Investigation of the Effect of Application of Non-Conventional Root Profiles for Reduction of Bending Stresses in Helical Gear Drives
The substitution of the conventional trochoid root profile in spur and helical gears by non-conventional root profiles, based on elliptical or Bèzier curves, to reduce the maximum bending stress at the gear root surfaces has been the subject of an intensive research recently. The application of finite element models in which the load is applied at the highest point of single tooth contact has been mainly used for those studies. However, a complete review of the stress field at the fillet surface and its variation along a cycle of meshing is still missing. The adjacent pair of teeth when it carries part of the load causes compressive stresses on the root area that deserves to be considered for a comprehensive study of the possible benefits of application of non-conventional root profiles. This paper focuses on the investigation of the variation of the normal stress in the perpendicular direction to the root line between adjacent teeth. Such variation will be obtained for two cycles of meshing by considering finite element models with five pairs of teeth, so that the effect of load sharing between adjacent pairs of teeth will be considered. This study will provide the variation of the alternating range normal stresses on the root surface in longitudinal direction of the gear teeth for tooth root profiles based on Hermite, elliptical, and Bèzier curves and their comparison in terms of the mentioned stresses with those obtained for conventional root profiles. Several numerical examples corresponding to an existing design of a helical gear drive show that the reduction of the maximum principal stress is possible using non-conventional root profiles, although an increment of the alternating component of the normal stress occurs, which may lead to the reduction of the expected fatigue life of the gear drive.
Authors: Ignacio Gonzalez-Perez, Alfonso Fuentes-Aznar, Jose Calvo-Irisarri, Alfredo Fernandez-Sison, Harri Aurrekoetxea-Arratibe
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