Refractory metals are favorable materials in applications where high strength and ductility are needed at elevated temperatures. In some cases, operating temperatures may be near the melting point of the material. However, as temperature drops, refractory metals typically undergo a significant mechanical response change - ductile-to-brittle transition. These materials may be subjected to high strain rate loading at an ambient temperature state, such as an impact or crash. Knowledge of the high rate material properties are essential for design as well as simulation of impact events. The high rate stress-strain behavior of brittle metallic materials at ambient temperature is rarely studied because of experimental challenges, particularly when failure is involved. Failure typically occurs within the non-gage section of the material, which invalidates any collected stress-strain information. In this study, a method to determine a specimen geometry which will produce failures in the gage section is presented. Pure tungsten in thin-sheet form was used as a trial material to select a specimen geometry for high rate Kolsky tension bar experiments. A finite element simulation was conducted to derive a strain correction for more accurate results. The room temperature stress-strain behavior of pure tungsten at a strain rate of 24 s−1 is presented. The outcome of this experimental technique can be applied to other brittle materials for dynamic tensile characterization.

中文翻译：

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薄板脆性金属材料的动态拉伸特性

在高温下需要高强度和延展性的应用中，难熔金属是有利的材料。在某些情况下，操作温度可能接近材料的熔点。然而，随着温度的下降，难熔金属通常会发生显着的机械响应变化——韧性到脆性的转变。这些材料可能会在环境温度状态下承受高应变率载荷，例如撞击或碰撞。了解高速率材料特性对于设计和模拟撞击事件至关重要。由于实验挑战，特别是在涉及失效时，很少研究脆性金属材料在环境温度下的高速率应力应变行为。失效通常发生在材料的非规格部分，这会使任何收集的应力应变信息无效。在这项研究中，提出了一种确定试样几何形状的方法，该几何形状将在量具截面中产生故障。薄板形式的纯钨被用作试验材料，以选择用于高速率 Kolsky 拉杆实验的试样几何形状。进行了有限元模拟以获得更准确的结果的应变校正。呈现了应变速率为 24 s-1 时纯钨的室温应力-应变行为。这种实验技术的结果可以应用于其他脆性材料的动态拉伸表征。薄板形式的纯钨被用作试验材料，以选择用于高速率 Kolsky 拉杆实验的试样几何形状。进行了有限元模拟以获得更准确的结果的应变校正。展示了纯钨在 24 s-1 应变速率下的室温应力应变行为。这种实验技术的结果可以应用于其他脆性材料的动态拉伸表征。薄板形式的纯钨被用作试验材料，以选择用于高速率 Kolsky 拉杆实验的试样几何形状。进行了有限元模拟以获得更准确的结果的应变校正。呈现了应变速率为 24 s-1 时纯钨的室温应力-应变行为。这种实验技术的结果可以应用于其他脆性材料的动态拉伸表征。