Influence of thermal boundary conditions on stress-strain distribution generated in blade-shaped samples

Abstract Cyclic thermal fatigue experiments have been performed on a single-edge wedge specimen of the polycrystalline nickel-based superalloy INI00 to simulate the conditions experienced by a turbine blade during operation. Induction heating and forced-air cooling of the wedge tip was used. The temperature at the leading edge was cycled between 200 and 1100 °C and the surface temperature distribution was measured by thermocouples throughout the thermal cycle. Thermal and stress analysis calculations have been carried out to determine the time-temperature-stress-strain histories generated in a specimen. It has been found that the magnitudes of the stresses and strains produced are sensitive to the precise surface temperature assumed. In particular, plastic deformation will generally be incurred during the heating and/or cooling phases of a cycle. This can have important consequences in making lifetime predictions from isothermal data. Failure is always predicted to initiate at the leading edge, in agreement with the experimental observations.