Experiments have shown that for quasi-static and moderate strain-rates (of the order of 102–103/s) the mechanical response of additively manufactured (AM) and traditionally processed high-strength steels is similar whereas the impact behavior is markedly different. In this paper, we reveal that the main reason for this difference is the retained porosity in the AM material. Fully-implicit finite element calculations are presented in which we simulate both the launching of the impact plate and the impact between the two plates. The constitutive model used is the elastic/plastic model for porous ductile materials with matrix displaying tension-compression asymmetry and Johnson-Cook hardening law that accounts for both strain-rate effects and plastic history. It is shown that even a very small initial porosity changes the wave front, decreases the Hugoniot while increasing the shock rise time, when compared to a void free material. Furthermore, quantitative comparisons between simulation results and plate impact data for both the AM and the wrought AF9628 steel are provided. The good agreement show that the model captures the impact response and illustrates the model capabilities to provide information on field variables that cannot be directly measured.

中文翻译：

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关于孔隙率对增材制造高性能钢冲击响应的影响：实验、本构模型和有限元预测


实验表明，对于准静态和中等应变率（大约 102-103/s），增材制造 （AM） 和传统加工高强度钢的机械响应相似，而冲击行为明显不同。在本文中，我们揭示了这种差异的主要原因是增材制造材料中保留的孔隙率。提出了完全隐式的有限元计算，其中我们模拟了冲击板的发射和两块板之间的冲击。使用的本构模型是多孔延性材料的弹性/塑性模型，其基体显示拉伸-压缩不对称性和 Johnson-Cook 硬化定律，该定律同时考虑了应变率效应和塑性历史。结果表明，与无空隙材料相比，即使是非常小的初始孔隙率也会改变波前，降低 Hugoniot，同时增加冲击上升时间。此外，还提供了增材制造和锻造 AF9628 钢的模拟结果和板材冲击数据之间的定量比较。良好的一致性表明，该模型捕获了影响响应，并说明了模型提供无法直接测量的场变量信息的能力。