Influence of Protuberance Geometry on Gear Tooth Root Stress and Grinding Notch Formation

Abstract

The tooth root region of gears is a critical area where bending stresses reach their maximum values. During grinding operations, micro-notches, known as grinding notches, may form in the tooth root transition zone, leading to localized stress concentration. This effect is particularly critical in hardened and ground gears due to the high notch sensitivity of the material.

The grinding notch effect, together with increased surface roughness, geometric discontinuities, and potential grinding burns, can significantly reduce fatigue strength and promote tooth root failures. Within the framework of ISO 6336, this phenomenon is indirectly considered in tooth root bending strength calculations, highlighting the importance of manufacturing quality and surface integrity in gear design.

The negative effects of grinding notches can be mitigated through appropriate grinding wheel selection, optimization of grinding parameters, and ensuring a sufficient tooth root fillet radius. Additionally, post-grinding surface improvement techniques such as polishing or shot peening may further reduce stress concentrations. These measures play a crucial role in enhancing gear fatigue performance, service life, and overall reliability.