Physics Based Gear Health Prognosis via Modeling Coupled with Component Level Tests

A "smart steel" concept is proposed by QuesTek Innovations to enable a major advance in physics-based gear health prognosis. The concept is based around idea that the decay of stable austenite within the cases of gear steels during high-cycle fatigue (HCF) may provide a "state expressive" signature that can be used as input into physics-based predictions of remaining HCF life. Under a Phase I effort, the evolution of surface retained austenite under HCF conditions in existing high performance gear steels will be measured and modeled. The goal will be to assess the feasibility of achieving a sufficiently gradual transformation to serve as a desired "state signature" of fatigue lifetime. In parallel, the 3D characterization of nucleation sites and numerical mechanics modeling of nucleation under the ONR/DARPA "D3D" Digital 3D Structure consortium will be leveraged to assess feasibility of coupling the retained austenite state to the prediction of remaining HCF life. Due to the large difference in magnetic permeability between austenite and martensite, magnetic sensor approaches will be surveyed for continuous in-flight monitoring of case austenite contents. The cyclic testing and austenite measurements in Phase I will be conducted at Northwestern University (the institutional STTR partner).