Geometry optimisation of highly crowned gear couplings working in high misalignment applications to reduce tooth root stresses

Abstract

Crowned gear couplings are mechanical components used to transmit power between misaligned rotating shafts. Their geometry is characterised by a significant longitudinal crowning to accommodate angular misalignment. Recent studies reveal that high misalignments drastically reduce the number of teeth in contact and lead to an uneven load distribution among engaged teeth. Consequently, tooth root fracture becomes a common failure mode. Current standards only address misalignment angles below 1.5°, treating applications with greater misalignments as special cases without design guidelines or stress prediction methods. This study proposes a procedure to optimize the design of crowned gear couplings working in high misalignment applications by determining tooth root stress distribution. The geometry is analytically generated, while finite element models are used to calculate the stress distribution. Experimental validation is performed using a dedicated test rig. The obtained results are very close to the ones from the numerical model, demonstrating the suitability of the method for crowned gear couplings operating under significant angular misalignments. The optimized design reduces tooth root stress by 50%, which will increase the fatigue life of the component or enable the application of higher torque values.