Dynamic contact strain measurement by time-resolved stroboscopic energy dispersive synchrotron X-ray diffraction

Recent developments of synchrotron X-ray sources and dedicated high-energy
beamlines are now enabling strain measurements from large volumes of industrially relevant metallic materials. Such capability is allowing the validation of novel and alternative non-destructive experimental methods of strain measurement or computational models of complex deformation processes. This study describes the first dynamic contact strain measurement of a ball bearing using stroboscopic Energy Dispersive X-ray Diffraction (EDXD). The experiment probed the dynamic contact strain in the outer raceway of a test bearing. The inner raceway of the bearing was attached to a shaft rotating at 150 revolutions per minute and the outer raceway, where the measurements were made, was fixed in a stationary bearing housing. A triggering system was used to synchronise the data acquisition of the EDXD detector with the bearing rotation. Specifically, diffraction data was acquired, stroboscopically, from the material volume within the raceway, in a known location, when the ball was positioned directly below it. A total of 20 seconds of accumulated diffraction signal was recorded, acquiring 2 milliseconds of data per revolution, providing diffraction patterns of sufficient quality for the dynamic contact strain to be measured. Macromechanical stress field was calculated from the micromechanical
strains measured from five lattice planes. This allowed a comparison of the
experimentally measured stress field and that of finite element (FE) simulations. Good agreement was observed between the finite element results and experimental measurements indicating the applicability of this novel dynamic strain measurement technique for tribological systems.