Couple Diffusion-Thermo-Mechanical Model for Life Prediction of a Turbine Engine Blade

The failure of engines on jet aircrafts during the past few years has prompted the National Transportation Safety Board (NTSB) to issue an “urgent” recommendation to increase inspections of the engines on U.S. aircraft. Such uncontained engine failures are particularly dangerous, because flying engine parts could puncture fuel or hydraulic lines, damage flight surfaces or even penetrate the fuselage and injure passengers. At issue is older engines found on small number of jets, and the safety and economic impact damage and fracture risk can have on aircraft engines. For example, high-pressure turbine blades are commonly removed from commercial aircraft engines that had been commercially flown by airlines. These engines were brought to the maintenance shop for refurbishment or overhaul. The blades were removed and inspected for damage. The damage was cataloged into three modes of failure, which are thermal-mechanical fatigue (TMF), Oxidation/Erosion (O/E), and Other (O). These show the complexity of damage in turbine engines and the different mechanisms associated with cause of damage. Hence, life prediction of turbine engine is crucial part of the management and sustainment plan to aircraft jet engine. Fretting is often the root cause of nucleation of cracks at attachment of structural components at or in the vicinity of the contact surfaces. Previous effort presented a model to predict fretting fatigue in turbine engine, which is one of the primary phenomena that leads to damage or failure of blade-disk attachments. The influence of thermal effect and temperature fluctuation during engine operation on fretting fatigue damage were investigated. Leveraging these existing capabilities, the present effort focuses on modeling another important damage mechanism in turbine engine blades, which is erosion at high temperatures. Thus a reaction-diffusion model is implemented in addition to the thermo-mechanical one. The model provides a mean to investigate erosion initiation and propagation in turbine engine blades.