AGMA 08FTM06 PDF

Involute flanks are nominally well described and classified by different standard accuracy grades, depending on gear application and defining their tolerance limits for such parameters as runout, profile, lead, pitch variation, and others. The gear tooth fillet is an area of maximum bending stress concentration. However, its profile is typically marginally described as a cutting tool tip trajectory. Its accuracy is defined by a usually generous root diameter tolerance. The most common way to reduce bending stress concentration is application of the basic (or generating) rack with full radius. This paper presents a fillet profile optimization technique based on the FEA and random search method, which allows for a substantial bending stress reduction, by 15 to 30% compared to traditionally designed gears. This reduction results in higher load capacity, longer lifetime, and lower cost. It includes numerical examples confirming the benefits of fillet optimization.