Crystal plasticity and crack initiation in a single-crystal nickel-base superalloy Modelling, evaluation and applications
نویسندگان
چکیده
In this dissertation the work done in the projects KME-410/502 will be presented. The overall objective in these projects is to evaluate and develop tools for designing against fatigue in single-crystal nickel-base superalloys in gas turbines. Experiments have been done on single-crystal nickel-base superalloy specimens in order to investigate the mechanical and fatigue behaviour of the material. The constitutive behaviour has been modelled and verified by FE-simulations of the experiments. Furthermore, the microstructural degradation during long-time ageing has been investigated with respect to the material’s yield limit. The effect has been included in the constitutive model by lowering the resulting yield limit. Moreover, the fatigue crack initiation of a component has been analysed and modelled by using a critical plane approach in combination with a critical distance method. Finally, as an application, the derived single-crystal model was applied to all the individual grains in a coarse grained specimen to predict the dispersion in fatigue crack initiation life depending on random grain distributions. This thesis is divided into three parts. In the first part the theoretical framework, based upon continuum mechanics, crystal plasticity, the critical plane approach and the critical distance method, is derived. This framework is then used in the second part, which consists of six included papers. Finally, in the third part, details of the used numerical procedures are presented.
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