Microstructure-Sensitive Corrosion Fatigue Lifing Toolkit

Corrosion, fatigue, and their combined effects are extremely costly and difficult to predict. Corrosion alone costs the US Navy $3B-$4B per year while fatigue accounts for >50% of all aircraft failures. In order to reduce this cost, it is critical that the Navy be able to reliably predict corrosion fatigue life. However, both are complex phenomena that are driven by mechanism spanning nanoscale (effects of hydrogen and dislocations), microscale (effects of microstructure and pitting), and macroscale (effects of complex three-dimensional loading scenarios of aero-engine components). Further complicating the issue, corrosion and fatigue work synergistically, with pits creating stress risers for fatigue crack initiation, and cyclic stress exacerbating corrosion rates and destabilizing passivation films, driving pitting, in addition to hydrogen ingress embrittlement material and accelerating fatigue through stress-corrosion-cracking. The status quo is to use empirical/statistical methods to estimate corrosion fatigue life based on historical experimental data. Since there so many variables (e.g., alloy, process history/microstructure, loading conditions, environment) to consider, empirical modeling is severely limited for this application, and as a result, a lot of costly and time-consuming testing and inspection is required, along with overly conservative safety factors to guard against the unknowns, and still, failures and a great deal of cost is incurred. Recently, there have been several significant research breakthroughs in modeling of corrosion, hydrogen effects, and fatigue, however, they remain disjointed and there is no comprehensive solution available. QuesTek, in partnership with the University of Pittsburgh, propose a mechanistic microstructure-sensitive corrosion fatigue lifing toolkit, to be hosted on QuesTek’s ICMD® software platform. This toolkit will combine the state-of-the-art in modeling, including CALPHAD modeling to predict microstructure, phase field modeling to predict corrosion/pitting, atomistic-modeling to predict hydrogen effects on stress corrosion cracking, and crystal plasticity finite element method modeling to predict fatigue, incorporating all of the effects of microstructure, corrosion/pitting, and hydrogen, into a fatigue life simulation that can account for customizable materials and loading conditions. This framework will be validated experimentally with data generated by the University of Pittsburgh and integrated into the ICMD® software platform to provide a user-friendly graphical user interface for the Navy and industry to accurately predict corrosion fatigue life.