CRACK GROWTH UNDER THERMO-MECHANICAL FATIGUE IN NICKEL CAST ALLOYS [Poster #7]
Karl Michael KraemerGrand Ballroom D
This poster presentation summarizes the results from several projects in this field conducted at the TU Darmstadt to identify and describe the various influences on crack growth under thermo-mechanical fatigue (TMF) loading. The activation of damage mechanisms under TMF loading and interactions between them are dependent of the temperature cycle and the respective load phasing. Depending on the type of loading (force- vs. strain-control), contrary influences of the phase shift on the TMF crack growth rates are found. To describe crack growth under creep-fatigue and TMF conditions, the linear accumulation model ‘O.C.F.’ was developed - based on the contributions of fatigue, creep and oxidation to crack growth per load cycle. This model is capable to reproduce the effects of time-dependent damage, different load ratios and TMF phase shifts, as well as component geometries. The model’s linear formulation allows assessing the dominant driver of crack growth at each stage of an experiment. These predictions are compared with fractographic investigations and in-situ observations of crack paths to identify the mechanisms of crack growth under different TMF load cycle forms.