This paper provides the static and dynamic pullin behavior of nano-beams resting on the elastic foundation based on the nonlocal theory which is able to capture the size effects for structures in micron and sub-micron...This paper provides the static and dynamic pullin behavior of nano-beams resting on the elastic foundation based on the nonlocal theory which is able to capture the size effects for structures in micron and sub-micron scales. For this purpose, the governing equation of motion and the boundary conditions are driven using a variational approach. This formulation includes the influences of fringing field and intermolecular forces such as Casimir and van der Waals forces. The differential quadrature （DQ） method is employed as a high-order approximation to discretize the governing nonlinear differential equation, yielding more accurate results with a Considerably smaller number of grid points. In addition, a powerful analytical method called parameter expansion method （PEM） is utilized to compute the dynamic solution and frequency-amplitude relationship. It is illustrated that the first two terms in series expansions are sufficient to produce an acceptable solution of the mentioned structure. Finally, the effects of basic parameters on static and dynamic pull-in insta- bility and natural frequency are studied.展开更多
This paper aims at analyzing material-induced lateral pressure of RC cylinder silo in both static and dynamic condition using the finite element method( FEM). In the finite element software ABAQUS,concrete material is...This paper aims at analyzing material-induced lateral pressure of RC cylinder silo in both static and dynamic condition using the finite element method( FEM). In the finite element software ABAQUS,concrete material is modeled by concrete damaged plasticity model,and stored materials in silo is modeled by the hypoplastic theory.In terms of numerical model,shell elements( S4R) and solid elements( C3D8) are applied for model silo wall and stored materials respectively. The interaction between silo wall and stored materials is simulated by Coulomb friction model and penalty contact constrain provided by ABAQUS.The numerical results are verified with the existing experimental data that are designed to ensure the validation of such numerical model using FEM and it obtains good agreements between numerical results and experimental data. Then the material parameters are analyzed in both static and dynamic condition.According to the analysis,it is clear that critical friction angle,initial void ratio and minimum void ratio have an obvious effect on static lateral pressure while all the material parameters affect dynamic lateral pressure at different levels. In addition,differences of silo wall between elastic and plastic state are analyzed in dynamic condition. The numerical results show that it contributes to increasing dynamic pressure when silo wall enters into the plastic state. Finally,this paper discusses the time-history lateral pressure at different heights along silo wall,and analytical results indicate that larger acceleration values play main roles in producing the maximum lateral pressure at higher part of the silo wall.展开更多
Based on the theory of porous media, the quasi-static and dynamical bending of a cantilever poroelastic beam subjected to a step load at its free end is investigated, and the influences of its permeability on bending ...Based on the theory of porous media, the quasi-static and dynamical bending of a cantilever poroelastic beam subjected to a step load at its free end is investigated, and the influences of its permeability on bending deformation is examined. The initial boundary value problems for dynamical and quasi-static responses are solved with the Laplace transform technique, and the deflections, the bending moments of the solid skeleton and the equivalent couples of the pore fluid pressure are shown in figures. It is shown that the dynamical and quasi-static behavior of the saturated poroelastic beam depends closely on the permeability conditions at the beam ends. Under the different permeability conditions, the deflections of the beam may oscillate or not. The Mandel-Cryer effect also exists in liquid-saturated poroelastic beams.展开更多
In the present work, a finite element model is developed to analyze the response of isotropic and orthotropic beams, a common structural element for aeronautics and astronautic applications. The assumed field displace...In the present work, a finite element model is developed to analyze the response of isotropic and orthotropic beams, a common structural element for aeronautics and astronautic applications. The assumed field displacements equations of the beams are represented by a first order shear deformation theory, the Timoshenko beam theory. The equations of motion of the beams are derived using Hamilton’s principle. The shear correction factor is used to improve the obtained results. A MATLAB code is constructed to compute the natural frequencies and the static deformations for both types of beams with different boundary conditions. Numerical calculations are carried out to clarify the effects of the thickness-to-length ratio on both the Eigen values and the deflections of the beams due to the applied mechanical load. The obtained results of the proposed model are compared to the available results of other investigators, good agreement is generally obtained.展开更多
文摘This paper provides the static and dynamic pullin behavior of nano-beams resting on the elastic foundation based on the nonlocal theory which is able to capture the size effects for structures in micron and sub-micron scales. For this purpose, the governing equation of motion and the boundary conditions are driven using a variational approach. This formulation includes the influences of fringing field and intermolecular forces such as Casimir and van der Waals forces. The differential quadrature （DQ） method is employed as a high-order approximation to discretize the governing nonlinear differential equation, yielding more accurate results with a Considerably smaller number of grid points. In addition, a powerful analytical method called parameter expansion method （PEM） is utilized to compute the dynamic solution and frequency-amplitude relationship. It is illustrated that the first two terms in series expansions are sufficient to produce an acceptable solution of the mentioned structure. Finally, the effects of basic parameters on static and dynamic pull-in insta- bility and natural frequency are studied.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51478033,51179029)
文摘This paper aims at analyzing material-induced lateral pressure of RC cylinder silo in both static and dynamic condition using the finite element method( FEM). In the finite element software ABAQUS,concrete material is modeled by concrete damaged plasticity model,and stored materials in silo is modeled by the hypoplastic theory.In terms of numerical model,shell elements( S4R) and solid elements( C3D8) are applied for model silo wall and stored materials respectively. The interaction between silo wall and stored materials is simulated by Coulomb friction model and penalty contact constrain provided by ABAQUS.The numerical results are verified with the existing experimental data that are designed to ensure the validation of such numerical model using FEM and it obtains good agreements between numerical results and experimental data. Then the material parameters are analyzed in both static and dynamic condition.According to the analysis,it is clear that critical friction angle,initial void ratio and minimum void ratio have an obvious effect on static lateral pressure while all the material parameters affect dynamic lateral pressure at different levels. In addition,differences of silo wall between elastic and plastic state are analyzed in dynamic condition. The numerical results show that it contributes to increasing dynamic pressure when silo wall enters into the plastic state. Finally,this paper discusses the time-history lateral pressure at different heights along silo wall,and analytical results indicate that larger acceleration values play main roles in producing the maximum lateral pressure at higher part of the silo wall.
基金supported by the National Natural Science Foundation of China (Grant No.10872124)
文摘Based on the theory of porous media, the quasi-static and dynamical bending of a cantilever poroelastic beam subjected to a step load at its free end is investigated, and the influences of its permeability on bending deformation is examined. The initial boundary value problems for dynamical and quasi-static responses are solved with the Laplace transform technique, and the deflections, the bending moments of the solid skeleton and the equivalent couples of the pore fluid pressure are shown in figures. It is shown that the dynamical and quasi-static behavior of the saturated poroelastic beam depends closely on the permeability conditions at the beam ends. Under the different permeability conditions, the deflections of the beam may oscillate or not. The Mandel-Cryer effect also exists in liquid-saturated poroelastic beams.
文摘In the present work, a finite element model is developed to analyze the response of isotropic and orthotropic beams, a common structural element for aeronautics and astronautic applications. The assumed field displacements equations of the beams are represented by a first order shear deformation theory, the Timoshenko beam theory. The equations of motion of the beams are derived using Hamilton’s principle. The shear correction factor is used to improve the obtained results. A MATLAB code is constructed to compute the natural frequencies and the static deformations for both types of beams with different boundary conditions. Numerical calculations are carried out to clarify the effects of the thickness-to-length ratio on both the Eigen values and the deflections of the beams due to the applied mechanical load. The obtained results of the proposed model are compared to the available results of other investigators, good agreement is generally obtained.
