Miroslav M. Mijajlović

RADIAL FORCE IMPACT ON THE FRICTION COEFFICIENT AND TEMPERATURE OF A SELF-LUBRICATING PLAIN BEARING

Self-lubricating bearings are available in spherical, plain, flanged journal, and rod end bearing configurations. They were originally developed to eliminate the need for re-lubrication, to provide lower torque and to solve application problems where the conventional metal-to-metal bearings would not perform satisfactorily, for instance, in the presence of high frequency vibrations. Among the dominant tribological parameters of the self-lubricating bearing, two could be singled out: the coefficient of friction and temperature. To determine these parameters, an experimental method was applied in this paper. By using this method, the coefficient of friction and temperature were identified and their correlation was established. The aim of this research was to determine the effect of radial force on tribological parameters in order to predict the behavior of sliding bearings with graphite in real operating conditions.

Recommendations for the estimation of the strength of the railway wheel set press fit joint

Although press fit joints are very important in railway engineering, few authors have investigated the strength of press fit joints in terms of their application in railway vehicles. This study analyses the tribological parameters that influence the strength of press fit joints, especially the contact pressure and the static friction coefficient. This research was targeted towards the control of the friction coefficient value to obtain the required strength of a press fit joint in conditions close to the minimum contact pressure that results in less prestressed press fit joints. To estimate press fit joint strength, this study examines the use of minimum and maximum values of the friction coefficient as recommended in the literature considering wide tribological conditions, as well as the experimentally determined friction coefficient values for specific tribological conditions. The study also points out the discrepancy between current railway standards and engineering practice considering the inspection of wheel set press fit joint strength.

Analytical Model for Estimating the Amount of Heat Generated During Friction Stir Welding: Application on Plates Made of Aluminium Alloy 2024 T351

© 2012 Mijajlovic and Milcic, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Analytical Model for Estimating the Amount of Heat Generated During Friction Stir Welding: Application on Plates Made of Aluminium Alloy 2024 T351

Temperature dependent effective friction coefficient estimation in friction stir welding with the bobbin tool

The friction coefficient in many friction stir welding researches is generally used as an effective, constant value without concern on the adaptable and changeable nature of the friction during welding sequence. This is understandable because the main problem in analyzing friction in friction stir welding are complex nature of the friction processes, case-dependent and time dependent contact between the bodies, influence of the temperature, sliding velocity, etc. This paper is presenting a complex experimental-numerical-analytical model for estimating the effective friction coefficient on contact of the bobbin tool and welding plates during welding, considering the temperature at the contact as the most influencing parameter on friction. The estimation criterion is the correspondence of the experimental temperature and temperature from the numerical model. The estimation procedure is iterative and parametric – the heat transport parameters and friction coefficient are adapted during the estimation procedure in a realistic manner to achieve relative difference between experimental and model’s temperature lower than 3%. The results show that friction coefficient varies from 0.01 to 0.21 for steel-aluminium alloy contact and temperature range from 406 °C to 22 °C.