Bulletin of the American Physical Society
16th APS Topical Conference on Shock Compression of Condensed Matter
Volume 54, Number 8
Sunday–Friday, June 28–July 3 2009; Nashville, Tennessee
Session B5: ID-1: Shock Response of Aluminum |
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Chair: Eric Herbold, Georgia Institute of Technology Room: Magnolia Ballroom |
Monday, June 29, 2009 9:00AM - 9:15AM |
B5.00001: Elastic Wave Amplitude and Attenuation in Shocked Pure AL J.M. Winey, P.B. Trivedi, B.M. LaLone, Y.M. Gupta, R.F. Smith, J.H. Eggert, G.W. Collins Shock-induced elastic-plastic deformation in pure aluminum was examined at 4 GPa peak stress by measuring wave profiles in thin (40$-$180 $\mu$m) samples under plate impact loading. Large elastic wave amplitudes ($\sim$1 GPa) and rapid elastic wave attenuation with propagation distance were observed, indicating a time-dependent elastic-plastic response. These results are in contrast to the $\sim$0.1 GPa elastic wave amplitudes observed in past work (\textit{J. Appl. Phys.} \textbf{98}, 033524 (2005)) using thick ($>$1 mm) samples. The combination of large elastic wave attenuation in thin samples and differences in sample thicknesses between the present and past work suggests a consistent picture of shock wave propagation in pure aluminum: manifestations of time-dependent elastic-plastic response are confined to material very near the impact surface. The present results cannot be fully reconciled with recent shockless compression results (\textit{Phys. Rev. Lett.} \textbf{98}, 065701 (2007)). Work supported by DOE. [Preview Abstract] |
Monday, June 29, 2009 9:15AM - 9:30AM |
B5.00002: Constitutive Model Constants for Al7075-T651 and Al7075-T6 Nachhatter Brar, Vasant Joshi, Bryan Harris Aluminum 7075-T651 and 7075-T6 are characterized at quasi-static and high strain rates to determine Johnson-Cook (J-C) strength and fracture model constants. Constitutive model constants are required as input to computer codes to simulate projectile (fragment) impact or similar impact events on structural components made of these material. J-C strength model constants (A, B, n, C, and m) for the two alloys are determined from tension stress-strain data at room and high temperature to 250$^{\circ}$C. J-C strength model constants for Al7075-T651 are: A=527 MPa, B=676 MPa, n=0.71, C=0.017, and m=1.61 and for Al7075-T6: A = 546 MPa, B = 674 MPa, n = 0.72, C = 0.059, and m =1.56. J-C fracture model constants are determined form quasi-static and high strain rate/high temperature tests on notched and smooth tension specimens. J-C fracture model constants for the two alloys are: Al7075-T651; D$_{1}$ = 0.110, D$_{2 }$= 0.573, D$_{3}$= -3.4446, D$_{4 }$= 0.016, and D $_{5}$= 1.099 and Al7075-T6;~D$_{1}$= 0.451 D$_{2}$= -0.952 D$_{3}$= -.068, D$_{4 }$=0.036, and D$_{5 }$= 0.697. [Preview Abstract] |
Monday, June 29, 2009 9:30AM - 9:45AM |
B5.00003: High Strain-Rate Response of High-Purity Aluminum at Temperatures Approaching Melt Stephen Grunschel, Rodney Clifton, Tong Jiao High-temperature, pressure-shear plate impact experiments were conducted to investigate the rate-controlling mechanisms of the plastic response of high-purity aluminum at high strain rates (10$^{6}$ s$^{-1})$ and at temperatures approaching melt. Similar experiments were conducted by Frutschy and Clifton (\textit{JMPS }\textbf{46, }1998, 1723-1743) on OFHC copper. In the current study, temperatures that are larger fractions of the melting temperature were accessible because of the lower melting point of aluminum. Since the melting temperature of aluminum is pressure dependent, and a typical pressure-shear plate impact experiment subjects the sample to large pressures (2 GPa -- 7 GPa), a pressure-release type experiment was used to reduce the pressure in order to measure the shearing resistance at temperatures up to 95{\%} of the current melting temperature. The measured shearing resistance was remarkably large ($\sim $50 MPa at a shear strain of 2.5) for temperatures this near melt. Numerical simulations conducted using a version of the Nemat-Nasser/Isaacs constitutive equation (\textit{Acta Materialia} \textbf{45}(3), 1997, 907-919), modified to model the mechanism of geometric softening, appears to capture adequately the hardening/softening behavior observed experimentally. [Preview Abstract] |
Monday, June 29, 2009 9:45AM - 10:00AM |
B5.00004: The Effect of Heat Treatment on the Shock Response of the Aluminium Alloy 6061 Ming Chu, Ian Jones, Jeremy Millett, Neil Bourne, Rusty Gray The mechanical response of aluminium alloys such as 6061 is manipulated through heat treatment to create a fine distribution of intermetallic particles. Post shock recovered microstructures of similar alloys has shown that in the solution treated (T0) state, with all alloy additions dissolved in the aluminium, deformation occurs via the formation of dislocation cells, in a similar manner to other face centred cubic metals such as copper or nickel. Further, a significant post shock hardening has also been observed, in agreement with the observed increase in dislocation density. In contrast, in the fully aged (T6) material, deformation occurs results in a random distribution of dislocations, with no enhanced hardening. From these previous observations, it is expected that the variation of shock induced shear strength, both with shock amplitude and pulse duration will be significantly different between the two heat treated states, and thus it is these features that this investigation addresses. [Preview Abstract] |
Monday, June 29, 2009 10:00AM - 10:15AM |
B5.00005: The Shock Response of the Magnesium--Aluminium Alloy, AZ6 Jeremy Millett, Neil Bourne, Stewart Stirk, Rusty Gray The response of the magnesium alloy, AZ61 to shock loading has been investigated in terms of it's Hugoniot (Equation of State) and variation of shear strength with impact stress. Comparison of the Hugoniot with that of the similar magnesium alloy AZ31 shows very little difference, and hence gives us confidence in our results. Measurement of the lateral stress shows a decrease behind the shock front which suggests a degree of time dependent hardening. Similar results have been observed in fcc metals, corresponding to observed increases in dislocation density in recovered samples. British Crown Copyright MOD/2009. [Preview Abstract] |
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