Pressure-Shear Plate Impact Experiments on High-Purity Aluminum at Temperatures Approaching Melt Grunschel, Stephen E. creator 2009 21, 163 p. born digital Thesis (Ph.D.) -- Brown University (2009) Clifton, Rodney director Kim, Kyung-Suk reader Briant, Clyde reader Brown University. Division of Engineering. Mechanics of Solids sponsor theses High-temperature, pressure-shear plate impact experiments were conducted in order to measure the plastic response of high-purity aluminum at high strain rates (106 s-1) and at temperatures approaching melt. In similar experiments by Frutschy and Clifton (JMPS 46, 1998, 1723-1743) on OFHC copper, the flow stress decreases with increasing temperature and increases with increasing strain rate over the full range of temperatures and strain rates examined. No conclusive evidence of a change in rate-controlling mechanism was obtained. In the current study, temperatures that are larger fractions of the melting temperature were accessible because of the lower melting point of aluminum. Because 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. Again, no conclusive evidence of a change in rate-controlling mechanism was obtained. The measured shearing resistance was remarkably large (~50 MPa at a shear strain of 2.5) for temperatures this near melt. Numerical simulations of the high-temperature plate impact experiments show that heat conduction can affect the sample temperature significantly, despite the short duration of the test (~2 µs). Simulations conducted using a version of the Nemat-Nasser/Isaacs constitutive equation (Acta Materialia 45(3), 1997, 907-919), modified to model the mechanism of geometric softening, appears to capture adequately the hardening/softening behavior observed experimentally. high-temperature high strain-rate AluminumHigh temperatures RPB 20091218 engEnglish10.7301/Z0S180XPIn CopyrightCollection is open for research.dissertations