Wyniki wyszukiwania - BazTech

1

The Assessment of Resistance to Thermal Fatigue and Thermal Shock of Cast Iron Used for Glass Moulds

Stradomski G., Gzik S., Jakubus A., Nadolski M.

Archives of Foundry Engineering

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2018

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Vol. 18, iss. 3

173--178

EN

Constantly developing production process and high requirements concerning the quality of glass determine the need for continuous improvement of tools and equipment needed for its production. Such tools like forms, most often made of cast-iron, are characterized by thick wall thickness compared to their overall dimensions and work in difficult conditions such as heating of the surface layer, increase of thermal stresses resulting from the temperature gradient on the wall thickness, occurrence of thermal shock effect, resulting from cyclically changing temperatures during filling and emptying of the mould. There is no best and universal method for assessing how samples subjected to cyclic temperature changes behave. Research on thermal fatigue is a difficult issue, mainly due to the instability of this parameter, which depends on many factors, such as the temperature gradient in which the element works, the type of treatment and the chemical composition of the material. Important parameters for these materials are at high temperature resistance to thermal shock and thermal fatigue what will be presented in this paper.

2

Identification damage model for thermomechanical degradation of ductile heterogeneous materials

El Amri A., El Yakhloufi M. H., Khamlichi A.

International Journal of Applied Mechanics and Engineering

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2017

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Vol. 22, no. 2

475--481

EN

The failure of ductile materials subject to high thermal and mechanical loading rates is notably affected by material inertia. The mechanisms of fatigue-crack propagation are examined with particular emphasis on the similarities and differences between cyclic crack growth in ductile materials, such as metals, and corresponding behavior in brittle materials, such as intermetallic and ceramics. Numerical simulations of crack propagation in a cylindrical specimen demonstrate that the proposed method provides an effective means to simulate ductile fracture in large scale cylindrical structures with engineering accuracy. The influence of damage on the intensity of the destruction of materials is studied as well.

3

The thermal fatigue behaviour of creep-resistant Ni-Cr cast steel

Piekarski B.

Archives of Foundry Engineering

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2007

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Vol. 7, iss. 4

155-158

EN

The study gives a summary of the results of industrial and laboratory investigations regarding an assessment of the thermal fatigue behaviour of creep-resistant austenitic cast steel. The first part of the study was devoted to the problem of textural stresses forming in castings during service, indicating them as a cause of crack formation and propagation. Stresses are forming in carbides and in matrix surrounding these carbides due to considerable differences in the values of the coefficients of thermal expansion of these phases. The second part of the study shows the results of investigations carried out to assess the effect of carbon, chromium and nickel on crack resistance of austenitic cast steel. As a criterion of assessment the amount and propagation rate of cracks forming in the specimens as a result of rapid heating followed by cooling in running water was adopted. Tests were carried out on specimens made from 11 alloys. The chemical composition of these alloys was comprised in a range of the following values [...]. The specimens were subjected to 75 cycles of heating to a temperature of 900oC followed by cooling in running water. After every 15 cycles the number of the cracks was counted and their length was measured. The results of the measurements were mathematically processed. It has been proved that the main factor responsible for an increase in the number of cracks is carbon content in the alloy. In general assessment of the results of investigations, the predominant role of carbon and of chromium in the next place in shaping the crack behaviour of creep-resistant austenitic cast steel should be stressed. Attention was also drawn to the effect of high-temperature corrosion as a factor definitely deteriorating the cast steel resistance to thermal fatigue.

4

Alternative composite material solution in the frictional connections

Wojciechowski A., Sobczak J.

Journal of KONES

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2003

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Vol. 10, No. 3-4

379-389

EN

Metal matrix composites based on light metal alloys are, at present, one of the best promising and developing constructional material groups. Serious weight loss of construction and concurrently keeping the required mechanical properties and exploitation safety are the fundamental advantage coming from the application of composites as innovative materials of new generation. Unique properties of composite materials, in consequence, make possible the construction optimization of designed parts, i.e. subsequent improving of reliability and utility features of final product. Metal matrix composites dispersedly or local reinforced are mainly used for frictional connections, working in technically dry friction conditions in the frictional couple (i.e. clutch plate, brake disc-friction lining, piston-cylinder). Comparison investigations of different Al-alloy matrix composites reinforced by SiC or fly-ash (ALFAŽ composite) and of cast iron were assessed by the determination of: the thermal shock resistance, the abrasion resistance, physical and mechanical properties in connection with the structural characteristics. The obtained results have been proved that, in specified experimental conditions, Al/SiC and ALFAŽ composites are characterized repeatedly by higher thermal fatigue resistance, similar strength properties and better wear resistance comparable to the cast iron.

PL

Metalowe materiały kompozytowe na bazie stopów metali lekkich stanowią obecnie jedną z najbardziej obiecujących i rozwijających się grup materiałów konstrukcyjnych. Podstawową korzyścią płynącą z zastosowania ich jako innowacyjnych materiałów nowej generacji, może być znaczne obniżenie masy konstrukcji, przy jednoczesnym zachowaniu wymaganych właściwości mechanicznych i bezpieczeństwa eksploatacji. Unikalne właściwości materiałów kompozytowych w konsekwencji umożliwiają optymalizację konstrukcji projektowanych części, czyli dalszą poprawę niezawodności i cech użytkowych wyrobu finalnego. Zbrojone dyspersyjnie lub lokalnie metalowe materiały kompozytowe na bazie stopu aluminium są używane głównie na skojarzenia cierne, pracujące w warunkach tarcia technicznie suchego w parze ciernej (np. tarcza sprzęgłowa, hamulcowa - okładzina cierna, tłok-cylinder). Porównawcze badania różnych materiałów kompozytowych o osnowie ze stopów aluminium zbrojonych SiC i popiołami lotnymi (kompozyt ALFAŽ) oraz żeliwa, oceniano przez określenie odporności na szoki cieplne oraz odporności na ścieranie, a także właściwości fizycznych i mechanicznych w połączeniu z wyznaczaniem charakterystyk strukturalnych. Uzyskane wyniki wykazały, że w danych warunkach eksperymentalnych, kompozyty Al/SiC i ALFAŽ cechują się wielokrotnie wyższą odpornością na zmęczenie termiczne, porównywalnymi właściwościami wytrzymałościowymi i lepszą odpornością na zużycie w porównaniu do żeliwa.