Evaluation Of Thermal Stresses Research Articles

Evaluation of thermal stresses in transversely isotropic piezoelectric disc with rotation and internal pressure

The paper deals with the analytical solution of transitional stresses in thin rotating disc composed of piezoelectric material under temperature and internal pressure. The stresses are evaluated in the rotating disc by using transition theory of Seth. The electric displacement relations and stresses are computed by using stress strain relations. The non-homogeneous differential equation is derived by substituting the obtained relations into the equilibrium equation. The formulated differential equation is solved with specified boundary conditions, applied pressure, electric displacement and stresses. Obtained results are exhibited graphically, analysed numerically and it is then concluded that transversely isotropic beryl is better than transversely isotropic magnesium material and transversely isotropic piezoelectric materials BaTiO4 and PZT-4.

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.

Cortisone in saliva of pigs: validation of a new assay and changes after thermal stress

BackgroundCortisone is derived from cortisol through the action of the enzyme 11β-hydroxysteroid dehydrogenase type II, and it has gained importance in recent years as a biomarker of stress. This study aimed to develop and validate an assay for the measurement of cortisone in pig saliva and evaluate whether its concentration varies in stressful situations. For this purpose, a specific immunoassay was developed and validated analytically, and a study was performed to evaluate whether cortisone concentrations in saliva can vary under heat stress conditions.ResultsThe assay proved to be accurate, reliable, and sensitive for the measurement of cortisone in pig saliva. The limit of detection of the assay was set at 0.006 ng/ml, and the lower limit of quantification was 0.023 ng/ml. It also correlated significantly with the results obtained by LC‒MS/MS (P = 0.003; r = 0.64). In addition, the cortisone concentration in animals subjected to prolonged heat stress decreased significantly 15 days after treatment (P < 0.0001).ConclusionsAccording to these results, cortisone measured by this assay could be used as a tool for the non-invasive evaluation of thermal stress in pig saliva.

Evaluation of Thermal Stress on Heterogeneous IoT-Based Federated Learning

Evaluation of Thermal Stress on Heterogeneous IoT-Based Federated Learning

Compatibility study of mirtazapine with several excipients used in pharmaceutical dosage forms employing thermal and non-thermal methods

AbstractMirtazapine is an atypical antidepressant used in the management of insomnia, post-traumatic stress disorder, anxiety or panic disorder, obsessive–compulsive disorder and migraines. It is used worldwide in pharmaceutical formulations alongside various excipients in its hemihydrate form. The objective of the study was the compatibility evaluation between MRTHH and ten pharmaceutical excipients. The presence of incompatibilities between the API and the selected excipients was evaluated using Fourier transform infrared spectroscopy performed on all pure samples and prepared mixtures at room temperature (23 ± 2 °C), as well as a complete thermal stress evaluation (TG—thermogravimetric/DTG—derivative thermogravimetric/DSC—differential scanning calorimetry). The results showed particularities for all analyzed mixtures, α-lactose monohydrate, starch, sorbitol, magnesium stearate, calcium lactate and magnesium citrate proving to be safe to use together with mirtazapine in binary mixtures at temperatures below 130 °C, while for polyvinylpyrrolidone K30 and aerosol precautions need to be considered at temperatures over 100 °C. The association of mirtazapine with D-mannitol or stearic acid proved to raise concerns even at room temperature, indicating possible interactions that may alter the chemical integrity of the active pharmaceutical ingredient and with it, its therapeutic effect. These findings should be taken into consideration during the selection of the technological procedures used in the manufacturing process of dosage forms that include mirtazapine alongside with any of these excipients so that unwanted chemical interactions could be avoided.

Термические напряжения в изоляции тяговых электродвигателей локомотивов

Thermomechanical processes and cyclic temperature changes in the structure of insulation of traction electric motors lead to thermal gradient appearance. Increased temperature widens the elements of winding, damages insulation material (thermal fatigue, extreme deformation, creeping, etc.). Methods for the numerical study of stress-strain state of the material of the insulation of traction electric motors of diesel locomotives on different stages of static and cyclic loading have been developed. It is determined, that the main factor defining the intensiveness of insulation aging is the impact of alternating cyclic thermo-mechanical stresses, but not thermomechanical destruction of impregnating composition. Analytical expressions for the evaluation of stress-strain state of insulation of traction motor diesel locomotives are received and they are distinguished by the fact that they require a relatively small amount of basic data and let conduct accurate calculations taking into account the peculiarities of the electric drive system. An approximate predictive model for the evaluation of interphase thermal stresses in the assembly of the materials of winding slots of the traction electric motor of a diesel locomotive is developed. The insulation material is considered as linear elastic when the deformation level is less than the yield strength. The joining components can be considered from the view point of structural analyses as elongated rectangular plates suffering from linear elastic strains. The analyses results can be used for evaluation of thermomechanical stresses in the impregnating materials of traction electric motors of diesel locomotives and their analogues.

Evaluation of thermal stresses on thin Al and AZO films deposited on polyethylene terephthalate substrates for flexible electronics applications

Thin aluminum (Al) films are widely used in electronic devices and flexible photovoltaics. In a similar capacity, Aluminum Doped Zinc Oxide (AZO) serves the same purpose. This study examines the sensitivity of both films to thermal stresses when sputtered onto Polyethylene Terephthalate substrates. These stresses include a constant temperature of 100 °C and temperature fluctuations ranging from 0 °C to 100 °C. The resistance of the films was affected by isothermal aging, but not by thermal cycling. Interestingly, thermal cycling led to microcracks in the film, while isothermal aging resulted in a slight increase in bonding and oxygen content in the Al films. For AZO films, imaging did not reveal any noticeable changes in morphology. However, both thermal cycling and isothermal aging led to a minor increase in the resistance of AZO films. These findings highlight the pronounced impact of thermal stress on the performance and structural integrity of both thin films.

Performance and Thermal Stress Evaluation of Full-Scale SOEC Stack Using Multi-Physics Modeling Method

A three-dimensional computational fluid dynamics (CFD) method coupled with multi-physics phenomena is developed and applied for a 10-cell full-scale SOEC stack in this study. Effects of gas flow patterns, operating temperature, and manifold configurations are simulated and analyzed for stack performance and thermal stress. It is demonstrated the hydrogen production and thermal stress obtained in cross-flow mode stack are about 8% and 36 MPa higher compared to that in other flow cases. Furthermore, it is found the temperature gradient is the predominant factor affecting the thermal stress distribution and failure probability. Lastly, a stack arrangement with 2-inlet and 1-outlet is proposed and analyzed to enhance gas distribution uniformity within the cell channels. The findings of this study hold significance as a reference for investigating the impact on the SOEC stack performance and thermal stress distribution.

Ergodic evaluation of seismic and thermal stress on comparative durability and serviceability evaluations of beam column joints using finite element analysis

Ergodic evaluation of seismic and thermal stress on comparative durability and serviceability evaluations of beam column joints using finite element analysis

Crack Evolution and Computational Model Based Thermal Stress Evaluation of Laser Cladding Based on HVOF Sprayed WC/Co Deposits

A comprehensive experimental study on the high-velocity oxygen-fuel (HVOF) sprayed tungsten carbide/cobalt (WC/Co) deposits using laser cladding was conducted. A response surface methodology based on a central composite design was used to analyze, predict and optimize the WC/Co deposits of the laser-based HVOF sprayed coatings. The morphologies and microstructures of the laser clads were characterized using optical microscope, scanning electron microscope and X-ray diffraction techniques. The crack behavior and residual stress-based fractures were explored. In addition, the relationships between the residual stress of the laser clad and three factors: laser power, scanning speed and stand-off distance were examined. Further, optimization of the control factors: laser power, scanning speed and stand-off distance to minimize the residual stress was attained using a response surface methodology. The resulting lower residual stress has decreased the fracture crack activities and did not easily induce delamination in the laser clads. Findings from this study would greatly contribute to optimizing the experiments and achieve an enhanced structural evolution in the protective coating of traditional handicraft products by laser cladding.

Experimental and numerical analysis of transient thermal stresses on thick-walled cylinder

Thermal loading can be a significant source of stress, especially on pipelines, ducts, pressure vessels, and heat exchangers widely used in industry. Analytical and numerical studies of thermal stresses resulting from transient loads are restricted to simple geometries and simplified boundary conditions. Therefore, experimental data to confront these models are a necessity, particularly when analytical solutions are not available. This study aims at providing a mathematical model based on finite difference method to predict transient thermal stresses across a cylinder. To validate the model, experiments with strain gauges on the outer surface of a thick-walled cylinder were performed in a rig with controlled convective boundary conditions. Additionally, a numerical model based on Finite Element Method (FEM) was adjusted to reproduce the experimental and modeling results. Thermal stress evaluation occurs with temperature differences between the heat sink and source up to 70 °C, typical processing conditions of the oil and gas industry. Stresses are significant particularly during the startup and interruption of the production process. Peak thermal stress scales with mechanical stresses created by pressure difference of about 1050 bar. The agreement between experimental, finite difference method and numerical results paves the way to assess thermal processing equipment with complex geometry and boundary conditions.

Analysis of Temperature and Thermal Stress for a Solar Power Tower Molten Salt Receiver under Multi-Source Uncertainties

Although uncertainties such as solar radiation and material properties are generally involved in the solar receiver design process, current studies in the solar receiver field are based on deterministic models and do not incorporate these uncertainties into the design process. In this paper, based on a coupled deterministic thermal–structural model and an uncertainty analysis model, an analysis of temperature and thermal stress was conducted for a solar power tower (SPT) molten salt receiver under multi-source uncertainties to investigate the dispersions of responses. The results demonstrated that the maximum temperature inside the tube wall under multi-source uncertainties ranged from 847 K to 895 K, with an expectation of 871 K and a standard deviation of 8 K, and the maximum thermal stress ranged from 173 MPa to 245 MPa, with an expectation of 204 MPa and a standard deviation of 12 MPa, both of which had severer probabilities than the deterministic results (871 K and 204 MPa) and may cause failure in the receiver. Furthermore, the results of the global sensitivity analysis indicated that the peak incident solar flux was the most sensitive, and the specific heat of the tube material was the least sensitive to the maximum temperature and thermal stress of the tube wall. These results are beneficial to provide additional reliability and confidence in the temperature and thermal stress evaluation process of solar receiver tubes.

High-Temperature Stress Effect on the Red Cusk-Eel (Geypterus chilensis) Liver: Transcriptional Modulation and Oxidative Stress Damage.

Simple SummaryThe red cusk-eel (Genypterus chilensis) is a native Chilean species important for aquaculture diversification in Chile. The effect of high-temperature stress on the liver, a key organ for fish metabolism, is unknown. In this study we determined for the first time the effects of high-temperature stress on the liver of red cusk-eel. The results showed that high-temperature stress increased hepatic enzyme activity in the plasma of stressed fish. Additionally, this stressor generated oxidative damage in liver, and generated a transcriptional response with 1239 down-regulated and 1339 up-regulated transcripts associated with several processes, including unfolded protein response, heat shock response and oxidative stress, among others. Together, these results indicate that high-temperature stress generates a relevant impact on liver, with should be considered for the aquaculture and fisheries industry of this species under a climate change scenario.Environmental stressors, such as temperature, are relevant factors that could generate a negative effect on several tissues in fish. A key fish species for Chilean aquaculture diversification is the red cusk-eel (Genypterus chilensis), a native fish for which knowledge on environmental stressors effects is limited. This study evaluated the effects of high-temperature stress on the liver of red cusk-eel in control (14 °C) and high-temperature (19 °C) groups using multiple approaches: determination of plasmatic hepatic enzymes (ALT, AST, and AP), oxidative damage evaluation (AP sites, lipid peroxidation, and carbonylated proteins), and RNA-seq analysis. High-temperature stress generated a significant increase in hepatic enzyme activity in plasma. In the liver, a transcriptional regulation was observed, with 1239 down-regulated and 1339 up-regulated transcripts. Additionally, high-temperature stress generated oxidative stress in the liver, with oxidative damage and transcriptional modulation of the antioxidant response. Furthermore, an unfolded protein response was observed, with several pathways enriched, as well as a heat shock response, with several heat shock proteins up regulated, suggesting candidate biomarkers (i.e., serpinh1) for thermal stress evaluation in this species. The present study shows that high-temperature stress generated a major effect on the liver of red cusk-eel, knowledge to consider for the aquaculture and fisheries of this species.

Hemato-biochemical, Antioxidant Alteration in Thermal Stressed Cross-bred Cows and Mitigation using Micronutrients in Sub-tropical Zone of India

Background: Stress is a serious health problem in dairy cattle resulting in decreased milk production along with disturbances in reproductive functions. India is currently losing nearly 2 per cent of the total milk production, amounting to a whooping over Rs. 2,661 crore due to rise in thermal stress among lactating cattle and buffaloes because of the global warming (Upadhyay et al. 2007). Methods: The present study was conducted on 18 thermal stressed cross-bred dairy cattle for a period of about 45 days for detection and amelioration of thermal stress with the objective to evaluate clinic-haemato-biochemical, oxidative stress indices. Three different groups were taken in study with each group having 6 animals. Result: Reduced milk yield, increased physiological parameters; respiration rate, heart rate, rectal temperature, were observed in positive control animals. Cortisol a stress hormone was estimated for evaluation and amelioration of thermal stress. Haematological examination revealed decreased Hb, PCV and lymphopenia and concomitant neutrophilia in Group 1 animals. Biochemical evaluation revealed hyperglycemia, increased total protein and plasma glycine, decreased calcium, Na, K and Cl levels while as cortisol, AST, ALT levels were found to be increased in thermally stressed dairy cattle to which no supplement was given. Oxidative indices showed decreased activity of GSH, catalase, SOD activity in thermally stressed cattle which were ameliorated with micro-nutrients and mineral supplements.

Elevated Temperature Baseplate Effect on Microstructure, Mechanical Properties, and Thermal Stress Evaluation by Numerical Simulation for Austenite Stainless Steel 316L Fabricated by Directed Energy Deposition

In the present study, the effect of material deposition at the elevated temperature baseplate on the microstructure and mechanical properties was investigated and correlated to the unique thermal history by using numerical simulation. Numerical results agreed well with the experimental results of microstructure and mechanical properties. Numerical results revealed a significant decrease in temperature gradient and a 40% decrease in thermal stress due to material deposition on the elevated temperature baseplate. The reduced thermal stress and temperature gradient resulted in coarser grain features, which in turn led to a decrease in hardness and tensile strength, especially for the bottom region near the baseplate. Meanwhile, no significant effect could be found for ductility. In addition, an elevated temperature baseplate promoted less heterogeneity in hardness and tensile properties along the building direction. The current work demonstrates a collective and direct understanding of the baseplate preheating effect on thermal stress, microstructure and mechanical properties and their correlations, which is believed beneficial for the better utilization of baseplate preheating positive effects.

Systematic review of animal-based indicators to measure thermal, social, and immune-related stress in pigs.

The intense nature of pig production has increased the animals' exposure to stressful conditions, which may be detrimental to their welfare and productivity. Some of the most common sources of stress in pigs are extreme thermal conditions (thermal stress), density and mixing during housing (social stress), or exposure to pathogens and other microorganisms that may challenge their immune system (immune-related stress). The stress response can be monitored based on the animals' coping mechanisms, as a result of specific environmental, social, and health conditions. These animal-based indicators may support decision making to maintain animal welfare and productivity. The present study aimed to systematically review animal-based indicators of social, thermal, and immune-related stresses in farmed pigs, and the methods used to monitor them. Peer-reviewed scientific literature related to pig production was collected using three online search engines: ScienceDirect, Scopus, and PubMed. The manuscripts selected were grouped based on the indicators measured during the study. According to our results, body temperature measured with a rectal thermometer was the most commonly utilized method for the evaluation of thermal stress in pigs (87.62%), as described in 144 studies. Of the 197 studies that evaluated social stress, aggressive behavior was the most frequently-used indicator (81.81%). Of the 535 publications examined regarding immune-related stress, cytokine concentration in blood samples was the most widely used indicator (80.1%). Information about the methods used to measure animal-based indicators is discussed in terms of validity, reliability, and feasibility. Additionally, the introduction and wide spreading of alternative, less invasive methods with which to measure animal-based indicators, such as cortisol in saliva, skin temperature and respiratory rate via infrared thermography, and various animal welfare threats via vocalization analysis are highlighted. The information reviewed was used to discuss the feasible and most reliable methods with which to monitor the impact of relevant stressors commonly presented by intense production systems on the welfare of farmed pigs.

Influence of atmospheric stability on air ventilation and thermal stress in a compact urban site by large eddy simulation

The assumption of neutral atmosphere in conventional evaluation of air ventilation and thermal stress in a compact urban area with weak wind environment may lead to errors. To assess this effect, this paper presents air ventilation and thermal stress assessment in a real subtropical urban area in Hong Kong by large eddy simulation considering stable, neutral, and unstable stratification. The air ventilation and thermal stress are measured by wind velocity ratio and Universal Thermal Climate Index, respectively. The atmospheric stabilities are quantified by vertical profiles of equivalent potential temperature based on daily radiosonde records in recent five years. The simulated results show that the conventional isothermal assumption underestimates the air ventilation capacity and overestimates the heat stress in the urban area in terms of reduced wind speeds and increased areas of strong heat stress at pedestrian-level height, respectively. The influence of urban morphology on air ventilation and thermal stress is investigated based on two urban geometry indices, namely ground coverage ratio and frontal area ratio. It is found that the ground coverage ratio is more relevant to the urban ventilation and thermal stress, but the correlations are weakened under unstable condition. On the other hand, the influence of the frontal area ratio is little. The findings of this study aim to provide a reference to the amendment of the current air ventilation assessment methodology which neglects the influence of atmospheric stability.

Experimental evaluation of thermal stress on the surface of butterfly specimen through irreversible colour change of thermal paint

Gas Turbines have been used effectively and extensively in jet propulsion and the sectors of electricity production. The flame produced due to combustion of air & fuel propagates through the gas turbine’s parts. As the hot combustible gases flow through these components, high thermal stresses are imposed on these components. The material life of the individual elements of the gas turbine system depends on its operating temperature and thermal stress. To achieve higher efficiency, the operating temperature may be increased to a certain level. Temperature (or) thermal profiling of the engine components is mandatory to make the engine design reliable. Thermal paint used for temperature profiling of hot surfaces is estimated to be the structured method even after removing the heat source. The present research concentrates on the investigations on the evaluation of thermal stress induced on a hot specimen through the application of thermal paint. A butterfly specimen made of Mild Steel has been fabricated and used for the present experimental investigations. The current work also concentrates on the variation in the surface temperature of the specimen based on the heat input using the butterfly specimen. The colour change on the surface of the specimen has been related to temperature using the RGB values of colour through MATLAB’s fuzzy logic. The results of the experimental investigation prove that the usage of thermal paint reveals the exact deal of stress developed thermally on the surface of the specimen based on the colour change.

Effect of the heat treatment mode of high chrome iron rolling mills on chrome redistribution in the stress field

Heat treatment is an important stage in the technology of rolling rolls, due to the fact that the thermal stresses that occur during rapid or uneven heating summing up with the rather high residual stresses after casting, create a risk of cracking. Goal. The aim is improving the quality of rolling rolls by varying the modes of heat treatment. Therefore, it is important to assess the level of thermal stress. Method. Evaluation of thermal stresses arising in heating and cooling in the heat treatment process that summing up to the relatively high residual stresses after casting, creates the risk of fractures. The profile of the distribution of chromium in the cross section of the working layer at each time under the action of the stress gradient that occurs during heat treatment of the roll is obtained by calculation. Results To ensure a minimum temperature difference between the surface and the core, it is necessary to reduce the heating and cooling rate, as well as increase the duration of exposure at a given temperature. Reducing the cooling rate from 17 to 3.7°C/h decreases the temperature difference at the surface and in the center of the roll and the intensity of thermal stresses from 29 to 7 MPa. It is established that the rate of heating and cooling should not exceed 10– 15° C/h, and exposure to annealing should be at least 5–7 hours. Scientific novelty. The modes of heat treatment of rolling rolls with a high-chromium cast iron working layer are designed by estimating the level of thermal stresses. The profile of distribution of chromium after various modes of heat treatment is calculated analytically and its mode at which the most uniform distribution of chromium on section of a working layer remains is offered. Practical significance. The developed technique allows to calculate analytically the profile of distribution of chromium after various modes of heat treatment and to choose such a mode at which the most uniform distribution of chromium remains on the section of a working layer.

Numerical investigation on heat transfer and thermoelastic stress in a solar cavity receiver

Central receiver withstands a highly non-uniform concentrated solar irradiation during its daily operation, which produces temperature gradients in axial, circumferential and radial directions of the absorber tubes, inducing high thermal stress and deformation, even fatigue and creep damage to the tubes. Therefore, an accurate evaluation of thermal stress in receiver tubes is crucial for its safe operation. In the present study, an optical-thermal-stress computational model was adopted to analyze the heat transfer and thermoelastic stress in the absorber tubes of a cavity receiver using water/steam as the heat transfer fluid. The three-dimensional heat flux, wall temperature and thermal stress profiles of the boiling and superheated tubes were obtained. On the basis, the origin of thermal stress were investigated from the perspective of normal stress components and equivalent stress, and special attention was paid to the axial temperature gradient. The results indicate that a significant difference in terms of heat transfer can be observed between the boiling and superheated tubes. In comparison, the peak stress of the superheated tube is 54% higher than that of the boiling tube. Besides, increasing the mass flow rate in the superheated tube can effectively reduce its thermal stress, however this measure is invalid for the boiling tube. Moreover, careful control of boiling to avoid complete evaporation is suggested for the boiling tube, which would create a non-linear axial temperature gradient to the tube, resulting in appreciable stress at the location of sudden variation in wall temperature.