The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform

Z Y Cai - One of the best experts on this subject based on the ideXlab platform.

  • bending and free vibration of functionally graded piezoelectric Beam based on modified strain gradient Theory
    Composite Structures, 2014
    Co-Authors: W J Feng, Z Y Cai
    Abstract:

    Abstract A size-dependent functionally graded piezoelectric Beam model is developed using a variational formulation. It is based on the modified strain gradient Theory and Timoshenko Beam Theory. The material properties of functionally graded piezoelectric Beam are assumed to vary through the thickness according to a power law. The new model contains three material length scale parameters and can capture the size effect, unlike the Classical Beam Theory. To illustrate the new functionally graded piezoelectric Beam model, the static bending and free vibration problems of a simply supported Beam are numerical solved. These results may be useful in the analysis and design of smart structures constructed from piezoelectric materials.

Liyong Tong - One of the best experts on this subject based on the ideXlab platform.

  • bending effect of through thickness reinforcement rods on mode ii delamination toughness of enf specimen elastic and rigid perfectly plastic analyses
    Composites Part A-applied Science and Manufacturing, 2007
    Co-Authors: Liyong Tong
    Abstract:

    Abstract In this paper, a new simple metallic z-rod model is proposed to study the bending effect of the metallic z-rods on mode II delamination toughness of laminated composites. A new transverse shear force–deformation relationship for a metallic z-rod is obtained by using the Classical Beam Theory and modeling its surrounding matrix as linearly elastic, rigid–perfectly plastic or linearly elastic–perfectly plastic springs. The bridging traction provided by a metallic z-rod to the mode II delamination toughness is assumed to be only the shear force carried by a z-rod created by the relative slippage between two substrate Beams in an end-notched flexure (ENF) specimen, whereas the longitudinal sliding friction is assumed to make negligible contribution to the bridging traction. Mode II strain energy release rate (SERR) is employed to evaluate the influence of the metallic z-rods on the interlaminar fracture toughness of end-notched flexure (ENF) specimens. A parametric study of ENF specimens reinforced with the z-rods is conducted to demonstrate the effect of the new bridging mechanism by the metallic z-rods on the mode II delamination toughness.

  • bending effect of through thickness reinforcement rods on mode i delamination toughness of dcb specimen i linearly elastic and rigid perfectly plastic models
    International Journal of Solids and Structures, 2004
    Co-Authors: Liyong Tong
    Abstract:

    The use of through-thickness reinforcement in the form of short rods has been proposed to improve the interlaminar properties of laminated composites in the recent years. Compared to a fibrous short rod, which is often referred to as z-fiber, a metallic rod, referred to as z-rod in this paper, has reasonably high capability to carry transverse loading, i.e., a z-rod can provide both axial and transverse bridging tractions to the delamination crack. Therefore, a new analytical model is proposed to study the bending effect of the z-rods on mode I delamination toughness of laminated composites. In this new model, both the axial pull-out and the transverse bending are considered simultaneously. New bending moment and displacement relationships for a single z-rod are established by modeling the z-rod embedded in a linearly elastic and rigid-perfectly plastic matrix using the Classical Beam Theory. By using an approximate expression for mode I fracture toughness of double-cantilever-Beam (DCB) specimen, a parametric analysis of DCB specimen reinforced by the z-rods is conducted. The present numerical results show that the bending effect should not be ignored when stiffer z-rods are employed to reinforce the laminated composites.

Luan C Trinh - One of the best experts on this subject based on the ideXlab platform.

  • fundamental frequency analysis of functionally graded sandwich Beams based on the state space approach
    Composite Structures, 2016
    Co-Authors: Luan C Trinh, Adelaja Israel Osofero, Jaehong Lee
    Abstract:

    Abstract The state space approach is used to provide analytical solution for fundamental frequency analysis of functionally graded sandwich Beams. The Classical Beam Theory, first-order and higher-order shear deformation theories are employed to consider Beams of various Classical and non-Classical boundary conditions. Governing equations of motions are derived from Hamilton’s principle. The research investigates the effect of boundary conditions on the fundamental frequency with nine combinations of Classical boundary conditions created from clamped, hinged, pinned and free conditions in accordance with three combinations of non-Classical boundary conditions created from the assumption of an elastic support. In addition, the influence of material parameter and arrangement of layers as well as the slenderness ratio in vibration of functionally graded sandwich Beams is examined.

  • size dependent behaviour of functionally graded microBeams using various shear deformation theories based on the modified couple stress Theory
    Composite Structures, 2016
    Co-Authors: Luan C Trinh, Hoang X Nguyen, Trungkien Nguyen
    Abstract:

    This study investigates the mechanical behaviours of functionally graded (FG) microBeams based on the modified couple stress Theory. The material properties of these Beams are varied through Beam’s depth and calculated by using Classical rule of mixture and Mori–Tanaka scheme. The displacement fields are presented by using a unified framework which covers various theories including Classical Beam Theory, first-order Beam Theory, third-order Beam Theory, sinusoidal Beam Theory, and quasi-3D Beam theories. The governing equations of bending, vibration and buckling problems are derived using the Hamilton’s principle and then solved by using Navier solutions with simply-supported boundary conditions. A number of numerical examples are conducted to show the validity and accuracy of the proposed approaches. Effects of Poisson’s ratio, material length scale parameter, power-law index, estimation methods of material properties and slenderness ratio on deflections, stresses, natural frequencies and critical buckling loads of FG microBeams are examined.

Mesut şimsek - One of the best experts on this subject based on the ideXlab platform.

  • nonlinear static and free vibration analysis of microBeams based on the nonlinear elastic foundation using modified couple stress Theory and he s variational method
    Composite Structures, 2014
    Co-Authors: Mesut şimsek
    Abstract:

    Abstract In the present manuscript, a non-Classical Beam Theory is developed for the static and nonlinear vibration analysis of microBeams based on a three-layered nonlinear elastic foundation within the framework of the modified couple stress Theory and Euler–Bernoulli Beam Theory together with the von-Karman’s geometric nonlinearity. This non-Classical Beam model incorporates the length scale parameter which can account for the small size effect. By using the Hamilton’s principle, the equations of motion and the boundary conditions of the problem are derived. The nonlinear partial differential equation governing the motion of the system is reduced to the nonlinear ordinary differential equation with the help of the Galerkin discretization technique. He’s variational method is then applied for the first time to obtain approximate analytical expressions for the nonlinear frequency of the microBeams with pinned–pinned and clamped–clamped end conditions. Static analysis is also performed for uniformly distributed load. Some illustrative numerical examples are presented in order to investigate the influences of the length scale parameter and the stiffness coefficients of the nonlinear foundation on the static deflection and the ratio of nonlinear frequency to linear frequency (the nonlinear frequency ratio). Comparison studies are also performed to verify the present formulation and solutions. Close agreement is observed.

  • static bending of a functionally graded microscale timoshenko Beam based on the modified couple stress Theory
    Composite Structures, 2013
    Co-Authors: Mesut şimsek, Turgut Kocaturk, şeref Doguscan Akbas
    Abstract:

    Abstract A microscale functionally graded Timoshenko Beam model is developed for the static bending analysis based on the modified couple stress Theory (MCST). The material properties of the FG microBeams are assumed to vary in the thickness direction and are estimated through the Mori–Tanaka homogenization technique and the Classical rule of mixture. The equilibrium equations and the related boundary conditions are derived by using the principal of the minimum total potential energy. The governing equations are solved analytically for a simply-supported Beam subjected to a point and uniformly distributed load. The inclusion of an additional material parameter enables the new Beam model to capture the size effect. The new non-Classical Beam model reduces to the Classical Beam model when the length scale parameter is set to zero. The influences of the volume fraction index, the different estimation method of the material properties, length scale parameter, the aspect ratio and the Poisson effect on the static bending behavior are examined. Some of the present results are compared with the previously published results to establish the validity of the present formulation. It is found that the deflections of the microBeam by the Classical Beam Theory are always larger than those by the modified couple stress Theory.

Davood Toghraie - One of the best experts on this subject based on the ideXlab platform.

  • a comparison of the bolotin and incremental harmonic balance methods in the dynamic stability analysis of an euler bernoulli nanoBeam based on the nonlocal strain gradient Theory and surface effects
    Mechanics of Materials, 2020
    Co-Authors: Pezhman Sourani, Mohammad Hashemian, Mostafa Pirmoradian, Davood Toghraie
    Abstract:

    Abstract This study addresses the dynamic stability of an Euler–Bernoulli nanoBeam under time-dependent axial loading based on the nonlocal strain gradient Theory (NSGT) and considering the surface stress effects. The studied nanoBeam cross-section was rectangular, and simply-supported boundary conditions were assumed. Moreover, a uniform thermal gradient was applied to the nanoBeam. The elastic medium was modeled based on the Pasternak Theory. The strain–displacement relations were derived using the Von Karman equations. The governing equations were obtained by the energy method and applying the Hamilton's principle. Furthermore, the Bolotin and Incremental Harmonic Balance (IHB) methods were used to solve the differential equations. This study investigates the impact of such parameters as the small-scale parameter, the material length scale, surface effects, elastic medium parameters, temperature variations, geometry, and the static loading factor on the Dynamic Instability Region (DIR). The results are suggestive of the shift of the DIR to lower frequency zone by increasing the small-scale Eringen's nonlocal Theory parameter, whereas an increase in the material length scale from the strain gradient Theory moves the region to higher frequencies. In case the said parameters are equal, the result conforms to the Classical Beam Theory. In addition, assuming a Pasternak medium and taking into account the effects of surface stress (Young's modulus and the residual stress of the surface) shifts the DIR to higher frequencies, whereas applying a compressive static load moves the region to lower frequencies. Moreover, depending on the thermal expansion coefficient of the medium, temperature variations can also displace the DIR.