Dynamic Tensile Characterization of Thin-Sheet Brittle Metallic Materials
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RESEARCH PAPER
Dynamic Tensile Characterization of Thin-Sheet Brittle Metallic Materials B. Sanborn 1 & M. Hudspeth 2 & B. Song 1 Received: 8 August 2019 / Accepted: 23 May 2020 # Sandia National Laboratories 2020
Abstract 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. Keywords Tungsten . Tensile behavior . Stress-strain . High rate . Refractory metals . Brittle materials
Introduction Refractory metals have exceptional mechanical properties under extreme conditions. The most common refractory metals include niobium, molybdenum, tantalum, tungsten, and rhenium and are used in industrial applications at elevated temperatures ranging from nuclear fusion [1] to jet engines [2]. At temperatures below but near the melting point, refractory metals exhibit high strength and ductility but become brittle at lower temperatures. As such, studies are often conducted to characterize the brittle-to-ductile transition temperature of these metals [3]. For typical applications, high temperature is treated as a normal environment for refractory metals.
* B. Sanborn [email protected] 1
Sandia National Laboratories, 1515 Eubank SE MS0557, Albuquerque, NM 87123, USA
2
Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545, USA
Therefore, the mechanical properties of such refractory metals at cold, or even room temperature, can be considered as an abnormal or atypical environment and thus have been seldom studied. For a metal designed to be used at elevated operating temperature, an abnormal environment could occur at ambient temperature, for example, when equipment is shut down but could be mechanically load
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