Influence of surface layer properties on tooth root bending strength of cylindrical gears

Abstract

The trend of resource-efficient machine elements confronts design engineers with new challenges. Reduced component weight and ever increasing power densities require a gear design that enters the border area of material capacity. To embrace the potential offered by modern construction materials, calculation methods for component strength must rely on a deeper understanding of fracture and material mechanics in contrast to empirical-analytical approaches. The aim of lightweight designs in drive technology – particularly in relation to E‑mobility – can lead conventional design methods towards larger dimensioned and therefore heavier gears. Calculation methods that empower an accurate depiction of local load and material properties are able to safely push the boundary of gear design into areas that are closer to the ultimate fatigue limit of the material and help to conserve resources that way. For this reason, the aim of the report is to prove a general applicability of the higher-order calculation approach developed by Henser for all gear geometries and material properties. This method will make for more cost- and weight-effective gear design in the future. A two step approach shows the accuracy of the Inclusion-Based Weakest Link Model by validation on a small module helical gear and a parameter study proves the effectiveness of the Inclusion-Based Weakest Link Model by showing the influences of different sized gear geometries and material properties on calculated bending strength. In addition, the main influence parameters on the model and material properties that have different effects depending on gear size are identified.