VHCF: Material Model of Case-Hardened Steels for Turbo Gear Applications



01.04.2019 to 31.03.2023
Organizational Unit:
Chair of Machine Tools, Gear Technology
European Union EU



work Phone
+49 241 80 25368



Starting Situation

Ultra High Bypass Ratio (UHBR) technology has been identified as a promising approach to reducing aircraft engine emissions and fuel consumption. UHBR uses a reduction gear that reduces the fandeck speed and allows the use of larger fandeck diameters. The calculation of the gear carrying capacity is essential to predict the behaviour of the planetary gear during operation. One of the biggest challenges for gearboxes in UHBR applications is the high number of load cycles achieved by the gearbox components. Standards such as ISO 6336 provide design guidelines for bending strength up to a maximum number of load cycles of NG = 3 106, which is far below the expected service life of UHBR applications. The lack of test concepts and models for Very High Cycle Fatigue (VHCF) transmission applications leads to uncertainties in the design of high load transmissions. This condition is particularly unacceptable in the aerospace industry.

Research Objective

The aim of this project with the WZL of the RWTH Aachen and the Leibniz-IWT Bremen is to enable the fail-safe service life calculation for future case-hardened steels under consideration of the VHCF regime, which is indispensable for the new generation of planetary gear applications. The methods use FE-based strength analyses in weak-point models and analyses according to ISO 6336. In a first step, a fast rotating stress test bench for the determination of the tooth root bending strength under alternating bending load will be developed and set up. In the second step, material data for two new case-hardened steel developments are obtained in the VHCF system and the calculation model is validated.