Finite Element Analysis of Bending in High-Strength Steels

Abstract

In pursuit of the constant improvement of Advanced High Strength Steels (AHSS), this project aims to understand and improve the bendability of various steel grades, starting with Dual-Phase DP 980. To do this we have modeled 90° sheet metal bending in the common VDA V-Bend test and 3-point bend test configurations respectively. This modeling effort is undertaken using the Finite Element Analysis (FEA) method with HyperWorks and LS DYNA as the FEA software. Multi-scale multi-phase bend models using real microstructures that treat the stress and strain evolution of DP 980 steel are created; in essence, the macro models drive the micro models. Micro-models are created with accuracies exceeding 95% and are driven by the displacements of the nodes from the macro models. These are saved, exported, and used to run the micro-model microstructures. The final micromodel produces a homogenized material approximation within a 5% error of the macro-model curves. Uniaxial Tensile micro-models are also created to verify input macro-material curves before bend investigations. The overall research objective is to establish a repeatable procedure for creating multi-scale bend models for multi-phase materials, along with determining the role of microstructure in DP steel bending processes via a parametric analysis. Three major parametric investigations are analyzed: 1) How does the microstructure respond to varying the Bend Test Geometry and Punch Tip Radius? 2) How does the microstructure respond to varying Martensite Volume Fraction (MVF)? 3) How does the microstructure respond to varying %C?