Centrifugal load and its effects on bending strength and contact strength of a high speed thin-walled spur gear with offset web

Abstract

Abstract This paper discusses effects of centrifugal load on bending strength and contact strength of a thin-walled spur gear used at high speed. A three-dimensional (3D), finite element method (FEM) is presented in this paper for analyzing centrifugal deformations and centrifugal stresses of the thin-walled gear at high speed and the responsive FEM software are developed through many years’ efforts. It is verified that the developed FEM software can calculate correct centrifugal deformations and centrifugal stresses of the thin-walled gear by a cantilever model. Then centrifugal deformations and centrifugal stresses of a thin-walled spur gear with offset web are analyzed with the FEM software at speed range 5000–40,000 rpm. It is found that effects of centrifugal load on deformations and stresses of the thin-walled gear can be neglected when gear speed is below 10,000 rpm. But it is necessary to consider the effects of centrifugal stresses on strength design of the thin-walled gear when the gear speed exceeds 10,000 rpm. Effects of the centrifugal load-deformed thin-walled spur gear on tooth contact pattern, surface contact stress, root bending stress and tooth load-sharing ratio of the gear are also investigated through performing loaded tooth contact analyses of the gear when it is engaged with a solid mating gear under a torque. It is found that centrifugal deformation of the gear at high speed has greater effects on tooth contact pattern, tooth surface contact stress, root bending stress and tooth load-sharing ratio of the pair of gears. Finally it is pointed out that strength calculation methods of a thin-walled gear are quite different from a solid gear. Methods for exact bending strength and contact strength calculations of a thin-walled gear at high speed are presented in this paper.