Investigating fracture failure in origami-based sheet metal bending

Abstract

Origami-based sheet metal (OSM) bending is a promising new die-free folding technique for sheet metal. OSM bending principle is based on deforming the material along a pre-defined fold line, which is determined using material discontinuity (MD) produced by laser or waterjet cutting. The objective of this work is to study and evaluate the fracture in OSM bending under the influence of various MD types, kerfto-thickness (k/t) ratios, and sheet thicknesses. The research goal is to provide information on selecting an optimized k/t ratio and type of MD that allows for fracture-free bending. Four different ductile fracture criteria (DFC) are used and calibrated from experimental data to forecast fracture. The DFC calibration is used to produce a set of critical damage values (CDV) for assessing the possibility of fracture in the OSM bending. In addition, the study provides fracture evaluation using finite element analysis (FEA) integrated with experimental cases for a broader range of OSM bending parameters and MDs. The results demonstrated that an MD with a higher k/t ratio is less likely to fracture during the OSM bending, whereas a higher sheet thickness increases the possibility of fracture. Furthermore, the study identifies the k/t ratio limit that ensures successful bending without fracture and categorizes MD types into two groups based on fracture likelihood. The fracture in the first group is dependent on the limiting k/t ratio, whereas the possibility of fracture in the second group is independent of the k/t ratio due to its topology.

Effect of temperature and strain rate fluctuation on forming limit curve of 5083 Al-Mg alloy sheet

“…In general, the FLC is a good measure of failure caused by localized necking. However, under some particular process, for example hemming, hole expansion/ flanging, 17,18 Origami-based sheet metal (OSM) bending, 19 stretch-bending with small die radii, 20 incremental forming 21 etc., various failure types can occur, such as edge crack, 17 bending induced surface crack, 22 shear induced crack, 23 non-symmetric thinning 24 etc. It is often found that the local necking is suppressed and sheet metal can develop stable plastic deformation until fracture.…”