Experimental study of continuous-bending-under-tension of AA6022-T4

Abstract

This paper presents an experimental setup for continuous-bending-under-tension (CBT) of thin strips and sheets, aimed at the investigation of the observed elongation-to-fracture (ETF) enhancements under such conditions. In particular, the kinematics of the process are described and correlated with the evolution of axial force measured during testing. The main results of the effect of process parameters, such as crosshead velocity and bending depth, on the ETF and the reduction of axial force are presented for the aluminum alloy AA6022-T4. The force vs. displacement response is not found to be a strong function of the crosshead velocity, which is explained by the near rate-independence of the material in the strain-rate range that occurs in CBT. Similarly, ETF does not show a clear dependence on the bending depth or the crosshead velocity. On the other hand, the axial force decreases linearly with the bending depth and slightly increases with the velocity. From the detailed analysis, the optimal parameters for enhancing ductility of AA6022-T4 under CBT are 1.2 mm/s for crosshead velocity and 2.0 for normalized bending depth. Under these conditions, a significant finding is that the strain level achieved throughout the CBT specimen is comparable to that in the necked region of a specimen tested to rupture in uniaxial tension.