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1

Carbide Cutting Tool Coatings Characterization of 8YSZ

Kareem Shaimaa J., Wurood Asaad M., Abbas Sundus, Al-Ethari Haydar

Advances in Science and Technology. Research Journal

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2024

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Vol. 18, no 4

410--419

EN

Using a duplex deposition of TiO2/8YSZ on a carbide cutting tool, a successful sol-gel procedure was achieved, resulting in high homogeneity, good dispersion, and a low average value of surface roughness (223.6)nm. Thermal experiments were done to see how well the coating layers could withstand heat transfer and thermal deterioration. Residual stresses for coated and uncoated carbide cutting tools are measured after thermal shock (thermal shock). Both were immediately chilled in ice water after being heated for 90 minutes for coated inserts and 30 minutes for uncoated inserts at 500, 600, 700, 800, 900, and 1200 °C. For inserts, thermal shock from 900 °C results in significantly different damage mechanisms. The uncoated outside surface is still delineated by a crack network and is surrounded by nearby homogenous cells, but the coated insert (sol gel TBC) in this case really has a few tiny cracks beginning at the edge. The coated insert (sol-gel TBC) fails after being heated to 1200 °C and then cooled in water to freezing which is caused the start of the duplex coating degradation.

2

Non-destructive methods determination of thermal shock resistance of natural building stones applicated with different water repellent chemicals on their surfaces

Ekincioğlu Gökhan

Gospodarka Surowcami Mineralnymi

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2023

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T. 39, z. 3

81--101

EN

Natural stones are used as coating material on the exteriors and terraces of buildings in architecture, and in places such as entrances, halls, living rooms, kitchens, bathrooms and stairs in interior spaces. Limra limestone and travertine are used as natural building materials in many structures depending on their colors. However, the water absorption values of these two natural stones are high due to their porosity, resulting in negative effects from atmospheric conditions. In this study, two different carbonate-based natural stones, limra limestone and travertine, were treated with two different water-repellent chemicals, one solvent-based and one water-based. After application, thermal shock tests were performed with a sodium chloride solution consisting of twenty cycles. The changes in the weights of samples dried to constant mass, ultrasonic permeability, Leeb hardness, and color change values in the samples were determined after the thermal shock tests. In addition, the effects of water-repellent chemicals on the formation of NaCl crystals accumulated in the pores of the rocks were examined by SEM and EDX analysis. Changes in non-destructively measured values were compared with the values of reference samples without surface protection. The solvent-based water-repellent chemical made the sample surface more hydrophobic than the water-based repellent. In both types of natural stones, the solvent-based water repellent chemical showed more protective properties against salt crystallization under thermal shock conditions compared to the water-based repellent.

PL

Kamienie naturalne są stosowane jako materiał powłokowy na zewnątrz i tarasach budynków w architekturze oraz w miejscach takich jak wejścia, hole, pokoje dzienne, kuchnie, łazienki i schody w przestrzeniach wewnętrznych. Wapień limra i trawertyn są wykorzystywane jako naturalne materiały budowlane w wielu konstrukcjach w zależności od ich kolorystyki. Jednak wartości nasiąkliwości tych dwóch kamieni naturalnych są wysokie ze względu na ich porowatość, co skutkuje negatywnym oddziaływaniem warunków atmosferycznych. W tym badaniu dwa różne kamienie naturalne na bazie węglanów, wapień limra i trawertyn, potraktowano dwoma różnymi hydrofobowymi chemikaliami, jednym na bazie rozpuszczalnika i jednym na bazie wody. Po aplikacji przeprowadzono testy szoku termicznego z roztworem chlorku sodu składające się z 20 cykli. Zmiany masy suszonych do stałej masy próbek, przepuszczalność ultradźwięków, twardość Leeba oraz zmiany barwy w próbkach określono po testach szoku termicznego. Ponadto zbadano wpływ chemikaliów hydrofobowych na powstawanie kryształów NaCl gromadzących się w porach skał za pomocą analizy SEM (skaningowa mikroskopia elektronowa) i EDX (rentgenowska dyspersja energii). Zmiany wartości mierzonych w sposób nieniszczący porównano z wartościami próbek referencyjnych bez zabezpieczenia powierzchni. Środek hydrofobowy na bazie rozpuszczalnika sprawił, że powierzchnia próbki była bardziej hydrofobowa niż powierzchnia na bazie wody. W obu typach kamieni naturalnych hydrofobowa substancja chemiczna na bazie rozpuszczalnika wykazywała lepsze właściwości ochronne przed krystalizacją soli w warunkach szoku termicznego w porównaniu z substancją na bazie wody.

3

Wpływ długotrwałego oddziaływania cyklicznych zjawisk atmosferycznych na właściwości piaskowców istebniańskich

Figarska-Warchoł Beata, Sierakowska Joanna

Przegląd Geologiczny

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2021

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Vol. 69, nr 2

109--119

EN

The Istebna sandstones are one of the main stone materials used for centuries in the construction industry in Kraków and the surrounding area. It was supported not only by their decorative properties and technical parameters, but also the proximity of the outcrops. The results of research on changes in the physical and mechanical properties of samples taken from the Czasław and Sobolów deposits are presented. They represent two structural varieties, subjected to fatigue by cyclic processes of freezing and thermal shock. Such a treatment of the samples was aimed at recreating the natural conditions in which the stone elements are subjected to the destructive effects of atmospheric phenomena associated with temperature changes during winter and summer periods. Data on the weather conditions in Kraków for the period 1951-2020 were used to assess the effect of climate on the intensity of the impact of the two above factors and, additionally, the destructive effect of rock salt, used for de-icing road surfaces. An attempt was also made to forecast the expected rate of destruction of the Istebna sandstones, based on the analysis of climate change.

4

Short-beam shear fatigue life assessment of thermally cycled carbon-aluminium laminates with protective glass interlayers

Surowska Barbara, Dadej Konrad, Jakubczak Patryk, Bieniaś Jarosław

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 2

169--179

EN

Fibre metal laminates (FMLs) are attractive construction materials, especially for use in aerospace and transport facilities. Throughout their service life, thin-walled structures made of FMLs are exposed to static and dynamic loads, as well as corrosion and the unfavourable influence of environmental conditions. The paper presents an experimental analysis of the combined mechanical and environmental long-term behaviour of carbon-based fibre metal laminates and their variants with protective glass layers. The Al alloy/CFRP and Al alloy/GFRP/CFRP laminates in a 3/2 configuration were used. The tested laminates were subjected to 1500 thermal cycles with a temperature range of 130°C. The static and fatigue interlaminar shear strengths were tested before and after thermal conditioning. It was shown that the stable stiffness reduction in the tested laminates was observed with increasing fatigue cycles, due to the progressive fatigue damage accumulation. The thermally cycled laminates feature slightly smoother stiffness loss, while a more rapid decrease was observed in thermally untreated laminates. Moreover, the fatigue life of the tested laminates subjected to thermal cycling revealed nine times fewer fatigue cycles of laminates with glass protectors after thermal cycles in comparison to the laminates not subjected to thermal cycling.

5

Thermal shock as a cause of cracking of concrete in massive bridge support elements - a case study

Woyciechowski Piotr, Łukowski Paweł, Adamczewski Grzegorz

Roads and Bridges - Drogi i Mosty

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2020

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Vol. 19, no. 4

297--313

EN

The paper presents an example of analysis of concrete cracking during construction of a massive bridge element, together with a demonstration of the expert diagnostic work aimed at a comprehensive assessment of the causes of crack development. The finite elements method analysis software FE-tool ConTeSt Pro was used. In the presented case there were typical doubts as to the reason of concrete cracking, and the performed analysis enabled identification of thermal shock as the primary cause of the observed distress. Finite element numerical simulations were adopted in order to analyze the temperature impact on crack development in the bridge elements. The complex case study analysis presented in the article may be treated as guidance on the use of scientific analysis methods in practical reinforced concrete cracking diagnostics. As a result of the work, thermal shock was identified to be the main reason for the damage of the massive bridge elements.

PL

W artykule przedstawiono przykładową analizę zarysowań betonu powstałych w trakcie wykonywania masywnego elementu obiektu mostowego wraz z prezentacją eksperckich prac diagnostycznych mających na celu kompleksową ocenę przyczyn ich powstawania. W badaniu wykorzystano oprogramowanie do analizy metodą elementów skończonych FE-tool ConTeSt Pro. Ponieważ w przedstawionym przypadku wystąpiły typowe wątpliwości co do źródła powstania zarysowań przeprowadzono analizę, która wskazała na szok termiczny jako podstawową przyczynę stwierdzonych uszkodzeń. W celu analizy wpływu temperatury na rozwój zarysowań elementów obiektu mostowego zastosowano symulacje numeryczne metodą elementów skończonych. Przedstawioną w pracy kompleksową analizę przypadku traktować można jako wytyczne stosowania metod analizy naukowej w praktycznej diagnostyce zarysowań elementów żelbetowych. Przeprowadzone badania wskazały na szok termiczny jako podstawową przyczynę uszkodzeń elementów mostowych z betonu masywnego.

6

Investigation of thermomechanical processes in miniature membrane elastic elements

Tykhan M., Dilay I., Markina O., Markovych V.

Journal of Achievements in Materials and Manufacturing Engineering

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2020

|

Vol. 98, nr 1

24--31

EN

Purpose: The demand for the devices structures reliability and machines requires understanding elements operation, in particular elastic elements, under the effect of nonstationary temperature factors. Therefore, it is important to investigate the behaviour of these elements under variable temperature effecting. Design/methodology/approach: In this article, the temperature field and the thermal stresses of the membrane type elastic elements, as well as the thermal deformation of its body part were investigated by the method of numerical analysis. The theoretical results have experimental confirmation. Findings: The article shows possibilities significantly reduce the thermal stress in an elastic element, thereby increase its functional and structural reliability by varying the geometric parameters of the elastic element, the materials selection, and body shape. Research limitations/implications: Numerical modelling of thermal processes requires accurate information about the physico-mechanical properties of materials and heat-exchange coefficient, which in practice may differ from the theoretical ones. Therefore, experimental confirmation of research and decisions is needed. The influence of the "hot" thermal shock was investigated. There is performed interest to investigate the "cold" thermal shock. Practical implications: The obtained results allow creating elastic elements with better functional characteristics for operation in a wide temperature range. They can also be used in the designing of elastic elements not only of membrane type. Originality/value: Performed investigation of thermomechanical processes in the membrane elastic element has revealed important features of its temperature deformations with nonstationary thermal influence. Namely, the nature of thermal deformations can be changed by selecting the geometrical parameters of the element, its material, as well as the conditions of heat-exchange conditions with mating member (body). In this way, it is possible to obtain a controlled deformation and to design the elastic elements with predetermined functional tasks. On the other hand, the design of the membrane element body can create elastic hinges, which allows reducing the thermal stress in the membrane, which significantly increases the reliability of the element operation of this type in conditions of non-stationary temperatures. In general, the conducted investigations allow efficient design of elastic elements for devices, sensors and other precision mechanisms.

7

Thermal shock effects on the mechanical behavior of granite exposed to dynamic loading

Li Xiang, Li Baijin, Li Xibing, Yin Tubing, Wang Yan, Dang Wengang

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 3

30--40

EN

Under certain extreme conditions in rock engineering works, fast change in temperature in the load-bearing rocks can happen. Known as thermal shock (TS), such process involves rapid temperature rise or drop, which causes fracturing in the rock material and thus can pose as a threat to the stability of the rock structures. To investigate the influence of thermal shock caused by fast cooling on the mechanical property of rock, laboratory tests are performed on heated granite which are cooled with different methods, with the highest cooling rate reaching 167.4 °C/min. The dynamic loading tests are performed on the heated granite specimens utilizing the split Hopkinson pressure bar (SHPB) system. The test results show that the dynamic compressive strength drops with the increase in heating level or cooling rate. This pattern is explained by the nuclear magnetic resonance (NMR) test data that the pores inside the heated granite increase both in size and quantity as heating level or cooling rate rises. Damage patterns of the tested granite specimen fragments are analyzed based on the observation with scanning electron microscope (SEM), and the mechanisms of thermal shock in granite are also discussed.

8

The mixed FEM for analysis of quantum-dot systems based on gradient theory

Sladek Jan, Sladek Vladimir, Repka Miroslav, Hrcek Slavomir

Computer Methods in Materials Science

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2018

|

Vol. 18, No. 3

81--89

EN

The QD nanostructures are analyzed under a thermal load. The dimensions of the QDs are of the same order as the material length scale. Therefore, the gradient elasticity theory should be applied to account for the size-dependent behavior of such nano-sized QDs. Since governing equations contain higher order derivatives than in conventional approaches the C1-elements are required for approximation of primary fields in the FEM. The mixed FEM are developed here, where C0 continuous interpolation is applied independently for displacement and displacement gradients. The kinematic constraints between strains and displacements are satisfied by collocation at some cleverly chosen internal points in elements. A unit cell of Indium Arsenide QD in a finite sized Gallium Arsenide (GaAs) substrate is analysed.

9

Thermal Shock Resistance of Cast Iron with Various Shapes of Graphite Precipitates

Jakubus A., Soiński M. S.

Archives of Foundry Engineering

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2018

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Vol. 18, iss. 2

121--124

EN

The influence of a shape of graphite precipitates in cast iron on the thermal shock resistance of the alloy was initially determined. Investigations included the nodular cast iron and the vermicular one, as well as the cast iron containing flake graphite. The thermal shock resistance was examined at a special laboratory stand which allowed for multiple heating and cooling of specimens within the presumed temperature range. The specimens were inductively heated and then cooled in water of constant temperature of about 30°C. There were used flat specimens 70 mm long, 5 mm thick in the middle part, and tapering like a wedge over a distance of 15 mm towards both ends. The total length of cracks generated on the test surfaces of the wedge-shaped parts of specimens was measured as a characteristic value inversely proportional to the thermal shock resistance of a material. The specimens heated up to 500°C were subjected to 2000 test cycles of alternate heating and cooling, while the specimens heated up to 600°C underwent 1000 such cycles. It was found that as the heating temperature rose within the 500-600°C range, the thermal shock resistance decreased for all examined types of cast iron. The research study proved that the nodular cast iron exhibited the best thermal shock resistance, the vermicular cast iron got somewhat lower results, while the lowest thermal shock resistance was exhibited by grey cast iron containing flake graphite.

10

Problems of the starting and operating of hydraulic components and systems in low ambient temperature (Part V) methods ensuring correct start-up of hydraulic components of ship’s onboard devices in low ambient temperatures

Jasiński R.

Polish Maritime Research

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2017

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nr 4

47--56

EN

A large number of hydraulic devices and systems are started in low ambient temperatures. A good example of such a device is the hoisting winch on the ship. Starting hydraulic drive units in thermal shock conditions (rapid supply of hot oil to the cold unit) may lead to incorrect operation of the actuating system, for instance, due to the loss of clearance between cooperating elements. The article presents methods to prevent the disappearance of effective clearance in a hydraulic motor started in thermal shock conditions. For this reason, the structure of the hydraulic satellite motor was complemented by elements creating special channels through which hot oil could flow and additionally heat fixed parts of the motor. This solution ensures faster heating of motor housing, thus decreasing the temperature difference between the housing and the satellites during motor start-up in thermal shock conditions.

11

Problems of the starting and operating of hydraulic components and systems in low ambient temperature (Part IV) Modelling the heating process and determining the serviceability of hydraulic components during the starting-up in low ambient temperature

Jasiński R.

Polish Maritime Research

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2017

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nr 3

45--57

EN

Designers of hydraulically driven machines and devices are obliged to ensure during design process their high service life with taking into account their operational conditions. Some of the machines may be started in low ambient temperature and even in thermal shock conditions (due to delivering hot working medium to cold components). In order to put such devices into operation appropriate investigations, including experimental ones - usually very expensive and time-consuming, are carried out. For this reason numerical calculations can be used to determine serviceability of a hydraulic component or system operating in thermal shock conditions. Application of numerical calculation methods is much less expensive in comparison to experimental ones. This paper presents a numerical calculation method which makes it possible to solve issues of heat exchange in elements of investigated hydraulic components by using finite elements method. For performing the simulations the following data are necessary: ambient temperature, oil temperature, heat transfer coefficient between oil and surfaces of elements, as well as areas of surfaces being in contact with oil. By means of computer simulation method values of clearance between cooperating elements as well as ranges of parameters of correct and incorrect operation of hydraulic components have been determined. In this paper results of computer simulation of some experimentally tested hydraulic components such as axial piston pump and proportional spool valve, are presented. The computer simulation results were compared with the experimental ones and high conformity was obtained.

12

Badanie wpływu dodatku modyfikatorów na właściwości mechaniczne i termiczne wysokoglinowego tworzywa odpornego na szoki termiczne

Taźbierski P., Łosiewicz A., Tymowicz-Grzyb P., Jakubiuk T.

Materiały Ceramiczne

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2017

|

T. 69, nr 1

40--45

PL

W pracy badano wpływ dodatku proszków dwutlenku cyrkonu i spinelu glinowo-magnezowego o uziarnieniu nanometrycznym na właściwości tworzywa wysokoglinowego w warunkach wstrząsu cieplnego. Proszkiem bazowym był zestaw surowcowy tworzywa glinowego o podwyższonej odporności na szok termiczny. Badano wpływ modyfikatorów na mikrostrukturę, właściwości mechaniczne oraz odporność na szoki termiczne. Zestawy przygotowywano metodą ceramiczną, a homogenizację mieszaniny surowcowej prowadzono w środowisku wodnym. Z przygotowanych zestawów sporządzono granulat, wykonywano próbki badawcze, które po wypaleniu posłużyły do przeprowadzenia badań właściwości fizykochemicznych oraz termicznych tworzywa. Analizowano wyniki wytrzymałości na zginanie tworzyw wypalonych w piecu konwencjonalnym oraz po procesie szokowania, prowadzonego w zakresie temperatur 200-1000 ºC. Do analizy zależności właściwości materiałów od ich mikrostruktury wykorzystano obserwacje materiałów w mikroskopie skaningowym (SEM).

EN

The present work was undertaken to investigate the effect of zirconium oxide and aluminium-magnesium spinel powders of nanometer particle size on properties of high alumina material under thermal shocks. A base powder was a set of aluminium raw materials for manufacturing high thermal shock resistance alumina. The effect of the modifiers on the microstructure, mechanical properties and resistance to thermal shocks was studied. Samples were prepared using a ceramic method; homogenisation of raw material mixtures was carried out in an aqueous medium. The mixtures were granulated and compacted into test samples that after firing were used to study physicochemical and thermal properties of the material. There were studied bending strengths of materials fired in a conventional oven and of the same materials but after thermal shocking in the temperature range 200-1000 ºC. SEM observations were carried out to study a relationship between the measured properties and microstructure.

13

Calculation of Stress Intensity Factor for an Internal Circumferential Crack in a Rotating Functionally Graded Thick-Walled Hollow Circular Cylinder under Thermal Shock

Ghafoor E. M. R., Rokhi M. M.

Archive of Mechanical Engineering

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2017

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Vol. LXIV, nr 4

455--479

EN

In this article, the fracture behavior of functionally graded thick-walled cylinder under thermo-mechanical shock is investigated. For this purpose, classical coupled thermoelastic equations are used in calculations. First, these equations are discretized with extended finite element method (XFEM) in the space domain and then they are solved by the Newmark method in the time domain. The most general form of interaction integral is extracted for axially symmetric circumferential crack in a cylinder under thermal and mechanical loads in functionally graded materials and is used to calculate dynamic stress intensity factors (SIFs). The problem solution has been implemented in MATLAB software.

14

The experimental and theoretical investigations of damage development and distribution in double-forged tungsten under plasma irradiation-initiated extreme heat loads

Väli B., Laas T., Paju J., Shirokova V., Paduch M., Gribkov V. A., Demina E. V., Pimenov V. N., Makhlaj V. A., Antonov M.

Nukleonika

|

2016

|

Vol. 61, No. 2

169--177

EN

The influence of extreme heat loads, as produced by a multiple pulses of non-homogeneous flow of slow plasma (0.1–1 keV) and fast ions (100 keV), on double-forged tungsten (DFW) was investigated. For generation of deuterium plasma and fast deuterons, plasma-focus devices PF-12 and PF-1000 are used. Depending on devices and conditions, the power flux density of plasma varied in a range of 107–1010 W/cm2 with pulse duration of 50–100 ns. Power flux density of fast ions was 1010–1012 W/cm2 at the pulse duration of 10–50 ns. To achieve the combined effect of different kind of plasmas, the samples were later irradiated with hydrogen plasma (105 W/cm2, 0.25 ms) by a QSPA Kh-50 plasma generator. Surface modification was analysed by scanning electron microscopy (SEM) and microroughness measurements. For estimation of damages in the bulk of material, an electrical conductivity method was used. Investigations showed that irradiation of DFW with multiple plasma pulses generated a mesh of micro- and macrocracks due to high heat load. A comparison with single forged tungsten (W) and tungsten doped with 1% lanthanum-oxide (WL10) reveals the better crack-resistance of DFW. Also, sizes of cells formed between the cracks on the DFW’s surface were larger than in cases of W or WL10. Measurements of electrical conductivity indicated a layer of decreased conductivity, which reached up to 500 µm. It depended mainly on values of power flux density of fast ions, but not on the number of pulses. Thus, it may be concluded that bulk defects (weakening bonds between grains and crystals, dislocations, point-defects) were generated due to mechanical shock wave, which was generated by the fast ions flux. Damages and erosion of materials under different combined radiation conditions have also been discussed.

15

Odporność na szok termiczny kruszyw grubych przeznaczonych do mieszanek mineralno-asfaltowych

Wasilewska M., Zaśkiewicz S., Błażejowski K.

Drogownictwo

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2016

|

nr 10

327--332

PL

W artykule przedstawiono wyniki badań odporności na szok termiczny kruszyw grubych. Dodatkowo oznaczono ich nasiąkliwość, gęstość, odporność na rozdrabnianie i mrozoodporność w wodzie. Wykazano, że strata wytrzymałości VLA w przypadku poddanych szoku termicznemu kruszyw jest w zakresie od 0 do 10 %. Nie wykazano istotnej korelacji pomiędzy nasiąkliwością i mrozoodpornością a odpornością na szok termiczny. Zauważono natomiast różnice zachodzące na powierzchni kruszyw w wyniku poddawania ich oddziaływaniu wysokiej temperatury, które są związane z charakterystyką petrograficzną skał.

EN

The article presents the results of resistance to thermal shock of coarse aggregates. In addition, results of water absorption, density and resistance to freezing and thawing were concluded. It has been shown that the loss of strength VLA subjected to thermal shock aggregates is in the range from 0 to 10 %. There was no significant correlation between water absorption, resistance freezing and thawing and resistance to thermal shock. It is noted that the differences in aggregate after test are related to the petrographic rock.

16

Investigation on Magneto-thermoelastic Disturbances Induced by Thermal Shock in an Elastic Half Space Having Finite Conductivity under Dual Phase-lag Heat Conduction

Tiwari R., Kumar A., Mukhopadhyay S.

Computational Methods in Science and Technology

|

2016

|

Vol. 22, No. 4

201--215

EN

The present work seeks to investigate the propagation of magneto-thermoelastic disturbances produced by a thermal shock in a finitely conducting elastic half-space in contact with vacuum. Normal load has been applied on the boundary of the existing media that is supposed to be permeated by a primary uniform magnetic field. We employ both the parabolic type (dual phase-lag magneto-thermoelasticity of type I (MTDPL-I)) and hyperbolic type (dual phase-lag magneto-thermoelasticity of type II (MTDPL-II)) dual phase-lag heat conduction models to account for the interactions among the magnetic, elastic and thermal fields. The integral transform technique is applied to solve the present problem and the analytical results of both cases have been obtained separately. A detailed analysis of results has been made in order to understand the nature of waves propagating inside the medium and the effects of the phase-lag parameters. The effect of the presence of magnetic field has been highlighted. Numerical results have also been obtained to analyze the effect of magnetic field on the behavior of the solution more clearly and a detailed analysis of the results predicted by two models has been presented. It has been noted that in some cases there are significant differences in the solution obtained in the contexts of MTDPL-I and MTDPL-II theory of magneto-thermoelasticity.

17

Asymptotic solutions for generalized thermoelasticity with variable thermal material properties

Wang Y., Liu D., Wang Q., Zhou J.

Archives of Mechanics

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2016

|

Vol. 68, nr 3

181--202

EN

In this paper, a unified generalized thermoelastic solution with variable thermal material properties is proposed in the context of different generalized models of thermoelasticity, including thermoelasticity with one thermal relaxation time (LS theory), thermoelasticity with two thermal relaxation times (GL theory) and thermoelasticity without energy dissipation (GN theory). The unified form of governing equations is presented by introducing unifier parameters. The unified formulations are derived and given for isotropic homogenous materials with variable thermal material properties. The Laplace transform techniques and the Kirchhoff’s transformation are used to obtain general solutions for any set of boundary conditions in the physical domain. Asymptotic solutions for a specific problem of an elastic half-space with variable thermal conductivity and a specific heat, whose boundary is subjected to a thermal shock, are derived by means of the limit theorem of Laplace transform. In the context of these asymptotic solutions, some generalized thermoelastic phenomena are observed. Especially, the jumps at the wavefronts induced by the propagation of finite signal speed for the heat are clearly noticed. In addition, the effect of variable characteristics of material properties on thermoelastic behaviors is revealed by a comparison with the results obtained in the case of constant material properties.

18

Finite element modeling of material fatigue and cracking problems for steam power system HP devices exposed to thermal shocks

Pawlicki J., Marek P., Zwoliński J.

Archive of Mechanical Engineering

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2016

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Vol. LXIII, nr 3

413--434

EN

The paper presents a detailed analysis of the material damaging process due to lowcycle fatigue and subsequent crack growth under thermal shocks and high pressure. Finite Element Method (FEM) model of a high pressure (HP) by-pass valve body and a steam turbine rotor shaft (used in a coal power plant) is presented. The main damaging factor in both cases is fatigue due to cycles of rapid temperature changes. The crack initiation, occurring at a relatively low number of load cycles, depends on alternating or alternating-incremental changes in plastic strains. The crack propagation is determined by the classic fracture mechanics, based on finite element models and the most dangerous case of brittle fracture. This example shows the adaptation of the structure to work in the ultimate conditions of high pressure, thermal shocks and cracking.

PL

W pracy przedstawiono szczegółową analizę rozwoju pęknięć w wyniku niskocyklicznego zmęczenia materiału w warunkach szoków cieplnych i oddziaływania ustalonych obciążeń statycznych. Przeprowadzono analizę przebiegu procesu pękania na przykładzie korpusu zaworu redukcyjnego pary w elektrowni węglowej i wału wirnika turbiny parowej. Głównym czynnikiem w obydwu przypadkach są mniej lub bardziej gwałtowne powtarzalne cykle zmian temperatury .W przypadku inicjacji pęknięcia po stosunkowo małej liczbie cykli zmian obciążenia mechanizm zmęczenia zależy od naprzemiennej lub naprzemienno-przyrostowej zmiany odkształceń plastycznych. Propagację pęknięcia w głąb materiału wyznaczono metodami klasycznej mechaniki pękania na podstawie modeli MES i najbardziej niebezpiecznego modelu pękania kruchego. Przedstawiono przypadek przystosowania się konstrukcji do pracy w warunkach szoków cieplnych i pękania.

19

Zastosowanie porozymetrii rtęciowej do oceny wpływu wstrząsów cieplnych na zmiany teksturalne i rozkład wielkości porów w magnezjowo-chromowych tworzywach ogniotrwałych

Śliwa A.

Szkło i Ceramika

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2015

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R. 66, nr 5

11--16

PL

Metoda porozymetrii rtęciowej jest jedną z podstawowych technik pomiarowych dla przemysłu katalizatorów, węgli aktywnych i wielu innych. Istnieją również szerokie możliwości wykorzystania porozymetrii rtęciowej w obszarze badawczym związanym z projektowaniem, wytwarzaniem oraz wykorzystywaniem ceramiki, w szczególności ogniotrwałej. Celem artykułu jest przedstawienie jednego z możliwych przykładów rozwiązywania problemów badawczych związanych z określeniem zmian teksturalnych w materiałach magnezjowo-chromitowych, które poddano oddziaływaniu wstrząsów cieplnych. Przeprowadzono analizy rozkładu wielkości porów sześciu materiałów magnezjowo-chromitowych charakteryzujących się zróżnicowaną odpornością na wstrząsy cieplne. Badania zrealizowano na pojedynczych próbkach poddanych oddziaływaniu pięciu i dziesięciu powietrznych wstrząsów cieplnych, a ich wyniki porównywano do wartości uzyskanych dla próbek wyjściowych. We wszystkich badanych próbkach stwierdzono, że wzrosła wartość mediany średnicy próbek poddanych oddziaływaniu wstrząsów cieplnych. Jednocześnie zauważono, że wystąpiły zmiany w rozkładzie wielkości porów, które można powiązać z odpornością materiałów na wstrząsy cieplne. W przypadku materiałów wykazujących podwyższoną odporność na wstrząsy cieplne stwierdzono zwiększenie ilości porów o rozmiarach 10-30 μm, podczas gdy w materiałach o niższej odporności na wstrząsy cieplne zwiększenie udziału porów dotyczyło porów o rozmiarach 30-90 μm. Z punktu widzenia przytoczonego przykładu, badania porozymetryczne należy uznać za niezwykle użyteczne do rozwiązywania problemów związanych z oddziaływaniem czynników niszczących oddziałujących na ceramikę ogniotrwałą.

EN

The mercury porosimetry method is one of basic measuring techniques for the industry of catalysts, ceramics, active carbons and many others. There is also a wide range of possibilities of using mercury porosimetry in the research field related to refractory ceramics design, production and application. The aim of the article is to present one of possible examples of solving research problems related to the determination of textural changes in magnesia-chrome materials subjected to thermal shocks. Analyses of the pore size distribution of 6 magnesia-chrome materials characterised by different shock resistance were performed. The investigations were conducted on single samples subjected to 5 and 10 air thermal shocks and their results were compared to the values obtained for the original samples. It was found that in all the examined samples the median diameter of samples subjected to thermal shocks increased. At the same time changes in the pore size distribution were observed, which can be related to the materials’ resistance to thermal shocks. In the case of materials characterized by enhanced thermal shock resistance the number of 10-30 μm pores was increased, whereas in materials characterized by lower thermal shock resistance the increased number of pores was noted for the pore size of 30-90 μm. From the point of view of the quoted example, porosimetric tests should be considered very useful in the solving of research problems related to the effect of destructive factors on refractory ceramics.

20

Impact of thermal fatigue on young’s modulus of epoxy adhesives

Kłonica M.

Advances in Science and Technology. Research Journal

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2015

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Vol. 9, nr 28

103--106

EN

The following paper presents a comparative analysis of two epoxy-based adhesives: Hysol 9466 and Hysol 3421, prior to and after thermal shock testing. The tests focused on determining Young’s modulus. Epoxy-based materials are among the most widespread adhesive materials used as universal structural adhesives. The prepared epoxy samples (Hysol 9466 and Hysol 3421) were subjected to thermal shock cycling tests, according to a specified programme, in a thermal shock testing chamber, at a temperature range –40 °C to +60 °C and in the number of 200 cycles. Conclusions from the tests are presented at the final stage of the paper.