Thermoelastic Effect Research Articles

In-situ monitoring of rock slope destabilization with ambient seismic noise interferometry in southwest China

The damage evolving on rock slopes, including unstable mass failure events, is expected to be associated with a rigidity loss of geomaterials. Therefore, velocity changes (dv/v) inferred from ambient noise interferometry allow remotely assessing the damage state of the slope. However, the time scale and amplitude of the dv/v evolution associated with the slope destabilizations are not well known, and their detection and characterization require both high precision and high temporal resolution in dv/v. We herein report an in-situ one-year monitoring of the dv/v on the slow-moving Pubugou rock slope with a high temporal resolution up to 20-min by using two seismic stations in the mountainous region of Sichuan, China, where the slope is affected by both earthquakes and rainfall. The results confirm the feasibility of (1) detecting a possible precursor dv/v drop (−0.5%) ∼40 min before a slope destabilization; (2) characterizing the dv/v caused by the superimposed effects of moderate earthquakes and rainfall; and (3) quantifying the daily dv/v fluctuations of the slope caused by the environmental thermal forcing through thermoelastic effects. In addition, the measurement error and the detectable depth resolution of the dv/v are also addressed in this study. Finally, we suggest the high-resolution technique as a complementary means to be used for operational rock slope damage surveillance in the future.

Adhesive behavior between dissimilar materials subjected to thermo-elastic loadings with normal-tangential coupling effect

The temperature difference always exists between contacting objects in various thermal bonding technologies, where the adhesion strength is found to be very sensitive to the temperature. In this paper, the anisothermal adhesive contact between an elastic cylinder subjected to the external force with an inclined angle and an elastic substrate is investigated based on the non-slipping JKR model, where the coupling effect between the normal and tangential tractions within the contact region is taken into consideration. The stated problem is reduced to a system of coupled singular integral equations, which can be solved with the analytical function theory. The full analytical solutions of the oscillatory stress fields are obtained for the first time by taking the series expansion of the integrand induced by the thermoelastic effect, which is of substantial significance. The relationship between the contact size and the external loadings is established by virtue of the Griffith energy balance criterion. The difference between the oscillatory and non-oscillatory solutions of stress fields is discussed in detail. Numerical results demonstrate that the oscillatory solution cannot be well approximated by the corresponding non-oscillatory solution for the cases of large Dundurs’ index and external compressive force. Furthermore, it is found that both the thermoelastic effect and the inclined angle of the applied force have significant influences on the adhesive contact behaviors. The presence of temperature difference between contacting objects can either enhance or weaken the adhesion effect, which is related to the inclined angle of the external force. The results obtained from this paper may provide a new insight into the influence mechanism of the temperature on adhesion behaviors.

Nematic electron and phonon dynamics in SnS crystals

Tin sulfide (SnS) is one of the promising materials for the applications of optoelectronics and photovoltaics. This study determines the nematic dynamics of photoexcited electrons and phonons in SnS single crystals using polarization-dependent pump–probe spectroscopy at various temperatures. As well as the fast (0.21–1.38 ps) and slow (>5 ps) relaxation processes, a 36–41 GHz coherent acoustic phonon with a sound velocity of 4883 m/s that is generated by the thermoelastic effect is also observed in the transient reflectivity change (ΔR/R) spectra. Electrons and coherent acoustic phonons show significant in-plane anisotropy from 330 to 430 K due to strong electron–phonon coupling. However, this in-plane anisotropy weakens dramatically in the low-temperature (<330 K) and high-temperature (>430 K) phases. These results add to the knowledge about the anisotropy of electrons and coherent acoustic phonons that give SnS applications in photovoltaic or optoelectronic devices.

Flexural waves in thermoelastic higher-order shear micro-plate modelled by spatiotemporal fractional differential

An orthotropic higher-order shear micro-plate model is established with consideration the small-scale effect and the thermoelastic coupling effects to study the dispersion and attenuation of flexural waves in the present work. The nonlocal elasticity and the strain gradient elasticity are incorporated to lead the nonlocal strain gradient model to reflect the size effect. The generalized thermoelasticity (non-Fourier heat conduction) is introduced to reflect the history-dependent feature of heat conduction. Furthermore, the integer order derivatives are replaced by the fractional derivatives of Caputo-type to get a more refined model which can extend the range of application of model and provide more exquisite description of the spatial nonlocal behavior and temporal memory behavior at small scale. In addition, the nonlocal characteristic length and the memory characteristic length as new small scale parameters are first introduced in the present model to focus on describing the short-range nonlocal and the short-term memory behavior. A detailed parameter study is performed and the effects of nonlocal characteristic length, strain gradient characteristic length, the memory characteristic length and the spatiotemporal fractional order on the dispersion and attenuation of thermoelastic coupled flexural waves are discussed based on the numerical results.

A quantitative study on the thermomechanical coupling effect of elasticity and plasticity of polymethyl methacrylate

Quantitative study on the elastic and plastic thermomechanical coupling effect of solid materials has important theoretical significance for monitoring the deformation state and stability evaluation of engineering components. In this study, the sample is made of polymethyl methacrylate (PMMA), and uniaxial compression experiments are carried out. The sample experiences the elastic state and then the plastic state until the failure of the sample. The thermoelastic effect and thermoplastic effect in the deformation process of PMMA materials are monitored by infrared thermography and digital speckle system (DIC). That is, the relationship between the reversible elastic temperature change ΔTe and average stress change Δσm, and the relationship between the irreversible plastic temperature rise ΔTp and the dissipated energy ΔUp during the failure deformation process. The results show that when the sample is in the elastic regime, there is only elastic temperature change ΔTe inside the sample. When the sample enters the plastic deformation regime, the total temperature change ΔT includes elastic temperature change ΔTe and plastic temperature change ΔTp, and the temperature change has an obvious memory effect on the previous maximum load. When the previous maximum load exceeded, ΔTp increases rapidly. When the load P is removed, ΔTe disappears, and ΔTp remains. Combined with the theory of thermodynamics and solid mechanics, starting from the 3D stress state, the approximate linear incremental relationship between Te and σm, and the accurate exponential total quantity relationship are derived. The incremental relationship and the full relationship combined with thermodynamic theory and the energy conservation principle, the relationship between the overall plastic temperature rise ΔTp and local plastic temperature rise ΔTpmax of the sample and the energy dissipation value ΔUp experienced by the sample and the local dissipation specific energy Δup is obtained. The theoretical calculation results of ΔTe and ΔTp are in good agreement with the experimental results. The research results can provide a new method for monitoring and identifying the stress and deformation state of engineering components through the temperature field.

Thermoelastic damping analysis in nanobeam resonators considering thermal relaxation and surface effect based on the nonlocal strain gradient theory

With the extensive applications of the micro/nano-electro-mechanical systems, a great deal of attention has been paid to explore the influences of the arising size-dependent effect and surface effect on their performance. Along with these effects, the nonlocal elasticity, strain gradient theory, and surface elasticity theory were successively proposed. Moreover, it is inevitable for MEMS/NEMS to work in a variable temperature environment, correspondingly, the thermal-induced stress or deformation becomes another issue that needs serious concern. Thermoelastic damping (TED), as a main energy dissipation source, is a major challenge in designing higher-quality factor resonators. However, considering the thermoelastic coupling effect, the aforementioned theories are not capable enough to depict the thermoelastic performance of micro/nano-resonators. To amend this deficiency, based on nonlocal strain gradient theory, a new model for assessing the TED of nanobeam resonators by incorporating the thermal relaxation effect and the surface effect is developed. The corresponding governing equations for the Euler–Bernoulli microbeam resonator model are formulated, and then, solved by means of a complex frequency method. The influences of the nonlocal parameter, strain gradient coefficients, aspect ratio, surface stress and surface elasticity on the TED are examined and discussed in detail.

In-situ analysis of the elastic-plastic characteristics of high strength dual-phase steel

Modeling the elastic behavior of dual-phase steels is complex due to the strain dependency of Young's modulus and high elastic nonlinearity. Since it is assumed that reasons for this are to be found in microstructural behavior, microscopic in-situ analysis are necessary, but due to the overlap of the martensite and ferrite peaks, the evaluation of diffraction profiles is highly complex. Within this work, CR590Y980T (DP1000) is investigated in a continuous cyclic tensile and tension-compression test under synchrotron radiation at High Energy Material Science beamline P07 in Petra III, DESY. On basis of additional EBSD measurements, an evaluation approach is shown to analyze the dual-phase diffraction profiles in such a way that martensite and ferrite can be separated for three lattice planes. The origin of the specific elastic-plastic behavior of dual-phase steels in terms of onset of yielding, anelasticity or early re-yielding is analyzed on the basis of lattice strains and interphase stresses. For this, the time-synchronously measured micro data is correlated with the macro stress-strain relationship and thermoelastic effect. The results help to better understand strain-dependent elastic-plastic behavior of DP steels on a micro level and provide great potential to improve characterization and modeling in terms of springback prediction.

A three-dimensional investigation of the thermoelastic effect in an enhanced geothermal system reservoir

During heat extraction in enhanced geothermal system (EGS) reservoirs, thermal contraction is induced by cold fluid injection, resulting in thermoelastic deformation. The induced thermoelasticity can alter rock properties, including their fracture aperture and permeability; therefore, the thermoelastic effect is crucial in understanding EGS reservoir behaviour. Based on coupled thermo-hydro-mechanical (THM) processes extended in COMSOL Multiphysics to include the thermoelastic effect, this paper presents a three-dimensional (3D) numerical model of an EGS reservoir with a multiple planar fracture system to investigate the influence of thermoelasticity on reservoir thermal performance. The model is used to perform an in-depth analysis to determine the rate at which the thermoelastic effect develops during heat extraction in relation to a baseline THM model without thermoelasticity. After demonstrating that thermoelasticity influences the thermal performance of EGS reservoirs, the study is further extended to investigate the effect of injection temperature and Young's modulus on fracture aperture opening, reservoir impedance, thermal front propagation, and flow rate. The results show that thermoelasticity affects the long-term thermal performance of EGS reservoirs by reducing the energy extraction rate due to increased flow pathways. Due to high reservoir impedance, the thermoelastic effect appears to cause thermal short circuits (growth of rapidly cooling paths with high flow rates). The results suggest that thermoelasticity has a significant impact on system thermal performance for deep EGS reservoirs.

Effect of diffusion on acoustic deformation potential characterization through coherent acoustic phonon dynamics

Ultrafast spectroscopy of coherent acoustic phonon (CAP) dynamics has recently been proposed as a method to characterize acoustic deformation potential (ADP), a key standard to quantify carrier--acoustic phonon coupling in semiconductors. In this Letter, we illustrate the importance of addressing the diffusion effect in ADP characterization by this method, using Ge as the demonstration system. It is found that the ADP mechanism and the thermoelastic effect have comparable contributions to CAP generation in Ge. Due to the different dependences on pump photon energies, the roles of these two mechanisms were assessed by varying pump wavelengths, based on which the ADP coupling constant of Ge was obtained. The analysis reveals that the carrier diffusion has a considerable impact on the shape of the CAP wave packet and must be processed cautiously for the ADP characterization for Ge.

Miniature quartz tuning fork-based broad spectral coverage and high detectivity infrared spectroscopy

This paper reports a type of detector based on the thermoelastic effect of a miniature quartz tuning fork (mQTF) for infrared spectroscopy applications. Instead of using a pyroelectric infrared detector, a mQTF with a resonant frequency of ∼45 kHz was adopted as a detector for infrared light signal collection. To explore the capabilities of this technique, measurement of infrared absorption spectra of samples was conducted, and the effect of scattered light on the sensitivity was investigated. The experimental results indicate that the mQTF detector is sensitive to infrared radiation within a wide range of wavelengths, and packaging the mQTF could increase the sensitivity and signal-to-noise ratio (SNR) by 2.54, and 2.87 times, respectively. The infrared transmission spectrum of polystyrene (PS), polyethylene (PE) have been measured by the mQTF detector, and the experimental data show that the infrared characteristic absorption peaks appears in the same position as commercial pyroelectric detector. Finally, mid-infrared spectroscopy of acetone gas was measured by the mQTF with highprecision. It is worth noting that this is the first study of using the mQTF-based photodetector for gas phase infrared spectroscopy, the mQTF exhibits its cost-effectiveness, sensitivity, and broadband optical response advantages, could be used for qualitative analysis of components by the infrared spectrum.

Experimental Investigation of Factors Influencing the Determination of the Onset of Yielding by Temperature Measurement

The cooling of the material during elastic tensile loading is well known as the thermoelastic effect. It is already known that the temperature minimum at the elastic-plastic transition can be used for the determination of the onset of yielding. Conceivable parameters for this have already been presented and investigated. Within this study factors influencing the specimen temperature during tensile loading and unloading are experimentally analyzed to improve the determination approach and the understanding of it. Furthermore, the robustness and repeatability of the measurement and evaluation procedures are analyzed. Therefore, cyclic tensile tests with the mild steel DC06 and the high strength steel CR590Y980T (DP1000) are performed with four PT1000 sensors applied on the specimen. The temperature behavior during elastic loading, elastic-plastic elongation and elastic unloading is separately evaluated. Different strain rates are investigated to better understand the strain-dependent heat development and its influence on the temperature-dependent evaluation. In this way, correlations between strain rate and thermal conduction due to prevailing temperature differences are found and their influence on the temperature-based determination of the onset of yielding is analyzed. Therefore, the yield stress at temperature minimum YSTmin as well as an additional yield stress at zero plastic strain YS0 are evaluated for all experiment settings. In a comprehensive experimental study, the standard deviations are compared and thus conclusions can be drawn about the robustness of the determination methods.

Shock Wave Characterization Using Different Diameters of an Optoacoustic Carbon Nanotube Composite Transducer

Carbon nanotube–polymethyl siloxane (CNT-PDMS) composite transducers generate shock waves using optoacoustic technology. A thin layer of thermally conductive CNT and elastomeric polymer, PDMS, is applied on the concave surface of transparent polymethylmethacrylate (PMMA) to convert laser energy to acoustic energy using the thermoelastic effect of the composite transducer. The efficient conversion of laser energy requires an optimum utilization of the different properties of composite transducers. Among these properties, the diameter of composite transducers is a significant parameter. To practically verify and understand the effect of the diameter of composite transducers on the properties of shock waves, CNT-PDMS composite transducers with different diameters and focal lengths were constructed. Increases in the diameter of the composite transducer and input laser energy resulted in increased peak pressures of the shock waves. The maximum positive and negative pressures of the shock waves generated were 53 MPa and −25 MPa, respectively. This practically demonstrates that high peak amplitudes of shock waves can be achieved using larger transducers, which are suitable for practical applications in transcranial studies.

Changes in resonance frequency of rock columns due to thermoelastic effects on a daily scale: observations, modelling and insights to improve monitoring systems

Summary Slope instabilities, including prone-to-fall rock columns, are known to exhibit clear vibrational modes. The resonance frequencies of these modes can be tracked by seismic instrumentation, allowing the rock column's mechanical and structural properties to be monitored, as well as providing precursors of imminent irreversible failures. In previous studies, superficial thermoelastic effects were assumed to drive daily fluctuations in resonance frequencies, but no qualitative or quantitative evidence was provided. The results presented here corroborate this hypothesis and quantify the physical processes involved. We interpreted daily variations of resonance frequencies in the Les Arches study site (Vercors, French Prealps) using a thermo-mechanical finite-element model. Modelled fluctuations of the resonance frequencies over a day closely matched experimental observations, reproducing the daytime frequency increase of around 2 per cent. In addition, our model provides explanation of the various behaviours observed across study sites: the frequency response strongly depends on solar exposure, as well as the timing and intensity of both radiative and convective heat fluxes. We highlight acousto-elastic constants as key parameters of our semi-quantitative model, although they remain poorly constrained here. For future instrumentation, we therefore recommend the deployment of pyranometers on rocky sites to accurately invert these parameters over time, thus allowing rock fracturing to be quantitatively tracked by acousto-elastic monitoring.

In-situ analysis of the thermoelastic effect and its relation to the onset of yielding of low carbon steel

The thermoelastic effect indicates the dependency of temperature and volume change in the material and, due to the heat released during plastic deformation, a temperature minimum occurs in the region of the onset of yielding. An experimental setup is presented for the microscopic analysis of the thermoelastic effect, which allows high precision measurements of specimen. In-situ diffraction experiments were performed for a single phase low carbon steel HC260Y using synchrotron diffraction at the High Energy Material Science beamline P07 in Petra III, DESY. This allows a direct comparison of the onset of yielding by observing the evolution of lattice strains and dislocations densities with the specimen temperature in a continuous cyclic test having high measuring frequency and accuracy. Therefore, the lattice strains are evaluated based on the peak shift of several lattice planes and the dislocation density is estimated based on the micro strain due to peak broadening. The results prove existing assumptions about the relation between the thermoelastic effect and the onset of yielding and clearly qualify the temperature-based determination method for material characterization on a microstructural basis. The usefulness of the temperature elasticity parameters is shown exemplarily with the determination of loading moduli and compared to existing methods.

Thermoelastic coupling vibration analysis of precision coated TPU film

TPU (thermoplastic polyurethane) films are subjected to heating in production. As the temperature rises, thermal stress will be generated inside the TPU film. It causes defects, such as wrinkles and cracks, in the moving TPU film; therefore, it is of great significance to study the thermoelastic coupling effect of the moving TPU film in the printing process. To study the thermoelastic coupling vibration characteristics of the moving TPU film under the opposite edge tension, it includes combining the thermal conduction equation with temperature coupling term and the vibration differential equation with variable temperature effect to get the coupling equation. The differential quadrature method is used to discretize the vibration differential equation. The influence of the thermoelastic coupling coefficient, aspect ratio, and tension ratio on the vibration characteristics of the TPU film is studied.

Numerical simulation of deformation-induced temperature variations of a rubber ball under cyclic compression

The main objective of this study is to predict the temperature variation of a rubber ball under cyclic compression. The prediction scheme is composed of three parts: mechanical analysis, heat source identification and heat transfer analysis. In the mechanical analysis, a compressible hyper-viscoelastic model was employed to describe the mechanical behavior of rubber under cyclic compression, in which material constants were identified using experimental data. In the heat source identification, the heat sources caused by three effects, namely thermoelastic, entropic and viscous dissipation effects were evaluated based on a theoretical consideration. In the heat transfer analysis, the above-mentioned heat sources were used as input to calculate the time variation of the temperature field. The temperature variation inside and on the surface of the ball under both adiabatic and non-adiabatic conditions were discussed. In addition to that, the temperature amplitude and phase difference between temperature and displacement in the steady state were considered.

Thermoelastic effects in the contact mechanics of 1D+1D rough profiles

Rough contact mechanics is a challenging topic that has attracted the interest of many scientists in the past and recent years. Notwithstanding a large amount of literature on the topic, there is a lack of studies investigating the contact behaviour of rough elastic bodies exchanging heat at the interface.For this reason, we propose a deterministic model to investigate the thermoelastic contact of a linear elastic half-plane indented by a rigid rough punch.Surprisingly, an increase in the temperature difference between the contacting solids does not change the relationship between contact area and load as well as that between interfacial mean separation and load. However, the thermal expansion causes an increase in the force required to sustain the contact at a given penetration.In addition, thermal contact resistance (TCR) is predicted to be a decreasing function of the contact pressure in agreement with the trend suggested by experimental data available in the literature. On the contrary, the dependence on the temperature difference ΔT seems to be strictly related to the characteristics of the materials and, for the elastic case investigated in this work, TCR is found to be almost independent of ΔT.

Lamb wave based approach to the determination of acoustic material parameters

Abstract In this paper a measurement procedure to identify viscoelastic material parameters of plate-like samples using broadband ultrasonic waves is presented. Ultrasonic Lamb waves are excited via the thermoelastic effect using laser radiation and detected by a piezoelectric transducer. The resulting measurement data is transformed to yield information about multiple propagating Lamb waves as well as their attenuation. These results are compared to simulation results in an inverse procedure to identify the parameters of an elastic and a viscoelastic material model.

Phase Field Models for Thermal Fracturing and Their Variational Structures.

It is often observed that thermal stress enhances crack propagation in materials, and, conversely, crack propagation can contribute to temperature shifts in materials. In this study, we first consider the thermoelasticity model proposed by M. A. Biot and study its energy dissipation property. The Biot thermoelasticity model takes into account the following effects. Thermal expansion and contraction are caused by temperature changes, and, conversely, temperatures decrease in expanding areas but increase in contracting areas. In addition, we examine its thermomechanical properties through several numerical examples and observe that the stress near a singular point is enhanced by the thermoelastic effect. In the second part, we propose two crack propagation models under thermal stress by coupling a phase field model for crack propagation and the Biot thermoelasticity model and show their variational structures. In our numerical experiments, we investigate how thermal coupling affects the crack speed and shape. In particular, we observe that the lowest temperature appears near the crack tip, and the crack propagation is accelerated by the enhanced thermal stress.

Thermal Shear Waves Induced in Mesoscopic Liquids at Low Frequency Mechanical Deformation

Abstract We show that a confined viscous liquid emits a dynamic thermal response upon applying a low frequency (∼1 Hz) shear excitation. Hot and cold thermal waves are observed in situ at atmospheric pressure and room temperature, in a viscous liquid (polypropylene glycol) at various thicknesses ranging from 100 µm up to 340 µm, upon applying a mechanical oscillatory shear strain. The observed thermal effects, synchronous with the mechanical excitation, are inconsistent with a viscous behaviour. It indicates that mesoscopic liquids are able to (partly) convert mechanical shear energy in non-equilibrium thermodynamic states. This effect called thermo-elasticity is well known in solid materials. The observation of a thermal coupling to the mechanical shear deformation reinforces the assumption of elastically correlated liquid molecules. The amplitude of the thermo-elastic waves increases linearly by increasing the shear strain amplitude up to a transition to a non-linear thermal behavior, similar to a transition from an elastic to plastic regime. The thermo-elastic effects do not give rise to any change in stress measurements and thus the dynamic thermal analysis provides unique information about dynamic liquid properties.