Multiaxial Creep-fatigue criterion of Ni-base single crystal superalloys.

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Tension and torsion low cycle fatigue and that with tension strain hold-time tests were carried out using CMSX-2 single crystal superalloy at 1173K.Low cycle fatigue lives in torsion were far smaller than those in tension at the same Mises equivalent strain. The difference in fatigue lives due to loading mode was attributed to the anisotropy of elastic constant. The reduction in fatigue lives by introduction of 10 min hold-time did not depend on the loading mode.Stress and strain cocnentration exists in actual gas turbine blade like air film cooling hole. Conventional elastic-plastic finite element method is not available to single crystal superalloys since single crystal superalloys have a crystallographic texture and deformation behavior is influenced by preferential slips of crystal. This study developed the finite element code available to the elastic-plastic deformation analysis of single crystal superalloys. The code takes account of cubic and octahedral slip systems. Material constants required to the analysis were determined using CMSX-4 single costal superalloy. The stress and strain concentration of a plate with a circular hole of single crystal was proved to differ that of isotropic materials.