Key Engineering Materials Vol. 490

Abstract: The paper presents results of tests concerning slide bearing with helical groove on the journal selected properties. It has been stated that during lubrication with contaminated oil helical groove results in wear decrease. On the other hand while lubricating agent was clean oil helical groove results in load carrying capacity decrease and oil flow rate increase. The proposition of non-dimensional index describing the groove and helical line is also presented in the paper. This index is correlated with bearing characteristics and its wear

Abstract: This paper presents investigations of nitrided cases after the glow-discharge nitriding process. The nitrided cases were obtained by using a different chemical composition of gas mixture at the temperature of 450^OC. The glow-discharge nitriding process was carried out on austenitic stainless steel, grade of steel X5CrNi18-10. The chemical composition and phase identification of the nitrided cases were examined by using the glow-discharge optical emission spectrometry (GD-OES) and X-ray diffractometry (XRD)

Abstract: The article analyses the process of friction in the needle bearing as the function of the alterations of geometrical parameters, namely the diameter of the shaft – D, the needle – d and the bearing clearance. The change in the relation between the diameters D and d results in the change of the contact area of the friction pair; in the case of two shafts with parallel axes (the needle of the bearing and the shaft pin) the contact area, if compared with the analogical process in the ball bearing, alters significantly and leads to resistance in motion. There are two types of friction in the needle bearing: the rolling friction and the sliding friction; the analysis of the movement of the bearing elements enabled the estimation of the extent to which the sliding friction matters in the overall balance of motion resistance. The article also defines the type of wear as the function of initial clearance.

Abstract: In this paper, a FITNET analysis of the structural element made of ultra high strength steel was performed. The critical loadings at failure were estimated at three levels of analysis and two temperatures, -40°C and +20°C. The results of the analysis were verified by full scale experiments at -40°C, which proved that the predictions of the critical moment provide a sufficient safety margin.

Abstract: Finite difference method in solving classic problems in theory of plates is considered a standard one [1], [2], [3], [4]. The above refers mainly to solutions in right-angle coordinates. For circular plates, for which the use of polar coordinates is the best option, the question of classic plate deflection gets complicated. In accordance with mathematical rules the passage from partial differentials to final differences seems firm. Still final formulas both for the equation (1), as well as for border conditions of circular plate obtained in this study and in the study [3] differ considerably. The paper describes in detail necessary mathematical calculations. The final results are presented in identical form as in the study [3]. Difference of results as well as the length of arm in passage from partial differentials to finite differences for mixed derivatives are discussed. Generalizations resulting from these discussions are presented. This preliminary proceeding has the purpose of searching for solutions to technical problems in machine building and construction, in particular finding a solution to the question of distribution of load along contact line in worm gearing.

Abstract: A dynamic development of numerical methods enables even so complicated geometrical modelling as modelling of hypoidal teeth, and in particular of worm teeth. Building on the basis of the finite element method of this type of geometrical mathematical model enables observing and analysing physical phenomena taking place in the teeth, e.g. changes of pressure distribution along the contact lines depending on the phase of meshing for particular cooperating pairs of teeth. Due to limited technical possibilities and mathematical apparatus such analyses were carried out only on the basis of the theory of plates with constant thickness. An unquestionable advantage of such numerical modelling is a short time needed to obtain final results, which enables profound analysis of the transmitted load. The knowledge of course of pressure distribution along the contact lines of particular pairs of intermeshing teeth in worm gears already in the design phase enables taking into consideration in adequate correction or even modification of the working surface of teeth, with the aim to equalise the distribution of pressure.

Abstract: The application of various coatings on traditional material substrata (e.g. metal alloys) is a well established technology used to modify surface characteristics/performances of various components in technical systems exposed to adverse conditions, e.g. corrosive environment, high temperature, erosion and/or wear, etc. [1… 10]. Coatings can also provide a desired (mostly low) friction coefficient between solids forming various tribological systems. In recent years there has been a particular increase in interest in carbon-based coatings, either crystaline (diamond or graphite) or amorphous. This applies especially to amorphous carbon with high content of sp³ bonds characteristic of the diamond - known as DLC (diamond-like carbon). This coating can be "pure" form of DLC, if it contains only sp³ bonded carbon, but may also contain other elements and crystalline structures; Hydrogen, carbon with the "graphite" sp² bonds, metals and/or other modifiers, which can provide the required specific properties of the coating and reduce the cost of production.