The objective of this joint effort between WZL of RWTH Aachen and Leibniz-IWT Bremen is to allow the extension of a fail-safe calculation of material life for future case-hardening steels considering the VHCF regime, which is indispensable for the new generation of epicyclic gear applications. To achieve this top-level objective, several sub-objectives have to be completed such as:

• Develop fast rotating recirculating sub-element test rig for determining tooth root bending strength under reverse bending conditions;
• Gain material data for two new case hardening steel developments in the VHCF-regime;
• Develop and validate a VHCF material model.

With respect to the call, the consortium is able to fulfil the requirements of experience in test rig development, manufacture and instrumentation as well as a quality-controlled management of facilities and processes for a recirculating rig testing (WZL). The gear test processing includes all aspects of test gear design, instrumentation measurements, measurement uncertainties and limitations. Especially due to the fact, that WZL has a gear testing environment that is already officially approved by aircraft engine producers a high potential for a successful dissemination of the project results into industry is expected.

The methods utilise FE-based strength analysis in weakest link models and analysis to ISO 6336 standard (WZL). The consortium is capable to characterise the material and failure mechanisms by residual stress measurement by X-ray diffraction, electron microscopy, and metallography at highest standard as well as to describe material failure phenomena in the VHCF regime through theoretical models (Leibniz-IWT). Based on the combined experiences the collaboration of WZL and Leibniz-IWT allows for a successful derivation of VHCF material model for case hardened gear steels for application in an epicyclic power gearbox.