Bulletin of the American Physical Society
2005 14th APS Topical Conference on Shock Compression of Condensed Matter
Sunday–Friday, July 31–August 5 2005; Baltimore, MD
Session S3: Materials Science IV: Dynamic Effects I |
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Chair: Naresh Thadhani, Georgia Institute of Technology Room: Hyatt Regency Constellation D |
Thursday, August 4, 2005 9:30AM - 9:45AM |
S3.00001: The Influence of Interstitial Oxygen on the Alpha to Omega Phase Transition in Titanium and Zirconium Ellen Cerreta, George Gray, Angus Lawson, Chuck Morris, Robert Hixson, Paulo Rigg The pressure for the $\alpha $ to $\omega $ phase transition was investigated for two grades of titanium and three grades of zirconium. A series of shock experiments were conducted from 5 to 35GPa and revealed that the pressure for the phase transition increases with increasing interstitial oxygen content and is completely suppressed in low purity materials. For the high purity Ti and Zr in this study, the pressure for the phase transition occurred at 10.4 and 7.1GPa, respectively and no reverse transformation was observed upon unloading. Increasing the oxygen content increases the number of octahedral sites occupied; this is postulated to increase the pressure for the phase transition. Neutron diffraction and TEM were utilized to quantify the volume fraction of metastable $\omega $ phase and to characterize the microstructures within the high purity, shocked, and ``soft'' recovered specimens. Quasi-static reload experiments examined the effect of the shocked-induced substructure on post-shock mechanical properties. The reload response of materials shock prestrained above the $\alpha $ to $\omega $ phase transition displays enhanced hardening, while specimens shocked below the transition pressure do not when compared to their quasi-static constitutive behavior. [Preview Abstract] |
Thursday, August 4, 2005 9:45AM - 10:00AM |
S3.00002: The Taylor impact and high strain-rate response of poly(chlorotrifluoroethylene) PCTFE, poly(ether-etherketone) PEEK and Kel-F 800 Philip Rae, Eric Brown, George (Rusty) Gray III The mechanical properties of PCTFE, PEEK and Kel-F 800 have been investigated over a range of temperatures using both the Taylor impact geometry and Hopkinson bars. PCTFE and PEEK are both industrially important polymers. Kel-F 800 (comprising 75wt\% PCTFE and 25wt\% poly(vinylidene fluoride) PVDF) was a 3M product that is still used as a binder material in polymer bonded explosives. Compression and tensile Hopkinson bars have been used to generate stress vs. strain data over a range of temperatures for each polymer. Additionally, quasi-static tension and compression data has been collected with respect to strain-rate and temperature for comparison. The Taylor impact geometry has been used to study the ballistic response. High-speed photography was used to quantify sample deformation as a function of time. In each material, a transition velocity is identified between a ductile plastic response involving sample bulging and a brittle response initiated by cracking. Post-shot microscopy has been undertaken to elucidate failure mechanisms. [Preview Abstract] |
Thursday, August 4, 2005 10:00AM - 10:15AM |
S3.00003: Investigating Incipiently Spalled Tantalum through Multiple Section Planes and Serial Sectioning Benjamin Henrie, Thomas Mason, John Bingert Shock wave interactions within a material create a three-dimensional damage field of voids and/or strain localizations. Flyer plate and high explosive experiments were performed on high purity tantalum to improve the understanding of void and strain localization interactions. Using a miniature high explosive experiment seven identical shots were performed to test the reproducibility of incipient spallation experiments. These experiments along with flyer plate experiments demonstrated that multiple section planes are required to accurately quantify the damage within a specimen. To further understand the three-dimensional nature of incipient spallation, serial sectioning was performed on a 5.6 GPa flyer plate experiment. Serial sectioning is yielding void and strain localization interactions not available in a two-dimensional slice. [Preview Abstract] |
Thursday, August 4, 2005 10:15AM - 10:30AM |
S3.00004: DRX-Induced Solid-State Flow and Projectile-Target Mixing During [001] Single-Crystal Tungsten Rod Penetration into Steel Targets Carlos Pizana, L.E. Murr, I.A. Anchondo, C.Y. Pina, M.T. Baquera, T.L. Tamoria, H.C. Chen, Sheldon Cytron Residual [001] single-crystal W penetrators have been examined by light and electron microscopy. The post-impact residual penetrators examined using energy-dispersive x-ray mapping, revealed target and penetrator mechanical mixing. Considerable intercalation activity was found to concentrate specifically within the material being eroded by DRX-assisted flow. The solid-state flow features including shear bands facilitate the mixing of the two. Peripherally along the head of the penetrator and adjacent to the shear band itself, large bands of high Ni steel appear to influence the solid-state flow of the penetrator. Residual microstructures obtained within the penetrator suggest localized melt zones due to thermal instabilities caused by the turbulent behavior in the high-pressure regime. Supported by the U.S. Army TACOM-Picatinny Arsenal. [Preview Abstract] |
Thursday, August 4, 2005 10:30AM - 10:45AM |
S3.00005: High-Rate Compaction of Aluminium Alloy Foams J.J. Harrigan, Y.C. Hung, P.J. Tan, N.K. Bourne, P.J. Withers, S.R. Reid, J.C.F. Millett, A.M. Milne The response of aluminium foams to impact can be categorised by the impact velocity. Tests are reported ranging from quasi-static to impact velocities greater than the speed of sound in the foam. The techniques used ranging from drop-hammer and pneumatic launcher tests, to plate impact at velocities greater than 1000 m s-1. The quasi-static compression behaviour was elastic, perfectly-plastic, locking. For static and dynamic compression at low impact velocities, post-impact examination of partially crushed specimens showed that deformation was through the cumulative multiplication of crush bands. If the impact velocity is less than the velocity of sound, but above a certain critical impact velocity, the plastic compression occurs in a shock-like manner and the specimens deform by progressive cell crushing. At higher impact velocities the compaction front is not preceded by an elastic wave. Laboratory X-ray microtomography has been employed to acquire tomographic datasets of aluminium foams before and after tests. The morphology of the underformed foam was input as the input dataset to an Eulerian code. Hydrocode simulations were then carried out on real microstructure. These simulations provide insight to mechanisms associated with the localization of deformation. [Preview Abstract] |
Thursday, August 4, 2005 10:45AM - 11:00AM |
S3.00006: Dynamic Mechanical Behavior of Nickel-Aluminum Reinforced Epoxy Composites Morgana Martin, Sathyanaraya Hanagud, Naresh Thadhani Epoxy-based composites reinforced with a mixture of micron-sized Ni and micron or nano-sized Al powders were fabricated as bulk materials by cast/curing. The structural/mechanical behavior of these materials was evaluated using elastic and plastic property measurements via static and dynamic compression tests performed on rod shaped samples. Reverse Taylor anvil-on-rod impact tests combined with velocity interferometry gave qualitative and quantitative information about the transient deformation and failure response of the composites. The material containing 20wt{\%} epoxy and nano-sized Al powder showed the most superior mechanical properties in terms of elastic modulus, and static and dynamic compressive strength, and strain before fracture, as compared to the other reinforced cast materials. The results illustrate that nano-sized Al particles provide significant enhancement to strength of epoxy composites by dispersing in the epoxy and generating a nano-Al containing epoxy matrix with embedded Ni particles. Funding for this research was provided by AFOSR/MURI Grant No. F49620-02-1-0382. [Preview Abstract] |
Thursday, August 4, 2005 11:00AM - 11:15AM |
S3.00007: Substructure Evolution in Energetic-Driven Spherically Shock-Loaded Copper L. Sinisyna, S. Novikov, G.T. Gray, E. Cerreta, B.L. Henrie, M.F. Lopez, C.A. Yablinsky Post-shock-recovered metallurgical analysis of solid metal spheres shock loaded via spherical energetic(HE) loading provides a unique opportunity to quantify the substructure evolution in a material subjected to converging Taylor-wave (triangular-shock pulse) loading. In this paper detailed quantitative metallographic, orientation-imaging microscopy (OIM), and texture analysis is presented characterizing the gradient in substructure generated in Cu subjected to a spherical HE shock loading pulse at VNIIEF. The substructure in the recovered sphere is seen to include: 1) a spherical cavity generated in the center of the sphere due to shock-wave convergence and release, displaying ductile dimpled failure and no evidence of melting, 2) a gradient in deformation (slip and deformation twins) from the center outward to the highest defect density at the surface of the sphere consistent with the gradient in the calculated shock loading peak pressure, and 3) numerous shear cracks and/or spall planes. The substructure evolution is discussed relative to that previously observed in Cu shock prestrained via either 1-D triangular-shaped shockwave loading or 1-D square-topped pulse shock loading. [Preview Abstract] |
Thursday, August 4, 2005 11:15AM - 11:30AM |
S3.00008: Investigation of Shock-Induced Reaction in a Ni+Al Powder Mixture D.E. Eakins, N.N. Thadhani We will present initial results on the study of the effect of powder microstructure on the reaction response of nickel and aluminum mixtures. The shock-compression and reaction response of equi-volumetric micron-scale ($\sim $50-60{\%} dense) nickel and aluminum powder mixtures is investigated in the range of the crush-up pressure (P = 0.5 GPa) and up to 10 GPa. Time resolved stress measurements (using PVDF gauges) coupled with VISAR data is used to determine the shock states. Evidence of reaction or lack thereof is inferred by comparing the measured states with calculated hugoniot state of reaction products based on the ballotechnic model proposed by Bennett and Horie, (Shock Waves 4:127-136). Post-impact microstructural analysis of recovered material and comparison of calculated and measured product states is used to establish the criterion for reaction occurring in the shock or post-shock states. Funding for this research was provided by AFOSR/MURI Grant No. F49620-02-1-0382. [Preview Abstract] |
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