2008 年 57 巻 7 号 p. 681-687
It has been found that the shear strength of the A2024BE-T6 aluminum alloy is much lower than the tensile strength and that this alloy exhibits severe initial anisotropy. The purpose of this paper is to clarify the relation between initial and subsequent anisotropies by comparing with the results of the previous paper. Off-axis torsion tests by means of the combined loading of compression, internal pressure and torsion are carried out on thin-walled cylindrical specimens of the A2024BE-T6 alloy subjected to a torsional prestrain. In this test method, it is possible to detect both Bauschinger effect and planar anisotropy by changing the principal shear stress direction from 0 deg to 90 deg. Furthermore, the anisotropic hardening behavior is analyzed precisely by applying the subsequent yield function to the experimental results, and the degree of anisotropy is expressed as a function of offset strain. It is proved that the maximum anisotropy based on the flow stress corresponds to the Bauschinger effect when small offset strains are used in specifying the equi-strain locus, while it is related to the residual initial anisotropy when large offset strains are used.