A Study of FEA Springback Predictability With Channel Draw Test

• Main Authors: Huang, Mai, Brouwer, Jon
• Format: Conference Proceeding
• Language: English
• Subjects: BENDING; COMPUTERIZED SIMULATION; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; FINITE ELEMENT METHOD; FRACTURES; MATERIALS TESTING; METALS; SHEAR; SHEETS; STEELS; STRAINS; STRESSES; THICKNESS
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/1.2011230

FEA simulations have been successfully applied to various sheet metal forming processes to predict formability issues such as fractures, wrinkles, and thinnout; however, they have not achieved the same level of success in the springback predictions. As the former mainly dealt with stretch and the latter with bending, we contemplated that a fundamental underlying problem in the FEA springback predictability may lie with the thin shell theory, as it allows the thickness stress to be neglected and only uses an in-plane stretch and shear to balance the out-of-plane loads. A study was conducted to investigate the problem with channel draw test. Two steels, DP590 and HSLA350, were formed and simulated with same set of tooling and process conditions except for two different drawbead setups, i.e. with and without drawbead restraining force. Two different deformation modes, stretch bending and bending, were produced as a result. The testing and FEA results showed that the FEA simulation could not properly and accurately predict the bending strains. Also, it tended to underpredict the bending deformation while overpredicting the stretch. These findings proved that the inability of thin shell element to predict the bending strain is a major cause for the problematic and inaccurate FEA springback simulations. In order to correctly solve the springback problem with FEA simulations, the thin shell element formulations must be improved to include through thickness stress.