Hygrothermal analysis of heterogeneous piezoelectric elastic cylinders

The analytical solutions of hygrothermal effects in heterogeneous piezoelectric solid and hollow cylinders are obtained. The interaction of electric displacement, electric potentials, and elastic deformations is discussed. The present cylinder is subjected to a mechanical load at its lateral surfaces as well as an electric potential. The displacement, stresses and electric potentials in the heterogeneous piezoelectric cylinders are determined. The material properties coefficients of the present cylinder are assumed to be changed in the radial direction. The hygrothermoelastic responses of piezoelectric heterogeneous hollow and solid circular cylinders are presented. Numerical application examples for both cylinders are displayed. The significant of influence of material inhomogeneity, initial temperature, final moisture, and the pressure load and electric potential ratios are investigated. Suitable discussions and conclusions are presented

Nonlocal thermoelastic vibrations for variable thermal conductivity nanobeams due to harmonically varying heat

This article constructs a new model of nonlocal thermoelasticity beam theory with phase-lags considering the thermal conductivity to be variable. A nanobeam subjected to a harmonically varying heat is considered. The nonlocal theories of coupled thermoelasticity and generalized thermoelasticity with one relaxation time can be extracted as limited and special cases of the present model. The effects of the variable thermal conductivity parameter, the nonlocal parameter, the phase-lags and the angular frequency of thermal vibration on the lateral vibration, the temperature, the displacement, and the bending moment of the nanobeam are investigated

Torsional Dynamic Response of a Carbon Nanotube Embedded in Visco-Pasternak’s Medium

The torsional dynamics of carbon nanotubes embedded in viscoelastic medium are presented by using the nonlocal elasticity theory. The medium is considered as a foundation model which characterized by the linear Winkler’s modulus, Pasternak’s (shear) foundation modulus and the damping coefficient. The governing torsional equation is obtained and solved for nanotubes subjected to various boundary conditions and stated under different loads. The effects of some parameters like nonlocal parameter, nanotube length, Winkler’s modulus, and damping coefficient on the angular displacement of the nanotube are investigated in detail. The angular displacements are very sensitive to all parameters, especially the inclusion of the viscous damping foundation. Present results can be useful in design of future nano composites, nano electromechanical systems like nano position sensors and linear servomotors. Sample angular displacements are tabulated and plotted for sensing the effect of all used parameters and to investigate the visco-Pasternak’s parameters for future comparisons

Two-Dimensional Coupled Solution for Thermoelastic Beams via Generalized Dual-Phase-Lags Model

The generalized thermoelastic problem of a thick-walled simply-supported beam subjected to different applied heat source and mechanical loads at its surfaces is studied. The thermoelastic coupling differential equations of motion of the beam are established. The generalized thermoelasticity based on the dual-phase-lags (DPLs) theory is considered to treat this problem. An exact 2-D coupled solution is presented to deduce analytical expressions for the temperature, displacements and stresses. The time-harmonic motion behavior as well as the thermal and mechanical conditions at the bounded faces of the beam is used for this purpose. The effect of the DPLs on the field quantities against the axial and normal directions of the beam under thermomechanical loads is discussed. Final investigations to various thermoelastic models are made

Free vibration analysis of doubly convex/concave functionally graded sandwich beams

This paper presents the highly accurate analytical investigation of the natural frequencies for doubly convex/concave sandwich beams with simply-supported or clamped-supported boundary conditions. The present sandwich beam is made of a functionally graded material composed of metal and ceramic. The properties are graded in the thickness direction of the two faces according to a volume fraction power-law distribution. The bottom surface of the bottom face and the top surface of the top face are both metal-rich material. The core is made of a fully ceramic material. The thickness of the sandwich beam varies along its length according to a quadratic-law distribution. Two types of configuration with doubly convex and doubly concave thickness variations are presented. The governing equation and boundary conditions are derived using the dynamic version of the principle of minimum of the total energy. The objective is to study the natural frequencies, the influence of constituent volume fractions and the effect of configurations of the constituent materials on the frequencies. Natural vibration frequencies of sandwich beams versus many parameters are graphically presented and remarking conclusions are made

Axiomatic/asymptotic evaluation of multilayered plate theories by using single and multi-points error criteria

AbstractThis paper deals with refined theories for multilayered composites plates. Layer-Wise (LW) and Equivalent Single Layer (ESL) theories are evaluated by means of axiomatic–asymptotic approach. Theories with forth order displacement fields in the thickness layer/plate direction z are implemented by referring to the Unified Formulation by Carrera. The effectiveness of each term of the made expansion is evaluated by comparing the related theories with a reference solution. As a result a reduced model is obtained which preserve the accuracy of the full-model (model that include the whole terms of the z-expansion) but it removes the not-significant terms in the same expansion (those terms that do no improve the results according to a given error criteria). Various single-point and multi-point error criteria have been analyzed and compared in order to establish such an effectiveness: error localized in an assigned point along z, error localized at each interface, error located at the z-value corresponding to the maximum value of the considered variables, etc. Applications are given in case of closed form solutions of orthotropic cross-ply, rectangular, simply supported plates loaded by bisinusoidal distribution of transverse pressure. Symmetrically and unsymmetrical laminated cases are considered along with sandwich plates. It is found the reduced model is strongly influenced by the used localized error and that in same case the reduced model which is obtained by of single point criteria can be very much improved by the use of multi-point criteria

Even and Uneven Porosities on Rotating Functionally Graded ‎Variable-thickness Annular Disks with Magneto-electro-thermo-‎mechanical Loadings

This paper investigates the porosity effect on rotating functionally graded piezoelectric (FGP) variable-thickness annular disk. Even and uneven porosity distributions for the disk are approximated. The porous annular disk is subjected to the influence of electromagnetic, thermal, and mechanical loadings. Material coefficients are graded and described as a power law in the radial direction of the annular rotating disk. The resulting differential equation with boundary conditions is solved using the semi-analytical technique. Two cases are studied for the porous annular disk, circular disk, and mounted disk. The effectiveness of the porosity factor and grading index on the temperature, stresses, and displacement are reported. Comparisons between non-porous and porous annular disks for even and uneven porosity are executed and discussed. The obtained results are presented to conclude the important role of porosity on the rotating variable-thickness annular disk for the purpose of engineering mechanical design

Bending of symmetric cross-ply multilayered plates in hygrothermal environments

The bending analysis of symmetric cross-ply laminated plates in a hygrothermal environment is presented. The sinusoidal shear deformation plate theory is used for this purpose. It enables the trial and testing of different through-the-thickness transverse shear-deformation distributions and, among them, strain distributions that do not involve the undesirable implications of the transverse shear correction factors. The governing differential equations for the bending of laminated plates are obtained using various plate theories. Displacement functions that identically satisfy boundary conditions are used to reduce the governing equations to a set of coupled ordinary differential equations with variable coefficients. Numerical results for deflection and stresses are presented. The effect of different types of sinusoidal hygrothermal/thermal loadings is investigated. The influence various parameters such as material anisotropy, aspect ratio, side-to-thickness ratio, thermal expansion coefficients ratio and stacking sequence on the hygrothermally induced response is also investigated. A concluding remark is made

Two-temperature dual-phase-lags theory in a thermoelastic solid half-space due to an inclined load

This article addresses the thermoelastic interaction due to inclined load on a homogeneous isotropic half-space in context of two-temperature generalized theory of thermoelasticity with dual-phase-lags. It is assumed that the inclined load is a linear combination of both normal and tangential loads. The governing equations are solved by using the normal mode analysis. The variations of the displacement, stress, conductive temperature, and thermodynamic temperature distributions with the horizontal distance have been shown graphically. Results of some earlier workers have also been deduced from the present investigation as special cases. Some comparisons are graphically presented to estimate the effects of the two-temperature parameter, the dual-phase-lags parameters and the inclination angle. It is noticed that there is a significant difference in the values of the studied fields for different value of the angle of inclination. The method presented here maybe applicable to a wide range of problems in thermodynamics and thermoelasticity