Due to rapid development of process manufacturing, composite materials with porosity have attracted commercial attention in promoting engineering applications. For this regard, in this research wave ...propagation-thermal characteristics of a size-dependent graphene nanoplatelet-reinforced composite (GNPRC) porous cylindrical nanoshell in thermal environment are investigated. The effects of small scale are analyzed based on nonlocal strain gradient theory (NSGT). The governing equations of the laminated composite cylindrical nanoshell in thermal environment have been evolved using Hamilton’s principle and solved with the assistance of the analytical method. For the first time, wave propagation-thermal behavior of a GNPRC porous cylindrical nanoshell in thermal environment based on NSGT is examined. The results show that by increasing the thickness, the effect of porosity on the phase velocity decreases. Another important result is that by increasing the value of the radius, the difference between the minimum and maximum values of the phase velocity increases. Finally, influence of temperature change, wave number, angular velocity and different types of porosity distribution on phase velocity are investigated using the mentioned continuum mechanics theory. As a useful suggestion, for designing of a GPLRC nanostructure should be attention to the GNP weight function and radius, simultaneously.
This is the first research on the nonlinear frequency analysis of a multi-scale hybrid nanocomposite (MHC) disk (MHCD) resting on an elastic foundation subjected to nonlinear temperature gradient and ...mechanical loading is investigated. The matrix material is reinforced with carbon nanotubes (CNTs) or carbon fibers (CF) at the nano- or macroscale, respectively. We present a modified Halpin–Tsai model to predict the effective properties of the MHCD. The displacement–strain of nonlinear vibration of multi-scale laminated disk via third-order shear deformation theory (TSDT) and using Von Karman nonlinear shell theory is obtained. Hamilton’s principle is employed to establish the governing equations of motion, which is finally solved by generalized differential quadrature method (GDQM) and perturbation method (PM). Finally, the results show that FG patterns, different orientation angle of the fiber, the
V
F
and
W
CNT
parameters, axial load, nonlinear temperature gradient, and applied temperature of the top surface play an essential impact on the linear and nonlinear dynamic responses of the MHCD. The more significant outcome of this research is that the effects of the
V
F
,
W
CNT
,
θ
, and
β
parameters on the nonlinear frequency of the MHCD can be considered at the higher value of the large deflection parameter and the effect of negative axial load on the dynamic responses of the structure is more intensive. As an applicable result show that the best functionally graded (FG) pattern for serving the highest nonlinear dynamic response of an MHC reinforced annular plate is FG-A.
In this paper, size-dependent effect of an embedded magneto-electro-elastic (MEE) nanoshell subjected to thermo-electro-magnetic loadings on free vibration behavior is investigated. Also, the ...surrounding elastic medium has been considered as the model of Winkler characterized by the spring. The size-dependent MEE nanoshell is investigated on the basis of the modified couple stress theory. Taking attention to the first-order shear deformation theory (FSDT), the modeled nanoshell and its equations of motion are derived using principle of minimum potential energy. The accuracy of the presented model is validated with some cases in the literature. Finally, using the Navier-type method, an analytical solution of governing equations for vibration behavior of simply supported MEE cylindrical nanoshell under combined loadings is presented and the effects of material length scale parameter, temperature changes, external electric potential, external magnetic potential, circumferential wave numbers, constant of spring, shear correction factor and length-to-radius ratio of the nanoshell on natural frequency are identified. Since there has been no research about size-dependent analysis MEE cylindrical nanoshell under combined loadings based on FSDT, numerical results are presented to be served as benchmarks for future analysis of MEE nanoshells using the modified couple stress theory.
In this article, wave propagation characteristics of a size-dependent graphene nanoplatelet (GNP) reinforced composite cylindrical nanoshell coupled with piezoelectric actuator (PIAC) and surrounded ...with viscoelastic foundation is presented. The effects of small scale are analyzed based on nonlocal strain gradient theory (NSGT) which is an accurate theory employing exact length scale parameter and nonlocal constant. The governing equations of the GNP composite cylindrical nanoshell coupled with PIAC have been evolved using Hamilton’s principle and solved with assistance of the analytical method. For the first time in the current study, wave propagation electrical behavior of a GNP composite cylindrical nanoshell coupled with PIAC based on NSGT is examined. The results show that, by decreasing the PIAC thickness, extremum values of phase velocity occur in the lower values of the wave number. Another important result is that, by increasing GPL%, the effects of PIAC thickness on the phase velocity decrease. Finally, influence of PIAC thickness, wave number, applied voltage, and different GPL distribution patterns on phase velocity is investigated using mentioned continuum mechanics theory. Useful suggestion of this research is that for designing of a nanostructure coupled with PIAC attention should be given to PIAC thickness and applied voltage, simultaneously. The outputs of the current study can be used in the structural health monitoring and ultrasonic inspection techniques.
This is the first research on the smart control and frequency analysis of a cylindrical sandwich nanoshell in the framework of the numerical-based generalized differential quadrature method ...(2D-GDQM). The current sandwich smart nanostructure is made of a honeycomb core and piezoelectric face sheets as sensor and actuator (PFSA). For modeling the size-dependent nanoshell, nonlocal stress-strain gradient theory (NSGT) is presented. Also, this nanostructure is under conveying viscous fluid, and the related force is calculated by the modified formulation of Navier-Stokes. Also, the current structure rotates around its axial direction. The stresses and strains are obtained using the higher-order shear deformation theory (HSDT). The external voltage is applied to the sensor layer, and a Proportional-Derivative (PD) controller is used for sensor output control. Governing equations and boundary conditions of the cylindrical sandwich nanoshell are obtained by implementing Hamilton's principle. The results show that the geometry of honeycomb core, PD controller, velocity of fluid flow, length to radius ratio (L/R), and applied voltage and have a significant influence on the frequency characteristics of a cylindrical sandwich nanoshell. Another important consequence is that applying the PD controller leads to an increase in the critical velocity of fluid flow in the smart nanostructure.
In this study, buckling and vibrational characteristics of a nanoshell reinforced with graphene nanoplatelets under uniform axial load are investigated. The material properties of the piece-wise ...graphene-reinforced composites (GPLRCs) are assumed to be graded in the thickness direction of a nanoshell and are estimated using a nanomechanical model. The effects of the small scale are analyzed based on nonlocal stress–strain gradient theory (NSGT). The governing equations and boundary conditions (BCs) are developed using Hamilton’s principle and are solved with assistance of the generalized differential quadrature method. The novelty of the current study is the consideration of GPLRC and size effect as well as satisfying various boundary conditions implemented on the proposed model using NSGT. The results show that, nonlocal parameter, graphene platelet (GPL) distribution pattern, length scale parameter, number of layers, and GPL weight function have significant influence on the buckling and natural frequency of the GPLRC nanoshell. Another significant result is that nonlocal parameter does not have any effect on the buckling load for each BC. The results of the current study are useful for design of the nanoactuators and nanosensors.
In this article, vibrational behavior and critical voltage of a spinning cylindrical thick shell covered with piezoelectric actuator (PIAC) carrying spring-mass systems are investigated. It should be ...noted that, the installed sensors on the proposed systems are considered as a tip mass. This structure rotates about axial direction and the formulations include the Coriolis and centrifugal effects. In addition, various cases of thermal (uniform, linear, and nonlinear) distributions are studied. The modeled cylindrical thick shell covered with PIAC, its equations of motion, and boundary conditions are derived by the principle of minimum total potential energy and based on a new three-dimensional refined higher-order theory (RHOST). For the first time in the present study, attached spring-mass systems have been considered in the rotating cylindrical thick shells covered with PIAC. The accuracy of the presented model is verified compared with previous studies. The novelty of the current study is consideration of the applied voltage, rotation, various temperature distributions and spring-mass systems implemented on the proposed model using the RHOST. The generalized differential quadrature method is presented to discretize the model and to approximate the governing equations. In this study the simply supported conditions have been applied to edges
θ
=
π
/
2
,
3
π
/
2
and cantilever (clamped-free) boundary conditions have been studied in x = 0, L, respectively. The results show that, applied voltage, angular velocity, temperature changes and spring-mass systems play an important role on the critical voltage, critical angular speed, critical temperature, and natural frequency of the structure. Another significant result is that, by increasing the lumped mass and coefficient of the spring in the first frequency of the cantilever cylindrical shell, increase or decrease of the natural frequency depends on the nonlinear temperature change parameter. The results of the current study are useful suggestions for designing electromechanical systems such as hydraulic pipes with the installation of the sensors to them.
In this article, thermal buckling and frequency analysis of a size-dependent laminated composite cylindrical nanoshell in thermal environment using nonlocal strain–stress gradient theory are ...presented. The thermodynamic equations of the laminated cylindrical nanoshell are based on first-order shear deformation theory, and generalized differential quadrature element method is implemented to solve these equations and obtain natural frequency and critical temperature of the presented model. The results show that by considering C–F boundary conditions and every even layers’ number, in lower value of length scale parameter, by increasing the length scale parameter, the frequency of the structure decreases but in higher value of length scale parameter this matter is inverse. Finally, influences of temperature difference, ply angle, length scale and nonlocal parameters on the critical temperature and frequency of the laminated composite nanostructure are investigated.
The stability analysis of cantilevered curved microtubules in axons regarding various size elements and using the generalized differential quadrature method for solving equations is reported. The ...impacts of covering MAP Tau proteins along with cytoplasm are taken into account as the elastic medium. Curved cylindrical nanoshell considering thick wall is used to model the microtubules. The factor of length scale (
l/R
= 0.2) used in modified couple stress theory would result in more accuracy when it comes to comparison with experiments, while alternative theories presented in this paper provide less precise outcomes. Due to the reported precise results, at the lower value of the time-dependent viscoelastic factor (
τ
s
)
by rising the size-dependent factor, the frequency response of the cantilever microtubule increases and this relation between the size-dependent parameter and the structure’s natural frequency is changed from direct to indirect for the higher amount of the time-based viscoelastic factor that scientists should attend to this matter when it comes to the microtubule. Furthermore, physical neighboring situations in a cell will be prominent in microtubules’ dynamic stability responses, such as membrane and cell-matrix. Since microtubules are likely to be applied as biosensors, this feature could be employed to disclose virulent tumors.
In this paper, thermal buckling and free/forced vibration characteristics of size-dependent composite cylindrical nanoshell reinforced with graphene platelets (GPLs) is presented. Also, the nanoshell ...is embedded in an elastic pasternak medium, which is obtained by adding a shear layer to the Winkler model. The present nano-resonator is based on a vibrating first order nanoscale cylindrical shell subjected to transverse pressure. The temperature-dependent material properties of piece-wise functionally graded graphene-reinforced composites (FG-GRCs) are assumed to be graded in the thickness direction of a cylindrical nanoshell and are estimated through a nanomechanical model. Also, Halpin–Tsai nanomechanical model in used to surmise the effective material properties of each layer. The size-dependent FG-GRCs nanoshell is analyzed using modified couple stress parameter. The novelty of the current study is in considering the effects of FG-GRCs and thermal in addition of size effect on resonance frequencies, thermal buckling and dynamic deflections of the FG-GRCs nanoshell. The governing equations and boundary conditions have been developed using Hamilton’s principle and have been solved with the aid of analytical method. The results show that, GPL distribution pattern, modified couple stress parameter, length to radius ratio, mode number, winkler coefficient and thermal environment have important role on resonance frequency, relative frequency change, thermal buckling and dynamic deflections of the FG-GRCs cylindrical nanoshell in thermal environments.
