Study on Bending Fatigue Strength of Helical Gears : 2nd Report, Bending Fatigue Strength of Casehardened Helical Gears

Abstract

Casehardened helical gears with different degrees of helix angle and comparatively small face width were tested using the bending fatigue testing machine of hydraulic type. The bending fatigue limit loads (circumferential loads) were found to be almost the same regardless of degree of helix angle (β0 <__= 30°). The effects of partial loading (maldistribution of load) on the root stresses and the bending fatigue strength of helical gear teeth were investigated experimentally and the relationship between the bending fatigue strength of a helical gear and that of its virtual spur gear was discussed by carrying out a bending fatigue test for the virtual spur gear. Furthermore the existing equations for bending strength of cylindrical gears were compared on the basis of the experimental results. It was found that there exists a considerably large difference between the calculated allowable transmitted loads for gear teeth according to the equations used.