Thermal Mechanical Crack Growth Rate of a High Strength Nickel Base Alloy

An understanding of thermal mechanical fatigue (TMF) crack propagation is fundamental to the application of fracture mechanics to gas turbine components. Typical operating conditions for a cooled turbine disk rim consist of a complex mechanical history and an associated variable amplitude thermal history. While thermally induced stress gradients are commonly incorporated in the mechanical history, the effects of thermal cycling on crack growth must be addressed in an appropriate fatigue model. A current computer-based empirical crack propagation modeling system has demonstrated effectiveness under isothermal conditions and can be readily expanded to include thermal-mechanical effects. The existing isothermal models were developed from an extensive data base and describe crack growth over a broad range of temperature and loading conditions. Building on this established system, a model of thermal-mechanical crack growth is being developed.