Utvrđivanje uzroka nastanka havarije motora SUS na osnovu retrospektivne funkcije dijagnostike

The was a failure on the drive engine of the road vehicle. On it, maintenance procedures were carried out in the service. After an extremely short period of operation, engine failure by the same mechanism of occurrence occurred again. The paper sheds light on the problem of engine malfunctions, establishes cause-and-effect relationships and proposes measures to eliminate the causes of failure.Publishe

Determination analysis of temperature regimes, functional characteristics and sliding curves of a hydrodynamic clutch

Analysis of output quality of power transmitters is possible in position when characteristics are determined earlier. This is the reason why we focused on determination of these characteristics for a concrete power hydro-transmitter. This means that the investigation task primarily consisted of determination of functional characteristics, defining of the sliding curves and temperature regimes of a concrete hydrodynamic clutch. Results of velocity and pressure field investigations in the working space of this clutch, obtained by use of the same test setup, are the basis for determination and analysis of the functional characteristics, sliding curves and temperature regimes. In this work we also analyzed function of the hydrodynamic transmitter in assembly with an internal combustion engine, as well as a process of acceleration and deceleration of a vehicle with this assembly in it

Correlation between Emission and Combustion Characteristics with the Compression Ratio and Fuel Injection Timing in Tribologically Optimized Diesel Engine

Diesel engines are economical thanks to their combustion process characteristics, which is why they have a high noise emission level as well as exhaust emissions of nitrogen oxide and particulate matters. By continuously changing the value of compression ratio, it is possible to control the power and emissions. Implementation of variable compression ratio has many benefits, such as being able to work with different types of fuel. In this way, it is possible to optimize the combustion process for operation with minimum fuel consumption and emission generation, so that diesel engines can be applied to the framework of future hybrid vehicle concepts, and so forth. As far as the crucial objective of the manuscript is concerned, experimental diesel engine investigation was performed on a roller test-bench by using zero-dimensional computer model (specifically AVL IndiCom Indicate Software). Engine indication was executed with the factory compression ratio value and with three lower values. During our examination, the change in the compression ratio value was achieved by changing the volume of a combustion chamber at a piston-bowl. The results of laboratory research on the experimental engine are presented in the paper when discussing a series of specific parameters (characteristics), such as compression ratio, fuel injection timing, engine speed, as well as load influence on combustion process and exhaust emissions

Fizikalne i metalurške promjene tijekom zavarivanja trenjem brzoreznog i kaljenog čelika

This paper outlines the basic principles of welding by friction of high-speed cutting steel and tempered steel from the viewpoint of metallurgic processes that are going on in the material. The bases of welding by friction of different materials are outlined in a theoretical way. The experimental part of the paper also relates to friction welding of samples made of different metals: high-speed cutting steel (HS 6-5-2-5) on one hand and the tempered steel (C60) on the other.Ovaj rad daje osnovne principe zavarivanja trenjem brzoreznog čelika i kaljenog čelika s motrišta metalurškog procesa koji se odvija u materijalu. Osnove zavarivanja trenjem različitih materijala navedene su teorijski. Eksperimentalni dio rada odnosi se na zavarivanje trenjem uzoraka izrađenih od različitih metala: brzoreznog čelika (HS 6-5-2-5) s jedne i kaljenog čelika (C60) s druge strane

Analiza kvalitete Al-Cu spoja ostvarenog zavarivanjem trenjem

This paper outlines the bases of the friction welding process, especially when it comes to friction welding of different materials. This was illustrated on an example of friction welding of aluminum and copper, which is often applied in electrical engineering. The analysis of influential parameters was conducted based on the data obtained by an experiment, since the data on this topic are very seldom in the available literature.Ovaj članak daje osnove procesa zavarivanja trenjem, naročito kada je u pitanju zavarivanje trenjem različitih materijala. To je ilustrirano na primjeru zavarivanja trenjem aluminija i bakra, koji se često primjenjuje u elektrotehnici. Analiza utjecajnih parametara provedena je na temelju podataka dobivenih eksperimentom jer su podaci o ovoj temi vrlo rijetko u dostupnoj literaturi

Solving the Problem of Friction and Wear in Auxiliary Devices of Internal Combustion Engines on the Example of Reciprocating Air Compressor for Vehicles

Using vehicles and other mobile systems to transport passengers and goods, approximately 25% of Europe\u27s greenhouse gases are generated. At the same time, many research papers, published by researchers and students, promote the use of electric vehicles as zero-emission vehicles. Given that, more broadly, the emission of electric vehicles is higher, especially in countries where electricity is obtained by burning coal, the use of internal-combustion engines is still dominant. There are other reasons for using an internal-combustion engine, such as already developed pumping station infrastructure, which is not the case when recharging electric vehicles. Improvements in engine design contribute to meet the regulations relating to the fuel consumption and toxic gas emissions. This refers to the use of alternative fuels, improving the combustion process, and increasing efficiency (efficiency coefficient) by reducing losses. The research is focused on the problem of friction and wear in internal combustion engines and reciprocating air compressors, as auxiliary devices on engines. For that purpose, construction of the reciprocating air compressor in motor vehicles was redesigned. The paper presents the characteristic test results of material used to strengthen liner of the aluminum cylinder. Specifically, a method for testing the performance characteristics of a single-cylinder reciprocating compressor inside of an experimental installation for compressed air supply has also been proposed

Синтеза, карактеризација и биолошка активност комплекса Pt(II) са стероидним тиосемикарбазонима

In this work, Pt(II) complexes of previously synthesized steroidal thiosemicarbazones were synthesized and characterized. The ligands and their metal complexes were studied by analytical and spectroscopic data (elemental analysis, IR, 1D NMR and 2D NMR, HSQC, HMBC, NOESY, COSY), the analysis of which enabled complete 1H and 13C assignments of each compound including E and Z isomers. All the synthesized ligands and complexes were screened for their cytotoxic and antimicrobial activity. The results demonstrate that new steroidal thiosemicarbazone complexes were significantly less cytotoxic than corresponding steroidal thiosemicarbazones. Also, complexes show lower antimicrobial activity than the standard drugs, similar to the activity of the starting thiosemicarbazones.Почевши од претходно синтетисаних стероидних тиосемикарбазона, у овом раду су синтетисани и окарактерисани комплекси платине(II). Лиганди и њихови метални комплекси проучавани су аналитичким и спектроскопским методама (елементална анализа, ИЦ, 1D NMR и 2D NMR, HSQC, HMBC, NOESY, COSY). Анализом добијених података омогућена је потпуна 1H и 13C асигнација свих једињења укључујући Е и Z изомере. За синтетисане лиганде, као и њихове комплексе испитивана је цитотоксична и антимикробна активност. Резултати указују на то да нови стероидни тиосемикарбазонски комплекси испољавају значајно нижу цитотоксичност од одговарајућих стероидних тиосемикарбазона. Поред тога, комплекси поседују антимикробну активност сличну активности полазних тиосемикарбазона, a нижу од стандардних леков

The Impact of Lubricant Viscosity and Materials on Power Losses and Efficiency of Worm Gearbox

The results of the experimental research of the power losses and efficiency of single-stage worm gearbox, which is designed for such purpose, are presented in this paper. Three worm pairs (coupled gears) ZI type with the same geometric characteristics were used in the research, where worms are made of the same material (hardened and ground steel type 42CrMo4) and worm gears are made of three different types of material (zinc-aluminium alloy ZA12, aluminium alloy A356 and tin bronze CuSn12). The main part of the research is conducted to investigate the application of new materials for the manufacturing of worm gears (alloys ZA12 and A356) and their impact on the power losses and efficiency in comparison to tin bronze CuSn12. The values of efficiency are determined for different operating modes of the gearbox, that is, for different values of input rotational speed and load, where different viscosity lubricants were used. Depending on the operating mode and measured operating temperatures, the calculation of power losses and coefficient of friction for all experimental worm pairs was performed. Based on the obtained results, it can be concluded that the best tribological characteristics has worm pair 42CrMo4/ZA12, which is the recommendation for the use of ZA alloy for manufacturing of worm gears as the alternative for tin bronze and other non-ferrous metals

Influence of Vanadium Content on the Tribological Behaviour of X140CrMo12-1 Air-Hardening Steel

The paper presents experimental testing of wear resistance of steel samples from the same groups of steel. Test results were recorded and presented in the form of diagrams showing the wear resistance of the tested materials in different sliding conditions. The tested steels have high carbon content; the addition of chromium and molybdenum results in the high hardness and low impact toughness of the steels. The addition of vanadium changes the microstructure when the metal grain becomes smaller and the whole structure is martensitic, with chromium and vanadium carbides in the metal matrix. A change in the microstructure causes a change in mechanical properties. The obtained results showed that the addition of vanadium increases impact toughness. However, it is not known how it affects wear resistance and hardness. This type of steel belongs to a new group of steels resistant to wear. A change in the vanadium content causes a decrease in the hardness and wear resistance of the steel and an increase in its impact toughness

Selection of the most appropriate welding technology for hardfacing of bucket teeth

A possibility of extending the service life of the working parts of construction machinery with particular attention to hardfacing of loader bucket teeth was investigated. In the first part of this paper the tribological processes typical for this machinery is analysed. Worn excavator parts are made of conditionally weldable cast steel that requires a special hardfacing technology, so numerous investigations were performed to obtain the most appropriate technology. In the experimental part of the paper, the selection of the optimum hardfacing technology for bucket teeth and the procedure of the manual arc hardfacing are presented. The samples were first hardfaced using different techniques and technologies and then the microstructure and microhardness of characteristic hardfaced layers were studied. Specially prepared samples were used for tribological investigations. The results of experimental investigations enabled the selection of the most suitable hardfacing technology and its application to real parts. The bucket teeth, with their hardfaced layers applied vertically, horizontally or in a honeycomb pattern were mounted onto a loader bucket, alternated with the new non-hardfaced teeth and their performance during the operation was regularly monitored. After a certain period, the degrees of the wear for the non-hardfaced and differently hardfaced teeth were measured. Taking into account both technical and economic factors, the most suitable hardfacing technology was determined