Temperature-dependent Model Research Articles

A parameters identification method and experimental analysis of contact friction interface in thermal environment

This article presents groundbreaking research in parameter identification for mechanical friction interfaces in thermal environments. First, a temperature-dependent model was developed to accurately identify interface parameters at different temperatures. Second, a specialized experimental setup was designed for friction parameter identification to identify interface parameters under various load conditions in thermal environments. This design ensured both usability and accuracy, maintaining a high resolution. By comparing with the experimental data, we find that the difference in the interface parameters of theoretical model identification is small, which proves the feasibility of our method. These research findings serve as a vital reference for future studies on interface parameter identification in thermal environments, establishing a solid foundation for achieving precise and efficient identification of interface parameters.

Stress relief simulation for post-weld heat treatment process of pressure equipment: Creep constitutive equation considering temperature and stress variations

Due to the limited testing methods and high costs, researches on the evolution law of residual stress in the post-weld heat treatment (PWHT) process of pressure equipment are mainly by numerical simulation, in which the selection of a reasonable and reliable creep constitutive model is crucial to ensure the accuracy of numerical predictions. It is worth noting that the temperature changes and residual stress variation during the heat treatment process result in the following creep characteristics: the creep occurs under different temperatures during the heat treatment processes of heating, holding, and cooling; the creep occurs under different residual stress level where the residual stress varies during the heat treatment stages. Thus, to accurately simulate the stress release behavior during the PWHT process, the proper creep constitutive model must involve the influences of the temperature and the stress state. Meanwhile, current heat treatment simulation usually adopts simplified qualitative approaches, and the creep constitutive models often ignore the physical mechanisms and characteristics of actual creep processes, such as the Norton, the Norton-Bailey, and the Omega models. As a result, the accuracy of heat treatment simulation is limited. In this paper, a new creep constitutive relation under varying temperature and stress is proposed. The hyperbolic-sinusoidal function is used to represent the complete three stages of creep, which compensate the inaccuracy prediction at the first and the third creep stages. Moreover, the Arrhenius function is introduced to characterize the creep response under varying temperature conditions, which enables the prediction of residual stress evolution throughout the entire heating-holding-cooling process of heat treatment. Then, a typical pressure vessel cylindrical circumferential weld is simulated. The stress release during the heat treatment is calculated, and the efficacy of the proposed model is validated through surface residual stress testing. It is found that the creep behavior is a crucial factor in numerical simulation of heat treatment, and the creep constitutive relation can significantly affect the accuracy of heat treatment simulation. The simulation utilizing the hyperbolic-sinusoidal temperature-dependent creep model is much more accurate compared to the classical simulation. The simulation results are much more consistent to the experimental results. Specifically, the traditional model often underestimates the stress state, the residual stress drops abruptly during the heating stage. The residual stress evolution mechanism is simulated using the new model: The majority of residual stress are released during the heating process which primarily relies on the creep strain transformation (contributes up to 85%). The stress state does not change during the holding stage and slight higher at the cooling stage.

A Rate- and Temperature-Dependent Thermomechanical Internal State Variable Model of the Directed Energy Deposition Process

A Rate- and Temperature-Dependent Thermomechanical Internal State Variable Model of the Directed Energy Deposition Process

Temperature-dependent hysteresis model based on temporal convolutional network

The variation of temperature modifies the magnetic behavior of ferromagnetic cores which may affect the performance of electrical equipment. Therefore, it is imperative to develop a temperature-dependent hysteresis model to precisely calculate electromagnetic characteristics of electrical equipment. In this paper, a Temporal Convolutional Network (TCN) in combination with the Play operator is developed. The proposed model incorporates the temperature-dependent spontaneous magnetization intensity as the model input to introduce the temperature effect. To enhance the accuracy of model training outcomes, the Bayesian optimization approach for automatically selecting network model parameters is provided. The results show that the proposed model can accurately predict the hysteresis characteristics of materials under varying temperature and frequency conditions.

Predicting extreme sub-hourly precipitation intensification based on temperature shifts

Abstract. Extreme sub-hourly precipitation, typically convective in nature, is capable of triggering natural disasters such as floods and debris flows. A key component of climate change adaptation and resilience is quantifying the likelihood that sub-hourly extreme precipitation will exceed historical levels in future climate scenarios. Despite this, current approaches to estimating future sub-hourly extreme precipitation return levels are deemed insufficient. The reason for this can be attributed to two factors: there is limited availability of data from convection-permitting climate models (capable of simulating sub-hourly precipitation adequately) and the statistical methods we use to extrapolate extreme precipitation return levels do not capture the physics governing global warming. We present a novel physical-based statistical method for estimating the extreme sub-hourly precipitation return levels. The proposed model, named TEmperature-dependent Non-Asymptotic statistical model for eXtreme return levels (TENAX), is based on a parsimonious non-stationary and non-asymptotic theoretical framework that incorporates temperature as a covariate in a physically consistent manner. We first explain the theory and present the TENAX model. Using data from several stations in Switzerland as a case study, we demonstrate the model's ability to reproduce sub-hourly precipitation return levels and some observed properties of extreme precipitation. We then illustrate how the model can be utilized to project changes in extreme sub-hourly precipitation in a future warmer climate only based on climate model projections of temperatures during wet days and on foreseen changes in precipitation frequency. We conclude by discussing the uncertainties associated with the model, its limitations, and its advantages. With the TENAX model, one can project sub-hourly precipitation extremes at different return levels based on daily scale projections from climate models in any location globally where observations of sub-hourly precipitation data and near-surface air temperature are available.

Parametric Analysis on Creep Deformation of Deep-Sea PMMA Observation Window

Observation windows are core components of the submersible manned cabins. The strength and stiffness of the observation window during the loading and load-sustaining process are crucial to ensure the safety of the equipment and personnel inside the manned cabin. It is extremely important to accurately calculate the structural creep performance of the observation window under a long-period sustaining load in seawater. In the present study, finite element analyses based on a temperature-dependent time-hardening creep model are conducted to investigate the performance of the observation window. The mesh convergence is studied first and the parametric analysis is accordingly carried out, taking different combinations of temperatures from 2~30 °C, different loading rates of 2.3 MPa/min, 4.5 MPa/min, 6 MPa/min, and 8 MPa/min, and different friction coefficients of 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3 into account. The results show that the displacement in the y-axis direction of the center point of the lower surface of the viewport window increases with the increasing temperature and loading rate. On the contrary, the axial displacement of the observation window gradually decreases with the increase of the friction coefficient, and the axial displacement is the largest when the lowest friction coefficient is applied. This study aims to offer a more unified analysis and design methodology for the creep deformation of PMMA structures in underwater facilities.

Numerical simulation of solidification of boiler molten ash impinging on vertical wall based on Smoothed Particle Hydrodynamics method

In order to study the whole process of the high temperature liquid slag fly ash produced after the combustion of high alkali coal as power coal in the boiler furnace, which moves in the furnace and impinges on the water wall, the heat exchange occurs and then the cooling phase transformation deposits and slags, and the possible factors of slagging particles are studied by changing the environmental variables. In this paper, based on Smoothed Particle Hydrodynamics (SPH), the dynamic behavior of boiler molten ash impacting vertical wall is studied, and the flow spreading and solidification model of molten slag impacting vertical wall is established. Thus, the process of phase change deposition of slag particles against wall is simulated. By observing the phase distribution of slag and the change in spreading process, the complete process of the slag particles hitting the wall, spreading, shrinking and solidifying is analyzed. Based on the cohesive and repulsive surface force method, a temperature-dependent surface tension model is established to simulate the effect of surface tension on flow characteristics when molten ash impinges on low-temperature vertical walls. The influences of slag impact velocity, initial temperature and water wall temperature on deformation and solidification heat transfer are discussed. The results show that the initial velocity and initial temperature of slag particles affect the phase change deposition velocity and the final spreading factor of slag, while the temperature of the water wall has little effect on the deposition deformation and solidification process of slag.

Nonlinear bond-slip model for fiber-reinforced polymer laminates externally bonded to thermally damaged concrete

This paper presents a novel nonlinear local bond-slip model for fiber-reinforced polymer (FRP) laminates externally bonded to thermally damaged concrete substrates. The proposed model is an extension of an existing two-parameter bond-slip model and incorporates two key parameters including interfacial fracture energy ([Formula: see text]) and interfacial brittleness index ([Formula: see text]). To study the variations of [Formula: see text] and [Formula: see text] with different thermal damage levels of the concrete substrate, an extensive experimental database of shear tests on FRP-to-thermally damaged concrete bonded joints was collected from the existing literature. The [Formula: see text] values were calculated from the peak pull loads with proper consideration of the bond length and width effects, while the [Formula: see text] values were obtained by least-squares regression analysis using experimental load-displacement curves or measured strain distributions in the FRP laminates. The results have indicated that the [Formula: see text] values initially exhibit a slight increase accompanied by mild thermal damage of the concrete substrate after exposure to moderately high temperatures; however, these values significantly decrease when the exposure temperature exceeds 300°C. The [Formula: see text] values initially decrease with high-temperature exposure and stabilize at around 50% of the initial values when the temperatures reach around 400°C. Despite the inherent variability in the test database, the proposed temperature-dependent bond-slip model has demonstrated its accuracy, as demonstrated by the comparisons between the theoretical predictions generated by the model and the corresponding shear test results. This interfacial bond-slip model is expected to serve as a constitutive law to characterize the bond behavior between externally bonded FRP laminates and thermally damaged concrete substrate, thus facilitating the practical application of high-performance FRP composites in the repair and strengthening of thermally or fire-damaged RC members.

Elasto-viscoplastic material modelling using the multiaxial Prandtl operator approach

The closed-form solution for Prandtl model implemented into the finite element method is presented which enables elasto-viscoplastic simulations of engineering materials. A nonlinear temperature-dependent damper is combined in series with the temperature-dependent spring-slider model for the description of the material stress–strain behaviour. The simulation capabilities allow a separate study of influence due to plastic or viscous properties of the material. Several load cases are studied, including constant temperature relaxation and variable thermomechanical loads. The simulation results are then compared to the Abaqus-implemented material model for elasto-viscoplastic simulations. The models provide similar solutions for simpler load cases whereas higher discrepancies can be observed for more complex load histories since the positions of the nonlinear damper in the models differ.

Temperature-dependent self-trapped models regulating energy transfer in rare earth double perovskites via 5s2 electron doping

Sb3+/Sm3+ co-doping can effectively modulate the luminescence by adjusting the energy transfer in Cs2NaYCl6 double perovskites. Two minima in the excited state of 3P1 enable the double self-trapped exciton emission at low temperatures.

Winter is not coming: evaluating impacts of changing winter conditions on coregonine reproductive phenology

Fishes in northern latitude lakes are at risk from climate-induced warming because the seasonality in water temperature is degrading, which can change ecosystem properties and the phenology of life-history events. Temperature-dependent embryo development models were developed for a group of cold, stenothermic fishes (Salmonidae Coregoninae) to assess the potential impacts of climate-induced changes in water temperature on cisco (Coregonus artedi) from two populations in Lake Superior (Apostle Islands [USA] and Thunder Bay [Canada]) and one in Lake Ontario (USA), vendace (C. albula) in Lake Southern Konnevesi (Finland), and European whitefish (C. lavaretus) in lakes Southern Konnevesi, Constance (Germany), Geneva (France), and Annecy (France). Water temperatures for each study group were simulated and changes in reproductive phenology across historic (1900–2006) and three future climatic-warming scenarios (2007–2099) were investigated. Models predicted that increases in water temperatures are likely to cause delayed spawning, shorter embryo incubation durations, and earlier larval hatching. Relative changes increased as warming scenarios increased in severity and were higher for littoral as compared to pelagic populations. Our simulations demonstrated that slower cooling in the autumn and (or) more rapid warming in spring can translate into substantial changes in the reproductive phenology of coregonines among our study groups. We expect that the changes in reproductive phenology predicted by our models, in the absence of thermal or behavioral adaptation, will have negative implications for population sustainability.

Imprint of pairing correlation in (n, γ) and Maxwellian-averaged cross sections of an odd-odd 166Ho nucleus

The present paper investigates the impact of pairing correlation on the nuclear level density (NLD) and radiative strength function (RSF) of an odd-odd and rare-earth 166Ho nucleus. By employing the exact thermal pairing (EP) solution in conjunction with both the temperature-dependent independent-particle model (EP+IPM) for the NLD and the phonon damping model (EP+PDM) for the RSF, we achieve good agreement with the experimental NLD and RSF data, which have been recently extracted by using the Oslo method. Notably, without adding any extra parameters, our calculations successfully reproduce the pygmy dipole resonances (PDR) and a portion of the strength around the region of scissor resonance (SR) in the RSF. This suggests that the SR in this nucleus may be less pronounced than that obtained in the previous analysis within the phenomenological model. These features are the consequences of the EP and the couplings of the PDM phonon to all the particle-hole (ph), particle-particle (pp), and hole-hole (hh) configurations within the EP+PDM, thus insisting on the importance of the underlying physics involved in this model. Utilizing the obtained NLD and RSF, we predict the 165Ho(n,γ)166Ho and Maxwellian-averaged cross sections, which exhibit remarkable agreement with all the available experimental data from the Experimental Nuclear Reaction Data and Karlsruhe Astrophysical Database of Nucleosynthesis in Stars. These results reflect the imprint of the pairing correlation on those quantities.

Cryogenic damage mechanisms of CFRP laminates based on in-situ X-ray computed tomography characterization

Carbon fiber reinforced polymer (CFRP) composites possess excellent properties suitable for use in spacecraft liquid fuel tanks. However, the cryogenic reliability of composites remains challenging owing to the variation in mechanical responses under cryogenic environments. So far, most previous studies have focused on the cryogenic properties of composites, and little has been devoted to the cryogenic damage behaviors of laminates. Herein, the cryogenic damage evolution of CFRP laminates was investigated by micro-computed tomography (μCT) characterization and micromechanical analysis for the first time. To this end, in-situ μCT tensile tests for quasi-isotropic CFRP laminates were conducted at temperatures of 293 K, 193 K, and 93 K, and the observed cryogenic damage characteristics were analyzed. A micromechanical computational model was then developed, and the temperature-dependent constitutive model of epoxy resin was utilized to investigate the cryogenic damage evolution process of laminates. The effects of matrix property variation and thermal stresses on the cryogenic damage of laminates were examined, and the cryogenic fracture toughness for transverse cracking was deduced. The characterization results revealed a significantly increased damage volume fraction of laminates from 0.65% to 1.56% at cryogenic temperatures, mainly originating from the increased delamination (from 0.08% to 0.54%) and 90° ply transverse cracks (from 0.48% to 0.87%). The numerical analyses indicated the cryogenic brittle transition of the matrix as the primary factor responsible for the delamination, while the transverse cracks were influenced by matrix properties and thermal stresses. This study provides critical insight into the cryogenic damage behavior of CFRP laminates, essential for cryogenic applications of composites.

Comparison of Coupled Electrochemical and Thermal Modelling Strategies of 18650 Li-Ion Batteries in Finite Element Analysis-A Review.

The specificities of temperature-dependent electrochemical modelling strategies of 18650 Li-ion batteries were investigated in pseudo-2D, 2D and 3D domains using finite element analysis. Emphasis was placed on exploring the challenges associated with the geometric representation of the batteries in each domain, as well as analysing the performance of coupled thermal-electrochemical models. The results of the simulations were compared with real reference measurements, where temperature data were collected using temperature sensors and a thermal camera. It was highlighted that the spiral geometry provides the most realistic results in terms of the temperature distribution, as its layered structure allows for a detailed realisation of the radial heat transfer within the cell. On the other hand, the 3D-lumped thermal model is able to recover the temperature distribution in the axial direction of the cell and to reveal the influence of the cell cap and the cell wall on the thermal behaviour of the cell. The effect of cooling is an important factor that can be introduced in the models as a boundary condition by heat convection or heat flux. It has been shown that both regulated and unregulated (i.e., natural) cooling conditions can be achieved using an appropriate choice of the rate and type of cooling applied.

Thermal-structural analysis for reusable thrust chamber using temperature-dependent CuZr alloy model adapted to cryogenic to elevated temperature

The inner liners of reusable regeneratively-cooled thrust chambers endure significant thermal and mechanical loads, resulting in doghouse deformation and even cracks during cyclic operations. To correctly reveal the failure mechanism of the thrust chamber inner liner, this study investigates the material properties for CuZr alloy and develops a temperature-dependent material model spanning from cryogenic to elevated temperatures. Firstly, we experimentally obtain the thermal and mechanical properties of the material in the temperature range from 77 K to 900 K. The experimental data reveal that the material properties vary considerably with temperature. Then, to precisely characterize the mechanical behavior of CuZr alloy under cyclic loading across a wide temperature range, a material model that combines Voce nonlinear isotropic hardening model with Chaboche nonlinear kinematic hardening model is proposed, and temperature-dependent parameters of this model are calibrated and verified. Finally, the developed material model is applied to perform the thermal-structural analysis on a reusable thrust chamber, with the aim of investigating its failure mechanism. The results demonstrate the capability of the developed model to accurately replicate the doghouse deformation of the inner liner and quantitatively capture the ratcheting effect.

Investigating the effects of a temperature dependent photodynamic dose: A numerical study

SignificancePhotodynamic therapy (PDT) and photothermal therapy (PTT) show promise as cancer treatments, but challenges in generating large ablative volumes for deep-seated tumours persist. Using simulations, this study investigates combined PDT and PTT to increase treatment volumes, including the impact of a temperature-dependent PDT dose on the treatment volume radius. ApproachA finite-element model, using the open-source SfePy package, was developed to simulate combined interstitial photothermal and photodynamic treatments. Results compared an additive dose model to a temperature-dependent dose model with enhanced PDT dosimetry and examined typical clinical scenarios for possible synergistic effects. ResultsFindings revealed that the temperature-dependent dose model could significantly expand the damage radius compared to the additive model, depending on the tissue and drug properties. ConclusionsCharacterizing synergistic effects of PDT and PTT could enhance treatment planning. Future work is ongoing to implement additional variables, such as photosensitizer photobleaching, and spatial and temporally varying oxygenation.

Physics-based model to predict yield strength of single-phase FCC high-entropy alloys over wide temperature range

A physics-based temperature-dependent yield strength model without fitting parameters was developed for single-phase FCC high-entropy alloys. The model considered the temperature dependence of lattice friction stress, solid solution strengthening, grain boundary strengthening, dislocation strengthening, and their evolution with temperature to the overall yield strength. The results show that a quantitative relationship between temperature, material parameters, and yield strength was successfully captured by the model. This model can predict the yield strength at different temperatures only by using the easily available material parameters at room temperature. The accuracy of model was well verified by 17 sets of available experimental data over a wide temperature range (4.2–1273 K). Moreover, the contribution of different strengthening mechanisms to the yield strength was quantitatively analyzed and discussed from 4.2 to 1273 K, and some suggestions for improving the temperature-dependent yield strength were put forward.

The Impact of Ambient Temperature on Electrothermal Characteristics in Stacked Nanosheet Transistors with Multiple Lateral Stacks.

With characteristic size scaling down to the nanoscale range, the confined geometry exacerbates the self-heating effect (SHE) in nanoscale devices. In this paper, the impact of ambient temperature (Tamb) on the SHE in stacked nanosheet transistors is investigated. As the number of lateral stacks (Nstack) increases, the nanoscale devices show more severe thermal crosstalk issues, and the current performance between n- and p-type nanoscale transistors exhibits different degradation trends. To compare the effect of different Tamb ranges, the temperature coefficients of current per stack and threshold voltage are analyzed. As the Nstack increases from 4 to 32, it is verified that the zero-temperature coefficient bias point (VZTC) decreases significantly in p-type nanoscale devices when Tamb is above room temperature. This can be explained by the enhanced thermal crosstalk. Then, the gate length-dependent electrothermal characteristics with different Nstacks are investigated at various Tambs. To explore the origin of drain current variation, the temperature-dependent backscattering model is utilized to explain the variation. At last, the simulation results verify the impact of Tamb on the SHE. The study provides an effective design guide for stacked nanosheet transistors when considering multiple stacks in circuit applications.

Numerical development of a thermo-mechanical prediction model at high temperature: case of rubber concretes

The constitutive models have an important role in understanding the thermo-mechanical behavior of concrete and predicting its durability under fire loading. In this paper, the authors have developed a new constitutive temperature-dependent model for rubber concrete based on several models, such as European and American models, to predict the mechanical behavior of rubber concrete subjected to fire loading. The thermal parameters such as thermal conductivity, heat capacity, and density are variables as a function of temperature. First, the temperature is computed using the finite difference method (FDM) using the implicit scheme. The mechanical parameters in the literature are computed and plotted, such as compressive strength, tensile strength, peak strain, and stress-strain relationship, and then the mean value is estimated to develop a new probabilistic model at elevated temperatures. To validate the developed model, we compare the behavior of rubber concrete with experimental measurements.

Surface waviness of continuous fiber-reinforced thermosets – Experimental and numerical studies considering the viscoelasticity of the resin

This contribution aims to understand surface waviness formation during cooling and post-curing of glass fiber-reinforced plastics (GFRP). GFRP plates were manufactured by resin transfer molding (RTM). Part surface waviness is determined by tactile contour measuring at ambient temperature up to 1008 h after initial cooling. Additionally, the manufactured plates were exposed to elevated post-curing temperatures to study the influence of resins’ viscoelasticity on their surface waviness. In parallel, the curing and post-curing processes were analyzed using a cure- and temperature-dependent viscoelastic simulation model. The experimental results of this work capture the influence of the resin’s viscoelastic behavior on the surface waviness at ambient and temperatures. The numerical results show a satisfactory agreement with experimental values. Surface waviness amplitude increases up to 25 % for the applied post-curing cycle. The results of the present work underline the importance of the resin’s temperature-dependent viscoelasticity on the process-related formation of surface waviness.