Permissible exposure

Based on the maximum value for exposure, a statement can be made on whether a hazard exists for the component under the existing operating and heat management parameters. For damage well below the component surface (flank fracture), the exposure limit above which a risk of damage must be expected is approximately 0.8 [1].

The exposure limit of 0.8 indirectly considers, for example, influences from inclusions, which according to tests from [2] can lead to local stress increases. It is calibrated by experimental tests from multiple research projects as well as practical experience [1].

With more precise knowledge of the condition of the microstructure and the distribution of inclusions of the current gear (neither of which has a direct influence on the computational consideration according to current knowledge), the exposure limit from which the risk of damage must be expected may be modified [1].

[1] Witzig J.: Flank Breakage - A Limitation of the Gear Load Capacity Beyond the Material Depth. Dissertation TU Munich 2012
[2] SCHMIDT, W. Untersuchungen zur Grübchen- und zur Zahnfußtragfähigkeit geradverzahnter evolventischer Innenstirnräder. TU Munich 1984