Southwest Research Institute, in collaboration with four major gas turbine manufac-turers*, has developed a probabilistically-based damage tolerance design code calledDARWIN 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 titaniumstructures.

This software integrates finite element stress analysis results, fracture-mechanics-basedlife assessment for low-cycle fatigue, material anomaly data, probability of anomalydetection and inspection schedules to determine the probability of fracture of a rotordisk as a function of applied operating cycles. The program also indicates the regions ofthe 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 nickeldisks and manufacturing and maintenance-induced surface defects in all disk materialsin 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

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