COMPARATIVE BENDING FATIGUE-STRENGTH OF PRECISION FORGED SPUR GEARS

To determine the bending fatigue strength of precision forged spur gea rs and to compare the results with those obtained from conventional cu t gears, single tooth bending fatigue tests were carried out on both t hrough-hardened and induction-hardened gear teeth. The gears were prod uced from rolled bar cut blanks, disc forged blanks or precision forge d teeth blanks. For this purpose, a special test fixture was designed and built for an Amsler high-frequency vibrophore fatigue testing mach ine. The results show that the endurance limit of precision forged gea rs is significantly higher than those obtained from cut gears. The ben ding fatigue strength of forged gears was some 12.5 per cent higher th an the cut teeth in a through-hardened condition and 8.4 per cent high er for the induction-hardened teeth. The effect of surface roughness a t the tooth root area on the bending fatigue strength of the forged ge ars is also shown.