The Experts below are selected from a list of 5349 Experts worldwide ranked by ideXlab platform

Nguyen Dinh Duc - One of the best experts on this subject based on the ideXlab platform.

  • nonlinear forced vibrations analysis of imperfect stiffened fg doubly curved shallow Shell in thermal environment using multiple scales method
    Composite Structures, 2021
    Co-Authors: Habib Ahmadi, Nguyen Dinh Duc, Aliakbar Bayat
    Abstract:

    Abstract This study investigates the non-linear vibrations of stiffened imperfect functionally graded double-curved shallow Shells, as rested on nonlinear elastic foundations. The Shells are exposed to external harmonic excitation and are placed in the thermal situations. The modeling of Shells is derived according to the Classical Shell Theory and the non-linear geometric von Karman relationships. It is considered that the distribution of material properties changes along the thickness direction based on a power law index. The smeared stiffener technique is considered to model the stiffened Shells. An approximation, according to Galerkin’s approach, is utilized to reduction of the Shell governing equations into the non-linear coupled ordinary differential relations. The ODE equations are analytically solved and analyzed through the perturbation methodology for investigating the resonance behavior of Shells. Simulation results are reported to examine the influences of stiffeners, initial imperfection, foundation coefficients, thermal environment, and geometrical characteristics on the non-linear primary resonance response of doubly curved shallow Shells. Also, the nonlinear dynamic behaviors are analyzed by numerical methods through the bifurcation diagrams, and the nonlinear dynamical behaviors of the Shell for different value of parameters are examined.

  • nonlinear dynamic analysis and vibration of eccentrically stiffened s fgm elliptical cylindrical Shells surrounded on elastic foundations in thermal environments
    Thin-walled Structures, 2017
    Co-Authors: Nguyen Dinh Duc, Pham Dinh Nguyen, Nguyen Dinh Khoa
    Abstract:

    Abstract Elliptical cylindrical Shell is one of Shells with special shape. Up to date, there is no publication on vibration and dynamic of functionally graded elliptical cylindrical Shells. Therefore, the purpose of the present study is to investigate the nonlinear dynamic response and vibration of imperfect eccentrically stiffness functionally graded elliptical cylindrical Shells on elastic foundations using both the Classical Shell Theory (CST) and Airy stress functions method with motion equations using Volmir's assumption. The material properties are assumed to be temperature - dependent and graded in the thickness direction according to a Sigmoid power law distribution (S-FGM). The S-FGM elliptical cylindrical Shell with metal-ceramic-metal layers are reinforced by outside metal stiffeners. Both the S-FGM elliptical Shell and metal stiffeners are assumed to be in thermal environment and both of them are deformed under temperature simultaneously. Two cases of thermal loading (uniform temperature rise and temperature variation through thickness) are considered. The nonlinear motion equations are solved by Galerkin method and Runge-Kutta method (nonlinear dynamic response, natural frequencies). The effects of geometrical parameters, material properties, elastic foundations Winkler and Pasternak, the nonlinear dynamic analysis and nonlinear vibration of the elliptical cylindrical Shells are studied. The some obtained results are validated by comparing with those in the literature.

  • thermal and mechanical stability of functionally graded carbon nanotubes fg cnt reinforced composite truncated conical Shells surrounded by the elastic foundations
    Thin-walled Structures, 2017
    Co-Authors: Nguyen Dinh Duc, Pham Hong Cong, Ngo Duc Tuan, Phuong Tran, Nguyen Van Thanh
    Abstract:

    Abstract The thermal and mechanical stability of a functionally graded composite truncated conical Shell reinforced by carbon nanotube fibers and surrounded by the elastic foundations are studied in this paper. Distribution of reinforcements across the Shell thickness is assumed to be uniform or functionally graded. The equilibrium and linearized stability equations for the Shells are derived based on the Classical Shell Theory. Using Galerkin method, the closed – form expression for determining the linear thermal and mechanical buckling load is obtained. The paper also analyzed and discussed the effects of semi-vertex angle, Shell length, volume fraction of fibers, distribution pattern of fibers, temperature, elastic foundations on the linear thermal and mechanical buckling loads of the functionally graded carbon nanotube fibers-reinforced composite (FG CNTRC) truncated conical Shell in thermal environment.

  • Thermomechanical buckling and post-buckling of cylindrical Shell with functionally graded coatings and reinforced by stringers
    Aerospace Science and Technology, 2017
    Co-Authors: Pham Toan Thang, Nguyen Dinh Duc, Trung Nguyen-thoi
    Abstract:

    Abstract The cylindrical Shells reinforced by stringers have been widely used in modern engineering structures such as storage tanks, missile, submarine hull, oil-transmitting pipeline, etc. In this present article, the thermomechanical buckling and post-buckling behaviors of a cylindrical Shell with functionally graded (FG) coatings are investigated by an analytical approach. The cylindrical Shell is reinforced by outside stringers under torsional load in the thermal environment. The layers of FG coatings are assumed to be made by functionally graded materials (FGMS) combining of ceramic and metal phases and the core of the Shell is made from homogeneous material. The Classical Shell Theory based on the von-Karman assumptions is used to model the thin cylindrical Shell. Using Galerkin's procedure and Airy stress function, the governing equations can be solved to obtain the closed-form solution for the critical buckling load and postbuckling load-deflection curves of simply supported Shells. Moreover, many important parametric studies of stringers, temperature field, material volume fraction index, the thickness of metal layer, etc. are taken into investigation. According to numerical examples, it is revealed that the outside strings have considerably impact on thermomechanical buckling and postbuckling behaviors of the Shells.

  • mechanical and thermal stability of eccentrically stiffened functionally graded conical Shell panels resting on elastic foundations and in thermal environment
    Composite Structures, 2015
    Co-Authors: Nguyen Dinh Duc, Pham Hong Cong, Ngo Duc Tuan, Phuong Tran, Vu Minh Anh, Vu Dinh Quang, Nguyen Hoa Thinh
    Abstract:

    Abstract Conical Shell panels made of functionally graded materials (FGMs) are rather commonly used by structural engineers. However, due to their complex geometric shape, there are only a few studies on conical Shell panels made from FGMs. This paper investigates the linear stability analysis of eccentrically stiffened FGM conical Shell panels reinforced by mechanical and thermal loads on elastic foundations. The FGM conical Shell is in thermal environment and both the panel and the stiffeners are deformed under temperature. The material properties of both the panels and stiffeners are assumed to be temperature-dependent. Classical Shell Theory and Lekhnitsky’s smeared stiffeners technique are used to set the balance equations and linear stability. Shells are reinforced by stringers and rings. The effects of stiffeners, material, and mechanical and temperature loads on stability of the eccentrically stiffened FGM conical Shell panels are analysed and discussed.

M M Aghdam - One of the best experts on this subject based on the ideXlab platform.

  • surface stress effect on nonlinear instability of imperfect piezoelectric nanoShells under combination of hydrostatic pressure and lateral electric field
    AUT Journal of Mechanical Engineering, 2018
    Co-Authors: S Sahmani, M M Aghdam, A H Akbarzadeh
    Abstract:

    In this paper, the nonlinear instability of piezoelectric cylindrical nanoShells under the combined radial compression and electrical load including the effects of surface free energy is studied. To consider the surface effects, the Gurtin-Murdoch elasticity Theory is utilized along with the Classical Shell Theory to develop an efficient size-dependent Shell model. To satisfy the balance conditions on the surfaces of nanoShells, a linear variation of normal stress is assumed through the thickness of the bulk. Electrical field is also exerted along the transverse direction. Based on the virtual work principle, the size-dependent nonlinear governing differential equations are derived in which transverse displacement and Airy stress function are considered as independent variables. After that, a boundary layer Theory is used incorporating the surface free energy effects in conjunction with the nonlinear prebuckling deformation, the large deflections in the postbuckling regime, and the initial geometrical imperfection. Finally, a two-stepped singular perturbation technique is employed to obtain the size-dependent critical buckling pressure and the associated postbuckling equilibrium path for alternative electrical loadings. It is revealed that the electrical load increases or decreases the critical buckling pressure and critical end-shortening of nanoShell which depends on the sign of applied voltage. Moreover, it is found that by taking surface free energy effects into account, the influence of electrical load on the postbuckling behavior of nanoShell increases.

  • boundary layer modeling of nonlinear axial buckling behavior of functionally graded cylindrical nanoShells based on the surface elasticity Theory
    Iranian Journal of Science and Technology-Transactions of Mechanical Engineering, 2018
    Co-Authors: S Sahmani, M M Aghdam
    Abstract:

    The main purpose of the present study is to examine the axial buckling and postbuckling response of cylindrical nanoShells made of functionally graded (FG) materials in the presence of surface free energy effects. To accomplish this purpose, an efficient size-dependent Shell model is introduced through combination of the Classical Shell Theory with the well-known Gurtin–Murdoch surface elasticity Theory. The volume fraction of FG nanoShells made of the mixture of aluminum and silicon is defined using a power law function. Also, in order to eliminate the stretching–bending coupling terms, the change in the position of physical neutral plane corresponding to different volume fractions is taken into account. Based upon the principle of virtual work, the non-Classical governing differential equations and boundary conditions are derived. Subsequently, the governing equations are deduced to the boundary layer-type equations incorporating simultaneously the nonlinear large deflections and size effect. Finally, a perturbation-based solving process is put to use to predict the size-dependent critical buckling loads and related postbuckling equilibrium curves for FG nanoShells with various values of material property gradient index and Shell thickness. It is found that the surface free energy effect is more prominent for FG nanoShell with lower Shell thickness and higher material property gradient index.

  • nonlocal strain gradient Shell model for axial buckling and postbuckling analysis of magneto electro elastic composite nanoShells
    Composites Part B-engineering, 2018
    Co-Authors: S Sahmani, M M Aghdam
    Abstract:

    Abstract The present study deals with the size-dependent nonlinear buckling and postbuckling characteristics of magneto-electro-elastic cylindrical composite nanoShells incorporating simultaneously the both of hardening-stiffness and softening-stiffness size effects. To accomplish this purpose, the nonlocal strain gradient elasticity Theory is applied to the Classical Shell Theory. Via the virtual work's principle, the size-dependent governing differential equations are constructed including the coupling terms between the axial mechanical compressive load, external magnetic potential and external electrical potential. The nonlinear prebuckling deformations and the large postbuckling deflections are taken into consideration based upon the boundary layer Theory of Shell buckling. Finally, an improved perturbation technique is employed to achieve explicit analytical expressions for nonlocal strain gradient stability curves of magneto-electro-elastic nanoShells under various surface electric and magnetic voltages. It is seen that a positive electric potential and a negative magnetic potential cause to increase both of the nonlocality and strain gradient size dependencies in the nonlinear instability behavior of axially loaded magneto-electro-elastic composite nanoShells, while a negative electric potential and a positive magnetic potential play an opposite role.

  • surface stress effects on the nonlinear postbuckling characteristics of geometrically imperfect cylindrical nanoShells subjected to axial compression
    International Journal of Engineering Science, 2016
    Co-Authors: S Sahmani, M Bahrami, M M Aghdam
    Abstract:

    Abstract For structures at nanoscale, the surface effects can be important due to the high ratio of surface area to volume. In the current investigation, the nonlinear axial postbuckling behavior of geometrically imperfect cylindrical nanoShells is studied including surface stress effects. For this purpose, Gurtin–Murdoch continuum elasticity Theory in conjunction with von Karman–Donnell-type geometric nonlinearity is implemented into the Classical Shell Theory. By the developed size-dependent Shell model, the surface effects which include surface elasticity and residual surface stress are taken into account. In order to satisfy balance conditions on the surfaces of nanoShell, a linear variation through the thickness is considered for the normal stress component of the bulk. Based on the variational approach using virtual work's principle, the non-Classical governing differential equations are derived. In order to solve the nonlinear problem, a boundary layer Theory is employed which contains simultaneously the nonlinear prebuckling deformations, initial geometric imperfections and large deflections corresponding to the postbuckling domain. Subsequently, a two-stepped singular perturbation methodology is utilized to predict the nonlinear critical buckling loads as well as the postbuckling equilibrium paths. It is observed that by taking surface stress effects into account, the both critical buckling load and critical end-shortening of a cylindrical nanoShell made of Silicon increase.

  • on the postbuckling behavior of geometrically imperfect cylindrical nanoShells subjected to radial compression including surface stress effects
    Composite Structures, 2015
    Co-Authors: S Sahmani, M M Aghdam, M Bahrami
    Abstract:

    Abstract The main objective of the present study is to investigate the effect of surface stress on the nonlinear buckling and postbuckling behavior of cylindrical nanoShells with initial geometric imperfection subjected to radial compressive load. Gurtin–Murdoch elasticity Theory is implemented into the Classical Shell Theory to develop a size-dependent Shell model which is capable to capture surface stress effects efficiently. In order to satisfy balance conditions on the surfaces of nanoShell, a linear variation through the thickness is considered for the normal stress component of the bulk. The principle of virtual work is put to use in order to formulate the non-Classical governing differential equations. Afterwards, a boundary layer Theory is employed including the nonlinear prebuckling deformations, initial geometric imperfection and large postbuckling deflections. Finally, a two-stepped singular perturbation methodology is utilized to obtain the size-dependent critical buckling loads and the postbuckling equilibrium paths of imperfect nanoShells corresponding to both lateral and hydrostatic pressure loading cases. It is found that for the positive and negative values of surface elastic constants, the both critical buckling load and critical end-shortening of nanoShell increase and decrease, respectively.

S Sahmani - One of the best experts on this subject based on the ideXlab platform.

  • surface stress effect on nonlinear instability of imperfect piezoelectric nanoShells under combination of hydrostatic pressure and lateral electric field
    AUT Journal of Mechanical Engineering, 2018
    Co-Authors: S Sahmani, M M Aghdam, A H Akbarzadeh
    Abstract:

    In this paper, the nonlinear instability of piezoelectric cylindrical nanoShells under the combined radial compression and electrical load including the effects of surface free energy is studied. To consider the surface effects, the Gurtin-Murdoch elasticity Theory is utilized along with the Classical Shell Theory to develop an efficient size-dependent Shell model. To satisfy the balance conditions on the surfaces of nanoShells, a linear variation of normal stress is assumed through the thickness of the bulk. Electrical field is also exerted along the transverse direction. Based on the virtual work principle, the size-dependent nonlinear governing differential equations are derived in which transverse displacement and Airy stress function are considered as independent variables. After that, a boundary layer Theory is used incorporating the surface free energy effects in conjunction with the nonlinear prebuckling deformation, the large deflections in the postbuckling regime, and the initial geometrical imperfection. Finally, a two-stepped singular perturbation technique is employed to obtain the size-dependent critical buckling pressure and the associated postbuckling equilibrium path for alternative electrical loadings. It is revealed that the electrical load increases or decreases the critical buckling pressure and critical end-shortening of nanoShell which depends on the sign of applied voltage. Moreover, it is found that by taking surface free energy effects into account, the influence of electrical load on the postbuckling behavior of nanoShell increases.

  • boundary layer modeling of nonlinear axial buckling behavior of functionally graded cylindrical nanoShells based on the surface elasticity Theory
    Iranian Journal of Science and Technology-Transactions of Mechanical Engineering, 2018
    Co-Authors: S Sahmani, M M Aghdam
    Abstract:

    The main purpose of the present study is to examine the axial buckling and postbuckling response of cylindrical nanoShells made of functionally graded (FG) materials in the presence of surface free energy effects. To accomplish this purpose, an efficient size-dependent Shell model is introduced through combination of the Classical Shell Theory with the well-known Gurtin–Murdoch surface elasticity Theory. The volume fraction of FG nanoShells made of the mixture of aluminum and silicon is defined using a power law function. Also, in order to eliminate the stretching–bending coupling terms, the change in the position of physical neutral plane corresponding to different volume fractions is taken into account. Based upon the principle of virtual work, the non-Classical governing differential equations and boundary conditions are derived. Subsequently, the governing equations are deduced to the boundary layer-type equations incorporating simultaneously the nonlinear large deflections and size effect. Finally, a perturbation-based solving process is put to use to predict the size-dependent critical buckling loads and related postbuckling equilibrium curves for FG nanoShells with various values of material property gradient index and Shell thickness. It is found that the surface free energy effect is more prominent for FG nanoShell with lower Shell thickness and higher material property gradient index.

  • nonlocal strain gradient Shell model for axial buckling and postbuckling analysis of magneto electro elastic composite nanoShells
    Composites Part B-engineering, 2018
    Co-Authors: S Sahmani, M M Aghdam
    Abstract:

    Abstract The present study deals with the size-dependent nonlinear buckling and postbuckling characteristics of magneto-electro-elastic cylindrical composite nanoShells incorporating simultaneously the both of hardening-stiffness and softening-stiffness size effects. To accomplish this purpose, the nonlocal strain gradient elasticity Theory is applied to the Classical Shell Theory. Via the virtual work's principle, the size-dependent governing differential equations are constructed including the coupling terms between the axial mechanical compressive load, external magnetic potential and external electrical potential. The nonlinear prebuckling deformations and the large postbuckling deflections are taken into consideration based upon the boundary layer Theory of Shell buckling. Finally, an improved perturbation technique is employed to achieve explicit analytical expressions for nonlocal strain gradient stability curves of magneto-electro-elastic nanoShells under various surface electric and magnetic voltages. It is seen that a positive electric potential and a negative magnetic potential cause to increase both of the nonlocality and strain gradient size dependencies in the nonlinear instability behavior of axially loaded magneto-electro-elastic composite nanoShells, while a negative electric potential and a positive magnetic potential play an opposite role.

  • surface stress effects on the nonlinear postbuckling characteristics of geometrically imperfect cylindrical nanoShells subjected to axial compression
    International Journal of Engineering Science, 2016
    Co-Authors: S Sahmani, M Bahrami, M M Aghdam
    Abstract:

    Abstract For structures at nanoscale, the surface effects can be important due to the high ratio of surface area to volume. In the current investigation, the nonlinear axial postbuckling behavior of geometrically imperfect cylindrical nanoShells is studied including surface stress effects. For this purpose, Gurtin–Murdoch continuum elasticity Theory in conjunction with von Karman–Donnell-type geometric nonlinearity is implemented into the Classical Shell Theory. By the developed size-dependent Shell model, the surface effects which include surface elasticity and residual surface stress are taken into account. In order to satisfy balance conditions on the surfaces of nanoShell, a linear variation through the thickness is considered for the normal stress component of the bulk. Based on the variational approach using virtual work's principle, the non-Classical governing differential equations are derived. In order to solve the nonlinear problem, a boundary layer Theory is employed which contains simultaneously the nonlinear prebuckling deformations, initial geometric imperfections and large deflections corresponding to the postbuckling domain. Subsequently, a two-stepped singular perturbation methodology is utilized to predict the nonlinear critical buckling loads as well as the postbuckling equilibrium paths. It is observed that by taking surface stress effects into account, the both critical buckling load and critical end-shortening of a cylindrical nanoShell made of Silicon increase.

  • on the postbuckling behavior of geometrically imperfect cylindrical nanoShells subjected to radial compression including surface stress effects
    Composite Structures, 2015
    Co-Authors: S Sahmani, M M Aghdam, M Bahrami
    Abstract:

    Abstract The main objective of the present study is to investigate the effect of surface stress on the nonlinear buckling and postbuckling behavior of cylindrical nanoShells with initial geometric imperfection subjected to radial compressive load. Gurtin–Murdoch elasticity Theory is implemented into the Classical Shell Theory to develop a size-dependent Shell model which is capable to capture surface stress effects efficiently. In order to satisfy balance conditions on the surfaces of nanoShell, a linear variation through the thickness is considered for the normal stress component of the bulk. The principle of virtual work is put to use in order to formulate the non-Classical governing differential equations. Afterwards, a boundary layer Theory is employed including the nonlinear prebuckling deformations, initial geometric imperfection and large postbuckling deflections. Finally, a two-stepped singular perturbation methodology is utilized to obtain the size-dependent critical buckling loads and the postbuckling equilibrium paths of imperfect nanoShells corresponding to both lateral and hydrostatic pressure loading cases. It is found that for the positive and negative values of surface elastic constants, the both critical buckling load and critical end-shortening of nanoShell increase and decrease, respectively.

Pizhong Qiao - One of the best experts on this subject based on the ideXlab platform.

  • buckling and postbuckling of anisotropic laminated cylindrical Shells under combined external pressure and axial compression in thermal environments
    Composite Structures, 2015
    Co-Authors: Zhimin Li, Pizhong Qiao
    Abstract:

    Abstract The buckling and postbuckling analysis for an anisotropic laminated thin cylindrical Shell of finite length subjected to combined loading of external pressure and axial compression using the boundary layer Theory is presented. The material of each layer in the Shell is assumed to be linearly elastic, anisotropic and fiber-reinforced. The governing equations are obtained utilizing Classical Shell Theory and von Karman–Donnell strain displacement relations. The nonlinear prebuckling deformations and initial geometric imperfections of the Shell are both taken into account. A boundary layer Theory of Shell buckling, which includes the effects of nonlinear prebuckling deformations, large deflections in the postbuckling range, and initial geometric imperfection of the Shell, is extended to the case of anisotropic laminated thin cylindrical Shells under combined loading cases. A singular perturbation technique is employed to determine interactive buckling loads and postbuckling equilibrium paths. Postbuckling response of perfect and imperfect, anisotropic laminated cylindrical Shells with respect to the material and geometric properties and load-proportional parameters under different sets of thermal environmental conditions is numerically illustrated. The analytical model developed can be used as a versatile and accurate tool to study the buckling and postbuckling behavior of composite structures.

N Kuruoglu - One of the best experts on this subject based on the ideXlab platform.

  • the stability of fgm truncated conical Shells under combined axial and external mechanical loads in the framework of the shear deformation Theory
    Composites Part B-engineering, 2016
    Co-Authors: A H Sofiyev, N Kuruoglu
    Abstract:

    Abstract The major goal of this research was to obtain a closed form of the solution for critical combined loads (combined effects of the axial load and l lateral pressure or the axial load and hydrostatic pressure) of functionally graded (FG) truncated conical Shell in the framework of the shear deformation Theory (SDT). The basic equations of FG truncated conical Shell Shells subjected to the combined loads are derived in the framework of the SDT. By using the Galerkin method to basic equations are obtained the expressions for critical combined loads of FG truncated conical Shell in the framework of the SDT. In particular, similar expressions in the framework of the Classical Shell Theory (CST) are obtained, also. Our numerical experiments reveal that the proposed solution may offer accurate critical combined loads for the FGM Shells as compared with reference solutions available in the literature. Finally, the calculation and presentation of the effects of many parameters included in the analysis conclude the goals to be reached in the study.

  • combined influences of shear deformation rotary inertia and heterogeneity on the frequencies of cross ply laminated orthotropic cylindrical Shells
    Composites Part B-engineering, 2014
    Co-Authors: A H Sofiyev, N Kuruoglu
    Abstract:

    Abstract The non-dimensional frequencies for symmetric and anti-symmetric cross-ply laminated heterogeneous composite circular cylindrical Shells are analyzed by taking into account the effects of first-order deformations such as transverse shear deformations and rotary inertia. By using the Donnell-type Shell Theory, a set of fundamental dynamic equations of laminated circular cylindrical Shells made of heterogeneous orthotropic materials is derived through Hamilton’s principle. The basic equations are reduced to the six-order algebraic equation. One of the lowest positive roots of the algebraic equation represents the fundamental frequency. Attention is focused on the case of cross-ply laminated heterogeneous orthotropic cylindrical Shells, from which solution for homogenous and heterogeneous orthotropic monolayer cylindrical Shells follows based on Classical Shell Theory (CST) and shear deformation Theory (SDT), as a special case. Moreover, further detailed numerical results dealing with non-dimensional frequencies and corresponding mode shapes of laminated heterogeneous cylindrical Shells having symmetric or anti-symmetric cross-ply lay-up are discussed. Furthermore, some comparisons are made to show the reliability and accuracy of the study.