Yasuhiro Hayashida

Yield function development for aluminum alloy sheets

In this work, yield surfaces were measured for binary aluminum-magnesium sheet samples which were fabricated by different processing paths to obtain different microstructures. The yielding behavior was measured using biaxial compression tests on cubic specimens made from laminated sheet samples. The yield surfaces were also predicted from a polycrystal model using crystallographic texture data as input and from a phenomenological yield function usually suitable for polycrystalline materials. The experimental yield surfaces were found to be in good agreement with the polycrystal predictions for all materials and with the phenomenological predictions for most materials. However, for samples processed with high cold rolling reduction prior to solution heat treatment, a significant difference was observed between the phenomenological and the experimental yield surfaces in the pure shear region. In this paper, a generalized phenomenological yield description is proposed to account for the behavior of the solute strengthened aluminum alloy sheets studied in this work. It is subsequently shown that this yield function is suitable for the description of the plastic behavior of any aluminum alloy sheet.

Yielding description for solution strengthened aluminum alloys

In this work, yield surfaces were measured for binary aluminum-magnesium sheet samples which were fabricated by different processing paths to obtain different microstructures. The yielding behavior was measured using biaxial compression tests on cubic specimens made from laminated sheet samples. The yield surfaces were also predicted from a polycrystal model using crystallographic texture data as input and from a phenomenological yield function proposed previously. In general, experimental and predicted yield surfaces were found to be in relatively good agreement. However, for samples processed with high cold rolling reduction prior to solution heat treatment, a significant difference was observed between the phenomenological yield surface and the experimental/polycrystal yield surfaces in the pure shear region. In this paper, a refinement was proposed for the phenomenological yield description to account for the behavior of the solute strengthened aluminum alloy sheets studied in this work, and in general, for any sheet metal. This yield function was implemented into a finite element code and sample computations were carried out to assess the validity and the accuracy of this improved material description.

Experimental analysis of aluminum yield surface for binary AlMg alloy sheet samples

Abstract In this work, the yield surfaces of binary aluminum-magnesium alloy sheet samples were measured using biaxial compression tests. Sheet samples of a given material were stacked and bonded together with epoxy and cubic compression specimens were machined out of the laminate. The yielding behavior was assumed to be independent of the hydrostatic pressure. In the analysis of the biaxial compression tests, the effects of friction and of the elasticity of the die were accounted for. These effects were studied with the aid of finite element method (FEM) simulations of the test which proved to be useful in avoiding systematic errors. The yield surfaces of three binary alloy sheet samples containing 5 wt% Mg but with different crystallographic textures were analyzed. The different textures resulted from processing under different thermomechanical conditions. The experimental yield surfaces were compared to predictions made with the Taylor-Bishop and Hill (TBH) model and with a phenomenological yield function. The experimental and polycrystal yield surfaces were found to be in fair agreement. The yield function was found to be a suitable description of the plastic behavio for only two of the materials studied.

Measurement of Work Hardening Behavior of Pure Titanium Sheet Using A Servo‐Controlled Tube Bulge Testing Apparatus

Biaxial stress tests of rolled pure titanium sheet (JIS ♯1, 0.5 mm thick) have been carried out in order to investigate the anisotropic plastic deformation under biaxial tension. Rolled pure titanium sheet was bent and welded to make tubular specimens. Combined tension‐internal pressure was applied to the tubular specimens using the servo‐controlled tube bulge testing apparatus developed by one of the authors [Kuwabara, T., Yoshida, K., Narihara, K., Takahashi S., Int. J. Plasticity 21 (1), 101–117 (2002)], so that the strain rate ratio, eφ:eθ, in the axial (φ) and circumferential (θ) directions of the specimen was controlled to be constant. Contours of plastic work at different levels of plastic strain and stress paths under constant strain rate ratios have been observed in the first quadrant of stress space. It is found that the test material exhibits significant differential work hardening behavior with the increase of plastic work.