Modified Logistical Creep Strain Prediction Method : A Constitutive Creep Strain Model Of A Nickel Based Super-Alloy

In turbine blade design, all three stages of creep are of concern. Moreover, for most commonly employed materials, creep rupture data is readily available where as long term creep strain data is not [1]. Recently, effort has been expended by many researchers in the development of material models incorporating all three stages of creep at varying stress and temperatures. Several developed models are complex or burdened by large numbers of material fitting constants. There is need for the development of a constitutive creep strain prediction formulation that is simplistic and requires minimal empirical data. In this thesis, the creep strain model proposed by Holmstrom et al., called the Logistic Creep Strain Prediction (LCSP) method was modified and used to model all three stages of creep of the well known nickel based super alloy Inconel 718 [1]. The LCSP is robustness and accurate, and possesses a simplistic formulation ideal for algebraic manipulation and differentiation making it a very attractive solution.