Abstract
The applicability of Hill's anisotropic yield condition was studied experimentally for the anisotropic state given by uniaxial prestrain. The change of Hill's anisotropic constants with the increase of prestrain was investigated by the test of the small tensile specimens cut from the initially prestrained brass plate in various orientations to the initial prestraining direction. The subsequent yield surfaces after uniaxial prestraining and the necking angles of the small specimens were calculated by Hill's anisotropic constants and compared with the experimental results.
Hill's original expression of the anisotropic yield condition became a simpler form for the plate with the anisotropy given by the uniaxial prestrain. The calculated yield surfaces by this formula did not coincide well with the experimental values when the value of the subsequent yield stress in the initial prestraining direction was determined as that of the yield point in the reloading stress-strain diagram. But the coincidence between them became a little better when the applied stress value for the prestrain was adopted for the subsequent yield stress.
Hill's formula of the necking angle was found to be impertinent in instances where the amount of the prestrain was smaller than that of the strain at fracture, unless the change of the anisotropy due to the deformation was taken into consideration.
