Şerafettin Ekinci

Enhancement of Wear and Friction Characteristics of Epoxy Resin by Multiwalled Carbon Nanotube and Boron Nitride Nanoparticles

Epoxy resins are widely used in engineering applications. However, their low thermal stability limits their usage at high sliding velocities and loads. The mechanical properties and thermal stability of a machine element subjected to friction and wear are very important. In this study, friction and tribology behaviors of multiwalled carbon nanotubes (MWCNTs) and boron nitride (BN)-modified epoxy resin have been investigated. Epoxy resin modified by three different nanoparticle configurations, 0.3% MWCNT, 0.5% BN, and 0.5% MWCNT/0.3% BN, was investigated. The tribological characteristics of nanoparticle-modified epoxy resin were compared with properties of neat resin. The friction and tribological behavior of modified epoxy resin were tested using a ball-on-disc test stand at 1.2 and 1.5 ms−1 sliding velocities under 10 N applied load. The tests were done under dry condition and 1,800 m distance. The friction coefficient, wear loss, and temperature increase during testing were recorded and compared with that obtained for neat epoxy. It is observed that nanoparticle modification resulted in enhanced wear resistance and a reduction in friction coefficient and working temperatures.

The Investigation of Lubrication Properties Performance of Euro-Diesel and Biodiesel

All diesel engines work with a specially designed injection system. The lubrication of these moving inner parts is achieved with fuel. The inadequacy of lubrication properties of the fuel either causes low pressure or wear. Applications carried out to decrease the sulfur level to lower than 10 ppm have also been effective in decreasing particulate emissions. However, this process decreases the lubrication properties of the fuel. As a solution to this problem, instead of diesel, biodiesel, which has comparatively better lubrication properties, is suggested. In this study, the physical and chemical properties of biodiesels produced from safflower oil, cottonseed oil, soybean oil, and sunflower oil are investigated and then their lubrication performances were investigated with a pin-on-disc test device under constant load with different sliding velocities. The results obtained were compared with euro-diesel. The coefficient of friction was the lowest in safflower oil biodiesel, which was followed by cottonseed oil biodiesel, soybean oil biodiesel, sunflower oil biodiesel; the highest coefficient of friction was for euro-diesel.

MODELING AND INVESTIGATION OF THE WEAR RESISTANCE OF SALT BATH NITRIDED AISI 4140 VIA ANN

Nitriding is usually used to improve the surface properties of steel materials. In this way, the wear resistance of steels is improved. We conducted a series of studies in order to investigate the microstructural, mechanical and tribological properties of salt bath nitrided AISI 4140 steel. The present study has two parts. For the first phase, the tribological behavior of the AISI 4140 steel which was nitrided in sulfinuz salt bath (SBN) was compared to the behavior of the same steel which was untreated. After surface characterization using metallography, microhardness and sliding wear tests were performed on a block-on-cylinder machine in which carbonized AISI 52100 steel discs were used as the counter face. For the examined AISI 4140 steel samples with and without surface treatment, the evolution of both the friction coefficient and of the wear behavior were determined under various loads, at different sliding velocities and a total sliding distance of 1000 m. The test results showed that wear resistance increased with the nitriding process, friction coefficient decreased due to the sulfur in salt bath and friction coefficient depended systematically on surface hardness. For the second part of this study, four artificial neural network (ANN) models were designed to predict the weight loss and friction coefficient of the nitrided and unnitrided AISI 4140 steel. Load, velocity and sliding distance were used as input. Back-propagation algorithm was chosen for training the ANN. Statistical measurements of R2, MAE and RMSE were employed to evaluate the success of the systems. The results showed that all the systems produced successful results.

TEMPERATURE-DEPENDENT EFFECT OF BORIC ACID ADDITIVE ON SURFACE ROUGHNESS AND WEAR RATE

Wear and friction hold an important place in engineering. Currently, scientific societies are struggling to control wear by means of studies on lubricants. Boric acid constitutes an important alternative with its good tribological properties similar to MO2S and graphite alongside with low environmental impacts. Boric acid can be used as a solid lubricant itself whereas it can be added or blended into mineral oils in order to yield better mechanical and tribological properties such as low shear stress due to the lamellar structure and low friction, wear and surface roughness rates. In this study, distinguishing from the literature, boric acid addition effect considering the temperature was investigated for the conventional ranges of internal combustion engines. Surface roughness, wear and friction coefficient values were used in order to determine tribological properties of boric acid as an environmentally friendly additive and mineral oil mixture in the present study. Wear experiments were conducted with a ball on disc experimental setup immersed in an oil reservoir at room temperature, 50∘C and 80∘C. The evolution of both the friction coefficient and wear behavior was determined under 10N load, at 2m/s sliding velocity and a total sliding distance of 9000m. Surface roughness was determined using atomic-force microscopy (AFM). Wear rate was calculated utilizing scanning electron microscope (SEM) visuals and data. The test results showed that wear resistance increased as the temperature increased, and friction coefficient decreased due to the presence of boric acid additive.