Cyclic Bending and Stationary Drawing Deformation of Metal Sheets : Experiments and Associated Numerical Simulations

A simple bend-draw experimental device is employed to analyze the behavior of narrow strips submitted to a nearly cyclic bending deformation mode followed by a steady state drawing. In this bending-drawing experiment, the strip is firstly bent over a central bead and two lateral beads by applying a controlled holding load and then is pulled out of device throughout the bead radii by a drawing load. The apparatus is mounted in a standard tensile test machine where the holding and drawing loads are recorded with an acquisition data system. The specimen is a rectangular strip cut with 320 mm long and 7 mm wide. The longitudinal (l) and width (w) strip plastic strains are determined from two hardness marks 120 mm spaced whereas the corresponding thickness (t) strain is obtained by volume conservation. Previous experiments showed a correlation between the plastic strain (ew/et)BD resulting from the bending-drawing and the Lankford R-values obtained from the uniaxial tensile test. However, previous 3D numerical simulations based upon Hill's quadratic and Ferron's yield criteria revealed a better correlation between the ( ew/et)BD and the stress ratio σPS /σ(α) , where σPS stands for the plane-strain tension yield stress and σ(α) for the uniaxial yield stress in uniaxial tension along the drawing direction making an angle α with the rolling direction (1) . In the present work, the behavior of an IF steel sheet is firstly evaluated by means of uniaxial tensile and drawing-bending experiments conducted at every 15 degrees with respect to the rolling direction. Afterwards, the bending-drawing experiment is investigated with the commercial finite element (FE) code ABAQUS/Standard in an attempt to assess the influence of cyclic loadings upon the bending- drawing strain-ratios.