• PDF / 8,568,749 Bytes
• 21 Pages / 608.4 x 786 pts Page_size
• 90 Downloads / 269 Views

DOWNLOAD

REPORT

---

8/11/04

3:47 AM

Page 2587

Materials Science Under Extreme Conditions of Pressure and Strain Rate B.A. REMINGTON, G. BAZAN, J. BELAK, E. BRINGA, M. CATURLA, J.D. COLVIN, M.J. EDWARDS, S.G. GLENDINNING, D.S. IVANOV, B. KAD, D.H. KALANTAR, M. KUMAR, B.F. LASINSKI, K.T. LORENZ, J.M. McNANEY, D.D. MEYERHOFER, M.A. MEYERS, S.M. POLLAINE, D. ROWLEY, M. SCHNEIDER, J.S. STÖLKEN, J.S. WARK, S.V. WEBER, W.G. WOLFER, B. YAAKOBI, and L.V. ZHIGILEI Solid-state dynamics experiments at very high pressures and strain rates are becoming possible with highpower laser facilities, albeit over brief intervals of time and spatially small scales. To achieve extreme pressures in the solid state requires that the sample be kept cool, with Tsample  Tmelt. To this end, a shockless, plasma-piston “drive” has been developed on the Omega laser, and a staged shock drive was demonstrated on the Nova laser. To characterize the drive, velocity interferometer measurements allow the high pressures of 10 to 200 GPa (0.1 to 2 Mbar) and strain rates of 106 to 108 s1 to be determined. Solid-state strength in the sample is inferred at these high pressures using the Rayleigh-Taylor (RT) instability as a “diagnostic.” Lattice response and phase can be inferred for single-crystal samples from time-resolved X-ray diffraction. Temperature and compression in polycrystalline samples can be deduced from extended X-ray absorption fine-structure (EXAFS) measurements. Deformation mechanisms and residual melt depth can be identified by examining recovered samples. We will briefly review this new area of laser-based materials-dynamics research, then present a path forward for carrying these solid-state experiments to much higher pressures, P  103 GPa (10 Mbar), on the National Ignition Facility (NIF) laser at Lawrence Livermore National Laboratory.

I. INTRODUCTION

HIGH-STRAIN-RATE materials dynamics and solid-state deformation mechanisms have been a topic of great interest for decades.[1–8] Materials response to shocks and other highstrain-rate deformation has led to a number of theories, both empirical and, more recently, physically based. There is a particular interest in developing and testing constitutive models that allow continuum hydrodynamic computer codes to simulate plastic flow in the solid state. Models such as the Johnson–Cook,[9] Zerilli–Armstrong,[10,11] mechanical threshold stress (MTS),[12] thermal-activation–phonon-drag,[13,14] Steinberg– Lund,[15] and Steinberg–Guinan[16] models are widely used in the materials-dynamics community. These models have typically been tested and “calibrated” with experiments on Hopkinson

B.A. REMINGTON, G. BAZAN, J. BELAK, E. BRINGA, J.D. COLVIN, M.J. EDWARDS, S.G. GLENDINNING, D.H. KALANTAR, M. KUMAR, B.F. LASINSKI, K.T. LORENZ, J.M. McNANEY, S.M. POLLAINE, D. ROWLEY, J.S. STÖLKEN, S.V. WEBER, and W.G. WOLFER are with the Lawrence Livermore National Laboratory, Livermore, CA. Contact e-mail: [email protected] M. CATURLA is with the Department of Applied Physics, Alicante, Spain. D.S. IVANOV and L.V. ZHIGILEI a