Modelling of TMF Crack Growth in Polycrystalline Gas Turbine Alloys : Accounting for Crack Closure Effects

Sammanfattning: The main objective of the work presented in this Licentiate of Engineering thesis is to investigate and model the fatigue crack propagation behaviour of the nickel-based superalloy Inconel 792, with special attention to the industrial lifing of high-temperature components. In-phase (IP) crack propagation tests have been performed at different temperatures and loading regimes, including extended hold times. The observations from these tests have been the basis for establishing several hypotheses to describe the crack growth behaviour, which progressively have been verified experimentally and numerically. Most prominently, it has been observed that crack closure has a substantial impact on crack growth and can explain, to a large degree, the crack growth behaviour for this material under the conditions studied. This phenomenon has been observed experimentally and modelled numerically to extend further the precision of the methodology.