A DSC Regularized Dirac-Delta Method for Flexural Vibration of Elastically Supported FG Beams Subjected to a Moving Load

2020 ◽  
Vol 20 (03) ◽  
pp. 2050039 ◽  
Author(s):  
L. H. Zhang ◽  
S. K. Lai ◽  
J. Yang
Keyword(s):  
Moving Load ◽  
Beam Theory ◽  
Flexural Vibration ◽  
Functionally Graded ◽  
Delta Method ◽  
Integration Scheme ◽  
Algebraic Equations ◽  
Dirac Delta ◽  
Dsc Method ◽  
Benchmark Solutions

This research presents a numerical approach to address the moving load problem of functionally graded (FG) beams with rotational elastic edge constraints, in which the regularized Dirac-delta function is used to describe a time-dependent moving load source. The governing partial differential equations of the system, derived in accordance with the classical Euler–Bernoulli beam theory, are approximated by the discrete singular convolution (DSC) method. The resulting set of algebraic equations can then be solved by the Newmark-β integration scheme. Such a singular Dirac-delta formulation is also employed as the kernel function of the DSC method. In this work, the material properties of FG beams are assumed to be changed in the thickness direction. A convergence study is performed to validate the accuracy and reliability of the numerical results. In addition, the effects of moving load velocity and material distribution on the dynamic behavior of elastically restrained FG beams are also studied to serve as new benchmark solutions. By comparing with the available results in the existing literature, the present results show good agreement. More importantly, the major finding of this work indicates that the DSC regularized Dirac-delta approach is a good candidate for moving load problems, since the equally spaced grid system adopted in the DSC scheme can achieve a preferable representation of moving load sources.

scholarly journals A Finite Element Formulation Of Active Constrained-Layer Functionally Graded Beam

2021 ◽  
Author(s):  
Ry Long
Keyword(s):  
Layer Structure ◽  
Equations Of Motion ◽  
Beam Theory ◽  
Functionally Graded ◽  
Viscoelastic Layer ◽  
Integration Scheme ◽  
Element Formulation ◽  
Constrained Layer Damping ◽  
Functionally Graded Beam ◽  
Active Constrained Layer

Active constrained-layer damping (ACLD) treatment is the combination of passive and active features in the control of structural vibrations. A three-layer structure that consists of a functionally graded (FG) host beam, with a bonded viscoelastic layer and a constraining piezoelectric fiber-reinforce composite (PFRC) laminate is modeled and analyzed. The assumptions for modeling the system are the application of Timoshenko beam theory for the host beam and PFRC laminate, and a higher-order beam theory for the viscoelastic layer. The formulation is assumed to have field variables that are expressed as polynomials through the thickness of the structure and linear interpolation across the span. The extended Hamilton's principle is utilized to determine the system equations of motion, which are then solved using the Newmark time-integration scheme. Many support conditions such as fully- and partial-clamped cantilevered, partially clamped-clamped and simply-supported are analyzed. The effects of ply angle orientaion, as well as FG properties, are also carefully examined.

Dynamic Responses of Functionally Graded Sandwich Beams Resting on Elastic Foundation Under Harmonic Moving Loads

2018 ◽  
Vol 18 (09) ◽  
pp. 1850112 ◽  
Author(s):  
Wachirawit Songsuwan ◽  
Monsak Pimsarn ◽  
Nuttawit Wattanasakulpong
Keyword(s):  
Boundary Conditions ◽  
Elastic Foundation ◽  
Natural Frequencies ◽  
Moving Load ◽  
Beam Theory ◽  
Equation Of Motion ◽  
Functionally Graded ◽  
Dynamic Responses ◽  
Harmonic Load ◽  
Sandwich Beams

This paper investigates the free vibration and dynamic response of functionally graded sandwich beams resting on an elastic foundation under the action of a moving harmonic load. The governing equation of motion of the beam, which includes the effects of shear deformation and rotary inertia based on the Timoshenko beam theory, is derived from Lagrange’s equations. The Ritz and Newmark methods are employed to solve the equation of motion for the free and forced vibration responses of the beam with different boundary conditions. The results are presented in both tabular and graphical forms to show the effects of layer thickness ratios, boundary conditions, length to height ratios, spring constants, etc. on natural frequencies and dynamic deflections of the beam. It was found that increasing the spring constant of the elastic foundation leads to considerable increase in natural frequencies of the beam; while the same is not true for the dynamic deflection. Additionally, very large dynamic deflection occurs for the beam in resonance under the harmonic moving load.

Vibration of functionally graded carbon nanotube-reinforced composite plates under a moving load

2015 ◽  
Vol 22 (1) ◽  
pp. 37-55 ◽  
Author(s):  
Parviz Malekzadeh ◽  
Mojtaba Dehbozorgi ◽  
Seyyed Majid Monajjemzadeh
Keyword(s):  
Carbon Nanotube ◽  
Moving Load ◽  
Equations Of Motion ◽  
Micromechanical Model ◽  
Shear Deformation Theory ◽  
Composite Plates ◽  
Functionally Graded ◽  
Integration Scheme ◽  
Aspect Ratios ◽  
Reinforced Composite

AbstractThe vibration behavior of functionally graded carbon nanotube (CNT)-reinforced composite (FG-CNTRC) plates under a moving load is investigated based on the first-order shear deformation theory of plates using the finite element method. An embedded single-walled CNT (SWCNT) in the polymer matrix and its surrounding interphase is replaced with an equivalent fiber to obtain the effective mechanical properties of the CNT/polymer composite plates using the Eshelby-Mori-Tanaka micromechanical model. The equations of motion of plate elements are derived by utilizing Hamilton’s principle. Newmark’s time integration scheme is employed to discretize the equations of motion in the temporal domain. The convergence of the method is numerically demonstrated and its accuracy is shown by performing comparison studies with existing solutions for the free vibration and static analysis of FG-CNTRC plates and also the exact solution of isotropic plates under a moving load. Then, the numerical results are presented to study the effects of various profiles of the CNT distribution, which includes both symmetric and asymmetric distributions, the velocity of the moving load, and thickness-to-length and aspect ratios together with boundary conditions on the dynamic characteristic of the FG-CNTRC plate under a moving load.

scholarly journals A Finite Element Formulation Of Active Constrained-Layer Functionally Graded Beam

2021 ◽  
Author(s):  
Ry Long
Keyword(s):  
Layer Structure ◽  
Equations Of Motion ◽  
Beam Theory ◽  
Functionally Graded ◽  
Viscoelastic Layer ◽  
Integration Scheme ◽  
Element Formulation ◽  
Constrained Layer Damping ◽  
Functionally Graded Beam ◽  
Active Constrained Layer

Active constrained-layer damping (ACLD) treatment is the combination of passive and active features in the control of structural vibrations. A three-layer structure that consists of a functionally graded (FG) host beam, with a bonded viscoelastic layer and a constraining piezoelectric fiber-reinforce composite (PFRC) laminate is modeled and analyzed. The assumptions for modeling the system are the application of Timoshenko beam theory for the host beam and PFRC laminate, and a higher-order beam theory for the viscoelastic layer. The formulation is assumed to have field variables that are expressed as polynomials through the thickness of the structure and linear interpolation across the span. The extended Hamilton's principle is utilized to determine the system equations of motion, which are then solved using the Newmark time-integration scheme. Many support conditions such as fully- and partial-clamped cantilevered, partially clamped-clamped and simply-supported are analyzed. The effects of ply angle orientaion, as well as FG properties, are also carefully examined.

Numerical analysis of nonlinear functionally graded piezoelectric energy harvester subjected to multi moving oscillators

2021 ◽  
pp. 095440622110036
Author(s):  
P Fatehi ◽  
M Mahzoon ◽  
M Farid
Keyword(s):  
Energy Harvesting ◽  
Nonlinear Vibration ◽  
Electromechanical Coupling ◽  
Damping Ratio ◽  
Beam Theory ◽  
Functionally Graded ◽  
Integration Scheme ◽  
Functionally Graded Beam ◽  
Piezoelectric Patch ◽  
Piezoelectric Energy

In this paper, energy harvesting from nonlinear vibration of a functionally graded beam covered by a piezoelectric patch under multi-moving oscillators is studied. The material of both the substructure and the piezoelectric patch is assumed to be functionally graded in the thickness direction. A coupled system of equations considering Euler-Bernoulli beam theory and von-Karman nonlinearity as well as electromechanical coupling are derived using the generalized Hamilton’s principle. Finite element method as well as Newmark time integration scheme are used to solve the coupled nonlinear time dependent problem. The effects of different parameters including material distribution, velocity of the moving oscillators, piezoelectric patch thickness and load resistance on the output voltage and harvested power are investigated. Moreover, the effects of oscillator characteristics such as damping ratio and stiffness on the nonlinear behavior of the beam and harvested power are also studied. Results indicate that the aforementioned parameters have considerable effects on the harvested power. It is also shown that ignoring nonlinear effects may lead to erroneous and unacceptable results. To the best of authors’ knowledge, there is no study about energy harvesting from nonlinear vibration of beams under moving oscillators.

Natural frequency analysis of a functionally graded rotor-bearing system with a slant crack subjected to thermal gradients

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Arnab Bose ◽  
Prabhakar Sathujoda ◽  
Giacomo Canale
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Power Law ◽  
Beam Theory ◽  
Functionally Graded ◽  
Thermal Gradients ◽  
Element Analysis ◽  
Rotor Bearing ◽  
Natural Frequency Analysis ◽  
Bearing System

Abstract The present work aims to analyze the natural and whirl frequencies of a slant-cracked functionally graded rotor-bearing system using finite element analysis for the flexural vibrations. The functionally graded shaft is modelled using two nodded beam elements formulated using the Timoshenko beam theory. The flexibility matrix of a slant-cracked functionally graded shaft element has been derived using fracture mechanics concepts, which is further used to develop the stiffness matrix of a cracked element. Material properties are temperature and position-dependent and graded in a radial direction following power-law gradation. A Python code has been developed to carry out the complete finite element analysis to determine the Eigenvalues and Eigenvectors of a slant-cracked rotor subjected to different thermal gradients. The analysis investigates and further reveals significant effect of the power-law index and thermal gradients on the local flexibility coefficients of slant-cracked element and whirl natural frequencies of the cracked functionally graded rotor system.

scholarly journals A Refined Theory for Bending Vibratory Analysis of Thick Functionally Graded Beams

Mathematics ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 1422
Author(s):  
Youssef Boutahar ◽  
Nadhir Lebaal ◽  
David Bassir
Keyword(s):  
Beam Theory ◽  
Functionally Graded ◽  
Effective Characteristics ◽  
Hyperbolic Function ◽  
Transverse Displacement ◽  
Refined Theory ◽  
Distribution Law ◽  
Fg Beam ◽  
The Impact ◽  
Beam Theories

A refined beam theory that takes the thickness-stretching into account is presented in this study for the bending vibratory behavior analysis of thick functionally graded (FG) beams. In this theory, the number of unknowns is reduced to four instead of five in the other approaches. Transverse displacement is expressed through a hyperbolic function and subdivided into bending, shear, and thickness-stretching components. The number of unknowns is reduced, which involves a decrease in the number of the governing equation. The boundary conditions at the top and bottom FG beam faces are satisfied without any shear correction factor. According to a distribution law, effective characteristics of FG beam material change continuously in the thickness direction depending on the constituent’s volume proportion. Equations of motion are obtained from Hamilton’s principle and are solved by assuming the Navier’s solution type, for the case of a supported FG beam that is transversely loaded. The numerical results obtained are exposed and analyzed in detail to verify the validity of the current theory and prove the influence of the material composition, geometry, and shear deformation on the vibratory responses of FG beams, showing the impact of normal deformation on these responses which is neglected in most of the beam theories. The obtained results are compared with those predicted by other beam theories. It can be concluded that the present theory is not only accurate but also simple in predicting the bending and free vibration responses of FG beams.

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