Wyniki wyszukiwania - Biblioteka Nauki

1

Rola tarcia wewnętrznego i zewnętrznego w transporcie minerałów sypkich

100%

Adamecki D. , Ścieszka S.

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2006

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tom T. 1, z. 4

5-17

PL

W zagadnieniach technicznych związanych z projektowaniem i użytkowaniem systemów transportowych minerałów sypkich (np. węgla, rud metali, piasku itd.) zasadnicze znaczenie ma rzetelna wiedza o kątach tarcia wewnętrznego i zewnętrznego dla ww. minerałów oraz elementów konstrukcyjnych systemu transportu (np. taśm przenośnikowych, wykładzin zbiorników itd.). Aktualne metody pomiaru tarcia dla minerałów sypkich, bazujące na statycznym ścinaniu próbki minerału, nie oddają w pełni dynamiki zmian obciążeń i względnych prędkości, jakie obserwuje się w warunkach przemysłowych. Dokładne modelowanie oddziaływań między cząsteczkami transportowanego minerału wymagałoby uwzględnienia indywidualnych własności ziaren oraz aktualnych parametrów, opisujących ruch transportowanego minerału. W pracy zawarto aktualny stan wiedzy na temat tarcia w ośrodkach sypkich.

EN

In design and maintenance of transportation systems for bulk solids such as copper ore, sand or coal accurate determination of the angle of internal and wall friction is essential for reliable prediction of flow behaviour in industrial bunkers and conveyors. Current methods of measurement of the friction behaviour of bulk solids in shear cell equipment suffer serious limitations when investigating the dynamic loading and velocity observed in practice. Accurate modelling of the frictional behaviour requires measurement of the friction angles as function of both the individual particle properties and the changes in the state of flow. The paper provides a critical review of the current techniques employed in measuring the angles of internal and wall friction.

2

Structural changes of Ni-base metallic glasses during thermal activation

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Poloczek T. , Griner S. , Nowosielski R.

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2008

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tom Vol. 31, nr 1

33-36

EN

Purpose: The paper presents a crystallization process of i68.7Cr6.6Fe2.65Si7.8B14C0.25 metallic glasses. The Ni68.7Cr6.6Fe2.65Si7.8B14C0.25 metallic glasses was produced by the CBMS method with cooling rate corresponding for amorphous structure manufacturing. Design/methodology/approach: The crystallization of Ni68.7Cr6.6Fe2.65Si7.8B14C0.25 metallic glasses by method internal friction (IF) differential thermal analysis (DTA), X-ray and transmission electron microscopy (TEM) were studied. Findings: The investigation showed, that metallic glasses during thermal activation go through from metastable amorphous state by few medial states to the stable crystalline state (relaxation and crystallization process). Research limitations/implications: During thermal activation of metallic glasses two processes can be distinguished: structural relaxation of amorphous structure and complex crystallization process of alloy. Practical implications: Perception of structural relaxation and crystallization processes of metallic glasses can used for analysis of thermal stability of metallic glasses. Originality/value: The paper presents, that the thermal activation of metallic glasses conduct to the structural changes, which the final stage is crystalline state.

3

Crystallisation process of Ni-base metallic glasses by electrical resistance measurements

100%

Poloczek T. , Griner S. , Nowosielski R.

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2007

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tom Vol. 28, nr 6

353-356

EN

Purpose: The paper presents a crystallization process of Ni68,7Cr6,6Fe2,65Si7,8B14C0,25 metallic glasses. The Ni68,7Cr6,6Fe2,65Si7,8B14C0,25 metallic glasses were produced by the CBMS method for two different conditions of the casting, with different cooling rate. Design/methodology/approach: The crystallization of Ni68,7Cr6,6Fe2,65Si7,8B14C0,25 metallic glasses by methods of electrical resistance measurements (ERM), differential thermal analysis (DTA), and transmission electron microscopy (TEM) was studied. Findings: The investigation has shown, that the conditions of vitrification (different, but higher than critical cooling rate) influence different course elementary crystallization processes during thermal activation. Research limitations/implications: The differences in temperature of beginning of elementary crystallization processes of alloy, as a function of thickness of strip was disclosed. Practical implications: The electrical resistance measurements method (ERM) can be used for analysis of thermal stability of metallic glasses. Originality/value: The paper presents, that the conditions of vitrification influence different course elementary crystallization processes during thermal activation.

4

Microstructure and behaviour of ZC63 alloy and composite

100%

Trojanová Z. , Lukáč P.

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2007

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tom Vol. 28, nr 9

541-548

EN

Purpose: of this paper is to study the damping behaviour of ZC63 magnesium alloy and the same alloy reinforced with short Saffil fibres. Design/methodology/approach: Samples were thermally cycled between room temperature and increasing upper temperature of the thermal cycle and the logarithmic decrement were measured at room temperature. Findings: The strain amplitude dependence of the logarithmic decrement can be divided to two components: the amplitude independent and the amplitude dependent. While the thermal treatment does not change the amplitude independent component, the amplitude dependent part increases with increasing upper temperature of the thermal cycle. Research limitations/implications: Redistribution of solute atoms during thermal cycles is the reason for the observed changes in the amplitude dependence of decrement. Thermal stresses arise in the composite at the interfaces between the matrix and the reinforcement owing to a considerable mismatch of the thermal expansion coefficients of the matrix and that of the reinforcement. Practical implications: The ZC63/Saffil composites may be used as damping materials. Originality/value: New results on the damping behaviour of ZC63 alloy and its composite including internal friction were obtained.