Experimental Investigation of Viscosity of Glycerol Based Nanofluids Containing Carbon Nanotubes

The addition of solid nanoparticles to liquids provide significant enhancement of heat transfer and hydrodynamic flow. The viscosity of nanofluids is important for nanofluid transport related to flow dynamics and heat transfer. The aim of the paper is to investigate experimentally the viscosity of nanofluids prepared with glycerol base and nitrogen-doped bamboo shaped multi-walled carbon nanotubes (MWCNTs). The samples are prepared with 0.1, 0.2, 0.5 and 1.0 wt.% MWCNTs. The viscosity of glycerol and MWCNTs nanofluid suspensions are measured at various temperatures and rotational speeds (shear rates). The influence of nanotubes amount, temperature and rotational speed on the viscosity is investigated

Tribological and design parameters of lubricated sliding bearings

High performance, longevity and tribological behavior of lubricated sliding bearings are in close connection with selected design and tribological parameters. Among others, the most important are load carrying capacity dimensions, clearance, material and surface properties. Selection of these parameters is discussed and some recommendations in accordance with operating conditions are shown

Tribological and design parameters of lubricated sliding bearings

High performance, longevity and tribological behavior of lubricated sliding bearings are in close connection with selected design and tribological parameters. Among others, the most important are load carrying capacity dimensions, clearance, material and surface properties. Selection of these parameters is discussed and some recommendations in accordance with operating conditions are shown

Experimental investigation of viscosity of glycerol based nanofluids containing carbon nanotubes

The addition of solid nanoparticles to liquids provide significant enhancement of heat transfer and hydrodynamic flow. The viscosity of nanofluids is important for nanofluid transport related to flow dynamics and heat transfer. The aim of the paper is to investigate experimentally the viscosity of nanofluids prepared with glycerol base and nitrogen-doped bamboo shaped multi-walled carbon nanotubes (MWCNTs). The samples are prepared with 0.1, 0.2, 0.5 and 1.0 wt.% MWCNTs. The viscosity of glycerol and MWCNTs nanofluid suspensions are measured at various temperatures and rotational speeds (shear rates). The influence of nanotubes amount, temperature and rotational speed on the viscosity is investigated

Thermal cycling behaviour of plasma sprayed nicr-al-co-y2o3 bond coat in thermal barrier coating system

The aim of this study was to investigate the thermal cycling behaviour of NiCr-Al-Co-Y2O3 bond coating in thermal barrier coating (TBC) system with ZrO2-MgO as a top coating. The coatings were deposited by atmospheric plasma spraying (APS) on stainless steel X15Cr13 (EN 1.4024) substrate. The used composite powder NiCr-Al-Co-Y2O3 was mechanically cladded, and the steel substrates were preheated to 160-180 degrees C. The thermal cycling performance of the obtained bond coat and the effect of formed complex ceramic oxides of the Al2O3-Y2O3 system were tested by heating to 1200 degrees C and cooling in air to 160-180 degrees C. The number of performed thermal cycles was 7, 32 and 79. The quality of the obtained coating, as well as its thermal cycling behaviour, was assessed through the microstructural analysis, microhardness and tensile bond strength measurements, and change in chemical composition and microhardness. The obtained results showed that the steel substrate, bond coat oxidation and interdiffusion at bond coat/substrate interface have a significant influence on changes in chemical composition and microhardness of the bond coat. The correlation between oxidation behaviour of NiCr-Al-Co-Y2O3 bond coat and number of thermal cycles was also discussed

Microstructure and mechanical properties of the Mo-NiCrBSi coating deposited by atmospheric plasma spraying

Prah koji je korišćen u ovom istraživanju (Mo-NiCrBSi) je mešavina dva praha, praha Mo i praha 'samotekuće' legure NiCrBSi, u procentualnom odnosu 75/25%. Nanošenjem ove mešavine prahova dobijena je 'samotekuća' prevlaka na bazi molibdena. Prevlaka je naneta plazma sprej postupkom u atmosferskim uslovima. Kvalitet ovako dobijene prevlake zavisi od nekoliko parametara kao što su: veličina čestica praha koji se nanosi, temperatura nanošenja, vrsta gasova koji se koriste, količina unetog praha, ugao i tempo nanošenja (kontinualno ili sa prekidima), rastojanje plazma sprej pištolja od osnove, temperatura osnove, primenjeni pritisak tokom postupka itd. Sve ove parametre treba pažljivo izabrati kako bi se dobile prevlake sa najboljim karakteristikama, a u zavisnosti od željene primene. U ovom istraživanju su korišćene tri grupe Mo-NiCrBSi prevlaka dobijene sa tri različita rastojanja plazma sprej pištolja od osnove. Mikrostrukture i mehaničke karakteristike dobijenih prevlaka su analizirane da bi se došlo do optimalnih parametara nanošenja tj. do onih koji daju najbolje rezultate.The powder used in this research (Mo-NiCrBSi) was a blend of powders composed of 75% Mo and 25% self-fluxing alloy NiCrBSi. With the deposition of this powder a molybdenum base self-fluxing coating is obtained. The process used for coating deposition was atmospheric plasma spraying (APS). The quality of the coatings deposited by APS depends on several parameters such as the sprayed particle size, the deposition temperature, the combustion gases, the feed speed, the angle and rate of deposition (continuous or intermittent), the spray distance, the temperature of the substrate, the pressure applied during the process, etc. All these parameters should be carefully selected in order to obtain the best coating properties for each application. In this research, three groups of the Mo-NiCrBSi coating specimens were produced with different spray distance parameter. Their microstructure and mechanical properties were analyzed in order to find the optimal spray parameters i.e the ones that give the best structural and mechanical characteristics of the coating

Investigation of abrasive wear resistance of ferrous-based coatings with scratch tester

Abrasive wear resistance is very important in many applications and in most cases it is directly correlated with hardness of materials. Possible solutions for overcoming poor abrasive wear resistance of light metals, like Al-alloys, is using of coatings. In this paper the investigated results of the two types of ferrous-based coatings were presented and compared with gray cast iron, known as a material with good abrasive wear resistance. Process used for coating deposition on an Al-Si alloy substrate was Atmospheric Plasma Spraying (APS). Scratch tests with diamond indenter were used to simulate abrasive wear process. The indenter velocity of 10 mm/min was used over a wear tracks of 10 mm, with different normal loads applied. Both, coefficient of friction and wear rate of the samples were investigated and analyzed in correlation with its mechanical properties.

A bibliometric analysis of scientific research on tribology of composites in Southeastern Europe

In recent years there is a small but increasing number of articles presenting and/or analyzing the scientific production from discrete geographical regions on a certain scientific topic. These articles applied the so-called bibliometric methods in order to evaluate the contribution of different countries in a scientific research field. In the present work, the research output of all countries in Southeastern Europe on the scientific field of composites tribology is presented by using bibliometric indicators such as the total number of publications and citations, the average number of citations per publication, and the h-index. Analysis spans the last ten years and the required scientific data in order to calculate the bibliometric indicators were retrieved using the Scopus (R) scientific database

Friction and wear processes-thermodynamic approach

Tribology, as the scientific and professional discipline within the mechanical engineering, studies phenomena and processes on the interacting surfaces, in direct and indirect contact and in relative motion. It includes the study and application of the principles of friction, wear and lubrication, as well as phenomena connected with these processes. Given that a process involving friction is always accompanied by transformation of energy, more precisely an energy dissipation process which generates entropy, the concept of thermodynamic entropy production analysis represents one of appropriate tools for studying and analysing the behaviour of complex friction and wear processes. This paper presents a review of published works in which the thermodynamic approach was used in analysing the friction and wear processes in tribosystems

Optimisation of the deposition parameters of thick atmospheric plasma spray coatings

Plasma spray process is one of the most versatile thermal spray deposition processes. There are great number of parameters that influence the quality and characteristic of deposited coating and their values must be defined precisely for each type of coating and used equipment particularly. A review of technology developed for deposition of ferrous-based powder spray (Fe-1.3Cr-1.5Mn-1.2C-0.3Ni, wt. %) on flat Al-Si alloy substrate surfaces is presented in this paper. Possible problems that may occur before and during the deposition process were pointed out as well as adequate solutions of those problems