Viscosity measurements on metal melts at high pressure and viscosity calculations for the earth's core

Минеев, В. П.; Funtikov, A. I.

doi:10.1070/pu2004v047n07abeh001746

Cited by 34 publications

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“…This implies that at sufficiently high pressures, geophysical materials might vitrify at the melting point, suggesting that parts of the earth's core [94] or lower mantle [95] are in the glassy state. Of course, such conclusions are speculative, given the absence of direct measurements [96,97].…”

Section: Discussionmentioning

confidence: 99%

Connection between dynamics and thermodynamics of liquids on the melting line

Fragiadakis

Roland

2011

Phys. Rev. E

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for a large number of non-associating liquids. Rigid, spherical molecules containing no polar bonds have Γ=γ; consequently, the reduced relaxation time, viscosity and diffusion coefficient are each constant along the melting line. For other liquids γ>Γ always; i.e., the dynamics is more sensitive to volume than is the melting point, and for these liquids the dynamics at the melting point slows down with increasing T m (that is, increasing pressure). ______________________________________________________________________

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Section: Discussionmentioning

confidence: 99%

Connection between dynamics and thermodynamics of liquids on the melting line

Fragiadakis

Roland

2011

Phys. Rev. E

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“…It should be pointed out that some preconditions were still put on their solution: (a) weak viscosity; (b) small-amplitude disturbance; (c) ideal discontinuity of the shock front; (d) a simple initial flow. These harsh requirements can not be satisfied in actual experiments [4,[6][7][8][9][11][12][13], so a lack of a widely used and reliable data analysis method has been the bottleneck of viscosity measurement for a long time.…”

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“…Sakharov and Mineev et al [4,[6][7][8][9] especially designed experiments for generating shock waves with sinusoidal geometrical disturbance on front and measuring the amplitude damping and oscillation by a combination of explosive loading and high-speed imaging techniques. In their analysis, Zaidel's [10] analytic solution for the disturbance development of shock front were adopted to constrain the shear viscosity coefficients of several materials.…”

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confidence: 99%

“…In this work the finite difference method is firstly applied to obtain the numerical solutions for disturbance amplitude damping behavior of sinusoidal shock front in inviscid and viscous flow. When water shocked to 15 GPa is taken as an example, the main results are as follows: (1) Viscosity of substance at high pressures is important for the description of dynamic evolution in the deeper earth [1,2] and of flow development of shock waves [3,4], which is described by shear and bulk coefficients in Newtonian viscous fluid theory [5]. However, data of these quantities are very lacking for metals and silicates because direct measurements become very difficult at high pressures of Mbar and high temperatures of several thousand Kelvin.…”

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Effects of viscosity on shock-induced damping of an initial sinusoidal disturbance

Liu

Jing

2010

Sci. China Phys. Mech. Astron.

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A lack of reliable data treatment method has been for several decades the bottleneck of viscosity measurement by disturbance amplitude damping method of shock waves. In this work the finite difference method is firstly applied to obtain the numerical solutions for disturbance amplitude damping behavior of sinusoidal shock front in inviscid and viscous flow. When water shocked to 15 GPa is taken as an example, the main results are as follows: (1) For inviscid and lower viscous flows the numerical method gives results in good agreement with the analytic solutions under the condition of small disturbance (a 0 /λ=0.02); (2) For the flow of viscosity beyond 200 Pa s (η = κ) the analytic solution is found to overestimate obviously the effects of viscosity. It is attributed to the unreal pre-conditions of analytic solution by Miller and Ahrens; (3) The present numerical method provides an effective tool with more confidence to overcome the bottleneck of data treatment when the effects of higher viscosity in experiments of Sakharov and flyer impact are expected to be analyzed, because it can in principle simulate the development of shock waves in flows with larger disturbance amplitude, higher viscosity, and complicated initial flow. viscosity coefficient, two-dimensional Eulerian flow, shock front, sinusoidal disturbance PACS: 66.20.Cy, 62.50.+p Viscosity of substance at high pressures is important for the description of dynamic evolution in the deeper earth [1,2] and of flow development of shock waves [3,4], which is described by shear and bulk coefficients in Newtonian viscous fluid theory [5]. However, data of these quantities are very lacking for metals and silicates because direct measurements become very difficult at high pressures of Mbar and high temperatures of several thousand Kelvin.The so-called oscillatory damping method was put forward for such an extreme condition, which relies on the correlation between viscosity of shock compressed state and amplitude damping and oscillation of an initial sinusoidal disturbance on shock front in concerned substance. Sakharov and Mineev et al. [4,[6][7][8][9] especially designed experiments for generating shock waves with sinusoidal geometrical disturbance on front and measuring the amplitude damping and oscillation by a combination of explosive loading and high-speed imaging techniques. In their analysis, Zaidel's [10] analytic solution for the disturbance development of shock front were adopted to constrain the shear viscosity coefficients of several materials. Two decades later, Miller and Ahrens [5] re-examined Zaidel's approximations in details. They considered the effect of bulk viscosity, and got an analytic solution for a more general non-uniform initial condition. It should be pointed out that some preconditions were still put on their solution: (a) weak viscosity; (b) small-amplitude disturbance; (c) ideal discontinuity of the shock front; (d) a simple initial flow. These harsh requirements can not be satisfied in actual experiments [4,[6][7][8][9][11][12][1...

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“…The comparison of some results will be useful and we will point out during the text the new advances in this paper. The viscosity depends on the temperature and is known under high hydrostatic compression but is poorly known under depression [7,8].…”

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confidence: 99%

A molecular dynamics simulation study of semi-solid-state Fe: high temperature elasticity and void formation in liquid

Monasse

Pradille

Chastel

2014

Metall. Res. Technol.

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-Hot tearing defects appear during the last steps of casting solidification of dendrites. The crystalline structure traps a small amount of liquid metal, which is depressed, and cavities are spontaneously initiated. Molecular dynamics (MD) simulations of pure iron are able to predict, on one hand, the high temperature elastic modulus of crystals, and on the other hand, the cavitation event in liquid metal and near the solid-liquid growth front. High values of elastic tensor components are predicted close to the melting temperature. We conclude that a weakening of the mechanical properties of the crystal is not the reason for failure initiation. The crystals are thinned by partial melting as the effect of negative pressure increases. The cavitation is spontaneously initiated under a very high negative pressure. The cavity expands very quickly and applies a pressure wave to the thinned crystals. We propose that this crystal thinning/pressure wave coupling is able to initiate cracks inside the crystal. Mots-clés :Dynamique moléculaire ; élasticité ; cavitation ; fer ; cristallisation Received 30 December 2013 Accepted 26 June 2014Résumé -La fissuration à chaud des aciers apparaît durant les derniers stades de la solidification des structures dendritiques. La structure cristalline est largement développée et piège une faible quantité de métal fondu qui est mise en dépression et cavite. La dynamique moléculaire (DM) de fer pur permet de prévoir, d'une part, l'évolution du module élastique du cristal à très haute température et, d'autre part, les conditions de cavitation du métal à l'état fondu et à proximité du cristal. Une valeur très élevée du module élastique est pré-dite même à la température de fusion. Ce n'est certainement pas la cause de l'amorçage de la fissuration. Elle est recherchée dans le phénomène de cavitation. Les cristaux fondent partiellement par l'application d'une dépression. Pour une très forte pression négative la cavitation est amorcée. Le volume de la cavité croit très rapidement vers des cristaux amincis et applique une onde de pression. Nous proposons que ce couplage amincissement/onde de pression peut amorcer la fissuration. D

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Viscosity measurements on metal melts at high pressure and viscosity calculations for the earth's core

Cited by 34 publications

References 109 publications

Connection between dynamics and thermodynamics of liquids on the melting line

Connection between dynamics and thermodynamics of liquids on the melting line

Effects of viscosity on shock-induced damping of an initial sinusoidal disturbance

A molecular dynamics simulation study of semi-solid-state Fe: high temperature elasticity and void formation in liquid

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