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Influence of load and reinforcement content on selected tribological properties of Al/SiC/Gr hybrid composites

Veličković S., Miladinović S., Stojanović B., Nikolić R. R., Hadzima B., Arsić D.

Production Engineering Archives

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2018

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Vol. 18

18--23

EN

Hybrid materials with the metal matrix are important engineering materials due to their outstanding mechanical and tribological properties. Here are presented selected tribological properties of the hybrid composites with the matrix made of aluminum alloy and reinforced by the silicon carbide and graphite particles. The tribological characteristics of such materials are superior to characteristics of the matrix – the aluminum alloy, as well as to characteristics of the classical metal-matrix composites with a single reinforcing material. Those characteristics depend on the volume fractions of the reinforcing components, sizes of the reinforcing particles, as well as on the fabrication process of the hybrid composites. The considered tribological characteristics are the friction coefficient and the wear rate as functions of the load levels and the volume fractions of the graphite and the SiC particles. The wear rate increases with increase of the load and the Gr particles content and with reduction of the SiC particles content. The friction coefficient increases with the load, as well as with the SiC particles content increase.

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Review of the Hard-Facing Technology Application for Reparation of the Given Parts in Various Branches of Industry

Lazić V., Arsić D., Mutavdžić M., Nikolić R., Meško J., Radović L., Ilić N.

Multidisciplinary Aspects of Production Engineering

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2018

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Vol. 1, Iss. 1

279--285

EN

This paper deals with the problem of defining the optimal procedure for reparation of the machine parts of large dimensions and complex shapes. The procedure consists of establishing the causes of the part's damages, definition of the reparation technology, with selection of its parameters and ways of execution. The reparation is done by hard-facing, with heat treatment that consists of preheating, additional heating and the post hard-facing tempering. The process parameters' selection includes choosing the right filler metal(s), ways and order of depositing the hard-faced layers, ways of reaching and maintaining the preheating temperatures, checking of the base metal's chemical composition and mechanical properties and deciding on the post-process heat and mechanical processing of the executed hard-facing. The executed reparation of the forging hammer's mallet, presented in details, serves as an example how the reparation can successfully serve as a substitute for procuring the new part and thus producing the savings both directly in lower costs and indirectly in shortening the down-time of the damaged part operation.

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Influence of welding time on quality of the friction welded joint of two dissimilar steels

Ratković N., Lazić V., Arsić D., Nikolić R., Hadzima B.

Zeszyty Naukowe. Quality. Production. Improvement

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2017

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No. 1 (6)

1--11

EN

There are several factors that influence the friction welding (FW) process, i.e. the quality of the welded joint, like the welding time, the contact pressure, the compacting pressure, the friction speed etc. The joining process is additionally complicated if the two different materials are to be welded to each other. The subject of research, presented in this paper, is the welding time of the FW process, since the level of axial and radial plastic deformation of the welded pieces and shortening of the welded part depend mainly on the welding time. The paper first presents some theoretical basics of the FW process and then, in the experimental part, the influence of the process duration is investigated. The two materials that the experimental samples were made of are the high-speed steel and the steel for tempering.

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Fracture analysis of the pulley of a bucket wheel boom hoist system

Bošnjak S., Arsić M., Savićević S., Milojević G., Arsić D.

Eksploatacja i Niezawodność

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2016

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Vol. 18, no. 2

155--163

EN

This paper presents the results of the pulley fracture analysis. Experimental investigations confirmed that the chemical composition and basic mechanical properties of the pulley material, except the impact energy at a temperature of –20°C, meet the requirements of the corresponding standard. The impact energy value at the temperature of –20°C is for ≈45% lower than the prescribed value which has considerable influence on the appearance of the brittle fracture, especially having in mind the fact that the bucket wheel excavators operate at low temperatures. Metallographic examinations as well as magnetic particle inspections indicated that initial cracks in the welded joints occurred during the manufacture of the pulleys. Characteristic levels of the rope load cycle are obtained by using in-house software which includes the dynamic effects of the resistance-to-excavation. The FEA results pointed out that in the representative load cases the combinations of the mean stress and the alternating stress in the pulley critical zone lie considerably below the limit line of the modified Goodman’s diagram. The conclusion, based on the presented results, is that the fracture of the pulley appeared as the result of the ‘manufacturing-in’ defects.

PL

Artykuł przedstawia wyniki analizy pęknięć koła pasowego. Badania doświadczalne potwierdziły, że skład chemiczny oraz podstawowe właściwości mechaniczne materiału, z którego zostało wykonane koło pasowe, za wyjątkiem energii udaru w temperaturze –20°C, były zgodne z odpowiednią normą. Wartość energii udaru w temperaturze –20°C była o ≈45% niższa od wartości zalecanej, co ma znaczący wpływ na występowanie pękania kruchego, zwłaszcza gdy weźmie się pod uwagę fakt, że koparki kołowe są przeznaczone do pracy w niskich temperaturach. Badania metalograficzne oraz badania magnetyczno-proszkowe wykazały, że pęknięcie pierwotne w połączeniu spawanym pojawiło się już w fazie produkcji koła pasowego. Charakterystyczne poziomy cyklu obciążenia liny uzyskano stosując własne oprogramowanie, które uwzględnia dynamiczne oddziaływanie odporności na urabianie. Wyniki MES pokazały, że w przypadku obciążeń reprezentatywnych, wartości średniego naprężenia w funkcji naprężenia zmiennego w strefie krytycznej koła pasowego były znacznie niższe niż wartości graniczne wyznaczone na podstawie zmodyfikowanego wykresu Goodmana. Na podstawie otrzymanych wyników stwierdzono, że pęknięcie koła pasowego powstało wskutek wad produkcyjnych.