Crack Propagation On Integrated Raceways

Abstract

Integrated raceways are often used within the design of helicopter main gearboxes aiming at a compact architecture with regards to a low overall gearbox weight. Due to the boundary conditions of using such raceways, a potential failure could have catastrophic consequences and it has to be ensured that all relevant failure modes are understood to ensure a safe and reliable operation. Rolling contact fatigue (RCF) and the related crack initiation and crack propagation plays a critical role in that context. Within an EASA initiated project fundamental research was conducted with the focus on RCF and crack propagation on integrated raceways. This paper will present the results from this research. As a first step, an analysis of key influencing parameters is performed, followed by a detailed description of the test campaign. Furthermore, the use of finite element analysis to predict crack propagation under RCF on integrated bearing raceways is studied, including the validation of simulation results through testing. Finally, a potential methodology for the implementation of the project results into the certification specification for helicopters CS27 and CS27 is presented.