The stress-range and path-shape dependencies of multiaxial nonproportional cyclic hardening were studied for annealed type 316 stainless steel at 600°C by means of stress controlled tests. Cyclic experiments along circular stress paths with constant effective stresses in the axial-torsional stress plane were first performed. The significant cyclic hardening and its stress-range dependency observed for the circular stress cyclings were quantitatively shown in reference to the cyclic stress-strain curves resulted from uniaxial stress cyclings. Then, to discuss the effect of path-shape, the cyclic tests along square stress paths inscribed by the above circular paths, as well as the tests where uniaxial cyclings and torsional ones were alternated, were also carried out. As a result of these tests, the cyclic hardenings for square paths were found to be almost equivalent to those for their circumscribed circular paths. The other type of stress cyclings caused almost the same amount of cyclic hardenings as those for the circular cyclings of the identical stress-ranges.

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