Modeling and determination of flow curves for the simulation of hot forming; Conference on the International Deep Drawing Research Group (IDDRG 2009); ; Material property data for more effective numerical analysis : proceedings 2009
Modeling and determination of flow curves for the simulation of hot forming; Conference on the International Deep Drawing Research Group (IDDRG 2009); ; Material property data for more effective numerical analysis : proceedings 2009
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发表时间：
2009
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通讯作者：
B. Hochholdinger;H. Grass;A. Lipp;P. Hora
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作者：
B. Hochholdinger;H. Grass;A. Lipp;P. Hora
由于越来越多的白色车身部件通过硼合金板材（22 MnB 5）的热成型制造，因此对这种特定制造工艺的虚拟表示的需求是显而易见的。为了真实地模拟热冲压成形过程，必须准确地模拟流动应力随应变、应变速率和温度的变化。在过去的几年中，大量的各种各样的解析以及物理为基础的屈服应力模型已被提出。三个现有的模型，已表现出良好的能力，代表22 MnB 5在最近的出版物的流动行为，并拟合到实验数据。流动应力的测定所依据的实验数据是通过在高速变形应变仪上进行的叠层压缩试验获得的。在第一步中，模型参数被拟合到实验流动曲线，而不考虑摩擦，这固有地存在于压缩测试中。由于模具与试件之间的摩擦力对试件内部的应力状态有重要影响，因此采用了一种基于模拟的反求方法来确定模型参数。为此目的，一个简单的二维有限元模型，为每个测试配置。结果表明，无摩擦屈服应力比不考虑摩擦屈服应力低15%。关于所考虑的模型，由Tong和Wahlen开发的基于Zener-Hollomon参数和Hockett-Sherby型配方的方法提供了最佳的实验数据。
Due to the increasing number of body-in-white parts that are manufactured by hot forming of boron alloyed sheet metal (22MnB5), the demand for a virtual representation of this specific manufacturing process is evident. For a realistic simulation of hot stamping processes, the accurat emodeling of lthe flow stress as function of strain, strain rate and temperature is essential. In the last years, a large variety of empirical-analytical as well as physically based models for the yield stress has been proposed. Three existing models that have shown a good capability to represent the flow behavior of 22MnB5 in recent publications are presented and fitted to the experimental data. The underlying experimental data for the determination of the flow stress is obtained by stack compression tests, which were conducted in a high-speed deformation dilatometer. In a first step, the model parameters are fitted to the experimental flow curves without considering the friction, which inherently is present in a compression test. Sin ce the friction between die and specimen has significant influence on the state of stress within the speciment, an inverse, simulation-based approach for the determination of the model parameters is employed. For this purpose, a simple 2D FE model for each test configuration is set up. The resultin "friction-free" yield stress is up to 15% lower than the one without considering friction. Regarding the models considered, the approach developed by Tong and Wahlen, which is based on the Zener-Hollomon parameter and a Hockett-Sherby type formulation, provides the best fir of the experimental data.