Measurement of Forming Stresses in Plain Spherical Bearings Using Neutron Diffraction

Nosing is a cold metal-forming process used in the manufacture of plain spherical bearings. This process ensures the outer bearing race conforms to the shape of the inner race (a ball), with a composite liner in-between to provide a low frictional moment. These bearings must be precision engineered due to the large forces and demanding environments they operate within in service. The manufacture of these bearings and related process settings is very much an experiential route, although increasingly Finite Element simulations are used to predict and characterise complex material behaviour. It is imperative the numerical nosing models are validated against experimental measurements due to uncertainties in material properties, process variables and part manufacture variations. In this paper, neutron diffraction is used to determine the residual stresses in a large nosed bearing. Measurements were made on the POLDI instrument at PSI, Switzerland. This paper compares the predicted stresses with measurement results, and draws conclusions concerning the validity and usability of the models.