High Velocity Behavior of Dislocations in Copper

Vreeland, T.; Wood, D. S.

doi:10.21236/ada025484

Cited by 2 publications

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“…6 Shock initiation of chemical reactions in highly reactive powder mixtures has been proposed to occur as a consequence of mechanochemical effects, via processes involving solid-state configurational changes and structural rearrangements. [8][9][10][11][12][13] The highly exothermic nature of Mo-Si powder mixtures (⌬H R ϭϪ31.5 kcal/mol for MoSi 2 ; Ϫ74.5 kcal/mol for Mo 5 Si 3 ) and the large differential in flow strength, density, and melt temperature between Mo and Si (⌬ y ϳ230 MPa, ⌬ϭ7.9 g/cm 3 , and ⌬T m ϭ800°C) make this an ideal system for investigating the effects of shock compression. [8][9][10][11][12][13] The highly exothermic nature of Mo-Si powder mixtures (⌬H R ϭϪ31.5 kcal/mol for MoSi 2 ; Ϫ74.5 kcal/mol for Mo 5 Si 3 ) and the large differential in flow strength, density, and melt temperature between Mo and Si (⌬ y ϳ230 MPa, ⌬ϭ7.9 g/cm 3 , and ⌬T m ϭ800°C) make this an ideal system for investigating the effects of shock compression.…”

Section: Introductionmentioning

confidence: 99%

Time-resolved measurements of the shock-compression response of Mo+2Si elemental powder mixtures

Vandersall

Thadhani

2003

Journal of Applied Physics

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Investigation of shock-induced reaction behavior of as-blended and ball-milled Ni + Ti powder mixtures using time-resolved stress measurementsThe shock-compression response of Moϩ2Si elemental powder mixtures was investigated using instrumented experiments in the velocity range of 500 m/s to 1 km/s. The experiments employed polyvinyl difluoride stress gauges placed at the front and rear surfaces of the powder mixtures to determine the crush strength, densification history, and shock-induced reaction initiation characteristics. Experiments performed on ϳ58% dense Moϩ2Si powder mixtures at input stresses less than 4 GPa showed characteristics of powder densification and dispersed propagated wave stress profiles with rise time Ͼϳ40 ns. At input stress between 4 and 6 GPa, the powder mixtures showed a shock-compression response following the Hugoniot of the solid-density mixture. In the stress regime of 6 -7 GPa, shock-induced melting of silicon was observed, which appears to inhibit a shock-induced chemical reaction on the time scale of the time-resolved measurements. The results of the present work on Mo-Si, taken in conjunction with prior work on the Nb-Si and Ti-Si systems, illustrate that premature melting of silicon and its capillary flow can limit the deformation and mixing between reactants, thereby inhibiting the initiation of ''shock-induced'' chemical reactions.

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Section: Introductionmentioning

confidence: 99%

Time-resolved measurements of the shock-compression response of Mo+2Si elemental powder mixtures

Vandersall

Thadhani

2003

Journal of Applied Physics

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“…If they are sufficiently separated, however, this effect will be small, and a simple idea of the rate at which different slip bands extend can then be obtained if one assumes that the dislocations are approximately evenly distributed inside the bands. As pointed out by Vreeland [21] the slip band then approximates to a shear crack. The stress concentration at the tip of the band will therefore increase with the length of the band, and slip bands should be expected to accelerate as they grow.…”

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confidence: 82%