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1

Identyfikacja parametrów modelu fizycznego materiału lepkosprężystego na podstawie doświadczalnej charakterystyki pełzania

Gnatowska R., Gnatowski A.

Modelowanie Inżynierskie

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2013

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T. 17, nr 48

52--56

PL

Podejmowanie i realizacja prac badawczych nad właściwościami materiałów, jak również nad metodami kształtowania ich właściwości fizycznych i użytkowych to sprawa szczególnie istotna. W dziedzinie tworzenia nowych materiałów dąży się do przewidywania ich właściwości mechanicznych. W oparciu o określoną i trafnie dobraną teorię, można zająć się teoretycznym przewidywaniem właściwości materiałów lepkosprężystych na podstawie znanych cech ich składników. Publikacja dotyczy modelowania matematycznego materiału lepkosprężystego.

EN

Implementation of research on the materials properties, as well as the methods to determine their physical and performance properties is particularly important. In the development of new materials, the aim is to predict their mechanical properties. Based on the theory, we can predict the properties of viscoelastic materials based on characteristics their ingredients. Publication concerns mathematical modeling of viscoelastic material.

2

Evaluation of reformer tubes degradation after long term operation

Łabanowski J.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 43, nr 1

244-251

EN

Purpose of this paper is to show the effect of long-term service at elevated temperatures on microstructural changes of cast steel reformer tubes made of the alloy IN-519 (24%Cr, 24%Ni, Nb). The relationship between mechanical properties and microstructure degradation is discussed. Design/methodology/approach: Investigations were performed on five tubes taken from ammonia reformer furnace. Tubes worked at temperature of 880şC and 3.2 MPa pressure. The operation time varied from 24000 to 95000 hours. Microstructure of the material has been examined with the use of light optical microscopy and scanning electron microscopy (SEM). The energy dispersive X-ray analysis (EDX) was used for phase identification. The mechanical properties have been evaluated in static tensile tests at room temperature. Findings: Metallographic investigations of IN-519 cast steel catalytic tubes show that structural changes occur in non-monotonic way with operating time at elevated temperatures. For this reason the evaluation of tube degradation can not be based only on the microstructure examinations. The presence of a good correlation between mechanical properties of the catalytic tubes and service conditions, i.e. temperature, time, and internal stress was confirmed. Research limitations/implications: The surface condition of the tubes walls like carburization and oxidation is not considered in this study. Practical implications: The method for assessing the current degradation level and for predicting residual lifetime of creep-resistant tubes has been established. The method uses elongation values as the main factor characterizing structural degradation of catalytic tubes. It respects all degradation mechanisms involved in tubes degradation, and can give reliable information on reformer tube condition through almost whole period of operation. Originality/value: Microstructure transformations occur in the IN-519 cast steel tubes during long-term operation in the reformer furnace were revealed and described

3

Konstruowanie odlewów pracujących w warunkach cyklicznych zmian temperatury

Piekarski B., Drotlew A.

Archiwum Technologii Maszyn i Automatyzacji

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2008

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Vol. 28, nr 3

95-102

PL

W artykule na przykładzie odlewanych elementów służących do uformowania i transportu wsadu w piecach do obróbki cieplnej - przedstawiono podstawowe zasady obowiązujące przy projektowaniu odlewów pracujących w warunkach cyklicznych zmian temperatury. Zestawiono wytyczne dotyczące doboru grubości i sposobów łączenia ścianek odlewów.

EN

In this paper, on an example of cast elements for charging batch in heat-treatment furnaces, the basic rules of designing of castings working in conditions of cyclic changes of temperature have been show. The guiding principles of the choice of wall thickness and wall commotions have been presented.

4

Degradation of the cast steel parts working in power plant pipelines

Renowicz D., Hernas A., Cieśla M., Mutwil K.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 18, nr 1-2

219--222

EN

Purpose: Purpose of this paper is to identify the influence of loading history and the processes of material degradation on the initiation of cracking and on durability under creep and fatigue conditions. Design/methodology/approach: The aim of the research was to identify the properties of the material of the fittings cut out of a start-up pipeline connecting two OP-140 boilers with turbines, as well as to identify the reasons of failure of these parts after 100000 hours of operation. Results of the investigations were the basis of predicting the lifetime of machine parts and components of devices subjected to complex mechanical and thermal influence. Numerical simulation of work conditions was also performed. Problem of life assessment of the pipelines is currently the object of interest of many research centers. Findings: Due to extreme conditions of the start-up pipeline operation, its T-connections are subject to quick wear, and their properties determine the operational reliability and safety of the whole pipeline. For the reason it is necessary to verify the criteria of pipelines’ durability evaluation applied so far, based on the parameters characteristic of the creep process exclusively. Research limitations/implications: In the case discussed, i.e. a T-connection being a start-up pipeline part, the present criteria should be expanded with critical values describing fatigue/corrosion processes. Practical implications: The paper introduces the results of investigations of the 0.2C-1.2Cr-0.6Mo-0.3V cast steel used for parts of live steam pipelines working in power plants. Such parts include, e.g. T-connections. Originality/value: The paper show the possibilities of numerical models application.

5

Cracking processes during creep test of ŻS6U superalloy with aluminium coatings

Cieśla M., Swadźba L.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 17, nr 1-2

177--180

EN

Purpose: The paper presents the evaluation of the influence of aluminium layers used as protective coatings of aircraft turbine engine blades upon durability of ŻS6U nickel base superalloy under the conditions of short time creep. The conditions of cracks formation and growth in specimens with aluminium coatings have been analysed while taking into account the microstructure properties of coatings as well as the microstructure of specimen core material. Design/methodology/approach: The creep tests have been performed on MTS apparatus in the conditions corresponding to the extreme operating conditions of aircraft engine blades. The specimens were heated in a resistance furnace up to the temperature of 950ºC and then constant axial force was applied which induced stress σo=300 MPa in their cross-section. Findings: The obtained results have proved a significant influence of the type, protective coating thickness and the specimen core structure upon the secondary creep rate. Research limitations/implications: To ensure the most effective use of aluminium protective coatings it is important to understand the creep mechanisms in temperature lower than DBTT (ductile brittle transition temperature). Therefore, it is necessary to perform some creep tests in temperatures much lower than 900ºC. Practical implications: The obtained results could constitute the base for suggesting the guidelines on selecting proper aluminium coatings for specific designs of aircraft engine blades. Originality/value: It has been found that the reduction of creep durability of specimens made of ŻS6U alloy with diffusive aluminium coatings is caused by the reduction of the lateral surface of specimens core, which effectively transfers loads in creep tests.