Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 109, Issue 33, Pages 13204-13207Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1203285109
Keywords
high strain-rate plasticity; relaxation of non-hydrostatic stresses; thermodynamics under uniaxial straining
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Funding
- National Science Foundation
- Army Research Office
- US Department of Energy [DE-AC52-06NA25396]
- Div Of Civil, Mechanical, & Manufact Inn
- Directorate For Engineering [0969143] Funding Source: National Science Foundation
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Generation and motion of dislocations and twinning are the main mechanisms of plastic deformation. A new mechanism of plastic deformation and stress relaxation at high strain rates (10(9)-10(12) s(-1)) is proposed, under which virtual melting occurs at temperatures much below the melting temperature. Virtual melting is predicted using a developed, advanced thermodynamic approach and confirmed by large-scale molecular dynamics simulations of shockwave propagation and quasi-isentropic compression in both single and defective crystals. The work and energy of nonhydrostatic stresses at the shock front drastically increase the driving force for melting from the uniaxially compressed solid state, reducing the melting temperature by 80% or 4,000 K. After melting, the relaxation of nonhydrostatic stresses leads to an undercooled and unstable liquid, which recrystallizes in picosecond time scales to a hydrostatically loaded crystal. Characteristic parameters for virtual melting are determined from molecular dynamics simulations of Cu shocked/compressed along the < 110 > and < 111 > directions and Al shocked/compressed along the < 110 > direction.
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