An anisotropic constitutive model based on crystallographic slip theory was formulated for nickel-base single crystal superalloys. The current equations include both drag stress and back stress state variables to model the local inelastic flow. Specially designed experiments have been conducted to evaluate the existence of back stress in single crystals. The results showed that the back stress effect of reverse inelastic flow on the unloading stress is orientation dependent, and a back stress state variable in the inelastic flow equation is necessary for predicting anelastic behavior. Model correlations and predictions of experimental data are presented for the single crystal supperalloy Rene´ N4 at 982°C.

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An anisotropic constitutive model based on crystallographic slip theory was formulated for nickel-base single crystal superalloys. The current equations include both drag stress and back stress state variables in the inelastic flow equation for slip in each slip system. Experiments were conducted to evaluate the need of back stress in the model. The test results showed the effect of reverse inelastic flow on unloading is orientation dependent, and that a back stress state variable in the inelastic flow equation is necessary for predicting the anelastic behavior. Model correlations and predictions with experimental data are presented for the single crystal superalloy Rene’ N4 at 760C and 982C.

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