On the Veering Phenomenon Potential in High Speed Gears Design

In modern industry, the design process of most mechanical components is aimed at reducing their mass and increasing the performance, especially in weight-critical applications like aero-space engines. This approach often results in components that can have resonances in the operative range that could cause excessive vibrations and a consequential reduction of the life of the component itself. For this reason, a modal analysis check is always performed and the design process is iterated until also the dynamic behavior is acceptable. However, this approach is non-optimal, as not all resonances are excited during operation. Hence a design process that aims also to reduce the real dynamic response is proposed in this paper. By changing the geometry of thin-webbed high speed helical gears the dynamic response is altered to modify the mode shapes to obtain ones that are non-excitable by the external forces in the operative range, thus greatly improving its dynamic response. The original contribution of the paper relies on the improvement of the dynamic design process by means of the optimal balance between geometrical parameters and dynamic behavior governing phenomena like veering and crossing. Due to the high flexibility of these components, the design process is developed considering the stress-stiffening effect of the centrifugal force on the resonance frequencies and also the high influence of gyroscopic effects. To prove the effectiveness of this approach, a test case is presented with the main rotation-induced phenomena considered and the results obtained highlight the importance of the veering phenomenon in the switching between different mode shapes, and the great reduction in the response of the component.