http://arthra.ugal.ro/handle/20.500.14043/25297 2026-04-07T17:02:24Z http://arthra.ugal.ro/handle/20.500.14043/25332 The Effect of Wiberg Angle on the Contact Pressure Pistribution in Natural and Artficial Joint Tudor, Andrei; Parsu, Carmen; Sorina, Opriș The analogies and differences between the mechanical joints and the biological ones, in the presence of relative motion, are based on the pressure distribution. The paper analysed a numerical model of the pressure distribution and friction torque applicable to the spherical joint, specifically to hip. The effect of Wiberg angle about maximum pressure contact is analysed as a function to clearance joint. THE ANNALS OF UNIVERSITY “DUNĂREA DE JOS“ OF GALAŢI FASCICLE VIII, 2008 (XIV), ISSN 1221-4590 TRIBOLOGY 2008-01-01T00:00:00Z http://arthra.ugal.ro/handle/20.500.14043/25331 Nitrogen Influence on Indentation Fracture Toughness of Stainless Steel Coatings Thompson, Mioara; Palaghian, Liviu This paper studies some aspects of coatings fracture theory and the possibility of extending Lawn’s equation from Vickers indenter geometry to the Rockwell one. Indentation tests were performed on stainless steel coatings deposited on 35.CD.4 steel substrate. The stainless steel coatings were nitrogen added in order to improve the fracture toughness. A comparison between different nitrogen concentrations has been made, based on the normal critical load at the first crack appearance. This load was very accurate measured with an acoustic emission state-of-the-art device, Vallen System AMSY4. Based on measured diameters of the ring cracks, the crack length was calculated. The normal critical load was precisely measured, due to acoustic emission method. Thus, it was calculated the fracture coefficient, K. A fracture pattern diagram as a function of normal load was plotted for stainlessnitrogen coating deposited on 35.CD.4 steel substrate. THE ANNALS OF UNIVERSITY “DUNĂREA DE JOS“ OF GALAŢI FASCICLE VIII, 2008 (XIV), ISSN 1221-4590 TRIBOLOGY 2008-01-01T00:00:00Z http://arthra.ugal.ro/handle/20.500.14043/25330 The Influence of the Applied Load on the Friction Coefficient of the Sintered Iron-Base Bearings Teișanu, Cristina; Gheorghe, Ștefan; Tudor, Andrei; Ciupitu, Ion In the recent years the iron base sintered bearings production was considerable increased at the expense of the copper based ones, due to the low cost and availability of the iron powders as well as the higher strength. The mechanical properties of a part are strongly related to the composition of the materials. For tribological applications, the properties of the surface are related to the different metallic and intermetallic phases formed in the material. The friction nature of the bearing type couple having the bearing bush made from sintered material is a function of pores size, applied load, velocity, temperature, the quality and quantity of the stored oil and can appear as hydrodynamic, mixed and limit friction. The tribological features of the selected iron-copper based materials have been studied using an experimental device for wear testing of the sliding bearings. The friction coefficient and wear resistance have been analyzed in dry friction conditions. The influence of the applied load and p x v values on the friction coefficient was studied. Also, the dependence of the functioning time until the failure of the bearing (seizing) with the friction coefficient for the applied forces was analyzed. THE ANNALS OF UNIVERSITY “DUNĂREA DE JOS“ OF GALAŢI FASCICLE VIII, 2008 (XIV), ISSN 1221-4590 TRIBOLOGY 2008-01-01T00:00:00Z http://arthra.ugal.ro/handle/20.500.14043/25329 Industrial Gear Oils from Renegerable Feed Stocks Tănăsescu, Constantin; Petre, Diana; Bogatu, Liana; Antonescu, Niculae Napoleon The aim of this research study is to obtain industrial gear oils. The formulation of this type of lubricant is based on vegetable oils or mixtures of vegetable oils with more stable base oils and appropriate additives. The study evaluates the laboratory testing results regarding vegetable oil-based lubricating characteristics and oils obtained from base oil mixture and suitable additives. The extreme pressure, antiwear properties and biodegradability of the industrial gear oils composed of vegetable and mineral oils mixtures or vegetable and synthetic oils mixtures are acceptable. THE ANNALS OF UNIVERSITY “DUNĂREA DE JOS“ OF GALAŢI FASCICLE VIII, 2008 (XIV), ISSN 1221-4590 TRIBOLOGY 2008-01-01T00:00:00Z