Thermoelastic Damping in Auxetic Plate

The paper deals with the thermoelastic damping in a rectangular auxetic plate during its free and forced vibrations.Contrary to existing descriptions the relaxation properties of the thermal field as well as the negative material(auxetic-material of negative Poisson′s ratio)properties are taken into considerations.

THERMOELASTIC DAMPING IN A MICRO-BEAM RESONATOR TUNABLE WITH PIEZOELECTRIC LAYERS

In this paper,thermoelastic damping （TED） in a micro-beam resonator with a pair of piezoelectric layers bonded on its upper and lower surfaces is investigated.Equation of motion is derived and the thermoelasticity equation is governed using two dimensional non-Fourier heat conduction model based on continuum theory frame.Applying Galerkin discretization method and complex-frequency approach to solve the equations of coupled thermoelasticity,we study TED of a clamped-clamped micro-beam resonator.The presented results demonstrate that thickness of the piezoelectric layers and application of DC voltage to them can affect the TED ratio and the critical thickness value of the resonator.

Thermoelastic Damping of Functionally Graded Material Micro-Beam Resonators Based on the Modified Couple Stress Theory

Thermoelastic damping(TED)is one of the main internal energy dissipation mechanisms in micro/nano-resonators.Accurate evaluation of TED is important in the design of micro-electromechanical systems and nano-electromechanical systems.In this paper,a theoretical analysis on the TED in functionally graded material(FGM)micro-beam resonators is presented.Equations of motion and the heat conduction equation governing the thermodynamic coupling free vibration of non-homogenous micro-beams are established based on the Euler Bernoulli beam theory associated with the modified couple stress theory.Material properties of the FGM micro-beam are assumed to change in the depth direction as power-law functions.The layer-wise homogenization method is used for solving the heat conduction equation.By using the mathematical similarity of eigenvalue problem between the FGM beam and the reference homogeneous one,the complex natural frequency including TED is expressed in terms of the natural frequency of the isothermal homogenous beam.In the presented numerical results,influences of various characteristic parameters,such as beam thickness,material gradient index,structure size,vibration mode and boundary conditions,on TED are examined in detail.It shows that TED decreases with the increases in the values of length scale parameters because the latter lead to the increase in structural stiffness.

Surface and Nonlocal Effects on the Thermoelastic Damping in Axisymmetric Vibration of Circular Graphene Nanoresonators

In nanoresonators,thermoelastic damping(TED)is a primary energy dissipation mechanism.As a result,when designing nanoresonators,it is critical to limit this type of dissipation.This paper investigates the nonlocal TED of circular single-layered graphene sheet(SLGS)nanoresonators in axisymmetric out-of-plane vibration utilizing the generalized dual-phase-lag thermoelasticity theory.The nonlocal elasticity and Gurtin-Murdoch surface elasticity theories are employed to capture the small-scale and surface energy effects,respectively.By incorporating these effects into the model,the non-classical equations of the coupled thermoelastic problem are first obtained and then an analytical expression is introduced to predict TED in circular nanoplates.Moreover,the results obtained herein are validated by those of the classical continuum theory which can be found in the open literature.The influences of the aspect ratio,surface elastic modulus,surface residual stress and nonlocal parameter on TED of circular SLGS nanoresonators are investigated using numerical data.The calculated results show the significance of surface and nonlocal effects in nanoplate TED continuum modeling.