Cyclic Loading Tests Based on the In-Plane Torsion Test for Sheet Metal

In-plane torsion test has attracted a lot of attention recently. As a novel shear test, it can avoid unwanted reaction torque compared with the traditional in-plane shear test. The in-plane torsion test with circular groove specimens can avoid early fracture at the free edges, and thus achieve actual fracture strain under pure shear state because it has no free boundaries. In this study, digital image correlation is implemented to measure the torsion angle to obtain the precise torque-torsion angle curves. For specimens with slits, strain hardening is calibrated by inverse engineering approach. The strain path at the center of the shear zone during the torsion test is observed to be very close to a pure simple shear state. Cyclic shear loading tests are carried out for twin bridge shear specimen. The combined isotropic-nonlinear kinematic hardening model, Yoshida–Uemori two-surface model, and homogeneous anisotropic hardening model are evaluated to characterize the cyclic loading behaviors.