| Abstract: | The respective influence of the Von-Mises equivalent stress and of the maximum principal stress on high temperature creep damage of two industrial alloys (INCO 718 and 17-12 SPH stainless steel) are pointed out in a quantitative way through tensile-torsion biaxial tests. Through inversions of the shear component, the important part taken by the principal direction corresponding to the maximum principal stress is also shown. The results are observed to be opposite according to whether the alloy suffers cyclic hardening as 17-12 SPH does or cyclic softening which is the case of Inco 718. These results are supported by metallographic observations. They demand an anisotropic form for the damage variable D, while besides a time dependence, the kinetic equation must include the part taken by the strain. |
