A simple phenomenological approach is devised based on the formalism introduced by Hill’s work on plasticity which allows for a unified description of the plastic-creep and fatigue responses of Single Crystal (SX) and Directionally Solidified (DS) nickel-base blades used in heavy duty gas turbines. To this end, the mechanical behavior of real SX and DS materials is approximated by adopting simplified classes of anisotropy able to reproduce the most relevant features of their material response. The hypotheses behind such choice depend from one side on a precise balance of various sources of uncertainties in both design analyses and experimental data and from the other side help in guaranteeing the respect of constraints on robustness, availability and maintainability of the design practice.
In this first part the modeling of plasticity and creep is discussed and accompanied by FEM analyses of real components. The set of tools presented here will be completed in the second part of this work where fatigue will be investigated.