Fatigue life prediction of crowned spline couplings at high misalignements

Abstract

Spline couplings are mechanical components used to transmit power between misaligned shafts by means of equally spaced teeth. Spline couplings are mechanical components used to transmit power between misaligned shafts by means of equally spaced teeth. Unlike in aligned conditions where all the teeth and the whole tooth flank surface are in contact, in such misaligned conditions only some teeth and part of each toothwidth are in contact, generating complex load behaviour and decreasing fatigue life. Moreover, such misalignments cause cyclic slip paths resulting in fretting wear of the teeth, which can reduce coupling life. Classical coupling sizing models that are still in use, made assumptions about the number of teeth in contact. However, these models do not account for tooth stiffness, applied torque and manufacturing errors which produces a sequential engagement of spline teeth. Therefore, stresses can be overestimated. In the present work, a numerical approach has been conducted in order to analyse highly crowned spline coupling geometry. First, a geometry generating procedure has been developed for both the hub with internal teeth and the crowned teeth shaft. Using this numerical model, the variation of the number of teeth in contact for different misalignments and torque has been observed. Using model results, tooth root bending fatigue life predictions were obtained for different misalignments and torques. Finally, experimental tests were conducted in order to validate numerical results.