جستجوی مقالات مرتبط با کلیدواژه « Modified strain gradient theory » در نشریات گروه « مکانیک »

Vibration analysis of vessels conveying blood flow embedded in viscous fluid is studied based on the modified strain gradient theory. The viscoelastic vessels are simulated as a non-classical EulerBernoulli beam theory. Employing Hamilton’s principle, the governing equations for size-dependent vessels are derived. The Galerkin method is used in order to transform the resulting equations into general eigenvalue equations. The effects of the blood flow profile and its modification factors, red blood cells (RBCs) and hematocrit are considered in the blood flow. Besides, the influences of the constitutional material gradient scale, blood flow, internal pressure, structural damping coefficient, viscous fluid substrate and various boundary conditions on the natural frequencies and critical buckling velocities are studied. It is revealed that as the hematocrit, fluid viscosity of substrate, internal pressure and mass ratio increase, the natural frequencies and critical buckling velocities decrease. Furthermore, the results indicated that the strain gradient theory predicts the highest natural frequencies and critical buckling velocities among others. The results are compared with those available in the literature and good agreement has been observed.

In this paper, the mechanical vibration analysis of functionally graded (FG) nanoplate embedded in visco Pasternak foundation incorporating magnet and thermal effects is investigated. It is supposed that a uniform radial magnetic field acts on the top surface of the plate and the magnetic permeability coefficient of the plate along its thickness are assumed to vary according to the volume distribution function. The effect of in-plane pre-load, viscoelastic foundation, magnetic field and temperature change is studied on the vibration frequencies of functionally graded annular and circular nanoplate. Two different size dependent theories also are employed to obtain the vibration frequencies of the FG circular and annular nanoplate. It is assumed that a power-law model is adopted to describe the variation of functionally graded (FG) material properties. The FG circular and annular nanoplate is coupled by an enclosing viscoelastic medium which is simulated as a visco Pasternak foundation. The governing equation is derived for FG circular and annular nanoplate using the modified strain gradient theory (MSGT) and the modified couple stress theory (MCST). The differential quadrature method (DQM) and the Galerkin method (GM) are utilized to solve the governing equation to obtain the frequency vibration of FG circular and annular nanoplate. Subsequently, the results are compared with valid results reported in the literature. The effects of the size dependent, the in-plane pre-load, the temperature change, the magnetic field, the power index parameter, the elastic medium and the boundary conditions on the natural frequencies are scrutinized. According to the results, the application of radial magnetic field to the top surface of plate gives rise to change the state of stresses in both tangential and radial direction as well as the natural frequency. Also, The temperature changes play significant role in the mechanical analysis of FG annular and circular nanoplate. This study can be useful to product the sensors and devices at the nanoscale with considering the thermally and magnetically vibration properties of the nanoplate.

In this study, the vibration behavior of functional graded (FG) circular and annular nanoplate embedded in a Visco-Pasternak foundation and coupled with temperature change is studied. The effect of in-plane pre-load and temperature change are investigated on the vibration frequencies of FG circular and annular nanoplate. To obtain the vibration frequencies of the FG circular and annular nanoplate, two different size dependent theories are utilized. The material properties of the FGM nanoplates are assumed to vary in the thickness direction and are estimated through the Mori–Tanaka homogenization technique. The FG circular and annular nanoplate is coupled by an enclosing viscoelastic medium which is simulated as a Visco- Pasternak foundation. By using the modified strain gradient theory (MSGT) and the modified couple stress theory (MCST), the governing equation is derived for FG circular and annular nanoplate. The differential quadrature method (DQM) and the Galerkin method (GM) are utilized to solve the governing equation to obtain the frequency vibration of FG circular and annular nanoplate. The results are subsequently compared with valid result reported in the literature. The effects of the size dependent, the in-plane pre-load, the temperature change, the power index parameter, the elastic medium and the boundary conditions on the natural frequencies are investigated. The results show that the size dependent parameter has an increasing effect on the vibration response of circular and annular nanoplate. The temperature change also play an important role in the mechanical behavior of the FG circular and annular nanoplate. The present analysis results can be used for the design of the next generation of nanodevices that make use of the thermal vibration properties of the nanoplate

Deflection analysis of a simply supported microbeam subjected to a concentrated load at the middle is investigated on the basis of a shear deformable beam theory and non-classical theory. Effects of shear deformation and small size are taken into consideration by hyperbolic shear deformable beam theory and modified strain gradient theory, respectively. The governing differential equations and corresponding boundary conditions are obtained by implementing minimum total potential energy principle. Navier-type solution is employed to achieve an analytical solution for deflections of simply supported homogeneous microbeams. The effects of shear deformation, material length scale parameter and slenderness ratio on the bending response of microbeams are investigated in detail.

In this paper, thermal effects in nonlinear buckling analysis of micro beams is investigated. Modified strain gradient theory with nonlinear von-Karman strain displacement relations and small scale parameters are used to derive the buckling behavior of micro beams. The Poisson’s effect is included and its significance is demonstrated. Buckling behavior for two different cases: 1) immovable axial boundary condition 2) movable axial boundary condition, are studied and for each one the results for hinged-hinged and clamped-clamped beams are presented. The analysis shows that modified strain gradient theory leads to a higher critical buckling load in comparison with the classical and couple- stress theories. The results are verified using previous related works.