Norihisa Arai

Reserarch on the Force-Fitted Gear : 7th Report, On the Change of Stresses at the Circumference of the Force-Fitted Part in the Slipping Test

The present test has been carried out for the purpose of investigating the change of stresses at the circumference of force-fitted surface caused by a load acting on tooth under running conditions. Momentary change of the stresses when a slip at the force-fitted surface between gear rim and hug occurs and when this slip is repeated three to four times, has been examined. Conclusions are that by a load that acts on tooth contact point, a partial decrease of internal pressure caused by force-fitting at the circumference of the inside diameter of gear rim occurs in the part corresponding to the meshing tooth and that the limit torque for the slip in a driving test of the force-fitting gear becomes much smaller than that in a slipping test of the force-fitting gear becomes much smaller than that in a slipping test under static condition.

Research on the Force-Fitted Gear : 8th Report, On the Fillet Stress of the Gear Tooth in Case when Hubs of Various Shapes are force-fitted and a Solid Shaft is double force-fitted in the Hollow Hub

The main objective of this paper is to discuss on the theoretical formula and practical equation for the fillet stress of the gear tooth in case when the hollow hub is force-fitting in the hollow hub, and also is to investigate the fillet stress in case when hollow hubs of various shapes are force-fitting. The authors measured the fillet stress of gear tooth by means of strain gauge and photo-elastic experiments for each force-fitted hub, and these experimental results were compared with calculated ones by the transform function and finite element method. Consequently the theoretical and practical formula could be introduced for the fillet stress of gear tooth with force-fitted hubs mentioned above, and it was found that calculated values agree fairly well with experimental results.

Research of Force-Fitted Gear : 3rd Report, On the Bending Fatigue Strength of Shrinkage-Fitted Gears

Theoretical analysis of stress at the root fillet of the shrinkage-fitted gears correspond with that of the force-fitted gears in the two-dimensional theory of elasticity. But practical stresses induced at the root fillet of gear tooth are not equal in both cases. To explain the reason for this, the residual stresses induced and their change at the loaded side and the opposite side of the root fillet, roughness and hardness at the root fillet of tooth, and bending fatigue strength of the shrinkage-fitted gears were investigated. Results obtained are as follows. (1) Bending fatigue strength of the shrinkage-fitted gears show lower values in comparison with that of the force-fitted gears. (2) This decrease of bending fatigue strength is caused by the stress at the root fillet of tooth induced by air-cooling, which occurs in taking out the gear rim from electric furnace to shrinkage-fit. (3) Practical formulas for the residual stress along the fillet curve of the shrinkage-fitted gears are introduced by modifying formulas for the force-fitted gears.

Research of Force-Fitted Gear : 4th Report, On the Improvement of Bending Fatigue Strength by Surface Rolling at the Root Fillet of the Force-Fitted Gear Tooth

As are evident from experimental results of the 2nd report, bending fatigue limits of the force-fitted gears show lower values in comparison with those of the solid gears. In this paper, as an attempt to increase the bending fatigue strength of the force-fitted gears, surface rolling on the root fillet of gear tooth was adopted success fully. The following are the conclusions obtained : (1) By fillet surface rolling the bending fatigue limits are increased by 37% at the most suitable rolling conditions. (2) Whichever process, surface rolling or force-fitting, may be taken previously, the order of process has no influences on the bending fatigue strength, the bending static strength etc.