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| NESSUS® |
| Turbine Rotor Material Design |
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Company: Southwest Research Institute Purpose: The purpose of this on-going program is to develop a probabilistically based damage tolerance design code to augment the current safe-life philosophy for life management of commercial aircraft gas turbine rotors and disks. Background: Aircraft gas turbine industry experience shows the occurrence of material and manufacturing anomalies which can potentially degrade the structural integrity of high energy rotors. Conventional rotor life management methodology does not explicitly address the occurrence of these types of anomalies. The conventional safe-life methodology is founded on the assumption of nominal material and manufacturing conditions, and under these conditions, the methodology provides a structured process for the design and life management of high energy rotors. Undetected material and manufacturing anomalies represent a departure from the assumed nominal conditions and have resulted in incidents such as the Sioux City accident in 1989. As a result of this accident, the FAA requested that industry review available techniques to see whether a damage tolerance approach could be introduced to reduce the rate of uncontained rotor events. The industry working group concluded that additional enhancements to the conventional rotor life management methodology could be established which explicitly address anomalous conditions. These enhancements could be structured to enforce design and life management adaptations which enhance rotor integrity under anomalous material or manufacturing conditions.
Key Publications: Leverant, G.R., Littlefield, D.L., McClung, R.C., H.R. Millwater, Y.-T. Wu, 1997, "A Probabilistic Approach to Aircraft Turbine Rotor Material Design," The International Gas Turbine and Aeroengine Congress and Exhibition, Paper No. 97-GT-22, Orlando, Florida, June 2-5, 1997. |
| SwRI Home |
Performance: The methodology developed can address the uncertainties in material defect occurrence, location, and size in the rotor structure and how these uncertainties effect rotor performance. Versions 1 and 2 of the primary product, the DARWIN™ (Design Assessment of Rotors with INspection) code, have been delivered. DARWIN™ integrates finite element stress analysis, defect growth analysis, nondestructive inspection simulation, and probabilistic analysis to assess the risk of rotor disk fracture with in-service inspection. The code is currently being evaluated by the participating engine companies. The code has the ability to model random inspection schedules and probability of detection, and compute the probability-of-fracture as a function of flight cycles with and without inspection. DARWIN™ can be used to reveal critical rotor zones and provide information for design and inspection planning. The methodology can be applied to other structures that are characterized by rare defects.