Southwest Research Institute, in collaboration with four major gas turbine manufacturers, has developed a probabilistically-based damage tolerance design code called Design Assessment of Reliability With INspection (DARWIN) to determine the risk of fracture of turbine engine rotor disks containing undetected 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 risk reduction associated with single and multiple inspections. This 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.

DARWIN is sponsored by the Federal Aviation Administration.