|About this Abstract
||NUMIFORM 2019: The 13th International Conference on Numerical Methods in Industrial Forming Processes
||S-01: Modeling of the Anisotropic Behavior in Plasticity
||Measurement of Unloading Behavior of AHSS and Its Effect on the Springback Prediction in FEM Simulation
||Nobuyasu Noma, Taiki Maeda, Toshihiko Kuwabara, Tomoyuki Hakoyama
|On-Site Speaker (Planned)
The effect of unloading behavior of advanced high strength steel sheets on the accuracy of springback prediction is investigated. For enhancing the accuracy of springback prediction, cyclic tension-unloading tests for a large strain level over 0.1 are systematically performed for three dual phase steel sheets (DP590, DP780 and DP980) used for automotive body parts. Using a universal tensile testing machine, pre-strains in 0.005 increments up to a quarter of uniform elongation (UEL) strain and in 0.01 increments after that strain are applied to the test samples over a strain range of 0.1. The variation of the tangential slope of the stress-strain curve during each unloading process is measured and the variation of the Young’s modulus after pre-straining (apparent Young’s modulus) is determined. Unlike previous researches, the apparent Young’s modulus slightly increases after taking a minimum value. In addition, the effect of this behavior on the accuracy of springback prediction is investigated in detail for actual press-formed parts. It is revealed that the model considering the increasing behavior of the apparent Young’s modulus after taking a minimum value provides a good agreement with experiment. Therefore, we conclude that an accurate reproduction of unloading behavior is crucial for accurate springback prediction.