Effect of plasticity on the dynamic capacity of modern bearing steels

Dynamic capacity, defined as the load under which rolling element bearing raceways will survive for 1 million revolutions with 90% probability of survival, is commonly used in bearing life-rating standards. This term was introduced by Lundberg and Palmgren to simplify life prediction equations, and was derived using the elastic Hertzian-theory of contact mechanics for earlier, relatively impure bearing materials. Modern ultra-clean steels with fewer impurities can survive for multi-millions of contact stress cycles, even under elastic-plastic loading conditions. Under such conditions, elastic-plastic stresses are significantly different from the elastic Hertz contact stresses. Current experimental and finite-element study, shows accounting for plastic deformation of the material necessitates significant correction in the material parameters used in the expressions for dynamic capacity calculations.