal analysis of hybrid composite beams under higher frequency range. The results of mode shape, modal frequency of hybrid beams were reported and discussed. The effect of stacking sequence and effect of beam size on vibration characteristics at higher frequency range was also discussed.

Simulation and Analysis of Electromagnetic Wave Manipulation by Material with Permittivity and Permeability Very near Zero

2013 ◽  
Vol 538 ◽  
pp. 101-104
Author(s):  
Lin Zhao ◽  
Zhi Gang Zhang ◽  
Lei Ding ◽  
Fneg Nie
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Electromagnetic Wave ◽  
Effective Permittivity ◽  
Propagation Direction ◽  
Electromagnetic Properties ◽  
Phase Front ◽  
The Finite Element Method ◽  
Permittivity And Permeability ◽  
Element Method

Electromagnetic properties of the material with effective permittivity and permeability very near zero (double-near-zero, DNZ) have been simulated based on the finite element method and analyzed all-around. The results of simulation show that DNZ can be used to reshape the phase front of a wave perfectly. It can be used as an angular filter as well. Furthermore, The propagation direction and the shape of phase front of EM wave can be controlled by the device which is constructed by DNZ.

Partition of Unity Finite Element Method for 2D Vibro-Acoustic Modeling

2021 ◽  
Vol 29 (04) ◽  
Author(s):  
Christophe Langlois ◽  
Jean-Daniel Chazot ◽  
Li Cheng ◽  
Emmanuel Perrey-Debain
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Degrees Of Freedom ◽  
Coupled Model ◽  
Partition Of Unity ◽  
Single Element ◽  
Frequency Range ◽  
Knowing That ◽  
Main Challenge ◽  
Element Method

The Partition of Unity Finite Element Method (PUFEM) shows promise for modeling wave-like problems in the mid-to-high frequency range, allowing to capture several wavelengths in a single element. Despite the increasing attention it received in acoustics and in structural dynamics, its efficacy to deal with coupled problems has not been addressed. The main challenge in this case is to be able to represent different types of physical waves accurately, knowing that the wavelengths can be very different and vary differently, exemplified by the dispersion of flexural waves in a solid. Without a proper handling of the coupling between the coupled media, at best the number of degrees of freedom (DoF) will not be optimal, at worst the coupled model will not converge. Techniques like mesh refinement, wave enrichment and compatible or incompatible meshes might offer a potential solution to the problem, but the model usually needs to be adjusted through a time consuming trial-and-error procedure. To tackle the problem, this paper considers a 2D coupled vibro-acoustic problem, in which the structural and acoustic domains, modeled with PUFEM, are coupled using compatible and incompatible meshes based on different coupling strategies. Numerical analyses show that the proposed method outperforms the classical finite element method by several orders of magnitude in terms of number of DoF. Recommendations are proposed on the technique to choose depending on the frequency range of interest in relation to the critical frequency of the structure to ensure the best convergence rate. Finally, an application example is presented to highlight the performance of the proposed method.

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