Bulletin of the American Physical Society
21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 64, Number 8
Sunday–Friday, June 16–21, 2019; Portland, Oregon
Session N5: BIEP: Spall II |
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Chair: Justin Wilkerson, TAMU Room: Broadway I/II |
Wednesday, June 19, 2019 9:15AM - 9:45AM |
N5.00001: Spall and re-compaction in OFHC copper under high velocity impact Invited Speaker: M. Cameron Hawkins A research project to study spall and subsequent re-compaction of oxygen-free high thermal conductivity (OFHC) copper has begun using a single stage large bore (76.2 mm) light gas gun capable of planar impacts. This work was motivated by the recent results from Turley et. al$^{\mathrm{1}}$ using explosive drive, and the previous research of Becker et. al$^{\mathrm{2}}$. Gun experiments were done to produce an initial spall in the target with a re-compaction occurring to close the spall damage/layer (i.e. void closure) by use of a layered flyer plate. Symmetric spall experiments at similar conditions were also conducted as a control to the re-compaction experiments. Photonic Doppler Velocimetry (PDV)$^{\mathrm{3}}$ was used to obtain the velocity history of the back surface of the target, for analysis and comparison with numerical simulations. The copper targets were recovered for eventual analysis of the resulting microstructure using optical imaging microscopy (OIM) and Electron Backscatter Diffraction (EBSD). A re-compaction wave was clearly observed in the PDV data obtained at the back surface of the copper target. A metallurgical feature was also observed in the recovered samples. Time-resolved data will be presented and discussed, as will the microstructural analyses of the recovered samples. Investigating the phenomenon of re-compaction will provide a better understanding of material deformation and can be used to improve the available numerical simulation codes. 1. Turley, W.D., et al., Explosive-induced shock damage in copper and recompression of the damaged region, J. App. Phy. 120, 085904 (2006). 2. Becker, R., et al., Characterization of recompressed spall in copper gas gun targets, J. App. Phy. 102, 093512 (2007). 3. Strand O.T., et al., Compact system for high-speed velocimetry using heterodyne techniques. Review of Scientific Instruments. 77, 083108 (2006). This work was done by MSTS LLC, under Contract No. DE-NA0003624 with the US DOE, and supported by the SDRD Program. DOE/NV/03624---0387. [Preview Abstract] |
Wednesday, June 19, 2019 9:45AM - 10:00AM |
N5.00002: Shock structure and spall behavior of porous aluminum Zev Lovinger, Christian Kettenbeil, Suraj Ravindran, Guruswami Ravichandran, Christophe Czarnota, Alain Molinari Porous materials under shock and impact loading present significant potential for energy absorption and shock mitigation in various applications. Furthermore, additively manufactured materials which feature inherent levels of porosity due to the manufacturing process are increasingly used in shock applications. In this work, we have manufactured porous 6061 aluminum samples with different levels of porosity, by a modified process of 3D printing. To achieve pores smaller than the 3D printing resolution (\textless 50$\mu $m), the printing parameters were altered to control the pore sizes, resulting in porosities between 2{\%}-10{\%}. Plate impact experiments were conducted on these materials at pressures in the range of 3 to10 GPa for which the free surface velocity was measured using a PDV. The experiments were designed to extract both the shock structure properties and spall behavior. The structure of the steady shock was characterized as a function of porosity and compared with a recent analytical model. The spall behavior was found to change significantly with increasing levels of porosity. Finally, mesoscale modeling has been carried out, to study and examine the mechanisms underlying the observed phenomena. [Preview Abstract] |
Wednesday, June 19, 2019 10:00AM - 10:15AM |
N5.00003: Nucleation and Growth of Voids in Shock Loaded Copper Bicrystals Elizabeth Fortin, Benjamin Shaffer, Saul Opie, Matthew Catlett, Pedro Peralta Understanding the evolution of damage and deformation due to spall at grain boundaries can provide a basis for connecting micro- to macroscale failure behavior in metals under extreme conditions. Bicrystal samples were shock loaded using flyer-plated via light gas gun with pressures ranging from 3–5 GPa. Pulse duration as well as crystal orientation along the shock direction were varied for a fixed boundary misorientation to determine thresholds for void nucleation and coalescence as functions of these parameters. Samples were soft recovered and cross-sectioned to perform damage characterization using electron backscattering diffraction and Scanning Electron Microscopy to gather information on damage characteristics at and around the GB, with emphasis on void growth and lattice rotation around boundary and bulk voids. Chemistry and composition analysis were also performed on samples to determine if trace elements present in a sample affected the threshold for void nucleation. Initial results show that the kinetics of damage growth at the boundary are strongly affected by stress level and impurities, and that damage grows faster at the boundary compared to the bulk of the grains as pressure increases. [Preview Abstract] |
Wednesday, June 19, 2019 10:15AM - 10:30AM |
N5.00004: Shock Propagation and Spall Behaviour of Ceramic-doped Polyurea Composites. Andrew Oddy, Anton Lebar, Rafaela Aguiar, Oren Petel The use of polyurea retrofitting of building interiors to improve survivability from blast effects has increased in recent years due to its high tensile strength and strain to failure. Prior research has shown that the addition of some particle reinforcements to high toughness polymers results in an increase in the tensile strength under quasi-static loading conditions. In the present study, ceramic powders are added to polyurea at various concentrations to study the effects of volume fraction and particle shape on the spall strength and shock propagation through the polyurea matrix. The ceramic powder shape is determined using SEM, Fourier Transform Infrared Spectroscopy is used to measure the degree of chemical adhesion between the ceramic particles and the polyurea matrix. The composites were characterized through shock propagation and spall experiments using the Carleton University single-stage gas gun and its multi-channel Photonic Doppler Velocimetry system. [Preview Abstract] |
Wednesday, June 19, 2019 10:30AM - 10:45AM |
N5.00005: Void growth in ductile materials Laurianne Pillon, Laurent Soulard Breaking in ductile materials occurs by nucleation, growth and coalescence of voids. Several models aim at describing the evolution of cavities by accounting for different properties. Influence of linear elasticity [1], compressibility [2], viscoplasticity [3], triaxiality [4] have been inspected. Inertial effects are supposed to play an important role at high strain rates [1]. In this study, we propose to develop an extension of an existing model [2] in order to account for inertial effects and compressibility in a linear elastic and viscoplastic material. We compare the results of the model to the behavior of a hollow sphere described by a hydrocode (Finite Volume). The material is supposed to be elastic viscoplastic. We found a good agreement in a large range of solicitations. We measure the influence of each contribution (linear elasticity, viscoplasticity, compressibility, inertial effects) on the overall behavior of the hollow sphere and for different materials. References [1] M. N. Carroll and A. C. Holt, J. Appl. Phys., 43, p. 1626 (1972) [2] C. Denoual and J.M. Diani, Schock Compression of condensed Matter, (2001) [3] J. N. Johnson, J. Appl. Phys., 52, p. 2812-2825, (1981) [4] A.L. Gurson, J. Eng. Mater. Technol, 99, pp 2-15, (1977) [Preview Abstract] |
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