Thermal Mechanical Fatigue Crack Growth Testing

Turbines in aircraft turbojet engines are being subject to increasingly higher temperatures to improve fuel efficiency. High turbine efficiency requires the ability of turbine blades to withstand gas temperature of the order of 1350 to 1550 °C. In polycrystalline materials, these increased temperatures would cause creep strains along grain boundaries that would be unacceptable. Even single-crystal materials must be pushed to their limits to insure that engine performance is maximized. Airfoils in modern gas turbine aircraft use a systems approach for cooling to achieve required component life. There are three basic components to these systems: a cast nickel single-crystal superalloy in combination with thermal barrier coatings, and a sophisticated cooling scheme consisting of intricately designed channels and holes through the core and surface of the airfoil.