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Problem. The mathematical description of the temperature field of the rim of the brake pulley can have both an independent value and be the goal of solving a problem (for example, when calculating the time of heating or forced cooling), and also be used as an auxiliary result for solving another, more complex problem (for example, calculating thermoelastic stresses in brake pulley rim). Goal. The purpose of the work is to assess the energy load of metal friction brake elements during the braking process. Methodology. Solving the tasks involved taking into account the fact that the surface-volume temperatures of the polished working surface of the pulley rim are local when assessing the energy load of the belt pulley rim; surface-volume temperatures are always higher than the "pure" volume temperatures of the pulley rim; polished and matte surfaces of the pulley rim are considered. Results. It is proposed that a new approach to the calculation of local thermal stresses, which is implemented for the first time in the theory of friction and wear. The reliability of the obtained results was confirmed experimentally. Originality. The need to find the non-stationary field in the investigated single- ("pad-pulley") and in multi-pair ("tape-pad" and "pad-pulley") friction nodes is proposed. In the last friction nodes, the friction pads act as insulation between the tape, which is freed from the pads, and the working surface of the brake pulley rim. Practical value. The proposed approach made it possible to establish that the magnitude of stresses on the surface of heat release is almost 5 times greater than in the volume of the pulley rim. At the same time, the nature of the influence of the intensity of heat exchange on the magnitude of stresses is the same as during heating, which leads to a decrease in the formation of cracks on the surface of the pulley rim., Математичний опис процесу теплопровідності із залученням елементів теорії теп-лової подібності щодо обода шківа стрічково-колодкового гальма за умови режимів гальмування дали змогу встановити: через дискретність контакту мікровиступів пар тертя гальма дослі-джувані параметри мають локальний характер; до енергонавантаженості пар тертя гальма належать параметри поверхнево-об’ємних та об’ємних температур і їх градієнтів, що викли-кають термічні напруження, які впливають на фрикційні характеристики; за поверхнево-об’єм-них температур (100–400) °С сумарна кількість теплоти, що відводиться від полірованої та матової поверхонь шківа радіаційним теплообміном за 1,0 с, становила (1,43–23,04) кДж; у цьому разі поверхневий температурний градієнт обода шківа був майже вп’ятеро більший, ніж за його товщиною. За умови циклічного (повторно-короткочасного) режиму гальмування температурні напруження внаслідок нагрівання на поверхні обода шківа майже вдесятеро пе-ревищують значення напружень, що виникають в його об’ємі. Напруження досягають макси-муму, коли процес теплоізольований (Bi = 0), і дорівнює нулю, коли теплообмін нескінченний (Bi → 0). Величина напружень унаслідок охолодження обода шківа так само істотно залежить від критерію Біо. До того ж зі збільшенням тривалості процесу гальмування вплив його на ве-личину напружень також зростає. Величина термічних напружень на поверхні тепловиділення майже вп’ятеро більша, ніж в об’ємі обода шківа. У цьому разі характер впливу інтенсивності теплообміну на величину напружень такий самий, що й за умови нагрівання. Новий підхід до розрахунку локальних термічних напружень у теорії тертя та зношування реалізований уперше. Достовірність здобутих результатів підтверджена експериментально.

In this study, the modified Green and Lindsay model is utilized to discuss the effects of heating caused by surface absorption of laser radiation in a two-dimensional thermoelastic half-space. The temporal profile of the pulsed laser is taken as a non-Gaussian and the spatial one is a Gaussian. The medium surface is taken to be traction free. The integral transform method is utilized to obtain the general solution by applying the two transformations Hankel and Laplace, in which the inverse of Laplace is performed numerically. The Silicon material is considered as an example to verify the consistency of the obtained results of the new model.

The fabrication of poly(oxymethylene) by means of additive manufacturing is still a problematic procedure due to the low adhesion with standard printing plates and extended warping. The use of polymers as alternative substrates is an effective way, especially if their glass-transition temperature is below the processing temperatures. Using poly(methyl methacrylate) sheets as sacrificial substrate, standard samples of poly(oxymethylene) are successfully printed, a result achieved in the past only by means of expensive and complex equipment. Furthermore, the mechanical and thermal properties of poly(oxymethylene) upon UV aging up to 500 h are investigated. Our results demonstrate that aging of 3D-printed poly(oxymethylene) causes chain scission and weakening of intermolecular bonds, crystallization of part of the amorphous areas, and results in the embrittlement of the material. The intermolecular structure of poly(oxymethylene) has been investigated by means of Fourier transform infrared spectroscopy.

Разработана технология оплавления напыленного коррозионно-стойкого покрытия при индукционном нагреве стальной цилиндрической заготовки с указанным покрытием в условиях вращения. Выбраны частота тока и другие параметры индукционной установки повышенной частоты для обеспечения максимального тепловыделения в коррозионностойком покрытии при его оплавлении на поверхности стальной цилиндрической заготовки. Проведены расчеты и исследования поверхностных распределений плотности тока и температуры по длине заготовки при индукционном нагреве. Выполнены расчетные и экспериментальные исследования индукционного нагрева, теплового и термонапряженного состояния стальной заготовки с покрытием. Проведено сравнение расчетной и экспериментальной кривых нагрева поверхности стальной заготовки с покрытием с учетом двух точек Кюри. Анализ результатов показывает, что термонапряжения, возникающие в заготовке, не влияют на технологический процесс индукционного нагрева заготовки с оплавлением покрытия., A technology for melting a sprayed corrosion-resistant coating during induction heating of a steel cylindrical billet with the aforementioned coating under rotational conditions has been developed. The current frequency and other parameters of the high-frequency induction unit were chosen to ensure the maximum heat release in the corrosion-resistant coating during melting on the surface of a steel cylindrical billet. Calculations and analysis of the surface distributions of the current density and temperature along the workpiece during induction heating have been carried out. Theoretical and experimental studies of induction heating, thermal and thermally stressed state of a steel billet with a coating are performed. The calculated and experimental curves for heating the surface of a steel billet with a coating are compared taking into account two Curie points. The analysis of the results shows that the thermal stresses that arise in the billet do not affect the technological process of induction heating of the workpiece with melting of the coating., Промышленная энергетика, Выпуск 3 2023, Pages 45-51

In this study, a general analysis of one dimensional steady-state thermal stresses of a functionally graded hollow spherical vessel with spherical isotropy and spherically transversely isotropy is presented with material properties of arbitrary radial non-homogeneity. The material properties may arbitrarily vary as continuous or piecewise functions. The boundary value problem associated with a thermo-elastic problem is converted to an integral equation. Radial and tangential thermal stress components distribution can be determined numerically by solving the resulting equation. The influence of the gradient variation of the material properties on the thermal stresses is investigated and the numerical results are presented graphically.

Due to the elevated operating temperatures (800–1000 °C) of tubular solid oxide fuel cells (SOFC), severe thermal stresses are produced during their operation. Functionally graded materials (FGMs) are used in anodes and cathodes to reduce the specific thermal stresses. The use of FGMs compensates for the effect of any sudden shift in the coefficient of thermal expansion of these electrodes with respect to the electrolyte. In this study, the tubular SOFC efficiency, performance, and produced thermal stresses were numerically investigated. A 3D numerical model that includes the equations of mass conservation, momentum, charging transport, and electricity was developed. These coupled equations of the electrochemical phenomena were solved using ANSYS 19.1-Fluent Solver. The temperature values that were obtained were sequentially introduced into the structural finite element model as body loads, and the model was solved with ANSYS 19.1-MAPDL Solver. The numerical model was validated against previously published experimental results. For both electrodes, the FGM was identified by a grading index “m.” The use of the FGM for the anode and cathode instead of conventional electrodes increased the tubular SOFC efficiency and reduced the thermal stress. Optimum results were obtained at grading index m = 2.0, with the cell output increased by 8 % and induced thermal stresses well below the yielding levels.

The stress-strain state of ZrB2-SiC ultra-high-temperature ceramics, produced using commercial powders with different impurity levels, was investigated by X-ray diffraction. Upon analysis of ZrB2 and SiC diffraction lines shift, the level of thermal stresses (strains) of the different phases was determined. An increase of internal stresses in ceramics with rising viscous-brittle transition temperatures, Tve, was attributed to increased grain boundary strength. Ceramics, for which high Tve and high level of internal stresses were estimated, exhibited high strength, up to 700 MPa at 1400 °C. A field of compressive thermal stresses in the matrix phase resulted to be necessary for achieving high strength at low-temperatures. On the contrary, the presence of low-melting impurities at the grain boundaries negatively impacted on the stress level in ZrB2 boundaries in the high temperature regime.

Modern clutches are a critical component of a machine/equipment because they are designed to transfer and control torque, consequently producing movements, enabling safe operation, and controlling movement when necessary. When a clutch engages it transfers torque and allows a machine to produce mechanical work as a final result. The clutch engagement process generates heat due to the slipping of clutch discs. Although pressure applied on clutch discs generates stresses in the disc material, it was not clear how severe a combination of pressure and heat might raise the stresses. This study aimed to produce a numerical simulation to determine the impact of temperature also torque changes in the clutch discs when it transfers movement. Some static and thermal numerical simulations by Finite Element Analysis (FEA) (linear-elastic analysis) were performed, which considered two scenarios; (1) first with only pressures applied on clutch disc's face; (2) where heat was added to pressures. These mathematical simulations revealed that discs stresses are highly sensitive to thermal variations since for some cases the maximum von Mises stresses exceeded discs material mechanical strength leading it to failure. To overcome this problem it is compulsory to consider heat when designing a clutch and a cooling system for it.

Thermal stresses of a functionally graded hollow thick cylinder due to non-uniform internal heat generation are studied in this paper. Analytical solutions are obtained with radially varying properties by using the theory of elasticity. Thermal stresses distribution for different values of the powers of the module of elasticity and varying power law index of heat generation are studied. The results have been computed numerically and illustrated graphically.

In the present study, we have applied the reduced differential transform method to solve the thermoelastic problem which reduces the computational efforts. In the study, the temperature distribution in a two-dimensional rectangular plate follows the hyperbolic law of heat conduction. We have obtained the generalized solution for thermoelastic field and temperature field by considering non-homogeneous boundary conditions in the x and y direction. Using this method one can obtain a solution in series form. The special case is considered to show the effectiveness of the present method. And also, the results are shown numerically and graphically. The study shows that this method provides an analytical approximate solution in very easy steps and requires little computational work.

In this study, the thermal stress alterations generated in a tungsten fiber reinforced titanium composite (W/Ti composite) were evaluated by the neutron stress measurement method at cryogenic temperatures. The W/Ti composite thermal loads were repeated from room temperature to the cryogenic temperature (10 K), and alterations in thermal residual stress were evaluated using the neutron in situ stress measurement method. In this measurement, the stress alterations in the titanium matrix and the tungsten fibers were measured. This measurement was carried out by TAKUMI (MLF-BL19) of J-PARC, a neutron research facility in the Japan Atomic Agency. The measurement method of TAKUMI is the time-of-flight (TOF) method. Owing to this measurement method, the measurement time was significantly shortened compared to the angle-dispersion type measurement by a diffractometer. As a result of the measurement, large compressive stresses of about 1 GPa were generated in the tungsten fibers, and tensile stresses of about 100 MPa existed in the titanium matrix. The thermal stresses due to the temperature change between room temperature and cryogenic temperature is caused by the difference of thermal expansions between the tungsten fibers and the titanium matrix, and these stress values can be approximated by a simple elastic theory equation.

This paper presents numerical calculation of thermal stresses generated in a carbon fiber-epoxy laminated composite structure which is operating at low temperatures. The thermal stress evaluation is based on the finite element method. A sample problem involving generated thermal stresses in a real laminated composite structure, exposed to low temperatures (four different temperature levels), is analyzed and discussed. Obtained results suggest that these thermal stresses remarkably decrease the strength of the laminated composite structure.

A way how to select the ceramic coating thickness with respect to axially symmetrical thermal stresses in a casting machine piston with a horizontal shot sleeve has been discussed. An application of a technological ceramic outer layer in the piston enhances its tribological properties. The condition that stresses in tension in the outer ceramic layer are lower than the tensile strength has been proposed as a selection criterion.

Mathematical modeling of a thin circular plate has been made by considering a nonlocal Caputo type time fractional heat conduction equation of order 0 < α ≤ 2, by the action of a moving heat source. Physically convective heat exchange boundary conditions are applied at lower, upper and outer curved surface of the plate. Temperature distribution and thermal deflection has been investigated by a quasi-static approach in the context of fractional order heat conduction. The integral transformation technique is used to analyze the analytical solution to the problem. Numerical computation including the effect of the fractional order parameter has been done for temperature and deflection and illustrated graphically for an aluminum material.

In this article, a time fractional-order theory of thermoelasticity is applied to an isotropic homogeneous elliptical disk. The lower and upper surfaces of the disk are maintained at zero temperature, whereas the sectional heat supply is applied on the outer curved surface. Thermal deflection and associated thermal stresses are obtained in terms of Mathieu function of the first kind of order 2n. Numerical evaluation is carried out for the temperature distribution, Thermal deflection and thermal stresses and results of the resulting quantities are depicted graphically.

With the rise of renewable energy resources, especially offshore wind power plant, the DC transmission concept has attracted more and more attention. The selection of eco-friendly insulating gas, as most critical insulating part of gas-insulated equipment is top priority for developing highly reliable system. Moreover, it is acknowledged that eco-friendly C(3)F(7)CN/CO(2) gas mixtures have become a potential alternative to SF(6) gas due to its excellent performance. This study reviews the basic physical properties of C(3)F(7)CN gas/gas mixtures and insulation properties including the gas gap breakdown and surface flashover performance at DC, as well as lightning impulse voltage. Investigation about the gas stability is presented, including the compatibility of gas with solid materials in gas-insulated transmission line (GIL), and the decomposition characteristics under long-term electrical and thermal stresses. The important progress on the charge accumulation characteristics of gas–solid interface in the novel gas environment under DC voltage stress is analysed. Finally, the key issues that need to be paid attention to and further followed through regarding the application of this novel gas in GIL are summarised and put forward. This study hopefully can provide a complete reference for the development of eco-friendly DC gas insulation equipment with C(3)F(7)CN/CO(2) gas mixtures.

This paper presents a numerical approach to predict the thermal residual stresses in polymer nanocomposites reinforced with a periodic array of wavy carbon nanotubes. A three dimensional unit cell model is established to accurately account for the waviness of the nanotube. Periodic boundary conditions are determined for the unit cell with a pair of curved surfaces. Appropriate methods to evaluate the macroscopic stresses and strains are also determined for the unit cell model in which the interior pores of the nanotubes are explicitly included. It is demonstrated that the macroscopic behavior of the nanocomposites is orthotropic due to the symmetries manifested. By employing material properties of the two constituents, the thermal residual stresses and strains induced by high temperature curing and cooling-down are predicted for an epoxy/wavy-nanotube composite. It is also demonstrated that the curing process tends to increase the waviness of the nanotube and the waviness has a significant influence on the distribution of the microscopic residual stresses.

A new analytical solution is presented for functionally graded (FG) beams to investigate the bending behaviour under the hygro-thermo-mechanical loading using a new fifth order shear and normal deformation theory (FOSNDT). The material properties of the FG beam are varied along the thickness direction according to the power law index. In the present theory, a polynomial shape function is expanded up to fifth-order in terms of thickness coordinate to consider the effects of transverse shear and normal deformations. The present theory is free from the shear correction factor. Using the Navier’s solution technique the closed-form solution is obtained for simply supported FG beams. All the results are presented in non-dimensional form and validated it by developing the classical beam theory (CBT), first order shear deformation theory (FSDT by Mindlin) and third order shear deformation theory (TSDT by Reddy) considering the hygro-thermo-mechanical loading effects which is mostly missing in the literature. It is noticed that the presented FOSNDT is very simple and accurate to predict the bending behaviour of FG beams under linear and non-linear hygro-thermo-mechanical loadings.

The aim of this study is to develop an analytical model to determine temperature and thermal stresses distributions in a single plate clutch during the slipping phase. Proposed expressions enable calculation of temperature and thermal stresses on the contact surface as well as at any depth inside the friction material and at any instant during the slipping period. It was investigated how the maximum temperature on the friction surface varies with the thickness of the friction facings of the clutch disc and the intensity of convective cooling.

The braking system is one of the most important elements in vehicle systems from the aspect of vehicle safety, besides the steering system and the internal combustion engine. During the braking process, the disc and pads absorb a large amount of kinetic energy that converted to heat. Owing to this frictional heating, it is necessary to compute the temperature distribution that will be appeared during the braking process, which is the main goal of this research paper. There are many factors that can be influenced to the distribution of frictional heat generated. One of the significant factors is the applied pressure by the brake pad on the braking disc. The results proved that when increased the applied pressure then the frictional heat generated increased too. It was developed a new finite element model based on observed data from real vehicle. It was used ANSYS/WORKBENCH 14.5 software to perform the numerical analysis, module Transient Structural. Parts that are the most disposed to the thermal stress are braking pads. Also, it was found time period from 0 to 0.1 second is the most critical period during the whole braking period, because in this period, temperature rises rapidly, the maximum temperature occurred at 1.338 seconds, and after that it falls. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR35041: The research of vehicle safety as part of a cybernetic system: Driver-Vehicle-Environment]

Made available in DSpace on 2022-05-01T12:56:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-01-01 This study was conducted to evaluate the effect of genetic selection (Lines A and B; Line A pigs have a greater proportion of Pietrain genes than those from Line B and therefore, selected for improved lean tissue accretion) on the feeding behavior of group-housed pigs exposed to daily cyclic high ambient temperatures. Feeding behavior of 78 barrows housed together in a single room was recorded in real time by five automatic feeders. The feeders registered each visit of each pig (day, hour, min, and second) and the amount of feed requested. Daily cyclic high ambient temperature was induced exposing pigs at 22C from 18.00 to 10.00 h and 30C from 10.01 to 17.59 h. From this temperature variation, day-period was divided into: 22C(06-10h), from 6.00 to 10.00 h; 30C(10-18h), from 10.01 to 17.59 h; and 22C(18-06h), from 18.00 to 5.59 h. Meal criteria was estimated based on the probability of animals starting a new feeding event within the next minute since the last visit (Pstart). After defining the meal criteria, the number of meals (n), feed intake rate (g/min), feed intake (g/meal), feeder occupancy (min/meal), and interval between meals (min) of each animal were calculated. Greatest probability of starting to feed was observed at 22C(06-10h), followed by 30C(10-18h) and then 22C(18-06h). Regardless of time period, pigs from line A had greater feed intake rate and lower feed intake, feed occupancy per meal and probability of starting a meal when compared with line B pigs. Only line A pigs had greater feed intake and feeder occupancy per meal at 22C(18-06h) than remainder of the day. This indicates that pig feeding pattern is strongly related to the circadian rhythm. However, the genetic selection for improved lean tissue accretion may modulate pigs feeding behavior under daily cyclic high ambient temperatures. Department of Animal Science School of Agricultural and Veterinarian Sciences São Paulo State University, São Paulo PEGASE INRAE Institut Agro, Saint Gilles Department of Animal Science Universidade Federal de Viçosa, Minas Gerais, Viçosa Department of Statistics Universidade Federal do Rio Grande do Sul, Rio Grande do Sul Department of Animal Science Universidade Federal do Rio Grande do Sul, Rio Grande do Sul Department of Animal Science School of Agricultural and Veterinarian Sciences São Paulo State University, São Paulo

The article studies the influence of steel fiber on the change in temperature stresses in concrete at an early hardening stage. When hardening concrete is exposed to heat treatment, its volume and, conse-quently, density change. Under certain circumstances, this can lead to its structural damage and, ulti-mately, to a decrease in its physical and mechanical properties at the design age. Such structural dam-age of concrete can appear even at the earliest hardening stage, before the formation of the elastic properties of the material. When testing concretes subjected to heating, we recorded the development of temperature deformations and assessed their plastic viscosity. To determine the temperature stresses, we proposed a method based on the Kelvin-Voigt rheological model. Studies have shown that the pres-ence of steel fibers in concrete leads to a decrease in the deformations of concrete during heat treat-ment. To assess the thermal stresses arising at the early stage of hardening, we derived an analytical dependence, taking into account the viscosity of the hardening concrete. During the experiments, we obtained values for the viscosity of steel-fiber reinforced concrete depending on its fiber content. The results showed that, without changing its density, steel-fiber reinforced concrete can take significantly higher thermal stresses than unreinforced concrete at the early hardening stages. With an increase in the temperature, the change in the thermal stresses, depending on the fiber content, begins to have a more pronounced non-linear nature. We also showed that before a certain structural strength is reached, there are no thermal stresses in steel-fiber reinforced concrete due to the steel-fiber induced redistribution of temperature forces throughout the volume of concrete.

Dissecting the genetic basis of physiological and yield traits against tolerance to heat stress is an essential in wheat breeding programs to boost up the wheat yield for sustainable food security. Herein, a genome-wide association study (GWAS) was performed to reveal the genetic basis of heat tolerance using high-density Illumina 90K Infinium SNPs array through physiological and yield indices. These indices were phenotyped on a diverse panel of foreign and domestic genotypes of Pakistan, grown in normal and heat-stressed environments. Based on STRUCTURE analysis, the studied germplasm clustered into four sub-population. Highly significant variations with a range of moderate (58.3%) to high (77.8%) heritability was observed under both conditions. Strong positive correlation existed among physiological and yield related attributes. A total of 320 significant (-log10 P ≥ 3) marker-trait associations (MTAs) were identified for the observed characters. Out of them 169 and 151 MTAs were recorded in normal and heat stress environments, respectively. Among the MTA loci, three (RAC875_c103017_302, Tdurum_contig42087_1199, and Tdurum_contig46877_488 on chromosomes 4B, 6B, and 7B respectively), two (BobWhite_c836_422 and BS00010616_51) and three (Kukri_rep_c87210_361, D_GA8KES401BNLTU_253 and Tdurum_contig1015_131) on chromosomes 5A, 1B, and 3D at the positions 243.59cM, 77.82cM and 292.51cM) showed pleiotropic effects in studied traits under normal, heat-stressed and both conditions respectively. The present study not only authenticated the numerous previously reported MTAs for examined attributes but also revealed novel MTAs under heat-stressed conditions. Identified SNPs will be beneficial in determining the novel genes in wheat to develop the heat tolerant and best yielded genotypes to fulfill the wheat requirement for the growing population.

Metal AM processes produce significantly rough surfaces as compared to wrought or machined components. Currently, the as-EBM surfaces are extremely rough and consequently, the as-built components could not be directly used as commercial products. The state-of-the-art research has focused primarily on deeply machined (DM) samples. The mechanical properties of the EBM components as reported thus are not real representative of the process. This can largely dispute the main merits of the EBM process: print on demand and low buy-to-fly ratio. Hence, the research here was designed to bridge this research gap and systematically analyze the properties of net-shaped (NS) and near-net-shaped (NNS) components. This thesis is divided into three levels, including the fundamental, validation and optimization level. The fundamental research work is performed on the commercialized processing parameters from Arcam, for Inconel 718 (IN718). The NNS samples made with and without the commercial multi-spot contour are tested for their mechanical properties. These samples achieved smoother surfaces and better tensile behavior. Thus, they were later compared with the NS and DM samples which were made with the same parameter settings but varied machining depth. The purpose of this work was to test the NS and NNS samples and analyze the cause of the failure. It was found that the premature failure of these samples was linked to the porous surface and subsurface region. Therefore, a machining protocol was set up according to the depth of the porous region which can theoretically improve the tensile strength of the machined samples to a level comparable to wrought material. The findings in case of IN718 were also validated for another superalloy, Inconel 625(IN625). The results again showed that the machining requirement of the as-EBM samples with contour is more than 2 mm. Therefore, a novel contouring strategy was later developed, optimized and tested in order to eliminate the machining requirement. To do so, the continuous contour with different energy, overlapping ratio and sequence to the hatching region was tested. The high-energy continuous contour applied after hatching was found to be the optimal strategy, which was able to maintain a comparable surface condition as the multi-spot contour whilst it could generate a denser subsurface region. Accordingly, the NNS samples with such contour achieved comparable tensile properties as DM samples. It should be noted that all these research works were focused on the vertical samples (along the building direction) to avoid high thermal stresses in horizontal direction that seriously limit deformation free manufacturing of the samples. To deal with the challenge of thermal stresses and deformation, the last part of this research was designed to assess the thermal stresses and strains of EBM manufactured IN625 samples. The effects of different processing parameters and scanning strategies were tested to provide a set of guidelines about how to produce the horizontal and longer components. The results showed that one could effectively minimize the thermal stress/strain and deformation of the parts using a bidirectional scanning pattern with proper layer rotations angles to deliver shorter scans in each layer. Additiva tillverkningsprocesser i metall ger avsevärt grövre ytor jämfört med smidda eller maskinbearbetade komponenter. Ytor tillverkade med as-EBM blir, med dagens teknik, extremt grova och följaktligen kan dessa komponenter inte användas direkt som kommersiella produkter. Den senaste forskningen har primärt fokuserat på djupt bearbetade (DM) prover. De mekaniska egenskaperna som rapporterats för dessa EBM-komponenter är således inte representativa för processen. Detta kan till stor del ifrågasätta de viktigaste fördelarna med EBM-processen: beställtryck och låg volymkvot mellan materialbit och komponent. Således var denna forskning utformad för att överbrygga detta forskningsgap samt systematiskt analysera egenskaperna hos slutformade (NS) och nära slutformade (NNS) komponenter. Denna avhandling är indelad i tre nivåer bestående av grundläggande, validering och optimering. Det grundläggande forskningsarbetet har utförts på kommersialiserade processparametrar från Arcam och materialet Inconel 718 (IN718). NNS-proverna gjorda med och utan den kommersiella smältningsstrategin med flerpunktskontur har testats för utvärdering av mekaniska egenskaper. Dessa prover uppnådde jämnare ytor och bättre dragegenskaper. Således jämfördes de senare med NS- och DM-proverna vilka gjordes med samma parameterinställningar men olika bearbetningsdjup. Syftet med detta arbete var att testa NS- och NNS-proverna och analysera orsaken till brott. Det konstaterades för dessa provbitar att tidiga brott var kopplat till den porösa ytan och regionen nära ytan. Därför implementerades en bearbetningsprocedur upp i enlighet med djupet av den porösa regionen vilket teoretiskt kan förbättra draghållfastheten för de bearbetade proverna. Detta till en nivå som är jämförbar med smidda material. Utfallet med IN718 kunde även valideras för en annan superlegering, Inconel 625 (IN625). Resultaten visade återigen att bearbetningskravet för as-EBM-proverna med strategin för flerpunktskontur är mer än 2 mm. Därför utvecklades, optimerades och testades en ny kontureringsstrategi med syfte att eliminera bearbetningskravet. För att göra detta testades strategier med kontinuerlig kontur och olika energi, överlappningsförhållande och sekvens till regionen med fyllnadsläggning. Den kontinuerliga högenergi-konturen som applicerades efter fyllnadsläggning visade sig vara den optimala strategin som kunde bibehålla jämförbar kondition på ytan som strategin med multipunktskonturen, samtidigt som den generera en tätare struktur i regionen under ytan. Följaktligen uppnådde NNS-proverna med sådan kontur jämförbara dragegenskaper som DM-prover. Det bör noteras att forskningen var fokuserad på vertikala prover (längs byggriktning) för att undvika höga termiska spänningar i horisontell riktning som kraftigt begränsar deformationsfri tillverkning av provbitar. För att hantera utmaningen med termiska spänningar och deformation utformades den sista delen, inom denna avhandling, för att bedöma termiska spänningar och töjningar av EBM-tillverkade provbitar i IN625. Effekten av olika processparametrar och skanningsstrategier utvärderades för att ta fram en uppsättning riktlinjer gällande tillverkning av horisontella och längre komponenter. Resultaten visade att termisk spänning, töjning och deformation kund minimeras genom att använda ett dubbelriktat skanningsmönster med rätt lagerrotationsvinklar för att ge kortare skanningar i varje lager.

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., Здійснено аналіз термічних напружень, що виникають під час нагрівання та охолодження в процесі термічного оброблення, які разом з досить високими залишковими напруженнями після лиття створюють небезпеку виникнення тріщин. Проаналізовано перерозподіл хрому за перетином робочого шару валка в полі напружень

U eksploataciji, konstrukcije su podvrgnute različitim vrstama opterećenja, među kojima je toplinsko opterećenje. Toplinsko opterećenje uzrokuje promjenu temperaturnog polja konstrukcije te se manifestira kroz pomake, odnosno deformacije i pojavu naprezanja u određenim uvjetima. Takva vrsta opterećenja se analizira termomehaničkom analizom koja može biti potpuno spregnuta termomehanička analiza ili sekvencijalno spregnuta termomehanička analiza. Uslijed toplinskog opterećenja, ne dolazi do trenutnog stacioniranja novog temperaturnog polja već postoji vrijeme u kojem se vrijednosti stacioniraju. Takve pojave nazivaju se tranzijentnim pojavama čije se vrijednosti računaju raznim metodama vremenske integracije. Ovaj rad se bazira na sekvencijalno spregnutoj metodi koja podrazumijeva pronalazak temperaturnog polja, a potom se promjena temperature implementira u matematički model. Oba modela, termalni i mehanički, analiziraju se i opisuju jednadžbama Metode konačnih elemenata, dok se tranzijentne pojave obuhvaćaju i računaju eksplicitnom metodom vremenske integracije. Structures are subjected to a variety of loads during exploitation, including a heat load. The heat load generates a change in the structure's temperature field, which presents itself as displacements, or deformations, as well as the appearance of stress under particular conditions. Thermomechanical analysis, which can be fully coupled thermomechanical analysis or sequentially coupled thermomechanical analysis, is used to study this sort of stress. Due to the heat load, the current staticity of the new temperature field does not occur, but there is a time at which the values are stationed. These are known as transient phenomena, and their values can be determined using a variety of time integration methods. This thesis is based on a sequentially coupled method that entails first locating a temperature field, and then incorporating the temperature change into a mathematical model. Both models, thermal and mechanical, are analyzed and described by equations of Finite element methods, while transient phenomena are encompassed and calculated by explicit time integration method.

Coal-fired power units, now balancing power shortages in the power system, must be characterised by increasingly higher flexibility of operation. This means faster start-ups and the capacity for frequent decreases and increases in the power output. These processes cause large temperature gradients in elements of the power unit and the turbine and lead to an increase in the stress level. At such an operating regime it is impossible to ensure safety based on start-up characteristics only—it becomes necessary to constantly monitor stress levels in critical areas of machinery and equipment elements. The stress level in turbine elements can be monitored on-line using algorithms based on Green’s functions and Duhamel’s integral. This paper presents examples of modifications of stress calculations in turbine valves and casings during start-ups. By modifying basic algorithms, it is possible to take into account the impact of the variability of heat transfer coefficients on the thermal stress level. Additionally, individual Green’s functions and correction factors were determined for specific stages of start-ups. Due to modifications, it is possible to obtain satisfactory agreement with the results obtained from FEM-based calculations for the entire heating process. Equations are also given that enable estimation of values of the heat transfer coefficient in turbine valves. The proposed modification of the algorithm will substantially improve the accuracy of stress modelling in transient states of the turbine operation. On-line stress monitoring will enable an increase in the flexibility of the power unit operation and facilitate operational control, ensuring safety of individual elements at the same time. The stress values calculated in the on-line mode can also be used to estimate fatigue life consumption and forecast the residual lifetime of individual components.

In the railway traction drive system, the reliability of DC-link capacitor banks faces enormous challenges due to the multi-operation conditions, the complex physical structures, and the safe operation requirements. Considering these issues, this paper proposes a reliability evaluation method of the DC-link capacitors banks to provide a guideline for preventive maintenance in the traction drive system. In the electro-thermal stress analysis, different from the conventional methods, the dynamic power loss profile is obtained by the sliding-window discrete Fourier transform (DFT) and the equivalent series resistance is fitted by the neural network. Afterward, a bidirectional thermal model is established to estimate the thermal stress under the dynamic power losses, considering the impact of thermal capacity, thermal coupling, and air-cooling heat dissipation. In addition, according to stability analysis and the rated temperature limitation, an end-of-lifetime standard that meets the safe operation requirement of the train is firstly proposed, thereby evaluating the lifetime bottleneck of the DClink capacitor banks. The evaluation results can provide a reference to use the lower-cost on-condition maintenance instead of scheduled maintenance in the railway traction drive system. Furthermore, a prototype experiment is performed to verify the effectiveness of the electro-thermal stress model. In the railway traction drive system, the reliability of DC-link capacitor banks faces enormous challenges due to the multi-operation conditions, the complex physical structures, and the safe operation requirements. Considering these issues, this paper proposes a reliability evaluation method of the DC-link capacitors banks to provide a guideline for preventive maintenance in the traction drive system. In the electro-thermal stress analysis, different from the conventional methods, the dynamic power loss profile is obtained by the sliding-window discrete Fourier transform (DFT) and the equivalent series resistance is fitted by the neural network. Afterward, a bidirectional thermal model is established to estimate the thermal stress under the dynamic power losses, considering the impact of thermal capacity, thermal coupling, and air-cooling heat dissipation. In addition, according to stability analysis and the rated temperature limitation, an end-of-lifetime standard that meets the safe operation requirement of the train is firstly proposed, thereby evaluating the lifetime bottleneck of the DClink capacitor banks. The evaluation results can provide a reference to use the lower-cost on-condition maintenance instead of scheduled maintenance in the railway traction drive system. Furthermore, a prototype experiment is performed to verify the effectiveness of the electro-thermal stress model.

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.

The mosquito Aedes aegypti is the primary vector of many disease-causing viruses, including dengue (DENV), Zika, chikungunya, and yellow fever. As consequences of climate change, we expect an increase in both global mean temperatures and extreme climatic events. When temperatures fluctuate, mosquito vectors will be increasingly exposed to temperatures beyond their upper thermal limits. Here, we examine how DENV infection alters Ae. aegypti thermotolerance by using a high-throughput physiological ‘knockdown’ assay modeled on studies in Drosophila. Such laboratory measures of thermal tolerance have previously been shown to accurately predict an insect’s distribution in the field. We show that DENV infection increases thermal sensitivity, an effect that may ultimately limit the geographic range of the virus. We also show that the endosymbiotic bacterium Wolbachia pipientis, which is currently being released globally as a biological control agent, has a similar impact on thermal sensitivity in Ae. aegypti. Surprisingly, in the coinfected state, Wolbachia did not provide protection against DENV-associated effects on thermal tolerance, nor were the effects of the two infections additive. The latter suggests that the microbes may act by similar means, potentially through activation of shared immune pathways or energetic tradeoffs. Models predicting future ranges of both virus transmission and Wolbachia’s efficacy following field release may wish to consider the effects these microbes have on host survival., Author summary Changes in global climate, which include higher temperatures and more frequent extreme temperature events, are expected to cause dramatic shifts in the distributions of infectious diseases. The geographic range of the mosquito Aedes aegypti continues to expand, risking greater incidence of viral diseases including dengue (DENV), Zika, chikungunya, and yellow fever. One emerging solution to control these viruses is the release of the insect bacterium Wolbachia, whose infection in mosquitoes reduces virus transmission to humans. However, the effects of rising temperatures on the efficacy of this tool are unclear. Here, we studied whether DENV and Wolbachia can alter the thermal sensitivity of the mosquito Ae. aegypti by using a heat-based physiological assay. We demonstrate that, separately, DENV and Wolbachia infections increase mosquito thermal sensitivity, causing more rapid death when mosquitoes are exposed to extreme heat. The impacts of the microbes on mosquito thermal sensitivity were similar but not additive, suggesting they effect the mosquito in similar ways. Our work demonstrates that future global projections of DENV transmission risk and of Wolbachia’s potential efficacy may need to consider the impact of these microbes on vector survival.

In this study, thermo-mechanical simulation was conducted to predict thermal and stress behavior in Selective Laser Melting (SLM). Temperature-dependent material properties for processed material 304L stainless steel were incorporated into the model in order to capture the change from powder to fully dense solid stainless steel. Temperature and thermal stress history were tracked under conditions of different parameter sets which were designed to reduce defect formation. The thermal model predicted the temperature history for multi-track scans under different process parameters, such as laser power, effective scanning speed and hatch spacing. Subsequently, the corresponding melt-pool size, solidification rate and temperature gradients could be calculated from simulated temperature data. These three parameters from the simulation were compared with experimental melt pool size, grain structure and cell spacing data obtained from a Renishaw AM250. The experimental data were also used to determine unknown simulation parameters required by the continuum model, e.g., the optical penetration depth and thermal conductivity multiplier for the molten region. This allowed the simulation model to accurately predict melt pool size and solidification structure of SLM 304L stainless steel. Simulated stress showed that the subsequent thermal cyclic melting in successive scanned tracks resulted in alternating compressive and tensile thermal stresses. This work will provide insight for studying microstructure morphology, residual stress and deformations in the SLM process of 304L stainless steel.

Assessment is performed of the permissible nonuniformity of irradiation and temperature scatter as per the wafer area during the rapid thermal treatment, not causing the thermal stresses in it, resultant in the plastic melting or silicon disruption. It was shown, that formation of platinum silicide at Т≤ 810 °С does not cause the negative phenomena in silicon, and it should be performed in the nitrogen environment, whose flooding into the the sealed chamber is done after creation in it of vacuum of 10 –2 mm, mercury column.

This paper analyses the neutron irradiation impact on the electrical performances of unstressed, ON-state, OFF-state, and negative gate bias (NGB) stressed AlInN/GaN HEMTs. These irradiations have resulted in the creation of electron traps that are causing a decrease in the drain current and an increase in the access resistance of the unstressed, ON-state, or OFF-state stressed AlInN/GaN devices. These degradations have been correlated with gamma spectrometry measurements and transmutation reactions occurred during the thermalized neutron irradiation have been highlighted. Despite these phenomena, a rise in drain current and a reduction in access resistance have been observed when NGB stressed AlInN/GaN HEMTs were irradiated with a fluence of $1.2\times 10^{\mathbf {12}}$ neutrons/cm2. The differences between the electrical behaviors of unstressed, ON-state, OFF-state, and NGB stressed devices observed after the neutron bombardment are related to the presence of electron traps in these device structures.

The accurate thermal stresses estimation of any machine element that is subjected to high temperature gradient is considered as essential matter for the mechanical engineers to obtain a successful design. Friction clutches are subjected periodically to high thermal stresses during the beginning of engagement due to the relative motion between driving and driven parts. Axisymmetric finite element models were developed in the present work to simulate the multi-disc clutches during the initial period of engagement to compute thermal stresses, heat generation, and temperature field. Axisymmetric models were used to simulate a multi-disc clutch works under the dry condition during the sliding period. The results indicate that the highest values of the thermal stresses appeared on the last friction disc (5th) and less effect on the other friction discs. This study presents a promising design tool to investigate the effect of materials, surface roughness, sliding speed and boundary conditions on the thermal stresses induced in the contacting surfaces of the friction clutches.

Modular multi-level converter (MMC) with press-packing IGBT devices is the popular and key equipment of VSC-HVDC system, its reliability is directly related to the equipment safe operation. However, it is difficult to analyse the reliability using the failure statistical approach due to less fault data. In order to improve the reliability analyses accuracy, it is necessary to use the physical failure method by considering the main components fatigue failure mode. The reliability analysis models are presented for the MMC sub-module with the press-packing IGBT device and metallised film capacitors. First, based on the MMC-HVDC simulation model, the losses and the junction temperatures of the IGBT devices were derived by the temperature field model, which the failure rates can be calculated. Furthermore, based the corrosion failure mode, the failure rate calculation of the metallised film capacitor was investigated using the voltage stress and thermal stress, the reliability calculation of the MMC sub-module was presented by combining the main components failure rates. Finally, the reliability of the VSC-HVDC based MMC was also presented with the different operation mode. The achievement is helpful to assess and improve the reliability of the VSC-HVDC.

Structural defects in the rotor cage of large electrical machines significantly impact their expected operational lifetime. This work presents the results of simulating the thermal stresses developed in a rotor cage during a fatigue test in which a bar breakage was achieved. A combined model featuring electrical, thermal and mechanical stages as well as three different meshes reflecting a progressing narrowing of one of the bars in its junction to the end ring are used for this purpose. The experimentally implemented startup and plug stopping transients are reproduced as well as, for comparison, the stall operation. The resulting stress levels are in agreement with the progression of the damage and concur with the stator measurements. Based on the analysis of the simulated rotor magnitudes, a strategy to diminish the thermal stresses in a damaged cage is proposed.

Jedną z najważniejszych cech masywnych elementów betonowych, które odróżniają je od innych konstrukcji betonowych, jest ich zachowanie termiczne (1). W masywnych konstrukcjach betonowych, mających dużą grubość przekroju, mogą wystąpić wysokie temperatury w trakcie twardnienia oraz znaczne różnice temperatury między wnętrzem i powierzchnią konstrukcji. Wynikające z nich nierównomierne zmiany objętościowe zawsze powodują powstanie więzów wewnętrznych w konstrukcji, a także powstanie więzów zewnętrznych w przypadku zewnętrznego ograniczenia swobody odkształceń, na przykład w miejscu połączenia konstrukcji z podłożem. Konsekwencją ograniczenia swobody odkształceń konstrukcji jest powstanie naprężeń rozciągających, które mogą osiągać wartości powodujące zarysowanie. Takie wczesne rysy termiczne obniżają walory funkcjonalne i wygląd zewnętrzny konstrukcji.[...], [Excerpt] One of the most important property of massive concrete elements, that differentiates their behaviour from other concrete structures, is the thermal behaviour (1). The mass concrete structures of large thickness might be characterized by considerable hardening temperature inside their volume and its signifi cant differences between the interior and the surface of the structure. Such non-uniform volume changes result always in internal restraints, and also, in the case of external restraining conditions, in the simultaneous occurrence of external restraints e.g. such as connection to the subgrade. The mentioned circumstances may result in large tensile stresses causing cracking. Early-age thermal cracking can lead to detriment of the structural performance, serviceability and visual appearance.[...], Funding provided by: Silesian University of Technology (BKM547/RB6/2018 and BK-237/RB6/2018); the Portuguese Foundation for Science and Technology (FCT) to the Research Project IntegraCrete PTDC/ECM-EST/1056/2014(POCI-01-0145-FEDER-016841), as well by the Research Unit ISISE (POCI-01-0145-FEDER-007633).

The steels operating at elevated temperatures are well known to be exposed to premature failure due to cracking caused by constant thermal stress, i. e. secondary creep process. Therefore, creep crack growth tests were carried out on compact tension specimens machined from P91 weld joint at 600°C to determine its behavior in realistic conditions. At the same time, numerical method for predicting the creep crack growth in compact tension specimens by a series of incremental steady-state finite element analysis were performed using Norton’s law to represent creep behavior. Verification of the finite element predictions were obtained for weld metal and heat affected zone by comparison with experimental results, indicating at the same time that creep crack growth rates are significantly higher for weld metal than for base metal.

The main destructions of asphalt concrete pavement are rut, transverse cracking, fatigue failures, peeling, etc. When the pavement cools, lowtemperature damages can occur for various reasons. The sources of damages that cause such failures are not well studied, so this problem is relevant. Goal. The aim of this work was to determine the stress-strain state inside the volume of asphalt con-crete during cooling on the basis of a two composite three-dimensional model using the method of computer simulation in response to the changing structured bitumen properties. Methodology. The method of finite element analysis of the stress-strain state of the composite material was used. The material is represented by a three-dimensional (3D) model pro-posed by prof. B.S. Radovsky. Results. The finite element analysis method was used to calculate the average thermal stresses in asphalt concrete during cooling in accordance with increase of viscosity of bitumen section, which is located in asphalt concrete in a structured state. This consideration is realized on the basis of changes in a number of bitumen properties in the contact zone, in particular, the changes in the glass transition temperature. It is shown that the thermal stresses that occur during cooling by limiting the movement of asphalt concrete in the construction reach the strength values at negative temperatures, which can be used to estimate the temperature of crack formation in asphalt concrete under the condi-tion of its action in pavement (Tcr). The values of these stresses depend on the cooling rate, the bitumen content, its viscosity and structure. Originality. For the first time, it was found numerically that in the sample of asphalt concrete, which is free from restriction of movements, there are internal thermal stresses during cooling due to the difference of bitumen thermal expansion coefficients and stone materials. These stresses are up to 87 percent of the average thermal stresses that occur in the compressed sample. Practical value. The possibility of rapid estimation of thermal stresses with the possibility of predicting low-temperature cracks in asphalt concrete is shown., Показана оцінка температурних напружень в асфальтобетоні під час охолодження та запропонований метод визначення температури крихкості асфальтобетону на основі скінченно-елементної моделі. Установлено, що у вільному від обмеження переміщень зразку асфальтобетону виникають внутрішні температурні напруження в процесі охолодження за рахунок різниці коефіцієнтів температурного розширення бітуму й кам’яних матеріалів.

Background: Hosta ventricosa is a robust ornamental perennial plant that can tolerate low temperatures, and which is widely used in urban landscaping design in Northeast China. However, the mechanism of cold stress tolerance in this species is unclear. Methods:This study used a combination of transcriptomic and metabolomic analysis to explore the mechanism of low temperature tolerance in H. ventricosa.Results: A total of 12 059 differentially expressed genes (DEGs) and 131 differentially expressed metabolites were obtained, which were mainly concentrated in the signal transduction and phenylpropanoid metabolic pathways. In the process of low temperature signal transduction, H. ventricosa is mainly through the ion channels on the three cell membranes of COLD, CNGCs and CRLK to transmit Ca2+ inside and outside the cell to sense temperature changes, and stimulate SCRM to combine with DREB through the MAPK signal pathway and Ca2+ signal sensors such as CBL. Strengthen the low temperature resistance of H. ventricosa. The pathways of phenylpropanoid and flavonoid metabolism represent the main mechanism of low temperature tolerance in this species. The plant protects itself from low temperature damage by increasing its content of genistein, scopolentin and scopolin. It is speculated that H. ventricosa can also adjust the content ratio of sinapyl alcohol and coniferyl alcohol and thereby alter the morphological structure of its cell walls and so increase its resistance to low temperatures.Conclusions: In H. ventricosa that is subjected to low temperature stress, temperature changes are perceived through COLD, CNGCs and CRLK, and protection from low temperature damage is achieved by an increase in the levels of genistein, scopolentin and scopolin through the pathways of phenylpropanoid biosynthesis and flavonoid biosynthesis.

Extreme temperature exposure can reduce stored sperm viability within queen honey bees; however, little is known about how thermal stress may directly impact queen performance or other maternal quality metrics. Here, in a blind field trial, we recorded laying pattern, queen mass, and average callow worker mass before and after exposing queens to a cold temperature (4°C, 2 h), hot temperature (42°C, 2 h), and hive temperature (33°C, control). We measured sperm viability at experiment termination, and investigated potential vertical effects of maternal temperature stress on embryos using proteomics. We found that cold stress, but not heat stress, reduced stored sperm viability; however, we found no significant effect of temperature stress on any other recorded metrics (queen mass, average callow worker mass, laying patterns, the egg proteome, and queen spermathecal fluid proteome). Previously determined candidate heat and cold stress biomarkers were not differentially expressed in stressed queens, indicating that these markers only have short-term post-stress diagnostic utility. Combined with variable sperm viability responses to temperature stress reported in different studies, these data also suggest that there is substantial variation in temperature tolerance, with respect to impacts on fertility, amongst queens. Future research should aim to quantify the variation and heritability of temperature tolerance, particularly heat, in different populations of queens in an effort to promote queen resilience.

DNA methylation plays crucial roles in transposon silencing and genome integrity. CHROMOMETHYLASE3 (CMT3) is a plant-specific DNA methyltransferase responsible for catalyzing DNA methylation at the CHG (H = A, T, C) context. Here, we identified a positive role of CMT3 in heat-induced activation of retrotransposon ONSEN. We found that the full transcription of ONSEN under heat stress requires CMT3. Interestingly, loss-of-function CMT3 mutation led to increased CHH methylation at ONSEN. The CHH methylation is mediated by CMT2, as evidenced by greatly reduced CHH methylation in cmt2 and cmt2 cmt3 mutants coupled with increased ONSEN transcription. Furthermore, we found more CMT2 binding at ONSEN chromatin in cmt3 compared to wild-type accompanied with an ectopic accumulation of H3K9me2 under heat stress, suggesting a collaborative role of H3K9me2 and CHH methylation in preventing heat-induced ONSEN activation. In summary, this study identifies a non-canonical role of CMT3 in preventing transposon silencing and provides new insights into how DNA methyltransferases regulate transcription under stress conditions., Author summary DNA methylation is generally known to silence transposon and maintain genome integrity. Environmental stress has been reported to release the transcriptional silencing of some transposable elements. DNA methylation is involved in the transcriptional restriction of heat-induced Copia-type retrotransposon ONSEN in Arabidopsis when subjected to heat stress. Here, we identified a non-canonical and positive role of the DNA methyltransferase CMT3 in ONSEN reactivation under heat stress. We showed that CMT3 prevents CMT2-mediated CHH methylation and H3K9me2 accumulation under heat at ONSEN chromatin to modulate ONSEN transcription. Our work revealed the molecular mechanism of CMT3 in heat-induced ONSEN activation and sheds new light on the survival mechanism of certain transposons in the host genome under stress conditions.

In boilers operating in modern power plants, thick-walled elements of complex shapes, such as valves, superheater headers, T-pipes, Y-pipes, four-way pipes, and elbows, are especially prone to fatigue processes. Higher operation parameters and more frequent startups may speed up fatigue damage in these elements. Such damage is a local phenomenon and is caused by thermomechanical fatigue (TMF). This paper presents a method designed for predicting the behavior of components subjected to variable temperature and mechanical loading conditions. This method combines the results of measurements of operating parameters of devices under industrial conditions with those obtained using finite element modeling (FEM). Particular attention was given to the influence of the time-dependent heat transfer coefficient on the local thermomechanical stress–strain behavior of the material. It was stated that heat transfer conditions have a significant impact on local transient stresses and depend on the operation parameters of boilers. Consistency of the temperature changes as a function of time, determined in industrial conditions and calculated on the basis of the model approach, was obtained. This developed and described in the work approach enables defining the conditions of heat transfer on the surface of models of considered components.

With increasing carbon emissions rising temperatures are likely to impact our economies and societies profoundly. In particular, it has been shown that heat stress can strongly reduce labor productivity. The resulting economic perturbations can propagate along the global supply network. Here we show, using numerical simulations, that output losses due to heat stress alone are expected to increase by about 24% within the next 20 years, if no additional adaptation measures are taken. The subsequent market response with rising prices and supply shortages strongly reduces the consumers’ purchasing power in almost all countries including the US and Europe with particularly strong effects in India, Brazil, and Indonesia. As a consequence, the producing sectors in many regions temporarily benefit from higher selling prices while decreasing their production in quantity, whereas other countries suffer losses within their entire national economy. Our results stress that, even though climate shocks may stimulate economic activity in some regions and some sectors, their unpredictability exerts increasing pressure on people’s livelihood.

In a nuclear power plant, the last barrier under normal and accident operations is the containment building. This is normally constructed from concrete reinforced with steel bars, which are prestressed to enhance the overall capability to withstand thermodynamic stresses like over-pressurisation and high temperatures. The failure of this final barrier will lead to the release of radioactivity to the surrounding environment. To examine the effects of thermo-hydraulic stresses on PWR containment following a LOCA, a model is proposed with simulated scenarios performed at the Koeberg Nuclear Power Station as a case study. The accidents were simulated using the Koeberg engineering simulator to obtain the output data. The scenario for the proposed model correlates the critical mass flow from a double-ended guillotine break to the containment pressure and temperature increase. Different containment filtered venting systems (CFVS) are also investigated in this study as severe accident management systems. CFVS have historically been included in boiling water reactor (BWR) designs, but following the Fukushima Daiichi nuclear accident, they are being introduced as severe accident management systems to manage the threat of containment over-pressurisation in pressurised water reactors (PWR). Finally, the rate of change in containment pressure and temperature is analysed and compared to literature, with the incorporation of a simulated filtered venting system to the PWR containment building.

Fruit abscission is a complex physiological process that is regulated by internal and environmental factors. During early development, apple fruit are exposed to extreme temperature fluctuations that are associated with premature fruit drop; however, their effect on fruit abscission is largely unknown. We hypothesized that fruit abscission is triggered by cold stress and investigated the molecular basis of premature fruit drop using RNA-Seq and metabolomics data from apple fruit undergoing abscission following cold stress in the field. Genes responsive to abscisic acid signaling and cell wall degradation were upregulated during abscission, consistent with the increased abscisic acid concentrations detected by liquid chromatography-mass spectrometry. We performed ex vivo cold shock experiments with excised tree subunits consisting of a branch, pedicel, and fruit. Abscission induction occurred in the cold-stressed subunits with concurrent upregulation of abscisic acid biosynthesis (MdNCED1) and metabolism (MdCYP707A) genes, and ethylene biosynthesis (MdACS1) and receptor (MdETR2) genes in the pedicel. Another key finding was the activation of cytoplasmic streaming in abscission-zone cells detected by electron microscopy. Our results provide a novel insight into the molecular basis of fruit abscission physiology in response to cold stress in apple.

The etiology of necrotizing enterocolitis (NEC) is not known. Alterations in gut microbiome, mucosal barrier function, immune cell activation, and blood flow are characterized events in its development, with stress as a contributing factor. The hormone corticotropin-releasing factor (CRF) is a key mediator of stress responses and influences these aforementioned processes. CRF signaling is modulated by NEC’s main risk factors of prematurity and formula feeding. Using an established neonatal rat model of NEC, we tested hypotheses that: (i) increased CRF levels—as seen during stress—promote NEC in formula-fed newborn rats, and (ii) antagonism of CRF action ameliorates NEC. Newborn pups were formula-fed to initiate gut inflammation and randomized to: no stress, no stress with subcutaneous CRF administration, stress (acute hypoxia followed by cold exposure—NEC model), or stress after pretreatment with the CRF peptide antagonist Astressin. Dam-fed unstressed and stressed littermates served as controls. NEC incidence and severity in the terminal ileum were determined using a histologic scoring system. Changes in CRF, CRF receptor (CRFRs), and toll-like receptor 4 (TLR4) expression levels were determined by immunofluorescence and immunoblotting, respectively. Stress exposure in FF neonates resulted in 40.0% NEC incidence, whereas exogenous CRF administration resulted in 51.7% NEC incidence compared to 8.7% in FF non-stressed neonates (p

The experiment was conducted with an intent to know the effect of different farming systems on the growth performance, nutrient digestibility coefficients, reproductive traits, disease incidence, heat stress indices, and cost economics of Nellore sheep. The study includes two parallel trials to prevent the influence of age on heat stress indices (panting score and erythrocyte osmotic fragility (EOF)). One hundred and twenty lambs (60 ram-lambs and 60 ewe-lambs) were allotted in a randomized block design under extensive, semi-intensive, and intensive systems for trial I, whereas trial II include eighteen rams assigned to the three respective farming systems in a completely randomised design. Both, season (summer) and grazing practice increased the panting score and EOF. The heat stress indices were positively correlated (PCommelina benghalensis, while instantaneous bite frequency (IBF), instantaneous intake rate (IIR) were higher for Cyanodon dactylon and amaranthus viridis, respectively. The proportion of intakes were highest for Stylo hemata followed by Cynodon dactylon and Tridax procumbens species. No differences were observed for the weight at puberty, oestrus cycle length, oestrus duration, conception percent, gestation period, and lambing percent in three rearing systems; however, the age at puberty was lower (P

Extreme cold and frost cause significant stress to plants which can potentially be lethal. Low temperature freezing stress can cause significant and irreversible damage to plant cells and can induce physiological and metabolic changes that impact on growth and development. Low temperatures cause physiological responses including winter dormancy and autumn cold hardening in strawberry (Fragaria) species, and some diploid F. vesca accessions have been shown to have adapted to low-temperature stresses. To study the genetics of freezing tolerance, a F. vesca mapping population of 143 seedlings segregating for differential responses to freezing stress was raised. The progeny was mapped using ‘Genotyping-by-Sequencing’ and a linkage map of 2,918 markers at 851 loci was resolved. The mapping population was phenotyped for freezing tolerance response under controlled and replicated laboratory conditions and subsequent quantitative trait loci analysis using interval mapping revealed a single significant quantitative trait locus on Fvb2 in the physical interval 10.6 Mb and 15.73 Mb on the F. vesca v4.0 genome sequence. This physical interval contained 896 predicted genes, several of which had putative roles associated with tolerance to abiotic stresses including freezing. Differential expression analysis of the 896 QTL-associated gene predictions in the leaves and crowns from ‘Alta’ and ‘NCGR1363’ parental genotypes revealed genotype-specific changes in transcript accumulation in response to low temperature treatment as well as expression differences between genotypes prior to treatment for many of the genes. The putative roles, and significant interparental differential expression levels of several of the genes reported here identified them as good candidates for the control of the effects of freezing tolerance at the QTL identified in this investigation and the possible role of these candidate genes in response to freezing stress is discussed.