Thermal Stress Model Research Articles

WRF-HEATS coupling: Incorporating human behaviors and city topography into urban heat stress evaluation

Urban human thermal stress can be inaccurately estimated along with less-understood heat heterogeneity due to the absence of high-resolution meteorological information and realistic human behavior representation. To this end, we coupled a regional climate model (weather research and forecasting model, WRF) and a human energy balance model (human-environment adaptive thermal stress model, HEATS) to predict pedestrian's dynamic thermal stress at a neighborhood scale. The WRF-human coupling system resolves human-environment heat exchanges based on meteorological and topographical information with the consideration of dynamic human activities. The coupling system has been tested and utilized to study dynamic heat stress in a typical hot, humid, and mountainous city, Hong Kong. Our results revealed widespread heat heterogeneity with up to 7 °C difference in Physiological Subjective Temperature (PST) in the core urban area, and extreme heat exposure (up to 45 °C PST) in calm-wind zones at noon. Heat stress can be further aggregated considering realistic human behaviors such as extra clothing (e.g., protective facemask during pandemics) and physical exercise (e.g., walking along inclined terrain). Optimal-thermal-comfort routes have been designed and suggested based on the simulated neighborhood-scale heat stress map.

Numerical simulation and experimental analysis of thermal conduction and stress in laser cladding repair of thin-walled parts

To minimize the deformation of thin-walled parts during the laser cladding process and enhance the quality of the repaired parts, the Finite Element Abaqus software was used to develop a thermal conduction and 3D stress model, the heat source used in the experiments was a double ellipsoid heat source model. This model simulates the thermal process and the deformation resulting from residual stresses in the laser cladding process on a titanium alloy substrate with a thickness of 2 mm. Through the simulation, the temperature field of the substrate at the end of each pass was obtained, and the cladding sequence with the smallest temperature gradient during the multi-pass laser melting process was determined. By combining simulation and practice, the multilayer stacking pattern was optimized to achieve deformation control. Analog simulation experiments indicate that the optimized single-layer multi-pass laser cladding method results in less heat accumulation and thermal stress compared to the unidirectional sequential scanning method. The flatness test results show that the specimens have less deformation with the optimized multilayer stacking method. In addition, the metallographic organisation of the two cladding specimens is analysed in this paper, and the results show that the optimised specimens exhibit excellent microstructures and properties.

Metabolic responses of sea anemone and jellyfish to temperature and UV bleaching: Insights into stress adaptation using LCMS-based metabolomics, molecular networking and chemometrics

IntroductionClimate change poses various threats to marine life, particularly in shallow tropical waters. Objective: The impact of increased temperature and ultraviolet (UV) exposure on two photosymbiotic cnidarians, a common bubble-tip anemone and an upside-down jellyfish, was investigated. MethodsTo illustrate the response of aquatic organisms, the metabolomes of unstressed Entacmaea quadricolor and Cassiopea andromeda were compared for detailed metabolite profiling. UHPLC-MS coupled with chemometrics and GNPS molecular networking was employed for sample classification and identification of markers unique to stress responses in each organism. ResultsSeveral compounds with bioactive functions, including peptides and terpenoids, were reported for the first time in both organisms, viz. cyclic tetraglutamate, campestriene, and ceramide aminoethyl phosphonate (CEAP d18:2/16:0). Both anemone and jellyfish were subjected to either elevated UV-B light intensity up to 6.6 KJ m−2 or increased temperatures (28 °C, 30 °C, 32 °C, and 34 °C) over 4 days. Phospholipids, steroids, and ceramides emerged as chief markers of both types of stress, as revealed by the multivariate data analysis. Lysophosphatidylcholine (LPC 16:0), LPC (18:0/0:0), and echinoclasterol sulfate appeared as markers in both UV and thermal stress models of the anemone, whereas methyl/propyl cholestane-hexa-ol were discriminatory in the UV stress model only. In the case of jellyfish, nonpolar glycosyl ceramide GlcCer (d14:1/28:6) served as a marker for UV stress, whereas polar peptides were elevated in the thermal stress model. Interestingly, both models of jellyfish share a phospholipid, lysophosphatidylethanolamine (LPE 20:4), as a distinctive marker for stress, reported to be associated indirectly with the activity of innate immune response within other photosymbiotic Cnidaria such as corals and appears to be a fundamental stress response in marine organisms. ConclusionThis study presents several bioinformatic tools for the first time in two cnidarian organisms to provide not only a broader coverage of their metabolome but also broader insights into cnidarian bleaching in response to different stressors, i.e., heat and UV light, by comparing their effects in anemone versus jellyfish.

Finite element modeling of thermal residual stresses in functionally graded aluminum-matrix composites using X-ray micro-computed tomography

Metal-ceramic composites by their nature have thermal residual stresses at the micro-level, which can compromise the integrity of structural elements made from these materials. The evaluation of thermal residual stresses is therefore of continuing research interest both experimentally and by modeling. In this study, two functionally graded aluminum alloy matrix composites, AlSi12/Al2O3 and AlSi12/SiC, each consisting of three composite layers with a stepwise gradient of ceramic content (10, 20, 30 vol%), were produced by powder metallurgy. Thermal residual stresses in the AlSi12 matrix and the ceramic reinforcement of the ungraded and graded composites were measured by neutron diffraction. Based on the X-ray micro-computed tomography (micro-XCT) images of the actual microstructure, a series of finite element models were developed to simulate the thermal residual stresses in the AlSi12 matrix and the reinforcing ceramics Al2O3 and SiC. The accuracy of the numerical predictions is high for all cases considered, with a difference of less than 5 % from the neutron diffraction measurements. It is shown numerically and validated by neutron diffraction data that the average residual stresses in the graded AlSi12/Al2O3 and AlSi12/SiC composites are lower than in the corresponding ungraded composites, which may be advantageous for engineering applications.

Mechanic-electric-thermal coupling simulation method of Lamb wave under variable temperature

The propagation mechanism of Lamb waves exhibits more intricate in the variable operational environment of high-speed trains. Simulation methods are widely used to study Lamb wave propagation characteristics due to economic and time constraints. A mechanic-electric-thermal coupling simulation method to study the propagation mechanism of Lamb waves under variable temperatures is proposed in this paper. To accurately simulate the dynamic behavior of Piezoelectric Transducer (PZT) under variable temperature, a nonlinear numerical model of the dynamic parameters (piezoelectric coefficient, dielectric constant) of PZTs has been developed based on the experiment of the temperature influence on Lamb wave. The model emphasizes the nonlinear pattern of change in the key dynamic parameters of the PZT with temperature fluctuations. In addition, a thermal expansion stress model of the PZT-bonding layers-structure is established to reveal the mechanical-thermal coupling mechanism. Based on the COMSOL, a mechanical-electrical-thermal direct coupling simulation model of PZT-bonding layers- structure under variable temperature is established. The simulation results at −40 °C to 80 °C are obtained and compared to the experiment. The results show that the simulation signal is highly consistent with the experimental measurement signal, and the simulation method proposed in this paper has high accuracy.

Computational Modeling and Experimental Validation of Thermal Stress and Melt Pool Characteristics Using High Power Laser Diode Beam on 7075 Aluminum Alloy

Computational Modeling and Experimental Validation of Thermal Stress and Melt Pool Characteristics Using High Power Laser Diode Beam on 7075 Aluminum Alloy

Optimization design and performance improvement of ther-mal barrier coating (TBC) system

Thermal Barrier Coatings (TBC) technology has become one of the key technologies to improve the performance and prolong the service life of gas turbine and other high temperature equipment. In this study, the selection of materials, coating methods, the influence of environmental factors on the performance of TBC system and the thermal stress analysis and optimization strategy are discussed, improve the overall performance and stability of TBC system. TBC coatings were efficiently prepared by the use of Nikolay bonding layer and stabilized zirconia as top ceramic materials, combined with electron beam Physical vapor deposition (EB-PVD) and plasma spraying (APS) techniques. In addition, the thermal stress model was established by FEA, and the thermal stress distribution of TBC system under extreme operating conditions was analyzed in detail, to reduce thermal stress concentration and improve the thermal barrier effect of the coating. Finally, through the establishment of TBC system life prediction model and in-depth analysis of the failure mechanism, a series of preventive measures and performance improvement strategies are proposed, it provides theoretical basis and practical guidance for coating design of gas turbine and other high temperature equipment.

On the performance of carbon fiber structural batteries with temperature

Carbon fiber structural batteries, which combine structural and functional properties, have good energy storage capacity while bearing loads have received attention from scholars at home and abroad in recent years as a new type of energy storage device. However, in the process of use, temperature changes will lead to the occurrence of thermal stresses, which may cause structural failure under multiple cycles. In this paper, the thermal-stress coupled model of structural batteries was established first using the temperature and thermal stress models of structural batteries, considering the heat exchange with the external environment of structural batteries. Then based on the coupled model, the thermal stress in the structural battery was simulated and analyzed in COMSOL considering different charge and discharge rates and ambient temperatures of the structural batteries. The results show that: (1) The higher the charging and discharging rates, the higher the temperature of the structural battery, resulting in greater thermal stress. (2) The higher the ambient temperature of the structural battery, the longer its discharge time and the lower the voltage at which discharge terminates, which is beneficial for the electrochemical performance of the battery. But the higher the ambient temperature, the greater the temperature change inside the structural battery, which is not conducive to the mechanical performance of the structural battery. This study can provide reference for the safety analysis of structural batteries in thermal environments.

Hybrid bonding of GaAs and Si wafers at low temperature by Ar plasma activation

High-quality bonding of 4-inch GaAs and Si is achieved using plasma-activated bonding technology. The influence of Ar plasma activation on surface morphology is discussed. When the annealing temperature is 300 ℃, the bonding strength reaches a maximum of 6.2 MPa. In addition, a thermal stress model for GaAs/Si wafers is established based on finite element analysis to obtain the distribution of equivalent stress and deformation variables at different temperatures. The shape variation of the wafer is directly proportional to the annealing temperature. At an annealing temperature of 400 ℃, the maximum protrusion of 4 inches GaAs/Si wafers is 3.6 mm. The interface of GaAs/Si wafers is observed to be dense and defect-free using a transmission electron microscope. The characterization of interface elements by X-ray energy dispersion spectroscopy indicates that the elements at the interface undergo mutual diffusion, which is beneficial for improving the bonding strength of the interface. There is an amorphous transition layer with a thickness of about 5 nm at the bonding interface. The preparation of Si-based GaAs heterojunctions can enrich the types of materials required for the development of integrated circuits, improve the performance of materials and devices, and promote the development of microelectronics technology.

The Direct Effects of Climate Change on Tench (Tinca tinca) Sperm Quality under a Real Heatwave Event Scenario.

Global aquaculture growth will most probably face specific conditions derived from climate change. In fact, the most severe impacts of these changes will be suffered by aquatic populations in restrictive circumstances, such as current aquaculture locations, which represent a perfect model to study global warming effects. Although the impact of temperature on fish reproduction has been characterized in many aspects, this study was focused on recreating more realistic models of global warming, particularly considering heatwave phenomena, in order to decipher its effects on male gametes (spermatozoa). For this purpose, thermal stress via a heatwave simulation (mimicking a natural occurring heatwave, from 24 to 30 °C) was induced in adult tench (Tinca tinca) males and compared with a control group (55.02 ± 16.44 g of average body wet weight). The impact of the thermal stress induced by this climate change event was assessed using cellular and molecular approaches. After the heatwave recreation, a multiparametric analysis of sperm quality, including some traditional parameters (such as sperm motility) and new ones (focus on redox balance and sperm quality biomarkers), was performed. Although sperm concentration and the volume produced were not affected, the results showed a significant deleterious effect on motility parameters (e.g., reduced progressive motility and total motility during the first minute post-activation). Furthermore, the sperm produced under the thermal stress induced by this heatwave simulation exhibited an increased ROS content in spermatic cells, confirming the negative effect that this thermal stress model (heatwave recreation) might have had on sperm quality. More importantly, the expression of some known sperm quality and fertilization markers was decreased in males exposed to thermal stress. This present study not only unveils the potential effects of climate change in contemporary and future fish farming populations (and their underlying mechanisms) but also provides insights on how to mitigate and/or avoid thermal stress due to heatwave events.

Mathematical modelling of thermal stresses of induction surface hardening in axi-symmetric formulation

The paper presents the original general model of induction surface hardening based upon analysis of coupled electromagnetic, thermal, mechanical and metallurgical phenomena. The distribution of mechanical strains and stresses in surface layers of steel materials subjected to induction hardening is determined. This distribution is not caused only by the thermoelastic processes, but often, it is also influenced by plastic deformations of the exposed layers and transformation of particular levels of steel. An illustrative example shows the methodology of solution for an axi-symmetric configuration.

FEM Thermomechanical Simulation of Low Power LED Lamp for Energy Efficient Light Sources

Modeling and simulation of thermal distribution, heat transfer, and mechanical stress are virtually essential for any design of structures and devices in electronic industry simulation tools make the design easier and enable optimization of many different parameters before fabrication of new structure. This paper presents simulation validation of 3D model of solid state lighting LED bulb for energy efficient and durable light sources. The modeling of structures was performed by CoventorWare tools utilizing finite the element method (FEM). The calculated thermal distribution has been validated with thermal measurement on a commercial LED lamp. Materials parametric study has been carried out to discover problematic parts for heat transfer from power LEDs to ambient.

Study on thermo-mechanical properties of energy piles based on the improved exponential model

To further investigate the effects of temperature on the bearing capacity of the energy pile, the influence of soil temperature was considered and the pile top displacement corresponding to the ultimate side friction resistance of the energy pile was obtained. An improved exponential model that accounts for the influence of pile-soil temperature was developed. The feasibility of the model was verified through an indoor model test and numerical simulation. The results indicate that the error between the improved exponential model and the indoor model test was smaller compared with the numerical simulation. The maximum side friction error between the improved exponential model and the model test reached 0.8 % and 4.6 % at the end of the heating and cooling stages, respectively. The maximum additional thermal stress error between the improved model and the model test was 1.3% and 3.9% at the end of the heating and cooling stages, respectively. The error of the traditional and improved exponential model of additional thermal stress was 16 %. It is established that the improved exponential model was proved suitable for thermo-mechanical coupling analysis of energy piles. The temperature effect of the soil should be considered in the investigation of the energy pile.

Thermal stress analysis of laser cleaning ofaluminum alloy oxide film.

In this paper, a theoretical model for laser cleaning of aluminium alloy oxide film is presented from the perspective of thermal stress. Additionally, we developed a two-dimensional axisymmetric finite element model for calculation. Thermal stresses result from thermal expansion. Using thermodynamic equations, numerical calculations enablethe determination of a theoretical cleaning threshold by comparing the thermal stresses to the adhesion between the oxide film and the substrate. Through theory and experiments, it is known that the greater the laser fluence, the better is the cleaning effect. The findings indicate that cleaning of the oxide film on aluminum alloys can be achieved under appropriate parameters. The cleaning threshold for laser cleaning of the oxide film is determined to be 3629.47J/c m 2 (continuous laser fluence is 3628.73J/c m 2; nanosecond laser fluence is 0.74J/c m 2). The thermal stress model of laser cleaning is highly useful for selecting the appropriate laser flux in practical applications. Both a simulation and experimental results can provide an explanation for the mechanism of interaction between the laser and the aluminum alloy oxide film, demonstrating that thermal stress is one of the cleaning mechanisms during the laser cleaning process of the oxide film.

Regional source rock thermal stress modeling and map-based charge access modeling of the Port Isabel passive margin foldbelt, northwestern Gulf of Mexico

The Port Isabel passive margin foldbelt covers 17,000 km2 of the northwestern deepwater U.S. Gulf of Mexico. Seven oil exploration wells have been drilled in the area from 1996 to 2007, yielding a single uncommercial gas discovery. The 5–7 km thick Oligo-Miocene section prevents drilling from penetrating the underlying Paleogene and Mesozoic source rocks. Accommodation space for the Oligo-Miocene section is created by the collapse of a paleo-salt wall, leading to linked fault systems in the upper decollement to the east. We use 13 exploration wells to construct 1D and map-based 2D basin models to investigate the burial and thermal history of three inferred source rock horizons (Paleogene, Turonian, and Tithonian). We interpret a 2D seismic data grid tied to four wells to constrain stratigraphic depths and thicknesses of the younger and shallower Wilcox source rock horizons, and the Jurassic and Cretaceous source rock horizons. Our results indicate that vitrinite reflectance is a proxy for the thermal stress levels reached by the source rocks as supported by maps of hydrocarbon charge access. We conclude that all three source rock intervals have reached varying degrees of maturity, expelled hydrocarbons in late Paleogene to mid-Neogene, and likely continue expelling hydrocarbons to the present-day at a reduced rate. The deposition of the Oligocene and Middle Miocene sedimentary section has buried the underlying source intervals and likely brought them into the gas/condensate window in the present-day. Our mapping of the extensive seismic reflection grid reveals four-way structural closures, three-way stratigraphic traps, and salt truncation structures associated with amplitude anomalies which may support our predictions for maturity in the underlying source rocks. Our thermal stress maps predict that the modeled source rocks are mature and our charge access models for the available wells constrain migration patterns, although the timing of the early hydrocarbon charge and late trap formation remain significant risk factors.

Assessing brain function in stressed healthy individuals following the use of a combination of green tea, Rhodiola, magnesium, and B vitamins: an fMRI study.

This randomized, controlled, single-blinded trial assessed the effect of magnesium (Mg)-Teadiola (Mg, vitamins B6, B9, B12, Rhodiola, and green tea/L-theanine) versus placebo on the brain response to stressful thermal stimulus in chronically stressed, but otherwise healthy subjects. Impacts on stress-related quality-of-life parameters (depression, anxiety, sleep, and perception of pain) were also explored. The study recruited a total of 40 adults (20 per group), suffering from stress for more than 1 month and scaling ≥14 points on the Depression Anxiety Stress Scale (DASS)-42 questionnaire at the time of inclusion. Individuals received oral Mg-Teadiola or placebo for 28 days (D). fMRI analysis was used to visualize the interplay between stress and pain cerebral matrices, using thermal stress model, at baseline (D0) and after D28. Based on blood-oxygen-level-dependent (BOLD) signal variations during the stress stimulation (before pain perception), a significantly increased activation between D0 and D28 was observed for left and right frontal area (p = 0.001 and p = 0.002, respectively), left and right anterior cingulate cortex (ACC) (p = 0.035 and p = 0.04, respectively), and left and right insula (p = 0.034 and p = 0.0402, respectively) in Mg-Teadiola versus placebo group. During thermal pain stimulation, a significantly diminished activation of the pain matrix was observed between D0 and D28, for left and right prefrontal area (both p = 0.001), left and right insula (p = 0.008 and p = 0.019, respectively), and left and right ventral striatum (both p = 0.001) was observed in Mg-Teadiola versus placebo group. These results reinforce the clinical observations, showing a perceived benefit of Mg-Teadiola on several parameters. After 1 month of treatment, DASS-42 stress score significantly decreased in Mg-Teadiola group [effect size (ES) -0.46 (-0.91; -0.01), p = 0.048]. Similar reductions were observed on D14 (p = 0.011) and D56 (p = 0.008). Sensitivity to cold also improved from D0 to D28 for Mg-Teadiola versus placebo [ES 0.47 (0.02; 0.92) p = 0.042]. Supplementation with Mg-Teadiola reduced stress on D28 in chronically stressed but otherwise healthy individuals and modulated the stress and pain cerebral matrices during stressful thermal stimulus.

Modeling of Thermal Stress and Control for Steam Turbine

Modeling of Thermal Stress and Control for Steam Turbine

Assessment of the thermal tissue models for the head and neck hyperthermia treatment planning

PurposeTo compare different thermal tissue models for head and neck hyperthermia treatment planning, and to assess the results using predicted and measured applied power data from clinical treatments. MethodsThree commonly used temperature models from literature were analysed: “constant baseline”, “constant thermal stress” and “temperature dependent”. Power and phase data of 93 treatments of 20 head and neck patients treated with the HYPERcollar3D applicator were used. The impact on predicted median temperature T50 inside the target region was analysed with maximum allowed temperature of 44 °C in healthy tissue. The robustness of predicted T50 for the three models against the influence of blood perfusion, thermal conductivity and the assumed hotspot temperature level was analysed. ResultsWe found an average predicted T50 of 41.0 ± 1.3 °C (constant baseline model), 39.9 ± 1.1 °C (constant thermal stress model) and 41.7 ± 1.1 °C (temperature dependent model). The constant thermal stress model resulted in the best agreement between the predicted power (P = 132.7 ± 45.9 W) and the average power measured during the hyperthermia treatments (P = 129.1 ± 83.0 W). ConclusionThe temperature dependent model predicts an unrealistically high T50. The power values for the constant thermal stress model, after scaling simulated maximum temperatures to 44 °C, matched best to the average measured powers. We consider this model to be the most appropriate for temperature predictions using the HYPERcollar3D applicator, however further studies are necessary for developing of robust temperature model for tissues during heat stress.

Influence of pore structure on thermal stress distribution inside coal particles during primary fragmentation

Thermal stress is an important reason of coal particle primary fragmentation, during which the role of pore structure is ambiguous. Thermal stress induced fragmentation experiments were conducted with low volatile coal/char particles, and the results show that the fragmentation severity enhances with increasing porosity. Various porous thermal stress models were developed with finite element method, and the influences of the pore shape, size, position and porosity on the thermal stress were discussed. The maximum thermal stress inside particle increases with pore curvature, the pore position affects the thermal stress more significantly at the particle center and surface. The expectation of the maximum tensile thermal stress linearly increases with porosity, making the particles with higher porosity easier to fragment, contrary to the conclusion deduced from the devolatilization theory. The obtained results are valuable for the analysis of different thermal processes concerning the thermal stresses of the solid feedstocks.

Integrated machine learning and probabilistic degradation approach for vessel electric motor prognostics

In the transition towards more sustainable ships, electric motors (EM) are being used in ship propulsion systems to reduce emissions and increase efficiency. The safe operation of ships is crucial, and prognostics and health management applications have emerged as effective solutions to transit towards monitored reliable systems. In this context, this paper presents a probabilistic EM prognostics model integrating data-driven operational models and physics-informed degradation models. Firstly, motor torque and winding temperature are estimated through connected machine learning models, which are based on operational and meteorological data. Operational and meteorological variables drive the EM degradation model and enable the analysis of EM degradation under different operational and environmental conditions. Subsequently, EM remaining useful life (RUL) is predicted within a probabilistic Monte-Carlo approach combining the thermal-stress model along with the associated uncertainties. The methodology is tested on a real case study of the OV Ryvingen vessel, with collected data during voyages along the Norwegian coast. Results confirm the validity of the designed RUL model showing that, under normal operation conditions, the degradation is mild, and the temperature measurement errors are important for RUL estimation.