Showing papers in "Mechanics of Advanced Materials and Structures in 2017"
TL;DR: In this paper, a semi-analytical differential transform method was used to analyze the vibrational properties of functionally graded (FG) size-dependent nanobeams exposed to various hygro-thermal loadings.
Abstract: In this article, hygro-thermo-mechanical vibration analysis of functionally graded (FG) size-dependent nanobeams exposed to various hygro-thermal loadings is performed via a semi-analytical differential transform method (DTM). Three kinds of environmental conditions, namely, uniform, linear, and sinusoidal hygro-thermal loading, are investigated. Temperature-dependent material properties of a nonlocal FG beam change gradually according to the power-law distribution. A size-dependency description of the nanobeam is conducted using the nonlocal elasticity theory of Eringen. Applying DTM, the nonlocal coupled governing equations obtained from Hamilton's principle are solved. Finally, the impacts of moisture concentration, temperature rise, nonlocal parameters, material composition, and slenderness ratio on the vibrational characteristics of nanosize FG beams with arbitrary boundary conditions are explored. These findings can be used for the accurate design of FG nanostructures in various environmenta...
113 citations
TL;DR: In this paper, free vibration analysis of functionally graded piezoelectric (FGP) plates with porosities is carried out based on refined four-unknown plate theory.
Abstract: Here, free vibration analysis of functionally graded piezoelectric (FGP) plates with porosities is carried out based on refined four-unknown plate theory. The present plate theory captures shear deformation impacts needless of shear correction factor. A modified power-law model is adopted to describe the graded material properties of a functionally graded piezoelectric plate. Implementing an analytical approach, which satisfies different boundary conditions, governing equations derived from Hamilton's principle are solved. The obtained results are compared with those provided in the literature. The impacts of applied voltage, porosity distribution, material graduation, plate geometrical parameters, and boundary conditions on vibration of porous FGP plate are discussed.
80 citations
TL;DR: In this paper, a higher-order shear deformation beam theory was proposed for free vibration analysis of functionally graded carbon nanotube-reinforced composite sandwich beams in a thermal environment.
Abstract: This article proposes a higher-order shear deformation beam theory for free vibration analysis of functionally graded carbon nanotube-reinforced composite sandwich beams in a thermal environment. The temperature-dependent material properties of functionally graded carbon nanotube-reinforced composite beams are supposed to vary continuously in the thickness direction and are estimated through the rule of mixture. The governing equations and boundary conditions are derived by using Hamilton's principle, and the Navier solution procedure is used to achieve the natural frequencies of the sandwich beam in a thermal environment. A parametric study is led to carry out the effects of carbon nanotube volume fractions, slenderness ratio, and core-to-face sheet thickness ratio on free vibration behavior of sandwich beams with functionally graded carbon nanotube-reinforced composite face sheets. Numerical results are also presented in order to compare the behavior of sandwich beams including uniformly distrib...
72 citations
TL;DR: In this article, the authors presented an innovative view of STF-impregnated ball-shaped ballistic fabrics and showed that shear thickening fluids (STF) with ballistic fabrics improve the protection performance of body protective systems.
Abstract: Applications of shear thickening fluids (STFs) with ballistic fabrics improve the protection performance of body protective systems. This article presents an innovative view of STF-impregnated ball...
71 citations
TL;DR: In this article, the effects of initial shear stress and surrounding elastic medium and boundary conditions on the vibration analysis of orthotropic single-layered graphene sheets (SLGSs) are studied considering five different boundary conditions.
Abstract: In this paper, the small scale effect on the vibration behavior of orthotropic single layered graphene sheets is studied based on the nonlocal Reddy's plate theory embedded in elastic medium with considering initial shear stress. Elastic theory of the graphene sheets is reformulated using the nonlocal differential constitutive relations of Eringen. To simulate the interaction between the graphene sheet and surrounding elastic medium we used both Winkler-type and Pasternak-type foundation models. The effects of initial shear stress and surrounding elastic medium and boundary conditions on the vibration analysis of orthotropic single-layered graphene sheets (SLGSs) are studied considering five different boundary conditions. Numerical approach of the obtained equation is derived by differential quadrature method (DQM). Effects of shear stress, nonlocal parameter, size of the graphene sheets, stiffness of surrounding elastic medium and boundary conditions on vibration frequency rate are investigated. ...
58 citations
TL;DR: In this article, the authors presented an analysis of the nonlinear dynamic response and vibration of imperfect functionally graded material (FGM) thick plates subjected to blast and thermal loads resting on elastic foundations.
Abstract: Based on Reddy's higher-order shear deformation plate theory, this article presents an analysis of the nonlinear dynamic response and vibration of imperfect functionally graded material (FGM) thick plates subjected to blast and thermal loads resting on elastic foundations. The material properties are assumed to be temperature-dependent and graded in the thickness direction according to a simple power-law distribution in terms of the volume fractions of the constituents. Numerical results for the dynamic response and vibration of the FGM plates with two cases of boundary conditions are obtained by the Galerkin method and fourth-order Runge–Kutta method. The results show the effects of geometrical parameters, material properties, imperfections, temperature increment, elastic foundations, and boundary conditions on the nonlinear dynamic response and vibration of FGM plates.
53 citations
TL;DR: In this article, an analytical method is presented for thermo-mechanical vibration analysis of functionally graded (FG) nanoplates with different boundary conditions under various thermal loadings including uniform, linear, and nonlinear temperature rise via a four-variable plate theory considering neutral surface position.
Abstract: In this article, an analytical method is presented for thermo-mechanical vibration analysis of functionally graded (FG) nanoplates with different boundary conditions under various thermal loadings including uniform, linear, and nonlinear temperature rise via a four-variable plate theory considering neutral surface position. The temperature-dependent material properties of FG nanoplate vary gradually along the thickness according to the Mori-Tanaka homogenization scheme. The exactness of solution is confirmed by comparing obtained results with those provided in the literature. A parametric study is performed investigating the effects of nonlocal parameter, temperature fields, gradient index, and boundary conditions on vibration behavior of FG nanoplates.
46 citations
TL;DR: In this article, the transverse vibration of a rotary tapered microbeam is studied based on a modified couple stress theory and Euler-Bernoulli beam model, and the governing differential equation and boundary conditions are derived according to Hamilton's principle.
Abstract: The transverse vibration of a rotary tapered microbeam is studied based on a modified couple stress theory and Euler–Bernoulli beam model. The governing differential equation and boundary conditions are derived according to Hamilton's principle. The generalized differential quadrature element method is then used to solve the governing equation for cantilever and propped cantilever boundary conditions. The effect of the small-scale parameter, beam length, rate of cross-section change, hub radius, and nondimensional angular velocity on the vibration behavior of the microbeam is presented.
45 citations
TL;DR: A review on the development of nondestructive vibrational evaluation approaches in identifying the elastic constants of composite plates, in experimental and numerical manners, in order to enlighten researchers with the current trends of nonsmooth vibrational approaches is presented in this article.
Abstract: Destructive identification approaches are no longer in favor since the advent of nondestructive evaluation approaches, as they are accurate, rapid, and cheap. Researchers are devoted to improving the accuracy, rate of convergence, and cost of such approaches, which depend greatly on the types of vibrational experiments conducted and the types of forward and inverse methods used in numerical section. Therefore, this article presents a review on the development of nondestructive vibrational evaluation approaches in identifying the elastic constants of composite plates, in experimental and numerical manners in order to enlighten researchers with the current trends of nondestructive vibrational approaches.
44 citations
TL;DR: In this paper, a new mathematical model of generalized thermoelasticity with memory-dependent derivatives for the dual-phase-lag heat conduction law is constructed and the governing equations of the new model are applied to a half-space subjected to ramp-type heating.
Abstract: A new mathematical model of generalized thermoelasticity with memory-dependent derivatives for the dual-phase-lag heat conduction law is constructed. The governing equations of the new model are applied to a half-space subjected to ramp-type heating. Laplace transforms technique is used. The solution is obtained for different types of functions representing the thermal shock and for different values of the parameter of the time fraction derivative of the model. The effects of time-delay and arbitrary kernel function on elastic material are studied and represented graphically. The predictions of the theory are discussed and compared with dynamic classical coupled theory.
43 citations
TL;DR: Graphene oxide incorporated cellulose acetate composite nanofibers were prepared via an electrospinning technique as mentioned in this paper, and the weight percentage of graphene oxide varied from 0.05 to 1.5
Abstract: Graphene oxide incorporated cellulose acetate composite nanofibers were prepared via an electrospinning technique. The weight percentage of graphene oxide varied from 0.05 to 1.5 wt.% in the polyme...
TL;DR: In this article, two-dimensional heat transfer mixed convection flow of a nanofluid over a vertical stretching permeable sheet is investigated, where simultaneous effects of spherical and nonspherical shapes of nanoparticles with different sizes in nanolayer are taken into account.
Abstract: In this article, two-dimensional heat transfer mixed convection flow of a nanofluid over a vertical stretching permeable sheet is investigated. Simultaneous effects of spherical and nonspherical shapes of nanoparticles with different sizes in nanolayer are taken into account. The human engineered fluids with Nimonic 80a metal nanoparticles are used as base fluids. Analytic solutions of velocity and temperature under the influence of the Buoyancy force (assists or opposes) are first obtained and then the role of pertinent parameters, such as volume friction, mixed convection, porosity, stretching, power law index, and temperature index, is illustrated through graphs and tables. In addition, correlation of Nusselt number and skin friction corresponding to active parameters are also analyzed.
TL;DR: In this article, the size-dependent effect on free vibration of double-bonded isotropic piezoelectric Timoshenko microbeams using strain gradient and surface stress elasticity theories under initial stress is presented.
Abstract: The size-dependent effect on free vibration of double-bonded isotropic piezoelectric Timoshenko microbeams using strain gradient and surface stress elasticity theories under initial stress is presented. This article is developed for isotropic piezoelectric material. Due to the high surface-to-volume ratio, surface stress has an important role with micro- and nanoscale materials. Thus, the Gurtin–Murdoch continuum mechanic approach is used. Governing equations of motion are derived by Hamilton's principle and solved by the differential quadrature method. The effects of pre-stress load, surface residual stress, surface mass density, surface piezoelectrics, Young's modulus of surface layers, three material length scale parameters, thickness to material length scale parameter ratios, various boundary conditions, and two elastic foundation coefficients are investigated. It is concluded that the effect of pre-stress load in greater modes is negligible for higher aspect ratios and this effect is similar ...
TL;DR: In this article, various sinusoidal shear deformation theories are used for the buckling analysis of functionally graded sandwich plates and the influence of the thickness stretching and the zig-zag effects on these problems is investigated.
Abstract: In this article various sinusoidal shear deformation theories are used for the buckling analysis of functionally graded sandwich plates. The theories may account for through-the-thickness deformations and/or zig-zag effect. The governing equations and boundary conditions are derived using the Principle of Virtual Work under a generalization of Carrera’s Unified Formulation and further interpolated by collocation with radial basis functions. A numerical investigation has been conducted on the buckling analysis of sandwich plates with functionally graded skins. The influence of the thickness stretching and the zig-zag effects on these problems is investigated. Numerical results demonstrate the accuracy of the present approach.
TL;DR: In this paper, a Fourier-Ritz method based solution approach for the free vibration analysis of moderately thick, functionally graded (FG) rectangular plates with general boundary restraints and internal line supports is presented.
Abstract: The objective of this article is to present a Fourier-Ritz method-based solution approach for the free vibration analysis of moderately thick, functionally graded (FG) rectangular plates with general boundary restraints and internal line supports. Under the current framework, regardless of boundary conditions, each of the displacements and rotations of the FG plates is invariantly expressed as a modified Fourier series in both directions. Then, the accurate solutions are obtained using the Ritz procedure based on the energy function of the plates. The convergence and accuracy of the present method are verified by a considerable number of convergence tests and comparisons.
TL;DR: In this article, a dynamic stability analysis of the viscoelastic piezoelectric polymeric nanocomposite plate reinforced by functionally graded single-walled carbon nanotubes (FG-SWCNTs) based on modified strain gradient theory (MSGT) is explored.
Abstract: In this article, dynamic stability analysis of the viscoelastic piezoelectric polymeric nanocomposite plate reinforced by functionally graded single-walled carbon nanotubes (FG-SWCNTs) based on modified strain gradient theory (MSGT) is explored. The viscoelastic piezoelectric polymeric nanocomposite plate reinforced is subjected to hydrothermal and electro-magneto-mechanical loadings. The viscoelastic piezoelectric polymeric nanocomposite plate is rested on viscoelastic foundation. Uniform distribution (UD), various functionally graded (FG) distribution types such as FG-V, FG-X, and FG-O are considered for single-walled carbon nanotubes (SWCNTs). The extended mixture approach is applied to estimation of the elastic properties. The equations of motion are derived by Hamilton's principle. The resonance frequency or the parametric resonance is obtained then dynamic stability region is specified. There is a good agreement between the present work and the literature result. Various parametric investiga...
TL;DR: In this article, the wave propagation in functionally graded nanocomposites reinforced with carbon nanotubes is investigated on the basis of second-order shear deformation theory, and the results for the free vibration are compared with the results of functionally graded plates available in the literature.
Abstract: In the present article, as a first endeavor, the wave propagation in functionally graded nanocomposites reinforced with carbon nanotubes is investigated on the basis of second-order shear deformation theory. Four different types of functionally graded nanocomposites are presented. An analytical method is used to find the circular frequencies and phase velocities. To show the accuracy of the present methodology, our results for the free vibration are compared with the results of functionally graded plates available in the literature. The influences of different parameters are also investigated on the circular frequencies and phase velocities.
TL;DR: In this paper, a nonlinear free vibration analysis of spherical and cylindrical composite shell panels embedded with shape memory alloy fibers is performed for aircraft and launch vehicle domains to enhance the payload gain and performance.
Abstract: High specific strength and stiffness are characteristics desired for aircraft and launch vehicle domains to enhance the payload gain and performance. The mechanical properties of the composites can be further tailored by embedding structural components, such as shape memory alloys, into the passive composite structure. The present study is primarily focused on the nonlinear free vibration analysis of spherical and cylindrical composite shell panels embedded with shape memory alloy fibers. The nonlinear finite element governing equations based on the higher-order shear deformation plate theory and principle of virtual work with nonlinear von-Karman strain displacement relations are employed for the analysis. The temperature-dependent material properties of shape memory alloy are considered in the formulation. A nine-noded isoperimetric element is accounted for synthesizing the element for the finite formulation. The Young's modulus and the recovery stress vary with temperature and higher nonlineari...
TL;DR: In this paper, low-velocity impact tests are performed on fiberglass/AZ31B-H24 magnesium fiber-metal laminates (FMLs) with various configurations in order to gain a better understanding of the effect of an impactor's features on the response of this type of FMLs.
Abstract: Low-velocity impact tests are performed on fiberglass/AZ31B-H24 magnesium fiber-metal laminates (FMLs) with various configurations in order to gain a better understanding of the effect of an impactor's features on the response of this type of FMLs. For that, impactors with two different shapes (hemispherical and sharp-edged) and sizes are used to impact the specimens. The impact response data, such as the deformation of the contact location and energy absorption, is obtained directly during the impact tests through the impact equipment, while mechanical sectioning was carried out to establish the extent of delaminated area and post-impact residual deformation. While the sharp-edged impactor caused the development of cracks on the metal constituent, and delamination within the specimens, the hemispherical ones imposed more influence over the residual deformation. Noticeable differences are observed in response of FML specimens made with two and three layers of magnesium, especially with respect to ...
TL;DR: In this article, a three-dimensional solution is presented for the bending analysis of functionally graded and layered neutral magneto-electro-elastic plates resting on two-parameter elastic foundations, considering imperfect interfacial bonding.
Abstract: In this article, a three-dimensional solution is presented for the bending analysis of functionally graded and layered neutral magneto-electro-elastic plates resting on two-parameter elastic foundations, considering imperfect interfacial bonding. The equations of motion, Gauss's equations for electrostatics and magnetostatics, and boundary and interface conditions are satisfied exactly regardless of the number of layers. No assumptions on deformations, stresses, and magnetic and electric fields along the thickness direction are introduced. The interfacial imperfection is modeled using a generalized spring layer. The state-space method is employed for solving the governing partial differential equations. Effects of a two-parameter elastic foundation, gradient index, bonding imperfection, and applied mechanical and electrical loads on the response of the functionally graded magneto-electro-elastic plate are discussed. The obtained exact solution can serve as a benchmark for assessing the accuracy of...
TL;DR: In this paper, the surface effect on the forced vibration of a double single-walled carbon nanotube system (DSWNTS) under excitation of a moving nanoparticle is analyzed based on the modified nonlocal elasticity theory.
Abstract: In the present study, the surface effect on the forced vibration of a double single-walled carbon nanotube system (DSWNTS) under excitation of a moving nanoparticle is analyzed based on the modified nonlocal elasticity theory. The nanotube surroundings are modelled by elastic medium and it is assumed that two nanotubes are connected to each other continuously, using elastic springs. In a parametric study, influences of nonlocal parameter, velocity of the moving nanoparticle, elastic layer between the nanotubes and order of derivative on dynamic responses of the DSWNTS are investigated in details. The results demonstrate that variation of order of derivative affects dynamic deflection and frequency of DSWNTS, considerably. In this study the influences of additional terms in nonlocal theory and improving the accuracy of results by presenting a modified version of nonlocal elasticity theory is investigated. As the results have presented, there is a noticeable difference in comparison with previous ca...
TL;DR: In this article, the optimal design of laminated composite panels with constrained layer damping (CLD) treatments is addressed, where the objectives are simultaneously to minimize weight and maximize modal damping.
Abstract: The optimal design of laminated composite panels with constrained layer damping (CLD) treatments is addressed in this article. The objectives are simultaneously to minimize weight and maximize modal damping. The design variables are the number and position of CLD patch treatments on the surface of the laminated plate. The problem is solved using Direct MultiSearch solver, which does not use any derivatives of the objective functions. A finite element model for sandwich plates with viscoelastic core and laminated face layers is used. Trade-off Pareto optimal fronts and the respective treatment configurations are obtained and the results are analyzed and discussed.
TL;DR: In this article, the effects of temperature variation, small scale, different boundary conditions, aspect ratio, and length on natural non-dimensional frequencies are studied for rotating and non-rotating nano-devices.
Abstract: In this article, the vibration frequency of an orthotropic nanoplate under the effect of temperature change is investigated. Using nonlocal elasticity theory, governing equations are derived. Based on the generalized differential quadrature method for cantilever and propped cantilever boundary conditions, the frequencies of orthotropic nanoplates are considered and the obtained results are compared with valid reported results in the literature. The effects of temperature variation, small scale, different boundary conditions, aspect ratio, and length on natural nondimensional frequencies are studied. The present analysis is applicable for the design of rotating and nonrotating nano-devices that make use of thermo-mechanical vibration characteristics of nanoplates.
TL;DR: In this paper, a compact analytical method for vibration analysis of gradient elastic beams is presented to solve any combination of boundary conditions, and the general frequency determinant for microbeams with general restraints are derived by using Stokes' transformation.
Abstract: In this article, a compact analytical method for vibration analysis of gradient elastic beams is presented to solve any combination of boundary conditions. The general frequency determinant for microbeams with general restraints are derived by using Stokes’ transformation. The main advantage of this determinant is capability of considering any possible combination of boundary conditions. By assigning proper values to spring parameters in the general frequency determinant, the solutions can also be determined for the rigid boundary conditions. Numerical results are presented to investigate the influences the material length scale parameter, rotational, and translational springs on the free vibration behavior of microbeams. Some of the present results are compared with the previously published results to establish the validity of the present formulation. The microbeams with restrained boundary conditions exhibit significant size dependence when the length of the microbeam approaches to the material ...
TL;DR: In this article, the propagation of SH-wave in a vertically heterogeneous viscoelastic layer lying over a micropolar elastic half-space is analyzed analytically in closed form.
Abstract: This article deals with the propagation of SH-wave in a vertically heterogeneous viscoelastic layer lying over a micropolar elastic half-space. Dispersion and damping equations are obtained analytically in closed form. Phase and damped velocities are computed numerically and depicted by means of a graph to exhibit the substantial effect of heterogeneity, viscoelasticity (internal friction), and micropolar parameter. As a special case of the problem, it is found that deduced dispersion relation is well in agreement to the classical-Love wave equation and damping equation vanishes identically for the isotropic case. Influence of micropolarity present in the medium of half-space is highlighted through comparative study.
TL;DR: In this article, the transient thermo-piezoelectric response of a functionally graded piezolectric rod subjected to a moving heat source is investigated in the context of fractional order theory of thermoelasticity proposed by Sherief.
Abstract: The transient thermo-piezoelectric response of a functionally graded piezoelectric rod subjected to a moving heat source is investigated in the context of fractional order theory of thermoelasticity proposed by Sherief. The material properties of the functionally graded piezoelectric rod are assumed to vary exponentially along the length, except for the thermal relaxation time and the specific heat, which are taken to be constant. To solve the governing equations of the problem, Laplace transform is applied, eliminating the time effect; the analytical solutions of the displacement, stress, temperature, and electric field in Laplace domain are obtained. Subsequently, the solutions of the considered variables in time domain are obtained by numerical Laplace inversion and illustrated graphically. In calculation, the effect of the fractional order parameter on the variations of the considered variables is presented.
TL;DR: In this article, the free vibration of laminated composite Euler-Bernoulli beams has been studied using finite strain assumptions and the generalized differential quadrature method has been engaged to solve the equation of motion.
Abstract: In this research, free vibration of laminated composite Euler-Bernoulli beams has been studied using finite strain assumptions. Governing equations of motion and boundary conditions have been obtained using the Green-Lagrange strain tensor and employing Hamilton's principle. The generalized differential quadrature method has been engaged to solve the equation of motion. Frequencies of the beam have been computed for carbon/epoxy material with various lay-ups subjected to different boundary conditions. The effects of fiber orientation change and lay-ups sequences of angle-ply composite beams on the frequency of the beam have been investigated. Also, dimensionless frequencies for different ratios of length to thickness of the beam subjected to different boundary conditions have been obtained.
TL;DR: In this article, an eight-noded shell element, which considers stress resultant-type Koiter's shell theory and transverse shear effect as per Mindlin's hypothesis having five degrees of freedom at each node, has been utilized for discretizing and analysis of such hybrid shell structures.
Abstract: The present work deals with the evaluation of elastic properties and dynamic analyses of thin hybrid composite shell structures, which consist of conventional carbon fiber as the reinforcing phase and multiwalled carbon nanotubes-based polymer as the matrix phase. The Mori-Tanaka and strength of material method has been implemented to determine the elastic properties of such hybrid composite structures without and with considering agglomerations. An eight-noded shell element, which considers stress resultant-type Koiter's shell theory and transverse shear effect as per Mindlin's hypothesis having five degrees of freedom at each node, has been utilized for discretizing and analysis of such hybrid shell structures. The Rayleigh damping model has been implemented in order to study the effect of carbon nanotubes (CNTs) on damping capacity of such hybrid composite shell structures. Different types of spherical shell panels have been analyzed in order to study the time and frequency responses. Results s...
TL;DR: In this article, the boundary integral equation method in conjunction with the degenerate kernel, the direct searching technique (singular value decomposition), and the only two-trials technique (2 × 2 matrix eigenvalue problem) are analytically and numerically used to find the degenerates scales, respectively.
Abstract: The boundary integral equation method in conjunction with the degenerate kernel, the direct searching technique (singular value decomposition), and the only two-trials technique (2 × 2 matrix eigenvalue problem) are analytically and numerically used to find the degenerate scales, respectively. In the continuous system of boundary integral equation, the degenerate kernel for the 2D Kelvin solution in the polar coordinates is reviewed and the degenerate kernel in the elliptical coordinates is derived. Using the degenerate kernel, an analytical solution of the degenerate scales for the elasticity problem of circular and elliptical cases is obtained and compared with the numerical result. Further, the triangular case and square case were also numerically demonstrated.
TL;DR: In this paper, the actuator is modeled in terms of a mass-spring-damper system utilizing the stop operator as one of the operators of the Prandtl-Ishlinskii (PI) model.
Abstract: The hysteresis nonlinearity in piezoelectric materials brings difficulties in controlling the systems. In order to mitigate the effect of hysteresis, such nonlinearity needs to be characterized and modeled under different load circumstances. For this purpose, the actuator is modeled in terms of a mass-spring-damper system utilizing the stop operator as one of the operators of the Prandtl-Ishlinskii (PI) model. Merging the structural model with the nonlinear hysteresis model, we observe that the results demonstrate better correspondence to the measured output compared to that of the classical PI model for a wide range of working conditions, i.e., different input frequency and amplitude.