New Insights into the Failure Front Phenomenon and the Equation of State of Soda-Lime Glass Under Planar Plate Impact
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RESEARCH PAPER
New Insights into the Failure Front Phenomenon and the Equation of State of Soda‑Lime Glass Under Planar Plate Impact S. Bauer1 · F. Bagusat1 · E. Strassburger1 · M. Sauer1 · S. Hiermaier1 Received: 9 June 2020 / Accepted: 27 August 2020 © The Author(s) 2020
Abstract A systematic study has been performed to gather more detailed experimental information on the equation of state and the Hugoniot elastic limit (HEL) of soda-lime glass as well as the failure front phenomenon. The key innovations of this study comprise experimental as well as analytical aspects. On the one hand, an extensive planar plate impact (PPI) test series has been carried out over a wide range of shock loading stress levels instrumented with two high-speed cameras and laser interferometers (PDV and VISAR). On the other hand, a systematic analysis concept has been developed and evaluated, including a combination of Lagrange diagrams with velocity profile data and a derivation of the equation of state together with an error estimation. Impact velocities ranged from 500 to 3000 m/s resulting in loadings of the soda-lime glass targets between 3.5 and 20.8 GPa. For stress levels between 3.5 and 6.7 GPa two high-speed cameras with 5 Mfps, positioned at the side and rear of the specimens, enabled the observation of shock waves and two different kinds of failure fronts. Therefore, visual information could be gathered not only in the purely elastic regime, but also in the transition region above 4 GPa and at stress levels beyond the HEL. The HEL of the soda-lime glass is determined to (5.0 ± 0.2)GPa . For the onset of an internal failure front a minimum longitudinal stress between 3.8 and 3.9 GPa is identified. The evaluated failure front velocities range from 800 to 2100 m/s. From the observed release response a minimum spall strength of 6.7 GPa and release wave velocities between 5740 and 9500 m/s are deduced. Keywords Soda-lime glass · Equation of state · Hugoniot data · Planar plate impact · High-speed video · Failure front
Introduction The continuous enhancement of ballistic threats poses permanently increasing requirements for the protective capabilities of armor systems. For military vehicles, for example the transparent parts of the armor should not present a weak point. In order to further improve transparent armor and support the development of new designs, it is essential to understand the response to shock loading. This can be achieved efficiently by combining ballistic tests with numerical simulations. Hereby, basic research experiments are used as input to establish the constitutive material models. The focus of this work is to gain new insights on the critical properties of soda-lime glass (SLG) during shock loading. SLG is a well-established material for the use in * S. Bauer [email protected] 1
Fraunhofer Institute for High Speed Dynamics, Ernst-MachInstitut, Ernst‑Zermelo Straße 4, 79104 Freiburg, Germany
transparent armor systems and has therefore been the subject of intensive research since decad
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