a b s t r a c tThe purpose of the current work is the development and application of a new experimental technique and testing device for investigating the complex behavior of sheet metals during non-proportional loading. The method is based on plain strain pure bending, enabling the investigation of large deformation cyclic reversed loading, orthogonal pure bending, as well as springback. The key feature of the pure bending experiment is the absence of contact forces, material slip and friction. Furthermore, during the pure bending test, the strain gradient through the thickness is kinematically prescribed because the specimen is subjected to a plane strain condition in de direction parallel to the rotational axis (Tan et al., 1995), which allows for a straightforward comparison of the pure bending experiments and parallel simulations. The latter is used here via the identification of a recent model for directional hardening effects and arbitrary strain path changes, (Wang et al., 2006(Wang et al., , 2008. The current method facilitates experimental investigation of hardening stagnation after reverse loading and cross hardening going well beyond that which is possible with existing methods based on the cyclic shear or tension-shear of sheet metal strips (Bouvier et al., 2005(Bouvier et al., , 2006aFlores et al., 2007.), or pure and three-point bending (
This paper presents a new contactless and frictionless pure bending technique for material testing purposes, along with a practical realization thereof. A contactless pure bending mode is realized through the relative rotations of two clamps that are mounted on frictionless sliders. The proposed generic device allows for large rotations, cyclic loading, reversed loading, creep testing, relaxation testing and is well-suited to test different classes of materials. On top of the classical benefits for materials testing through bending, a few illustrative examples are given that emphasize the potential of this bending instrument for particular material tests.
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