Showing papers on "Thermoelastic damping published in 2015"
TL;DR: In this article, the model of generalized thermoelasticity proposed by dual phase lag (DPL) was applied to study the thermo-elastic interactions in an infinite fiber-reinforced anisotropic medium with a circular hole.
Abstract: The model of generalized thermoelasticity proposed by dual phase lag (DPL), is applied to study the thermoelastic interactions in an infinite fiber-reinforced anisotropic medium with a circular hole. A decaying with time thermal field on the boundary of the hole, which is stress free, causes the thermoelastic interactions. The solutions for displacement, temperature, and stresses are obtained with the help of the finite element procedure. The effects of the reinforcement on temperature, stress, and displacement are studied. The exact solution in the case of isotropic medium is discussed explicitly. The accuracy of the finite element method validated by comparing between the finite element and exact solutions for absence the reinforcement.
120 citations
TL;DR: In this paper, a planar chiral lattice structure with Poisson's ratio approaching -1 is presented for controlled thermal expansion, which can be arbitrarily large positive or negative.
Abstract: Lattices of controlled thermal expansion are presented based on planar chiral lattice structure with Poisson’s ratio approaching -1. Thermal expansion values can be arbitrarily large positive or negative. A lattice was fabricated from bimetallic strips and the properties analyzed and studied experimentally. The eective thermal expansion coecient of the lattice is about = 3:5 10 4 K 1 . This is much larger in magnitude than that of constituent metals. Nodes were observed to rotate as temperature was changed corresponding to a Cosserat thermoelastic solid.
113 citations
TL;DR: In this paper, the performance of a single-stage cycle with NiTi alloy was evaluated based on a dynamic model developed in this study, and it was found that the system COP was 1.7 for a baseline case considering both driving motor and parasitic pump power consumptions, while COP ranged from 5.2 to 7.7 when estimated with future improvements.
Abstract: To avoid global warming potential gases emission from vapor compression air-conditioners and water chillers, alternative cooling technologies have recently garnered more and more attentions. Thermoelastic cooling is among one of the alternative candidates, and have demonstrated promising performance improvement potential on the material level. However, a thermoelastic cooling system integrated with heat transfer fluid loops have not been studied yet. This paper intends to bridge such a gap by introducing the single-stage cycle design options at the beginning. An analytical coefficient of performance (COP) equation was then derived for one of the options using reverse Brayton cycle design. The equation provides physical insights on how the system performance behaves under different conditions. The performance of the same thermoelastic cooling cycle using NiTi alloy was then evaluated based on a dynamic model developed in this study. It was found that the system COP was 1.7 for a baseline case considering both driving motor and parasitic pump power consumptions, while COP ranged from 5.2 to 7.7 when estimated with future improvements.
108 citations
TL;DR: In this paper, a few novel design options aiming to reduce the cyclic loss were proposed, and a multi-objective optimization problem was formulated and solved using the genetic algorithm to maximize the system capacity and coefficient of performance (COP).
Abstract: Thermoelastic cooling is a recently proposed, novel solid-state cooling technology. It has the benefit of not using high global warming potential (GWP) refrigerants which are used in vapor compression cycles (VCCs). Performance enhancements on a thermoelastic cooling prototype were investigated. A few novel design options aiming to reduce the cyclic loss were proposed. It was found that the maximum temperature lift increased from 6.6 K to 27.8 K when applying the proposed novel designs, corresponding to 0–152 W cooling capacity enhancement evaluated under 10 K water–water system temperature lift. In addition, a multi-objective optimization problem was formulated and solved using the genetic algorithm to maximize the system capacity and coefficient of performance (COP). With all the novel designs, the optimization could further enhance 31% COP, or 21% cooling capacity, corresponding to COP of 4.1 or 184 W maximum cooling capacity.
84 citations
TL;DR: In this article, the problem of fractional order thermoelastic interaction in a material placed in a magnetic field and subjected to a moving plane of heat source was considered and the basic equations have been written in the form of a vector-matrix differential equation in the Laplace transform domain, which is then solved by an eigenvalue approach.
76 citations
TL;DR: In this article, the authors studied a problem in fractional order theory of thermoelastic diffusion in an infinite medium with a spherical cavity at an elevated temperature field arising out of a ramp-type heating and loading bounding surface of the cavity.
76 citations
TL;DR: In this paper, the photoacoustic signals are predicted based on the successive resolution of a thermal diffusion problem and a thermo-elastic problem, taking into account the finite size of the gold nanosphere, thermoelastic and elastic properties of both water and gold, and the temperature dependence of the thermal expansion coefficient of water.
Abstract: We investigate theoretically the photoacoustic generation by a gold nanosphere in water in the thermoelastic regime. Specifically, we consider the long-pulse illumination regime, in which the time for electron-phonon thermalization can be neglected and photoacoustic wave generation arises solely from the thermoelastic stress caused by the temperature increase of the nanosphere or its liquid environment. Photoacoustic signals are predicted based on the successive resolution of a thermal diffusion problem and a thermoelastic problem, taking into account the finite size of the gold nanosphere, thermoelastic and elastic properties of both water and gold, and the temperature dependence of the thermal expansion coefficient of water. For sufficiently high illumination fluences, this temperature dependence yields a nonlinear relationship between the photoacoustic amplitude and the fluence. For nanosecond pulses in the linear regime, we show that more than $90%$ of the emitted photoacoustic energy is generated in water, and the thickness of the generating layer around the particle scales close to the square root of the pulse duration. The amplitude of the photoacoustic wave in the linear regime is accurately predicted by the point-absorber model introduced by Calasso et al. [Phys. Rev. Lett. 86, 3550 (2001)], but our results demonstrate that this model significantly overestimates the amplitude of photoacoustic waves in the nonlinear regime. We therefore provide quantitative estimates of a critical energy, defined as the absorbed energy required such that the nonlinear contribution is equal to that of the linear contribution. Our results suggest that the critical energy scales as the volume of water over which heat diffuses during the illumination pulse. Moreover, thermal nonlinearity is shown to be expected only for sufficiently high ultrasound frequency. Finally, we show that the relationship between the photoacoustic amplitude and the equilibrium temperature at sufficiently high fluence reflects the thermal diffusion at the nanoscale around the gold nanosphere.
74 citations
TL;DR: In this paper, the dispersion relations for the existence of various types of possible modes of vibrations in the considered hollow sphere are derived and the numerical results have been presented graphically in respect of natural frequencies, thermoelastic damping, and frequency shift.
Abstract: For a free vibration problem of a thermoelastic hollow sphere into the context of the generalized thermoelasticity theory with one relaxation time, exact analytic solutions are obtained with the use of eigenvalue approach. Both the inner and outer curved surfaces of the sphere are considered stress-free and isothermal surfaces. The dispersion relations for the existence of various types of possible modes of vibrations in the considered hollow sphere are derived. The numerical results have been presented graphically in respect of natural frequencies, thermoelastic damping, and frequency shift.
72 citations
TL;DR: In this paper, measurements from a two-beam structure with several bolted interfaces in order to characterize the nonlinear damping introduced by the joints are presented, which is attributed to linear viscous behavior of the material and/or damping provided by the support structure.
Abstract: Measurements are presented from a two-beam structure with several bolted interfaces in order to characterize the nonlinear damping introduced by the joints. The measurements (all at force levels below macroslip) reveal that each underlying mode of the structure is well approximated by a single degree-of-freedom (SDOF) system with a nonlinear mechanical joint. At low enough force levels, the measurements show dissipation that scales as the second power of the applied force, agreeing with theory for a linear viscously damped system. This is attributed to linear viscous behavior of the material and/or damping provided by the support structure. At larger force levels, the damping is observed to behave nonlinearly, suggesting that damping from the mechanical joints is dominant. A model is presented that captures these effects, consisting of a spring and viscous damping element in parallel with a four-parameter Iwan model. As a result, the parameters of this model are identified for each mode of the structure and comparisons suggest that the model captures the stiffness and damping accurately over a range of forcing levels.
69 citations
TL;DR: In this paper, the authors proposed a systematic micromechanical modeling scheme in conjunction with a new interphase model to determine the coefficients of thermal expansion (CTEs) of a nano-tailored composite.
Abstract: Owing to their remarkable thermoelastic and scale-dependent physical properties, carbon nanotubes (CNTs) have emerged as promising reinforcements to enhance the thermomechanical response of nano-tailored composite materials. Two fundamental aspects influencing the thermoelastic response of a nano-tailored composite are investigated herein; namely, CNT waviness and the existence of an interphase between a CNT and the polymer matrix. We propose a systematic micromechanical modelling scheme in conjunction with a new interphase model to determine the coefficients of thermal expansion (CTEs) of a nano-tailored composite. The proposed modelling approach has been applied to a case study involving the need to determine the effective CTEs of a novel nano-tailored composite–fuzzy carbon fiber heat exchanger. The results reveal that (i) the interphase between a CNT and the surrounding polymer matrix plays a crucial role in the modelling of the thermoelastic properties of the CNT-based composite, (ii) planar orientation of CNT waviness has a significant influence on the effective CTEs of the hybrid nano-tailored composite, and (iii) for the particular planar orientation of CNT waviness and the value of CNT wave frequency, the effective CTEs of the hybrid nano-tailored composite become zero, making the nanocomposite a “super-insulator”.
69 citations
TL;DR: It is theoretically and experimentally demonstrated that phonon-electron interactions, under appropriate conditions, can result in a significant acoustic gain manifested as an improved quality factor (Q) in PS-BAW resonators.
Abstract: This work presents the first comprehensive investigation of phonon-electron interactions in bulk acoustic standing wave (BAW) resonators made from piezoelectric semiconductor (PS) materials. We show that these interactions constitute a significant energy loss mechanism and can set practical loss limits lower than anharmonic phonon scattering limits or thermoelastic damping limits. Secondly, we theoretically and experimentally demonstrate that phonon-electron interactions, under appropriate conditions, can result in a significant acoustic gain manifested as an improved quality factor (Q). Measurements on GaN resonators are consistent with the presented interaction model and demonstrate up to 35% dynamic improvement in Q. The strong dependencies of electron-mediated acoustic loss/gain on resonance frequency and material properties are investigated. Piezoelectric semiconductors are an extremely important class of electromechanical materials, and this work provides crucial insights for material choice, material properties, and device design to achieve low-loss PS-BAW resonators along with the unprecedented ability to dynamically tune resonator Q.
TL;DR: In this article, the problem of two-temperature generalized thermoelastic thin strip is investigated in the context of Green and Lindsay theory, and a particular type of moving heuristic is proposed.
Abstract: The problem of two-temperature generalized thermoelastic thin slim strip is investigated in the context of Green and Lindsay theory. As an application of the problem, a particular type of moving he...
TL;DR: In this article, the authors describe the potential of off-line thermographic signal processing by means of lock-in correlation algorithms, in order to implement structural health monitoring and stress analysis techniques.
Abstract: This paper describes the potential of off-line thermographic signal processing by means of Lock-In Correlation algorithms, in order to implement structural health monitoring and stress analysis techniques. Thermal datasets acquired by infrared thermocameras are locked-in and correlated numerically with opportune reference signals, and amplitude and phase values of various harmonics retrieved by means of a Fast Fourier Transform and time averaging based filtering. This information is then processed for NDT defect probing and for evaluating the Thermoelastic Effect induced temperature changes. Two case studies in particular are discussed, implementing the proposed signal lock-in processing: a Thermoelastic Stress Analysis of a Brazilian disc under cyclic compression, and NDT of a delaminated polymer matrix composite panel. The NDT case study evidences the ability of the lock-in algorithm to analyse the response of the component to multi-frequency modulated heat waves, while both case studies demonstrate the potentials of the off-line signal treatment to enable low cost thermal setups.
TL;DR: In this paper, the authors construct complete, quantitative, and predictive models with finite-element methods for the intrinsic energy dissipation mechanisms in MEMS resonators using full anisotropic representation of crystalline silicon and the temperature dependence of all parameters.
Abstract: The quality factor of a resonator represents the decay of vibrational energy over time, and is directly related to the frequency response and other key parameters that determine performance of inertial sensors and oscillators. Accurate prediction of the quality factor is essential for designing high-performance microelectromechanical (MEMS) devices. Several energy dissipation mechanisms contribute to the quality factor. Due to computational complexity, highly simplified models for the dominant dissipation mechanism, such as Zener’s model for thermoelastic dissipation (TED), are often employed. However, the intuition provided by these models is inadequate to predict the quality factor of more complex designs and can be highly misleading. In this paper, we construct complete, quantitative, and predictive models with finite-element methods for the intrinsic energy dissipation mechanisms in MEMS resonators using full anisotropic representation of crystalline silicon and the temperature dependence of all parameters. We find that TED is often a more significant source of damping than has been assumed, because of the previously neglected role of crystalline anisotropy and small geometric features, such as etch release holes—all of which can now be included in practical models. We show that these models, along with simpler scaling models for extrinsic dissipation mechanisms, explain measurements of quality factor in diverse sets of MEMS resonators with unprecedented accuracy. [2014-0106]
TL;DR: In this paper, a meshless computing environment based on Local Radial Basis Function Collocation Method (LRBFCM) for homogeneous isotropic body in two dimensions is proposed.
Abstract: Purpose – The purpose of this paper is to upgrade our previous developments of Local Radial Basis Function Collocation Method (LRBFCM) for heat transfer, fluid flow and electromagnetic problems to thermoelastic problems and to study its numerical performance with the aim to build a multiphysics meshless computing environment based on LRBFCM. Design/methodology/approach – Linear thermoelastic problems for homogenous isotropic body in two dimensions are considered. The stationary stress equilibrium equation is written in terms of deformation field. The domain and boundary can be discretized with arbitrary positioned nodes where the solution is sought. Each of the nodes has its influence domain, encompassing at least six neighboring nodes. The unknown displacement field is collocated on local influence domain nodes with shape functions that consist of a linear combination of multiquadric radial basis functions and monomials. The boundary conditions are analytically satisfied on the influence domains which co...
TL;DR: It is shown that engineering the dissipation allows one to control the dispersion and, conversely, engineering the dispersive affects the degree of dissipation, and increases in modal dissipation enhancement (metadamping) to be quantified as the type of damping transitions from viscoelastic to viscous.
Abstract: The dispersive behavior of phononic crystals and locally resonant metamaterials is influenced by the type and degree of damping in the unit cell. Dissipation arising from viscoelastic damping is influenced by the past history of motion because the elastic component of the damping mechanism adds a storage capacity. Following a state-space framework, a Bloch eigenvalue problem incorporating general viscoelastic damping based on the Zener model is constructed. In this approach, the conventional Kelvin-Voigt viscous-damping model is recovered as a special case. In a continuous fashion, the influence of the elastic component of the damping mechanism on the band structure of both a phononic crystal and a metamaterial is examined. While viscous damping generally narrows a band gap, the hereditary nature of the viscoelastic conditions reverses this behavior. In the limit of vanishing heredity, the transition between the two regimes is analyzed. The presented theory also allows increases in modal dissipation enhancement (metadamping) to be quantified as the type of damping transitions from viscoelastic to viscous. In conclusion, it is shown that engineering the dissipation allows one to control the dispersion (large versus small band gaps) and, conversely, engineering the dispersion affects the degree of dissipation (high or low metadamping).
TL;DR: In this paper, a modified couple stress theory was used to investigate the size-dependent thermoelastic damping in microplate resonators, and the results showed that the size effect has significant impact on the thermo-elastic vibration damping when the plate thickness has a similar value to the material length scale parameter.
Abstract: The dynamic properties and behaviors of microplate resonators have been experimentally shown to be size dependent. The thermoelastic damping plays an important role on the inherent energy dissipation of the microplate resonators. Based on the modified couple stress theory, the size-dependent thermoelastic damping in microplate resonators is investigated. The governing equation of motion is derived by using Hamilton principle. The thermoelastic damping is obtained via solving the heat diffusion equation. The presented results of thermoelastic frequencies have a good agreement with the reported values. The result shows that the size effect has significant impact on the thermoelastic damping when the plate thickness has a similar value to the material length scale parameter. It demonstrates that the thermoelastic damping can be suppressed and the quality factor can be enlarged as the material length scale parameter increases. The quality factor is improved by several orders of magnitude as the representative temperature drops from 500 to 80 K. However, the size-dependent quality factor at 400 K is larger than that at 293 K when the thickness of the plate has a similar value of the material length scale parameter. In addition, the differences among different plate materials are small, as the plate thickness is less than the characteristic thickness. However, those gaps become larger when the characteristic thickness is overtaken. [2013-0336]
TL;DR: In this paper, a nonlinear mathematical model of doubly curved shell panels is developed first time based on higher-order shear deformation theory and Green-Lagrange geometrical nonlinearity.
TL;DR: In this paper, the effect of axisymmetric heat supply on the phenomena of diffusion in a thermoelastic thick plate of infinite extent and finite thickness is discussed within the context of the theory of generalized thermo-elastic diffusion with one relaxation time.
Abstract: The main objective of the present paper is to study the effect of axisymmetric heat supply on the phenomena of diffusion in a thermoelastic thick plate of infinite extent and finite thickness. The problem is discussed within the context of the theory of generalized thermoelastic diffusion with one relaxation time. The upper and the lower surfaces of the thick plate are traction free and subjected to an axisymmetric heat supply. The solution is found by using integral transform technique and a direct approach without the use of potential functions. Inversion of Laplace transforms is done by employing a numerical scheme. The mathematical model is prepared for a Copper material plate, and the numerical results are discussed and represented graphically.
TL;DR: In this paper, a normal mode method is proposed to analyze the problem and obtain numerical solutions for the displacement components, stresses, temperature distribution and change in the volume fraction field in the dual phase lag model.
Abstract: The aim of the present study is concerned with the thermal loading due to laser pulse on thermoelastic medium with voids in the dual phase lag model (DPL). The material is a homogeneous isotropic elastic half-space and heated by a non-Gaussian laser beam with pulse duration of 8 ps. A normal mode method is proposed to analyze the problem and obtain numerical solutions for the displacement components, stresses, temperature distribution and change in the volume fraction field. The results of the physical quantities have been illustrated graphically by comparison between (DPL) and Lord-Schulman (L–S) theory for two values of time and for different values of a phase-lag of heat flux τ q .
TL;DR: In this paper, a quasi-3D hybrid type higher order shear deformation theory (HSDT) was used for the analysis of functionally graded sandwich plates, where the nonlinear term of the temperature field is modeled in such a way that can be different from the shape functions of the displacement field.
Abstract: This paper presents a thermoelastic bending analysis of functionally graded sandwich plates by using a new quasi-3D hybrid type higher order shear deformation theory (HSDT). The mathematical model contains only 5 unknowns as the first order shear deformation theory (FSDT). The nonlinear term of the temperature field is modeled in such way that can be different from the shape functions of the displacement field. The mechanical properties of functionally graded layers of the plate are assumed to vary in the thickness direction according to a power law distribution. The governing equations for the thermoelastic bending analysis are obtained through the principle of virtual work and solved via Navier-type solution. Results reveal: (a) the good performance of the present generalized formulation; (b) the significant influence of the nonlinear temperature field on the displacements and stresses results. Consequently, discussion on nonlinear temperature field influences should be further considered in the literature.
TL;DR: In this article, the authors provided a comprehensive stability analysis of the Bresse system with Gurtin-Pipkin thermal laws and provided necessary and sufficient conditions for exponential stability in terms of the structural parameters of the problem.
TL;DR: In this paper, the thermomechanical properties of alpha-iron, and in particular its isothermal and adiabatic elastic constants, using first-principles total energy and lattice-dynamics calculations, minimizing the quasiharmonic vibrational free energy under finite strain deformations.
Abstract: We calculate the thermomechanical properties of alpha-iron, and in particular its isothermal and adiabatic elastic constants, using first-principles total-energy and lattice-dynamics calculations, minimizing the quasiharmonic vibrational free energy under finite strain deformations. Particular care is made in the fitting procedure for the static and temperature-dependent contributions to the free energy, in discussing error propagation for the two contributions separately, and in the verification and validation of pseudopotential and all-electron calculations. We find that the zero-temperature mechanical properties are sensitive to the details of the calculation strategy employed, and common semilocal exchange-correlation functionals provide only fair to good agreement with experimental elastic constants, while their temperature dependence is in excellent agreement with experiments in a wide range of temperature almost up to the Curie transition.
TL;DR: In this paper, a micromechanics-based multiscale model coupled with a thermo-elastic progressive damage model is developed to simulate the elastic and damage behavior of a plain weave C/SiC composite system under thermal and mechanical loading conditions.
TL;DR: In this article, a nonlocal Euler-Bernoulli beam model is established based on the theory of nonlocal elasticity and the small scale effect is taken into consideration in the former theory.
TL;DR: In this paper, an experimental study of the properties of a layered beam partially treated with a damping element based on a granular material is presented, where the beam structure comprises two aluminium face strips connected at the tip by a hermetic, elastic envelope, filled with bulk granules.
TL;DR: In this paper, a fractional order Lord & Shulman model of generalized thermoelasticity with voids subjected to a continuous heat sources in a plane area has been established using the Caputo fractional derivative and applied to solve a problem of determining the distributions of the temperature field, the change in volume fraction field, and the deformation and the stress field in an infinite elastic medium.
Abstract: In the present work, a fractional order Lord & Shulman model of generalized thermoelasticity with voids subjected to a continuous heat sources in a plane area has been established using the Caputo fractional derivative and applied to solve a problem of determining the distributions of the temperature field, the change in volume fraction field, the deformation and the stress field in an infinite elastic medium. The Laplace transform together with an eigenvalue approach technique is applied to find a closed form solution in the Laplace transform domain. The numerical inversions of the physical variables in the space-time domain are carried out by using the Zakian algorithm for the inversion of Laplace transform. Numerical results are shown graphically and the results obtained are analyzed .
TL;DR: In this article, the authors proposed a mathematical model for non-contacting face seal with a flexibly mounted rotor (FMR) in a turbomachine, which describes thermal deformation processes.
Abstract: Reduction of noise and vibrations is one of the major requirements put on operation of modern machines. It can be achieved by application of new materials. The ability to utilize them properly requires learning more about their mechanical properties. Vibration attenuation depends on material damping as an important factor. This paper presents the results of research in a carbon composite material focusing on its internal damping, on the measurement of the damping coefficients and on its implementation into mathematical models. The obtained results were used for investigation of suppressing lateral vibrations of a long homogeneous carbon composite bar oscillating in the resonance area. During the transient period and due to nonlinear effects, the harmonic time-varying loading excites the bar response consisting of a number of harmonic components. The specific damping capacity referred to several oscillation frequencies determined by measurement. The results were evaluated from the point of view of two simple damping theories — viscous and hysteretic. The experiments showed that internal damping of the investigated material could be considered as frequency independent. Therefore, in order to carry out simulations, the bar was represented in the computational model by an Euler beam constituted of Maxwell–Weichert theoretical material. A suitable setting of material constants enabled reaching a constant value of the damping parameters in the required frequency range. The investigated bar vibration is governed by the motion equation in which the internal damping forces depend not only on instantaneous magnitudes of the system’s kinematic parameters but also on their past history. Solution of the equations of motion was performed after its transformation into the state space in the time domain. Results of the computational simulations showed that material damping significantly reduced amplitude of the bar vibrations in the resonance area. The producers of composite materials usually provide material parameters allowing to solve various stationary problems (density, modulus of elasticity, yielding point, strength, etc.), but there is only little or almost no information concerning the data needed for carrying out dynamical or other time-dependent analyses such as internal damping coefficients, fatigue limit, etc. Therefore, determination of the hysteretic character of material damping of the investigated carbon composite material, measurement of its specific damping capacity and implementation of the frequency-independent damping into the computational model are the principal contributions of this article.