Dynamic Behavior of Metals at Elevated Temperatures and Ultra-High Strain Rates†
AbstractThis paper presents the results of a series of reverse geometry normal plate impact experiments designed to investigate the onset of incipient plasticity in commercial purity polycrystalline magnesium (99.9%) under weak uniaxial-strain shock compression loading and elevated temperatures up to the melting point of magnesium. To enable the characterization of dynamic material behavior under extreme conditions, i.e., ultra-high strain rates (~106/s) and test temperatures up to sample melt (1000 °C), strategic modifications were made to the single-stage gas-gun facility at the Case Western Reserve University. In this configuration, thin metal samples (also representing the flyer plate), carried by a specially designed heat-resistant sabot, are heated uniformly across the diameter in a 100 mTorr vacuum prior to impact by a resistance coil heater at the breech end of the gun barrel. Moreover, a compact fiber-optics-based heterodyne normal displacement interferometer is designed and implemented to measure the normal component of the particle velocity history at the free surface of the target plate. Similar to the standard photonic Doppler velocimetry (PDV), this diagnostic tool is assembled using commercially available telecommunications hardware and uses a 1550-nm wavelength 2 W fiber-coupled laser, an optical probe and single mode fibers to transport light to and from the target. Using this unique approach, normal plate impact experiments are conducted on preheated (room temperature to near the melting point of magnesium) 99.9% polycrystalline magnesium using Inconel 718 target plates at impact velocities of 100–110 m/s. As inferred from the measured normal particle velocity history, the stress at the flyer/target interface shows progressive weakening with increasing sample temperatures below the melting point. At higher test temperatures, the rate of material softening under stress is observed to decrease and even reverse as the sample temperatures approach the melting point of magnesium samples. Scanning electron microscopy is utilized to understand the evolution of sample material microstructure including twinning following the impact event.
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Wang, T.; Zuanetti, B.; Prakash, V. Dynamic Behavior of Metals at Elevated Temperatures and Ultra-High Strain Rates. Proceedings 2018, 2, 372.
Wang T, Zuanetti B, Prakash V. Dynamic Behavior of Metals at Elevated Temperatures and Ultra-High Strain Rates. Proceedings. 2018; 2(8):372.Chicago/Turabian Style
Wang, Tianxue; Zuanetti, Bryan; Prakash, Vikas. 2018. "Dynamic Behavior of Metals at Elevated Temperatures and Ultra-High Strain Rates." Proceedings 2, no. 8: 372.