Studies on lubricated and unlubricated nonconforming rolling contact

Abstract

The relative sliding between two contact surfaces occur in all the machines used in newlineengineering industries; such contacts are rolling bearing, ball bearing, bush bearing and newlinecylinder piston sliding. Machineries invariably used rolling elements. The performance of newlinethese rolling elements depends on stress state. The deformation which is complicated in newlinesuch elements depends on the type of materials used to manufacture the elements and newlinenature of loading. Cases like piston and cylinder sliding where two surfaces confo rm to newlineeach other. In other cases like ball bearing and roller bearing where two sliding surfaces newlinedo not conform to each other. In case of conforming contact, the real area of contact is newlinealways a small portion of apparent area of contact. In case of non-conforming contact newlinesurface, the geometry of contact gives rise to Hertzian contact stresses. The Hertzian newlinecontact stresses arising due to dynamic and cyclic loading results in elastic, inelastic newlinefatigue and damages on surface o f contacts. Though lubricants are used many times, newlinethese lubricants fail and lead to dry contact. Prediction of performance of these bearings newlineneeds the knowledge of contact stresses, response to dynamic and fatigue loading and newlinecharacteristics of lubricants. In practice it has been found that the ball bearings and roller newlinebearings are found to fail due to fatigue loading. The defects like p itting and spalling are newlineobserved. Many researchers have tried to characterize the performance of such bearings newlineby conducting laboratory test, such as rolling disc contact, sliding contact and rolling of newlineball surfaces. newlineIn the present work, the complicated deformation has been studied systematically newlineby simulating the contact stress and deformation in the laboratory. Four ball test rig newlinewhich leads to Hertzian contact stress has been made use to simulate the field conditions. newline