Considerations regarding the pressures distribution on leads of spur gears

The standard methodology to verify gears' strength to rolling contact fatigue (RCF) is to compare the value for maximum Hertz pressure with a permissible value. However some experimental evidences can not be explained by this approach. Therefore the TCA was focused on both the surface distribution of contact pressures and depth distribution of von Mises stresses. Semi-analytic methods SAM and its variant for linear contacts with finite length SAM-C have been involved to obtain the pressures distribution, contact area and stresses state inside the stressed volume. For theoretical case of coincident line contact there are no edge effect but any modification of the relative position changes it to a non-coincident contact type where the end effects manifest. The spur gears with pinion teeth having a longitudinal crowned profile have indicated a good capacity to avoid the end edge effect when the operating conditions included a misalignment. For operating conditions without misalignment, the lead modification by end relief causes a quasi-Henzian pressures distribution; however, the existence even of a small misalignment changes it to a skewed distribution. The semi-analytical procedure appears as an accurate and very fast tool to establish the suitable values for parameters that define the flank modification of gears.