Showing papers by "Marc A. Meyers published in 1998"
TL;DR: In this article, the radial collapse of a thick-walled cylinder under high-strain-rate deformation was used for the investigation of shear-band initiation and pattern development in titanium.
107 citations
TL;DR: In this paper, a polycrystalline tungsten (less than 100 p.p.m. impurities) was subjected to different heat treatments to yield different grain morphologies and tested at quasi-static (3×10^(−3)) and dynamic (10^3-4×10/3/s) strain rates.
92 citations
TL;DR: In this article, the microstructural differences affected the microcracks propagation: either intergranular or transgranular fracture was observed, depending on the processing conditions, and the spacing between shear bands and the shear displacement within the shears were not significantly affected by the microstructure.
Abstract: Granular flow of comminuted ceramics governs the resistance for penetration of ceramic armor under impact. To understand the mechanism of the granular flow, silicon carbide was subjected to high-strain, high-strain-rate deformation by radial symmetric collapse of a thick-walled cylinder by explosive. The deformation, under compressive stresses, was carried out in two stages: the first stage prefractured the ceramic, while a large deformation was accomplished in the second stage. The total tangential strain (−0.23) was accommodated by both homogeneous deformation (−0.10) and shear localization (−0.13). Three microstructures, produced by different processing methods, were investigated. The microstructural differences affected the microcrack propagation: either intergranular or transgranular fracture was observed, depending on the processing conditions. Nevertheless, the spacing between shear bands and the shear displacement within the shear bands were not significantly affected by the microstructure. Within...
70 citations
TL;DR: Shih et al. as discussed by the authors used the Griffith fracture criterion and Weibull distribution of strength to predict break-up of large particles and plastic deformation of the smaller ones in silicon carbide powders.
61 citations
TL;DR: In this paper, a thermodynamically consistent kinetic theory of thermally activated structural changes is proposed for the shear band in both Ti-Si and Nb-Si mixtures, which includes martensitic phase transformations, plastic strain-induced chemical reactions and polymorphic transformations.
45 citations
TL;DR: In this article, temperature increases in shear localization regions can initiate chemical reaction inside a reac- tive powder mixture, and the reaction rate outside the shear bands, in homogeneously deformed material, which has a homogeneous deformation.
35 citations
TL;DR: In this paper, the problem of strain-induced chemical reaction (SICR) and structural changes (SCs) in a thin layer inside the shear band is formulated and solved for large strains.
23 citations
TL;DR: In this article, the authors show that shear bands can serve as ignition regions for the propagation of the reaction throughout the entire specimen for Ti-Si, whereas in the Nb-Si system (that has a much lower enthalpy of reaction), the reaction is always localized in the shear band.
Abstract: Chemical reactions in Ti–Si and Nb–Si powder mixtures were initiated in regions of high plastic strain induced by high-strain-rate deformation. These regions of high localized plastic strain had thicknesses of 10–25 μm and a characteristic spacing of 600–1000 μm. Scaling up of the experiments revealed a shear-band spacing that is constant and dictated by material and deformation parameters. The generation of heat due to plastic deformation and chemical reaction is treated in a one-dimensional calculation. The calculations are in qualitative agreement with experimental results: shear bands can serve as ignition regions for the propagation of the reaction throughout the entire specimen for Ti–Si, whereas in the Nb–Si system (that has a much lower enthalpy of reaction), the reaction is always localized in the shear bands. These results enable the estimation of a reaction time in the Ti–Si mixture (∼10 ms) and of a critical global strain required for the complete reaction to take place (eeff=0.38). This is a ...
16 citations
01 Nov 1998
TL;DR: In this article, an x-ray drive has been developed to shock compress metal foils in the solid state in order to study the material strength under high compression, and hydrodynamics experiments designed to study growth of the Rayleigh-Taylor instability in Cu foils at 3 Mbar peak pressures have been started.
Abstract: Summary -- An x-ray drive has been developed to shock compress metal foils in the solid state in order to study the material strength under high compression. The drive has been characterized and hydrodynamics experiments designed to study growth of the Rayleigh-Taylor (RT) instability in Cu foils at 3 Mbar peak pressures have been started. Pre-imposed modulations with an initial wavelength of 20-50 Ixm, and amplitudes of 1.0-2.5 ~tm show growth consistent with simulations. In this parameter regime, 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 AI foil where the effects of material strength on the RT growth are significantly enhanced. Improved x-ray drive design will allow the material to stay solid under compression throughout the experiment, and dynamic diffraction techniques are being developed to verify the compressed state. © 1999 Elsevier Science Ltd. All rights reserved.
1 citations