Tribological Assessment of Aluminum Cylinder Material for Piston Compressors in Trucks and Buses Brake Systems

Applying new technologies to reduce friction and wear in vehicles and equipment can minimize mechanical losses. This reduces power loss in internal combustion engines and reduces fuel consumption and emissions. Consumption of fuel energy can be reduced by the use of light metals, for example aluminum alloy, to produce vehicles and their aggregates and parts. In this case, the problem is poor tribological properties of those light weight metals, as well as the lower strength compared to the cast iron construction. For tribology research purposes, the contact surface of the aluminum cylinder of an experimental piston air compressor is reinforced with inserts of cast iron. The results of tribology research of the composite material are presented in the paper, explaining how parameters such as the sliding speed, contact time and contact area influence friction and wear of the material in relative tribological contacts, under constant normal force. The test procedures were performed on the ball-on-plate CSM® nanotribometer, in linear reciprocating sliding conditions with no lubricant. Material composition of the samples was determined using the Energy-Dispersive Spectroscopy. All measurements were realized at the Faculty of Engineering, University of Kragujevac

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

A review on mechanical and tribological properties of aluminium-based metal matrix nanocomposites

This paper provides a brief overview on the mechanical and tribological properties of aluminiumbased composites reinforced with various nanoparticles. The amount of reinforcement was, most often, up to 5 % (vol. or wt.). Based on the reviewed results, it can be observed that by increasing the amount of reinforcement, properties such as hardness and density increase significantly. Tribological tests were performed mostly on pin-on-disc tribometers under dry sliding conditions. Composites reinforced with ceramic nanoparticles such as Al2O3, SiC, TiC, TiO2 and TiB2 showed a higher wear resistance than their matrix alloys. The microstructure of the nanocomposites and morphology of the worn surfaces were in most cases studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS)

Analysis of pathohistological characteristics of pterygium

Pterygium internum (external eye layer) shows great recurrence tendency after surgical removal. Its etiology is still unclear and represents a significant problem. The main goal of our study was to explore the interrelationships of pathohistological characteristics of pterygium, namely presence of inflammation, vascularisation degree and fibrinoid changes and on the basis of their analysis to test the possibility of predicting its evolution and recurrence. The analysis was performed on the material taken from 55 patients surgically treated by the technique of Arlt. The specimens were stained using the classical histochemical methods: hematoxylin-eosin (HE), Masson’s trichrome, Gomori’s reticulin stain and PAS technique. Pterygium is mostly covered by conjunctival epithelium, while in the cap region shows morphology of modified stratified squamous epithelium of the cornea. Structural basis of the epithelium is composed of continuous basal lamina and continuous connective fibers underneath. This connective basis shows fibrinoid changes in the form of oval islets of different size, parallel to convexity of pterygium, or is in the form of unified focus. The number, caliber and the type of blood vessels showed excessive variability. Pathohistological analysis of morphological characteristics of pterygium is adequate basis for prediction of recurrences; as they present the biggest concern in treatment of this widely spread disease

Topographic localization of an intraocular foreign body by B-scan echography

Background/Aim. In cases of blurred optic media the ultrasound diagnostics offers useful data about eventual presence of intraocular foreign body as well as about its precise localization in the eye. The aim of this study was to retrospectively analyze echographic findings in patients with the diagnosis of intraocular foreign body with a special interest in localizations of a intraocular foreign body in the eye and the presence of an eventual infection - endophthalmitis. The aim of this study was also to confirm the localization of intraocular foreign body by echography and to test the precision of this method. Methods. We performed analysis of all cases that had been referred to the ultrasound diagnostices, in which the presence of intraocular foreign body had been confirmed in the period of one year. All examinations were done with B-scan and were confirmed during the surgery - vitrectomy. Results. In the one-year period we were contacted by 27 patients with intraocular foreign body. In one injured eye the intraocular foreign body was in the lens (3.7%), in 10 injured eyes (37.03%) intraocular foreign body was in the vitreal body. In 15 patients (55.5%) intraocular foreign body was fixed in the retina. In one patient (3.7%) there was a perforating injury, intraocular foreign body was found in the retrobulbar part of the orbit. In 7 injured eyes (25.9%), with the presence of intraocular foreign body, we found signs of endophthalmitis (organized blurring in vitreal space, thickened choroid). Other accompanying echographic findings were: blood in vitreal space, haemophthalmus in 12 cases (44.4%), retinal detachment in 5 cases (18.5%) and subretinal hemorrhagies in 4 cases (14.8%). Conclusion. Ultrasound diagnostics can very precisely show the localization of intraocular foreign body in the eye that is very important in the choice of approach and timing of surgical treatment. Also the echographic diagnostics may find an accompanying endophthalmitis in the posterior segment of the eye, that is very important for an urgent therapeutic approach