scholarly journals Damping Enhancement Using Axially Functionally Graded Porous Structure Based on Acoustic Black Hole Effect

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2480 ◽  
Author(s):  
Weiguang Zheng ◽  
Shiming He ◽  
Rongjiang Tang ◽  
Shuilong He
Keyword(s):  
Black Hole ◽  
Reflection Coefficient ◽  
Porous Structure ◽  
Power Law ◽  
Transient Analysis ◽  
Functionally Graded ◽  
Flexural Waves ◽  
Damping Effect ◽  
Power Law Index ◽  
Hole Effect

The acoustic black hole (ABH) effect for damping flexural waves using axially functionally graded porous (FGP) structure is investigated. With proposed power-law porosity of FGP structure, ABH can be achieved and damping effect is enhanced. The physics are explained from divergent conditions of the integrated wave phase at composite ends. Numerical results show the damping effect is increased with power law index. The phenomenon is expounded by the characteristics of reflection coefficient and impedance. It indicates that increasing power law index leads to smaller wavelength along to the end, then the wave needs more oscillation cycles to travel, which leads to more energy absorption. Transient analysis for 2D FGP structure also shows the focalization and ABH effect of the flexural waves.

Elastic Foundation Analysis of Uniformly Loaded Functionally Graded Viscoelastic Sandwich Plates

2012 ◽  
Vol 28 (3) ◽  
pp. 439-452 ◽  
Author(s):  
A. M. Zenkour ◽  
M. Sobhy
Keyword(s):  
Power Law ◽  
Sandwich Plate ◽  
Plate Theory ◽  
Functionally Graded ◽  
Sandwich Plates ◽  
Equilibrium Equations ◽  
Graded Material ◽  
Plate Aspect Ratio ◽  
Type V ◽  
Power Law Index

AbstractThis paper deals with the static response of simply supported functionally graded material (FGM) viscoelastic sandwich plates subjected to transverse uniform loads. The FG sandwich plates are considered to be resting on Pasternak's elastic foundations. The sandwich plate is assumed to consist of a fully elastic core sandwiched by elastic-viscoelastic FGM layers. Material properties are graded according to a power-law variation from the interfaces to the faces of the plate. The equilibrium equations of the FG sandwich plate are given based on a trigonometric shear deformation plate theory. Using Illyushin's method, the governing equations of the viscoelastic sandwich plate can be solved. Parametric study on the bending analysis of FG sandwich plates is being investigated. These parameters include (i) power-law index, (ii) plate aspect ratio, (iii) side-to-thickness ratio, (iv) loading type, (v) foundation stiffnesses, and (vi) time parameter.

scholarly journals Optimum response of functionally graded piezoelectric plates in thermal environments

2017 ◽  
Vol 35 (3) ◽  
pp. 606-617 ◽  
Author(s):  
Hossein Nourmohammadi ◽  
Bashir Behjat
Keyword(s):  
Power Law ◽  
Thermal Loading ◽  
Volume Fraction ◽  
Plate Theory ◽  
Poisson Ratio ◽  
Functionally Graded ◽  
Sensors And Actuators ◽  
Thermal Environments ◽  
Functionally Graded Piezoelectric ◽  
Power Law Index

AbstractIn this article, the static response of the functionally graded piezoelectric (FGP) plates with piezoelectric layers (sandwich FGPM) is studied based on the first order shear deformation plate theory. The plate is under mechanical, electrical and thermal loadings and finite element method is employed to obtain the solution of the equation. All mechanical, thermal and piezoelectric properties, except Poisson ratio, obey the power law distribution through the thickness. By solving the governing equation, optimum value of power law index is investigated in each type of loading. The effects of different volume fraction index, layer arrangements, various boundary conditions and different loading types, are studied on the deflection of FGPM plate. It is inferred that, the correlations between the deflection, power law index and layer arrangement are completely different in the mechanical and thermal loading and the optimum value of the power law index should be selected in each case separately. This optimum values can be used as a design criterion to build a reliable sensors and actuators in thermal environments.

Vibration and Dynamic Stability of Pre-Twisted Thick Cantilever Beam Made of Functionally Graded Material

2015 ◽  
Vol 15 (04) ◽  
pp. 1450058 ◽  
Author(s):  
Sukesh Chandra Mohanty ◽  
Rati Ranjan Dash ◽  
Trilochan Rout
Keyword(s):  
Dynamic Stability ◽  
Power Law ◽  
Twist Angle ◽  
Stability Boundary ◽  
Parametric Instability ◽  
Functionally Graded ◽  
Load Factor ◽  
Graded Material ◽  
The Stability ◽  
Power Law Index

In the present work, the vibration and dynamic stability of functionally graded ordinary (FGO) pre-twisted cantilever Timoshenko beam has been investigated. Finite element shape functions are established from differential equations of static equilibrium. Expressions for element stiffness and mass matrices are obtained from energy considerations. Floquet's theory is used to establish the stability boundary. The material properties along the thickness of the beam are assumed to vary according to the power law. The effects of power law index and pre-twist angle on the natural frequencies and dynamic stability of the beam have been investigated. Increase in pre-twist angle enhances the stability of the beam for first mode whereas it makes the beam more prone to parametric instability for the second mode. The increase in power law index is found to have a detrimental effect on the stability of the beam. The chance of parametric instability is enhanced with the increase in static load factor.

Studying the Critical Buckling Load of FG Beam Using ANSYS

2021 ◽  
Vol 1039 ◽  
pp. 7-22
Author(s):  
Khetam S. Ateah ◽  
Luay S. Alansari
Keyword(s):  
Power Law ◽  
Thermal Load ◽  
Mechanical Load ◽  
Functionally Graded ◽  
Thickness Ratio ◽  
Buckling Load ◽  
Mode Number ◽  
Critical Buckling Load ◽  
Fg Beam ◽  
Power Law Index

In this article, the critical buckling load of functionally graded beam is calculated using ANSYS APDL Software (version 17.2) under mechanical and thermal load. In mechanical load, the effects of length to thickness ratio, power law index and mode number on the non-dimension critical buckling load of fixed-fixed and fixed-free FG beam. The results show that the length to thickness ratio is not effect on the non-dimension critical buckling load while the power law index and mode number effect on the non-dimension critical buckling load. In thermal load, the critical buckling load for fixed-fixed and pinned-pinned FG beam depend on length to thickness ratio, power law index and mode number. The results show that the critical buckling load increases with decreasing length to thickness ratio.

Estimation of Wave Reflection Coefficient by Semi-Analytical Method in an Acoustic Black Hole Beam

2020 ◽  
Vol 12 (01) ◽  
pp. 2050004
Author(s):  
Shuai Cao ◽  
Heow Pueh Lee ◽  
Kian Meng Lim
Keyword(s):  
Finite Element Method ◽  
Black Hole ◽  
Reflection Coefficient ◽  
Analytical Method ◽  
Wave Reflection ◽  
Flexural Waves ◽  
The Finite Element Method ◽  
Wave Analysis ◽  
Plate Structures ◽  
Validity Condition

Acoustic Black Hole (ABH) has been deployed into beam-plate structures with the passive damping system to enhance its performance in absorbing flexural waves. The wave reflection coefficient can be used to measure this performance. This paper proposes a semi-analytical method to estimate the wave reflection coefficient, which is based on the Finite Element Method (FEM). The proposed method is validated by the exact solution for the wave analysis on the quadratic ABH beam. By this method, this study also investigates the performances of power-law ABH beams with exponent [Formula: see text] and 10. The numerical results indicate that the wave reflection coefficient of ABH shows a decreasing trend as frequency increases. Moreover, the validity condition of the geometrical acoustic approach (GAA) is explored through error analysis on the estimated wave reflection coefficient. An envelope of this condition is presented to recommend conservative criteria for GAA.

Two-Dimensional Stresses in a Hollow FG Sphere with Heat Source

2011 ◽  
Vol 264-265 ◽  
pp. 700-705 ◽  
Author(s):  
Amir Hossein Mohazzab ◽  
Mohsen Jabbari
Keyword(s):  
Steady State ◽  
Heat Source ◽  
Power Law ◽  
Thermal Stresses ◽  
Circumferential Stress ◽  
Functionally Graded ◽  
Power Functions ◽  
Legendre Series ◽  
Thermal Boundary Conditions ◽  
Power Law Index

This work studied the theoretical solution for axisymmetric steady-state mechanical and thermal stresses in hollow functionally graded spheres with respect to heat source. The material properties of the FG sphere change continuously across the thickness direction according to the power functions of radial direction. The steady-state temperature, displacements, and stresses are derived due to the general mechanical and thermal boundary conditions as function of radial and circumferential directions. The temperature and Navier equations are solved analytically, using Taylor and Legendre series. With increasing the power law indices the temperature distribution due to heat source is decreased. Circumferential stress and radial displacement due to heat source are decreased as the power law index increases.

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