Southwest Research Institute, in collaboration with four major gas turbine manufac- turers*, has developed a probabilistically-based damage tolerance design code called DARWIN to determine the risk of fracture of turbine engine rotor disks containing un- detected material anomalies. The current focus is on hard alpha defects in titanium structures. This software integrates finite element stress analysis results, fracture-mechanics-based life assessment for low-cycle fatigue, material anomaly data, probability of anomaly detection and inspection schedules to determine the probability of fracture of a rotor disk as a function of applied operating cycles. The program also indicates the regions of the disk most likely to fail and the sensitivity of the risk to each random variable. The software will be enhanced to handle anomalies in cast / wrought and powder nickel disks and manufacturing and maintenance-induced surface defects in all disk materials in the near future. DESIGN ASSESSMENT OF RELIABILITY WITH INSPECTION + WWW.DARWIN.SWRI.ORG Anomaly Distribution Probability of Detection Material Crack Growth Data Inspection Schedule Pf vs. Cycles Risk Contribution Factors Finite Element Stress Analysis Probabilistic Fracture Mechanics Cycle Usage Disk Risk Assesment vs. Flight Cycles (Volume effect included) With Inspection Without Inspection + Funded by the Federal Aviation Administration * General Electric, Honeywell, Pratt & Whitney, Rolls-Royce Allison DARWIN TM