Bending Strength of Carburized SCM420H Spur Gear Teeth

Abstract

For carburized spur gears of m = 5 which have effective case depths deff = 0.6, 0.9 and 1.3 mm as well as non-carburized gears and normalized gears, relations between the residual stress at the root and the hardness are made clear. Bending fatigue tests are carried out to obtain SN-curves of these gears. The effect of case depth on the fatigue limit is not very significant. Influences of the residual stress at the root surface, the surface hardness and the core hardness on the fatigue limit are quantitatively determined from the results of fatigue test and a formula which may be available to estimate the fatigue limit of spur gears is finally proposed as a function of these factors.