The Stress vactor and the Subsequent Yield Surface in Loading along the Strain Path with a Corner

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The stress strain relation and the subsequent yield surface in loading along the strain path with a corner are experimentally investigated in the deviatoric stress and strain space by subjecting thin-walled brass specimens to combined axial load, internal pressure and torsion. The change in direction of the stress vector can be uniquely associated with the length of strain path irrespective of the amount of prestrain and the corner angle of strain path, if the change in direction of the stress vector is represented by a nondimensional value divided by the corner angle. The minimum value of the magnitude of stress vector after turning the corner is independent of the amount of prestrain, if it is reduced to a nondimensional value divided by the magnitude of stress vector at the corner. The subsequent yield surface after preloading along the strain pat with a corner is not symmetric with respect to the direction of coresponding prestress. But, with an increase of prestrain, the symmetry of the yield surface is found and the shape is congruent with the subsequent yield surface after radial preloading to the same amount of prestrain.