Probabilistic Fatigue Crack Growth Analysis With Mixed Uncertainty on Equivalent Initial Damage Size

Probabilistic fatigue crack growth models constitute an essential part of structural risk analysis for USAF aircraft. These analyses involve characterizing the single flight probability of failure (SFPOF) which is dependent on understanding crack growth variability, stress profile variability, and variability in the equivalent initial damage size (EIDS) as inferred from inspection data and equivalent flight hour assessments. While it has been established that uncertainty in the EIDS distribution is the largest contributor to SFPOF uncertainty, the analysis of many drivers of uncertainty in EIDS have yet to be studied such as crack measurement uncertainty, crack growth rate characterization, and limited data. This study presents analyses determining the primary drivers of EIDS uncertainty which are to help prioritize future data collection efforts and inspection method improvements.