Effect of off-sized balls on contact stresses in a touchdown bearing

Contact stresses of a ball bearing type touchdown bearing with off-sized balls are studied. The touchdown bearing model includes descriptions of the stiffness, damping and friction between bearing components. The model gives the contact deformations between the balls and bearing races, contact forces, and Hertzian contact stresses in each ball. The bearing model is used in simulation together with a model of a flexible rotor. The results show that off-sized ball or balls alters the contact stiffness between the balls and bearing race and the localized deformation of race. The contact force and stresses consequently change. The stress values are dependent not only on the dimension of the off-sized ball or balls but also their location.