Search

The evolution of the contact area (junction growth) of an elastic-plastic preloaded spherical contact subjected to an additional tangential loading is investigated theoretically. The normal preloading, under full stick condition, leads to the formation of a junction that can support additional tangential load. A gradual increase of this tangential load, while the normal preload remains constant, can incept plasticity of the contact zone in case the initial normal preload was elastic or enhance an existing one, thus lowering the tangential stiffness of the junction. Finally, the tangential stiffness approaches zero, which corresponds to sliding inception (i.e., loss of stability). The evolution of the contact area during the tangential loading prior to sliding inception reveals an essential junction growth which depends on the magnitude of the normal preload. The mechanism causing this junction growth seems to be new points of the sphere surface, which originally lay outside of the initial contact area that are coming into contact with the rigid flat during the tangential loading. The theoretical results for the junction growth obtained in the present work correlate well with some limited experiments. [DOI: 10.1115/1.2772322] Keywords: elastic-plastic contact, combined loading, junction growth

Different aspects of the tribological performance of black oxidized surfaces in rolling–sliding boundary-lubricated or mixed lubricated contacts are overviewed in the present work. It covers the topics of antimicropitting resistance, antismearing effects, reduction in boundary friction, repelling tribochemical attacks of aggressive lubricants or additives, running-in behavior, and the effect of black oxide coating on bearing life. The results of the component laboratory experiments, full bearing tests, and theoretical modeling, performed within the frame of the present work, shed light upon the benefits and limitations of using black oxide coating for bearing applications. [ABSTRACT FROM AUTHOR]