Yoshio Terauchi

On the Bending Strength of Non-Metallic Gear Teeth

The authors have carried out an experimental study on bending strength of non-metallic material and the fatigue tests of non-metallic gear teeth, and found some facts about the relation of fatigue strength with static strength.In consequence, we got the following results.(1) The bending fracture of non-metallic gear tooth is not caused by the maximum local stress, but, rather by the mean stress.(2) The value of fatigue notch factor at root fillet of gear tooth is considerably smaller than the value of stress concentration factor.(3) For the laminate gear of canvas No. 11 base which is generally used, we can consider that the value of fatigue strength is equal to about a half of the value of static bending strength.

On the Fatigue Strength under Bending of Gear Teeth

The authors equipped the fatigue testing machine for gear previously reported with an automatic pressure controller, and by through the use of this testing machine carried out fatigue bending tests of gear teeth of various materials.These results were studied in comparison with static bending strength, impact strength and proportional limit.In consequence, we got the following results.(1) The stress concentration decreases as the radius of curvature on fillet curve, in particular at the weakest section, is enlarged.(2) It is important to take sufficiently deep hardened layer along root fillet of surface hardened gear, from the viewpoint of increasing fatigue strength.(3) We must take care of cut-scars, in particular, those which are left in the direction of tooth width, because fatigue strength decreases by those scars.(4) It would seem that fatigue strength have a relation with proportional limit.