In this article an engineering approach is described to model micropitting in rolling-sliding, heavily loaded lubricated contacts. The competitive mechanism between surface fatigue and mild wear is captured in the present approach as well as the effects of deterministic surface microgeometry (e.g., roughness). The fatigue model is based on the Dang Van fatigue criterion and the mild wear model uses a modified Archard approach. The complete modeling scheme is validated experimentally first using laboratory-controlled conditions, where the surface topography is varied as well as the operating conditions in the contact. Then the model is applied to describe the behavior of full-bearing tests. The behavior of the model agrees well with the experimental observations, qualitatively.
The fundamental problem of elastic-plastic normally loaded contact between a deformable sphere and a rigid flat is analyzed under perfect slip and full stick conditions for a wide range of the sphere mechanical properties. The effect of these properties on failure inception is investigated by finding the critical interference and normal loading as well as the location of the first plastic yield or brittle failure. The analysis is based on the analytical Hertz solution under frictionless slip condition and on a numerical solution under stick condition. The failure inception is determined by using either the von Mises criterion of plastic yield or the maximum tensile stress criterion of brittle failure. For small values of the PoissonÕs ratio the behavior in stick, when high tangential stresses prevail in the contact interface, is much different than in slip. For high values of the PoissonÕs ratio the tangential stresses under stick condition are low and the behavior of the failure inception in stick and slip is similar.
The behavior of an elastic-plastic contact between a deformable sphere and a rigid flat under combined normal and tangential loading with full stick contact condition is investigated theoretically. Sliding inception is treated as a plastic yield failure mechanism, which allows static friction modeling under highly adhesive conditio ns. Several contact parameters such as: junction tangential stiffness, static friction force and static friction coefficient are extensively investigated. The phenomenon of junction growth and the evolution of the plastic zone in the contact region are briefly described. It is found that at low normal dimensionless loads the static friction coefficient decreases sharply with increasing normal load, in breach with the classical laws of friction. As the normal load further increases the static friction coefficient approaches a constant value that is about 0.3 for many material properties combinations.
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