Pergamon Inf. J. Mech. Sci. Vol. 38, Nos 8-9, pp. 1001-1015, 1996 Copyright © 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0020-7403/96 $15.00 + 0.00 0020-7403(95) 00086-0 A PARAMETRIC STUDY OF STRESS SOURCES IN JOURNAL BEARINGS S. HACIFAZLIOGLU ~ and S. KARADENIZ Department of Mechanical Engineering, Karadeniz Technical University, Trabzon 61080, Turkey (Received 11 March 1994; and in revised form 29 August 1995) Abstract--In this paper, the effects of bearing and housing elasticity on the stress fields, which could result in surface fatigue in journal bearings, have been investigated. The parameters such as pressure gradient, flexibilities of backing and housing materials, presence of oil grooves, faulty or non- uniform housing supports and non-uniform temperature distributions have been individually considered as the sources of stresses in journal bearings. A parametric analysis of these has been carried out. The geometrical and physical interactions, that would affect the formation and magnitudes of tensile surface stresses to which the bearing alloys are particularly sensitive, have been investigated for both rigid and elastic housing conditions. Copyright © 1996 Elsevier Science Ltd. Keywords: journal bearing, bearing and housing elasticity, stress sources, stress fields, equi-stress curves, pressure film profile, finite elements, design, fatigue failure. NOTATION B width of the bearing E modules of elasticity P local film pressure Pm peak film pressure T temperature U~ radial displacement ct coefficient of thermal expansion 0 circumferential angle trx~ normal stress in the circumferential direction a, normal stress in the axial direction tr~z normal stress in the radial direction axy shear stress on the x-y plane tr~, shear stress on the x-z plane ¢ry~ shear stress on the y-z plane v Poisson's ratio 1. INTRODUCTION There are many factors and parameters that could cause bearing failure. These may occur in any stages of the designing, manufacturing and service conditions in a journal bearing. Journal bearing failures and their causes were the subject of many investigations. Some researchers have emphasized the importance of the failure types such as cavitation, oxida- tion, corrosion and wear connected with chemical, physical and geometrical interactions between lubricants and bearing materials [ 1-4]. The mechanical and thermal effects beyond the endurance limits of the bearing alloys have also been investigated [5-8]. Besides these, faults of designing, manufacturing and assembling may cause bearing failures [9]. Surface fatigue, known as the appearances of cracks on bearing surface which cause some particles on this surface to leave the main body, is a common type of bearing failure in dynamically loaded journal bearings. Obviously stresses being of varying nature, especially of the sign changing, can cause surface fatigue in journal bearings. These stresses can be classified into two groups as mechanical and thermal based. The main sources of stresses in journal bearings are the hydrodynamic oil film pressure in the mechanical sense, and the temperature in the thermal sense. Additionally, the flexibilities of backing and housing materials, non-uniform housing supports, the presence of oil grooves, surface discontinui- ties and different properties of thermal expansion of bearing elements also create the stresses. 1001