Showing papers by "Marc A. Meyers published in 2000"
TL;DR: In this article, a study of Haliotis rufescens (abalone) shells was carried out and the authors found that the abalone shell exhibited orientation dependence of strength, as well as significant strain-rate sensitivity; the failure strength at loading rates between 10×103 and 25×103 GPa/s was approximately 50% higher than the quasi-static strength.
360 citations
TL;DR: In this article, the authors investigated the damage evolution in silicon carbide by subjecting it to dynamic deformation in a compression Hopkinson-Kolsky bar (compressive stresses of 5 GPa), and a high-velocity impact under confinement (compressed stresses of 19-32 GPa) by a cylindrical tungsten alloy projectile.
122 citations
TL;DR: In this article, a pre-imposed modulation at the embedded Rayleigh-Taylor unstable interface was observed to grow and the growth rates were fluid-like at early time, but suppressed at later time.
Abstract: Experiments have been developed using high powered laser facilities to study the response of materials in the solid state under extreme pressures and strain rates. Details of the target and drive development required for solid-state experiments and results from two separate experiments are presented. In the first, thin foils were compressed to a peak pressure of 180 GPa and accelerated. A pre-imposed modulation at the embedded Rayleigh–Taylor unstable interface was observed to grow. The growth rates were fluid-like at early time, but suppressed at later time. This result is suggestive of the theory of localized heating in shear bands, followed by conduction of the heat into the bulk material, allowing for recovery of the bulk material strength. In the second experiment, the response of Si was studied by dynamic x-ray diffraction. The crystal was observed to respond with uni-axial compression at a peak pressure 11.5–13.5 GPa.
58 citations
TL;DR: In this article, a rotational mechanism is proposed and presented in terms of dislocation energetics, which necessitates the stages of high dislocation generation and their organization into elongated cells.
Abstract: The microstructural evolution inside shear bands was investigated experimentally and analytically. A fine recrystallized structure (grains with 0.05-0.3 mu m) is observed in Ti, Cu, 304 stainless steel, Al-Li, and Ta, and it is becoming clear that a recrystallization mechanism is operating. The fast deformation and short cooling times inhibit grain-boundary migration; it is shown that the time is not sufficient for migrational recrystallization. A rotational mechanism is proposed and presented in terms of dislocation energetics. This mechanism necessitates the stages of high dislocation generation and their organization into elongated cells. Upon continued deformation. the cells become sub-grains with significant misorientations. These elongated sub-grains break up into equiaxed grains with size of approximately 0.05-0.3 mu m. It is shown that grain-boundary reorientation can operate within the time of the deformation process.
29 citations
TL;DR: An X-ray drive has been developed to shock compress metal foils in the solid state using an internally shielded hohlraum with a high contrast shaped pulse from the Nova laser as discussed by the authors.
Abstract: An X-ray drive has been developed to shock compress metal foils in the solid state using an internally shielded hohlraum with a high contrast shaped pulse from the Nova laser. The drive has been characterized, and hydrodynamics experiments designed to study the growth of the Rayleigh-Taylor (R-T) instability in Cu foils at 3 Mbar peak pressures in the plastic flow regime have been started. Preimposed modulations with an initial wavelength of 20-50 μm and amplitudes of 1.0-2.5 μm show growth consistent with simulations. In the Nova experiments, the fluid and solid states are expected to behave similarly for Cu. An analytic stability analysis is used to motivate an experimental design with an Al foil where the effects of material strength of the R-T growth are significantly enhanced. The conditions reached in the metal foils at peak compression are similar to those predicted at the core of Earth.
9 citations
TL;DR: In this paper, the authors examined the shear-band initiation, propagation and spatial distribution in three different alloys ( stainless steel 304L, Ti, and Ti-6%Al-%V) through the radial collapse of a thick-walled cylinder under high-strain-rate deformation (∼10 4 s -1 ).
Abstract: Adiabatic shear bands self-organize themselves: this phenomenon was investigated in three different alloys ( stainless steel 304L, Ti, and Ti-6%Al-%V) through the radial collapse of a thick-walled cylinder under high-strain-rate deformation (∼10 4 s -1 ). This method was used to examine the shear-band initiation, propagation, as well as spatial distribution. The spacing of shear bands in the three materials varied widely and showed considerable differences during the initiation and propagation. Shear-band spacing is compared with the theories proposed by Grady and Kipp (momentum diffusion), Wright and Ockendon (perturbation), and Molinari (perturbation plus work hardening). Additionally, the effect of microstructural inhomogeneities on initiation is discussed. A discontinuous growth mode for shear localization under periodic perturbation is proposed based on two-dimensional growth considerations, not incorporated into the one-dimensional perturbation and momentum diffusion theories.
3 citations