Design of a Test Geometry to Characterize Sheared Edge Fracture in a Uniaxial Bending Mode 2023-01-0730

The characterization of sheet metals under in-plane uniaxial bending is challenging due to the aspect ratios involved that can cause buckling. Anti-buckling plates can be employed but require compensation for contact pressure and friction effects. Recently, a novel in-plane bending fixture was developed to allow for unconstrained sample rotation that does not require an anti-buckling device. The objective of the present study is to design the sample geometry for sheared edge fracture characterization under in-plane bending along with a methodology to resolve the strains exactly at the edge. A series of virtual experiments were conducted for a 1.0 mm thick model material with different hardening rates to identify the influence of gage section length, height, and the radius of the transition region on the bend ratio and potential for buckling. Two specimen geometries are proposed with one suited for constitutive characterization and the other for sheared edge fracture. It is shown that the local strains at the edge can be accurately resolved using basic image processing without the need for digital image correlation that cannot resolve the strain field at the edge. Finally, a technique to evaluate the location of the unstretched fibre is considered to determine the strain distribution across the gage width for use in constitutive characterization under bending.