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EN
In this second part, the pulse sources of heat, dependences among the intensive parameters of the friction process – temperature, unit pressures, friction velocity – and wear intensity, and some physical properties of the materials of solids in friction are presented. The flux densities are described in extensive quantities across the elementary surface dF of a nominal contact of solids. The thermodynamic criterion of galling is formulated, and the temperature characteristic of minimum wear and maximum resistance to wear is established. Minimum and maximum wear intensities and the specific work of wear are determined. It is proven that a temperature measured in a selected point of friction couple element does not uniquely characterise thermal processes in a tribological system. However, it does characterise the maximum gradient of temperatures measured in at least two points situated as close to a friction contact as possible. A method of determining unit real pressures is proposed. The presence of a cooling effect in the process of tribological wear is disclosed. Wear is interpreted as a disintegration of a solid caused by volumetric and superficial mechanical work. A system of new wear measures is suggested.
PL
W drugiej części pracy przedstawiono impulsowe źródła ciepła, ustalono zależności między intensywnymi parametrami procesu tarcia – temperaturą, naciskami jednostkowymi, prędkością tarcia a intensywnością zużywania i niektórymi własnościami fizycznymi materiałów trących się ciał. Opisano gęstości strumieni wielkości ekstensywnych przepływających przez elementarną powierzchnię dF styku nominalnego ciał. Sformułowano termodynamiczne kryterium zacierania, ustalono temperaturę charakterystyczną dla minimalnego zużycia i maksymalnej odporności na zużywanie. Ustalono maksymalne i minimalne wartości intensywności zużywania oraz graniczne wartości pracy właściwej zużycia. Wykazano, że temperatura zmierzona w wybranym punkcie elementu pary tarciowej nie charakteryzuje jednoznacznie procesów cieplnych zachodzących w systemie tribologicznym, lecz maksymalny gradient temperatur, zmierzonych w co najmniej dwóch punktach położonych możliwie blisko styku tarciowego. Zaproponowano sposób wyznaczania jednostkowych nacisków rzeczywistych. Ujawniono występowanie efektu chłodzenia w procesie zużywania tribologicznego. Zużywanie zinterpretowano jako rozdrabnianie ciała stałego, wywołane wykonaniem pracy mechanicznej objętościowej i powierzchniowej. Zaproponowano system nowych miar zużycia.
EN
The paper presents the results of the examination of the heating up of the basic elements of the actuating system of a single-disc lapping machine with standard kinematics, intended for machining flat surfaces. The increase of the temperature of the drive assembly, rollers and separator guide ring, as well as the lapping disc and machined elements were analysed. Heating up of the machining system was examined during the machining of a cast iron tool and flat surface lapping. Lapping is one of the methods of abrasive machining applied during the individual fitting of elements in assembly or when a technological compensator is used. The increase of temperature in the machining system influences, among others, the dimensional accuracy of lapped metal elements.
PL
Przedstawiono wyniki badań nagrzewania się podstawowych elementów układu wykonawczego docierarki jednotarczowej o standardowej kinematyce do obróbki powierzchni płaskich. Analizowano przyrost temperatury zespołu napędowego, rolek i pierścieni prowadzących separatory oraz tarczy docierającej i obrabianych elementów. Badano nagrzewanie się układu obróbkowego podczas wyrównywania żeliwnego narzędzia i docierania powierzchni płaskich. Docieranie jest jedną z metod obróbki ściernej stosowaną podczas indywidualnego dopasowywania elementów w montażu lub przy wykorzystaniu kompensatora technologicznego. Przyrost temperatury w układzie obróbkowym ma między innymi wpływ na dokładność wymiarową docieranych elementów metalowych.
3
EN
Aim: The aim of this article is to determine the characteristics of a pool fire, including the temperatures and thermal radiation densities caused by it. Mappings of pool fires occurring in actual emergency events were conducted by performing large-scale polygon tests. Project and methods: Experimental study of pool fire of technical ethanol was carried out on a specially built test stand in the training area of the Training Centre in Pionki of the Regional Headquarters of the State Fire Service in Warsaw. The pool fire test stand consisted of a test tray, with a test chamber with the diameter of 300 cm, founded on a reinforced concrete slab. Using a developed measurement system with data acquisition that included measurement sensors mounted at defined locations relative to the fire, temperatures and thermal radiation densities were measured at various distances/locations relative to the fire. Metrological data such as air temperature, atmospheric pressure, humidity, wind direction and speed were monitored and recorded using the weather station. The height of the fire flame was measured by comparing it to racks set up nearby with marked scales of specific lengths. Results: A polygon stand that was built to study pool fires, equipped with a temperature and thermal radiation density measuring system with measuring sensors distributed in defined locations, is discussed. A study of a pool fire resulting from the combustion of dehydrated, fully contaminated ethanol was conducted. The study measured temperatures, thermal radiation densities, and flame heights. The average and maximum values of temperatures and thermal radiation densities during the steady-state combustion stage (i.e., phase II of the fire) were determined. Conclusions: Based on the presented results of temperature and thermal radiation density measurements at various distances/locations relative to the pool fire site, there was a significant effect of wind direction and speed on these values. Higher temperature and heat radiation density were recorded at the sensors on the leeward side than on the windward side. As the wind speed decreased, there was an increase in the temperature values recorded on the thermocouples located above the centre of the bottom of the tray test chamber due to the flame, which, when not blown away, was allowed to rise vertically upward and fully sweep the temperature sensors.
PL
Cel: Celem artykułu jest określenie charakterystyki pożaru powierzchniowego, w tym temperatur i gęstości promieniowań cieplnych przez niego wywoływanych. Odwzorowania pożarów powierzchniowych mających miejsce w rzeczywistych zdarzeniach awaryjnych przeprowadzono poprzez wykonanie poligonowych badań w dużej skali. Projekt i metody: Badanie doświadczalne pożaru powierzchniowego etanolu technicznego zrealizowano na specjalnie do tego celu zbudowanym stanowisku badawczym na terenie poligonu Ośrodka Szkolenia w Pionkach Komendy Wojewódzkiej Państwowej Straży Pożarnej w Warszawie. W skład stanowiska do badania pożarów powierzchniowych wchodziła taca badawcza, o średnicy komory badawczej wynoszącej 300 cm, posadowiona na płycie żelbetowej. Przy pomocy opracowanego układu pomiarowego z akwizycją danych, w skład którego wchodziły czujniki pomiarowe zamontowane w zdefiniowanych lokalizacjach względem pożaru, dokonano pomiarów temperatur i gęstości promieniowań cieplnych w różnych odległościach/lokalizacjach względem miejsca pożaru. Za pomocą stacji pogodowej monitorowano i rejestrowano dane metrologiczne, takie jak temperatura powietrza, ciśnienie atmosferyczne, wilgotność, kierunek i prędkość wiatru. Pomiaru wysokości płomienia pożaru dokonano przez jego porównanie z ustawionymi w pobliżu stojakami z zaznaczonymi podziałkami o określonych długościach. Wyniki: Omówiono poligonowe stanowisko, które zostało zbudowane do badania pożarów powierzchniowych, wyposażone w układ pomiarowy temperatur i gęstości promieniowań cieplnych z czujnikami pomiarowymi rozmieszczonymi w zdefiniowanych lokalizacjach. Przeprowadzono badania pożaru powierzchniowego powstałego w wyniku spalania etanolu odwodnionego, całkowicie skażonego. W ramach badań dokonano pomiarów temperatur, gęstości promieniowań cieplnych oraz wysokości płomienia. Wyznaczono średnie i maksymalne wartości temperatur i gęstości promieniowań cieplnych w etapie ustalonego spalania (tzn. II faza pożaru). Wnioski: Na podstawie przedstawionych wyników pomiarów temperatur i gęstości promieniowań cieplnych w różnych odległościach/lokalizacjach względem miejsca pożaru powierzchniowego, odnotowano znaczący wpływ kierunku i prędkości wiatru na te wartości. Wyższą temperaturę i gęstość promieniowań cieplnych rejestrowano na czujnikach po stronie zawietrznej niż po stronie nawietrznej. Na skutek spadku prędkości wiatru następował wzrost wartości temperatur rejestrowanych na termoparach umieszczonych nad środkiem dna komory badawczej tacy, co było spowodowane przez płomień, który niezdmuchiwany, mógł unosić się pionowo do góry i w pełni omiatać czujniki temperatury.
4
Content available remote Badania pożarów strumieniowych propanu przeprowadzone w dużej skali
PL
Przedstawiono i omówiono wyniki pomiarów temperatury i promieniowania cieplnego w czasie pożaru strumieniowego propanu wydobywającego się pod ciśnieniem z instalacji gazowej. Badania pożaru strumieniowego w dużej skali przeprowadzono na poligonowym stanowisku badawczym zbudowanym na terenie Ośrodka Szkolenia w Pionkach Komendy Wojewódzkiej Państwowej Straży Pożarnej w Warszawie.
EN
A test of propane jet fire was performed in an outdoor test stand built in the fire brigade training center. A propane jet with a flow rate of about 196.1 m3/h for 110 s was continuously released from pressurized liquid propane tank. The values of temp. and thermal radiation were recorded at 20 and 4 measuring points, resp. A significant effect of even low wind speeds on the values of the recorded parameters was obsd. The results of measurements of temp., thermal radiation and flame dimensions allowed to estimate the effects of jet fire.
EN
This paper presents the results of a survey on the application of simple and multiple linear regression in wind power generation research. Relevant publications were searched for, found, reviewed, and summarised. An increasing trend of number of publications on this topic was found. The main categories of publications forecasting of wind output power, forecasting of wind speed, and wind turbine generator temperature monitoring. The paper presents coincise summaries of publications and details the references identified, all of this in one repository.
PL
W artykule przedstawiono wyniki badań ankietowych dotyczących zastosowania prostej i wielokrotnej regresji liniowej w badaniach energetyki wiatrowej. Odpowiednie publikacje zostały wyszukane, znalezione, zrecenzowane i podsumowane. Stwierdzono rosnący trend liczby publikacji na ten temat. Główne kategorie publikacji: prognozowanie mocy wiatru, prognozowanie prędkości wiatru oraz monitorowanie temperatury generatorów turbin wiatrowych. W pracy przedstawiono zwięzłe streszczenia publikacji i wyszczególnienie zidentyfikowanych pozycji literaturowych, a wszystko to w jednym repozytorium.
EN
Effects of temperature variation on the performance of silicon heterojunction solar cells are studied using opto-electrical simulations. It is shown that the low-temperature cell efficiency is determined by the fill factor, while at high temperatures it depends on the open-circuit voltage. Simulations revealed that the low-temperature drop in the fill factor is caused by poor tunnelling, in particular at the ITO/p-a-Si:H heterojunction. The authors link this drop in fill factor to a low maximum-power-point voltage and show how poor tunnelling is reflected in the charge redistribution determining the device voltage. The effect of the contact work function on temperature behaviour of efficiency by varying the electron affinity of ITO layers has been demonstrated. It was also demonstrated that increasing the electron affinity of ITO on the p-side minimises the work function mismatch, leading to significant improvements in efficiency, especially at low temperatures, while optimisation on the n-side results in maginal improvements over the entire temperature range. In addition to the cumulative effects of the temperature-dependent parameters, their individual contributions to the efficiency were also investigated. Moreover, it was presented that the thermal energy (kT) determines the efficiency temperature behaviour, while other parameters play only a minor role. This paper shows how temperature variations affect device performance parameters.
EN
Sensitive MEMS-based thermal flow sensors are the best choice for monitoring the patient’s respiration prompt diagnosis of breath disturbances. In this paper, open space micro-calorimetric flow sensors are investigated as precise monitoring tools. The differential energy balance equation, including convection and conduction terms, is derived for thermal analysis of the considered sensor. The temperature-dependent thermal conductivity of the thin silicon-oxide membrane layer is considered in the energy balance equation. The derived thermal non-linear differential equation is solved using a well-known analytical method, and a finite-element numerical solution is used for the confirmation. Results show that the presented analytical model offers a precise tool for evaluating these sensors. The effects of flow and thin membrane film parameters on thermo-resistive micro-calorimetric flow sensors’ performance and sensitivity are evaluated. The optimization has been performed at different flow velocities using a genetic algorithm method to determine the optimum configuration of the considered flow sensor. The geometrical parameters are selected as a decision variable in the optimization procedure. In the final step, using optimization results and curve-fitting, the expressions for the optimum decision variables have been derived. The sensor’s optimum configuration is achieved analytically based on flow velocity with the analytical terms for optimum decision variables.
EN
In a mountainous catchment, understanding the interaction between DEM resolution and climatic variables is essential for the accurate spatial interpolation of areal mean monthly and annual rainfall and temperature, which is required as an input for further applications such as hydrological and hydraulic modeling, agriculture, and environmental conservation. This case study applied the geostatistical interpolation technique, kriging with external drift (KED), with a digital elevation model (DEM) with various horizontal resolutions, which were used to assess the effects of the DEM horizontal resolutions on the spatial distributions of rainfall and temperature by focusing on interpolating the mean monthly and annual rainfall and temperature over a spatially diversified catchment. The assessment was undertaken using spatially and temporally complete sampled historical climatic datasets, and consequently, the spatial pattern of monthly and annual rainfall (temperature) from east to the west gradually increases or decreases following the DEM elevation increment along the same direction. As a result, the finer-resolution DEM (90-m SRTM-DEM) had a considerable impact on predicting the mean monthly minimum and maximum temperatures, whereas the resampled 500-m SRTM-DEM performed relatively better in mean monthly and annual rainfall and annual minimum temperature estimation values.
9
Content available remote Wpływ mączki granitowej na wybrane właściwości zapraw cementowych
PL
Celem badań było określenie wpływu częściowego zastąpienia cementu mączką granitową na wybrane właściwości zapraw cementowych. Stwierdzono, że wraz ze wzrostem zawartości mączki granitowej w zaprawie zmniejsza się średnica rozpływu. Jest to związane z dużą powierzchnią właściwą ziaren mączki granitowej w porównaniu z cementem. Gęstość objętościowa próbki referencyjnej jest mniejsza niż próbek z mączką granitową. Ponadto dodatek mączki granitowej skraca proces wiązania o ok. 25 min i ma pozytywny wpływ na temperaturę świeżej zaprawy w porównaniu z próbką referencyjną. Powoduje jej obniżenie, co może ułatwić proces betonowania w warunkach letnich. Częściowa zamiana cementu mączką granitową powoduje zmniejszenie wytrzymałości na ściskanie do 6% oraz wytrzymałości na rozciąganie przy zginaniu do 18,7% w porównaniu z próbką referencyjną.
EN
The aim of these studies is to determine the effect of partial replacement of cement with granite powder on selected properties of cement mortars. It was found that the spreading diameter decreased with the increase in the content of granite powder in the mortar. This is due to the large specific surface area of granite powder grains compared to cement. The volume density of the reference sample is lower than that of the samples with granite powder. The addition of granite powder shortens the setting process by 25 minutes, compared to the reference sample and has a positive effect on the temperature of the fresh mortar by lowering it, which may have a positive effect on the concreting process in summer conditions. Partial replacement of cement with granite powder results in a reduction up to 6% of the compressive strength compared to the reference sample and a reduction of up to 18.7% of the bending tensile strength.
EN
A morphological change due to Si contend into Al-based automotive alloys has been conducted on the characterization of machined surfaces in terms of roughness, temperature, chips formation as well as microstructure evaluation under different machining conditions. For this experiment, a shaper machine with HSS single point V-shaped cutting tool is used at different cutting speeds and depths of cut. The experimental results show that the surface roughness of the alloys decreases with the cutting speed and depth of cut but it is more prominent in the case of the cutting speed. This is because of a high cutting speed, which is more associated with the higher temperature and softening the work material leading to better surface finish. Higher Si added alloys also exhibit a better surface finish because the sample content is different fine and hard intermetallic due to ageing treatment, which also makes the alloys more brittle. For brittle and higher hardness, it produces a higher temperature during machining. During machining, relatively curly and short chips are formed by the high Si added alloy because of its low elongation properties. The fracture surfaces of higher Si added alloy display more crack propagation obtained by plate-like Si rich intermetallic.
EN
Anaerobic digestion consists of the biological decomposition of organic waste under anaerobic conditions by various types of microorganisms. The purpose of this study was to evaluate the effect of the fermentation starter of methanogenic bacteria on the anaerobic digestion of cattle manure in a bioenergy plant. The effect of various methods (physical, microbiological and chemical) on the digestion of cattle manure was studied under mesophilic (35°C) and thermophilic (50°C) modes. The results of the study showed that the content of volatile fatty acids and the pH of the medium was in the optimal range, the yield of methane biogas (CH4) during anaerobic digestion at 35°C was 0.45 m3/kg and at 50°C was 0.58 m3/kg. The data obtained indicate that the thermophilic mode (50°C) of anaerobic digestion of manure effectively affects the yield of methane biogas. Based on anaerobic digestion in mesophilic mode, a fermentation starter of methanogenic cultures adapted to thermophilic conditions was obtained. According to cultural and morphological characteristics, the cultures were assigned to the genera Methanopyrus and Methanococcus. The results of a study on the effect of the fermentation starter of methanogenic bacteria in fermented manure at 50°C showed that with an increase in the dose of the fermentation starter, the methane-forming ability of anaerobic bacteria increased and the process of methane biogas release intensified (from 0.36 m3/kg to 0.79 m3/kg). Besides, the dose of methanogenic fermentation starter based on Methanopyrus and Methanococcus isolates (28 kg) was determined. When the bioenergy plant is launched in thermophilic mode, the release of biogas increases by 2.2 times, and the digestion period decreases to 10 days.
EN
Urban plants play a significant role in shaping the microclimate of the modern city, in addition to the recreational and aesthetic functions. Climate change and sharp changes in temperature affect the plant growth and development, so the question of studying the adaptive potential of the plant range in cities to temperature variability is relevant and important. Researchers and scientists around the world are studying the impact of biotic and abiotic factors on plants, but the variability of the plant organisms in the urban ecosystem is still unexplored. The data from the analysis of the frequency of occurrence plants in Kyiv green spaces show that Tilia cordata Mill., Aesculus hippocastanum L., Spiraea×vanhouttei (Briot) Zabel. and Carpinus betulus L. are most represented among the researched species. The article presents the results of the assessment of heat resistance by using the method of Matskov (1976) of 13 ornamental woody and shrubby species. Besides, the plants were separated into groups of tolerance to high temperatures. It was established that the T. cordata plants are characterized by the highest indicators of heat tolerance and they can be recommended for the creation of open landscapes. The A. hippocastanum, Catalpa bignonioides Walt., S. vanhouttei and Forsythia europaea Degen & Bald. plants are characterized by ‘moderate tolerance’ indicators to high temperature stress, therefore they can be recommended for the creation of semi-open/open landscape types. Consequently, for the formation of semi-open landscapes, using the species Platanus occidentalis L., Quercus robur L., Q. rubra, Syringa vulgaris L., Berberis thunbergii DC. and Ligustrum vulgare L. which were assessed as ‘moderately sensitive’, is recommended. The leaves of the Carpinus betulus L. and Ribes aureum Pursh. plants were most vulnerable to high temperature stress; therefore, the species are recommended for the formation of closed landscape types. Despite the comparative classification of ornamental plants in terms of heat-resistance, many issues remain unstudied and need to be clarified in terms of ecology, physiology, biochemistry and phytopathology for the plants of urban green spaces.
13
Content available Gas temperature meter
EN
Purpose: of the article is to develop a digital portable gas temperature meter in the range of -50…+600°C. To measure the temperature of dusty gas flows in the air pollution sources with the least significant digit of the digital device 1°C. Design/methodology/approach: The microprocessor measuring unit, probe and software is proposed. It leads to build a high-precision temperature meter based on a thin film sensor HM220 type "pt100". Findings: The calculation of the electrical schematic diagram parameters for signal conditioning of the sensor relative to the input range of the analog-to-digital converter. The experimental measuring unit and the probe of the gas temperature meter are assembled. The principle of the gas temperature meter calibration with the help of a precision resistance box MSR-60M is considered. The experimental gas temperature meter has a total standard uncertainty determined by type B for a maximum value of the measurement range of 1.94°C. The error of the sensor "pt100" makes the largest contribution to the total standard uncertainty, so the error increases in proportion to the value of the measured temperature. Research limitations/implications: On the basis of the proposed design of gas temperature meter it is possible to construct devices with various lengths of probes. Practical implications: The proposed meter is designed for environmental laboratories that measure the velocity, flow and sampling of dust and gas emissions from sources of air pollution. Originality/value: The device design differs due to the use of thermostable wire made of constantan as extending conductors of the temperature sensor, which is included in the unbalanced Wheatstone bridge. This solution allows the use of unipolar power supply 3.3 V for both analog and digital part of the meter. Temperature meter based on a thin film resistance thermometer is characterized by relative ease of manufacture, low material consumption, cost and high reliability.
14
Content available remote Regulacja i koszty eksploatacyjne elektrycznych grzejników podłogowych
PL
Regulacja ilości i czasu poboru energii elektrycznej z sieci do ogrzewania pomieszczeń jest najistotniejszym (newralgicznym) momentem projektowania instalacji. Jest to związane z późniejszą eksploatacją, bezpieczeństwem i ponoszonymi kosztami. Jednocześnie zapewnia szybkość i komfort w utrzymywaniu warunków temperaturowych w pomieszczeniu z minimalizacją kosztów korzystania z tego rodzaju ogrzewania.
EN
Regulation of the amount and time of electricity consumption from the space heating network is the most important (critical) moment of installation design. This is related to subsequent operation, safety and costs. At the same time, it provides speed and comfort in maintaining temperature conditions in the room with minimizing the cost of using this type of heating.
PL
W artykule przedstawiono wybrane parametry życiowe człowieka wraz z urządzeniami umożliwiającymi ich pomiar. Następnie przedstawiono systemy przesyłania informacji wokół systemu badania parametrów życiowych człowieka. Zwrócono uwagę na potrzebę zastosowania wielu technologii w celu zapewnienia kompatybilności na wielu poziomach. W dalszej części przedstawione zostały przykładowe anteny które znajdą zastosowanie wokół sieci sensorycznej, po czym został przedstawiony projekt anteny tekstylnej mogącej zostać użytej na poziomie sensor-centrala wraz z charakterystykami opisującymi jej parametry.
EN
The paper presents selected human vital parameters along with devices that enable their measurement. Then, the information transmission systems around the human vital parameters study system are discussed. The need for multiple technologies to ensure compatibility at multiple levels has been highlighted. Further on, examples of antennas that will be used around the sensory network are presented, and then a design of a textile antenna that can be used at the sensor-control panel level was presented, along with the characteristics describing its parameters.
EN
Membrane technologies are widely used for desalination of water. These technologies are environmentally friendly, economical, energy efficient and material efficient. In the absence of pre-treatment of water, the membrane is contaminated, which leads to an increase in the amount of concentrate formation. Discharge of mineralized water leads to physical and chemical pollution of water bodies. Dissolution and removal of these sediments is a complex issue, so the use of sediment inhibitors is important. The use of antiscalants allows to prolong the service life of membrane elements, which, in turn, will reduce the intake of fresh water and reduce the volume of wastewater. The efficiency of gipan as a reagent in the stabilization treatment of low-mineralized, highly mineralized waters at a temperature of 60°C was determined. The dependences of water stability on sediments on the chemical composition of water, inhibitor concentration and time of ultrasonic treatment of gipan were established.
PL
Tematem artykułu jest analiza wpływu sposobu obliczeń strat ciepła do przestrzeni nieogrzewanych (piwnicy i poddasza) budynku na jego parametry energetyczne, tj. na obciążenie cieplne i zużycie energii użytkowej. Rozpatrzono trzy metody obliczeń przedstawione w normie PN–EN 12831:2006 „Instalacje ogrzewcze w budynkach. Metoda obliczania projektowego obciążenia cieplnego” przy różnych sposobach ocieplenia rozpatrywanego budynku wielorodzinnego. Wykazano, że zastosowanie do obliczeń potrzeb cieplnych budynku stałej wartości współczynnika redukcji temperatury lub stałej temperatury przestrzeni nieogrzewanej wiąże się z przeszacowaniem strat ciepła przez przegrody budowlane oddzielające przestrzeń ogrzewaną od nieogrzewanej, co sprawia, że model obliczeniowy budynku nie jest dostosowany do rzeczywistych warunków eksploatacji obiektu.
EN
The subject of the article is the analysis of the influence of the method of calculating heat losses to unheated spaces (basement and attic) of a building on its energy parameters, i.e. heat load and useful energy consumption. Three calculation methods presented in the standard PN – EN 12831: 2006 “Heating Systems in Buildings – Method for Calculation of the Design Heat Load” with different methods of thermal insulation of the considered multi-family building. It has been shown that the use of a constant value of the temperature reduction coefficient or a constant temperature of an unheated space to calculate the thermal needs of a building is associated with an overestimation of the heat loss through building partitions separating the heated and unheated space, which means that the building calculation model is not adapted to the actual operating conditions of the building
PL
W artykule przedstawiono analizę potencjalnych rozwiązań materiałowych dla betonów przeznaczonych dla konstrukcji masywnych. Głównym założeniem autorów było potwierdzenie możliwości zastosowania innych niż oparte na cemencie CEM III/A kompozycji spoiwowych zapewniających optymalne i bezpieczne warunki termiczne w dojrzewających masywnych elementach. Finalnym elementem analizy było wykonanie symulacji rozwoju temperatury w przykładowej masywnej płycie fundamentowej, która była ostateczną weryfikacją proponowanych rozwiązań materiałowych.
EN
The article presents analyze potentially materials solutions which we meet with concrete which is used in solid constructions. Main authors' assumption there was a confirmation possibility of usage different than based on cement CEM III/A binder compositions which provide optimally and safety thermal conditions in maturing massive elements. Final element this analyze was doing temperature development simulation in example of massive slab foundation which was finally verification of proposal material solutions.
EN
In the current paper, the effect of tool wear for a constant period of time (360 s) during conventional and ultrasonic assisted machining of Inconel 718 is investigated in terms of cutting forces, temperature, and deviation measurements. For fixed process parameters turning experiments have been performed with and without the application of tangential vibration. Ultrasonic assisted turning (UAT) experiments have been compared with conventional turning (CT). The experimental results reveal that cutting forces and temperature increase linearly in the case of UAT whereas remaining constant in CT for a constant period of time. Besides the tool wear rate in the case of UAT is more than that in the CT.
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This paper investigates experimentally the thermomechanical response of 42CrMo steel under several combinations of temperatures and strain-rate. To characterize the flow stress of this highstrength 42CrMo steel, two distinct test configurations were utilized. The first consisted of conventional uniaxial tensile tests conducted at room and elevated temperatures of 523◦K, 723◦K and 923◦K and three quasi-static strain-rates at 0.0015 s−1, 0.015 s−1, and 0.15 s−1. The second test configuration was carried out under dynamic compression using a drop mass bench at room temperature with three different dynamic strain-rates of 300 s−1, 400 s−1, and 500 s−1. Particular attention was paid to key features such as work-hardening (WH), grain size, dynamic strain aging (DSA), formation of microcavities, and their coupling with the influence of temperature/strain-rate combination. The dependence of 42CrMo steels’ flow stress on the quasi-static strain-rate at room temperature was almost insignificant. However, the strain-rate sensitivity increased with increasing temperatures. At high temperatures, different factors contributed to modifying the alloy microstructure which has a significant impact on the alloy’s mechanical properties. Quantification of the micro-cracks density and fractured specimens’ voids was established using scanning electron microscopy (SEM) images. The Voyiadjis–Abed (VA) constitutive model was utilized in describing the flow stress of 42CrMo steels and implemented in the ABAQUS software to develop a robust finite element model capable of accurately simulating variant structural responses of 42CrMo steel alloy.
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