Continuum Modeling and Simulation

Daniel Orlikowski, Christine Wu, Lorin Benedict

Methods: Arbitrary Lagrange/Eulerian codes (ALE3D)

Temperature of a high explosive (he) as a function of postion in two directions after a planar impact. — (Top image) The temperature of a high explosive (HE) as a function of postion in two directions after a planar impact indicating a slip plane (along the diagonal) terminating in a "hot spot" (red); (right) particle velocity history from a gas-gun planar shock experiment compared to current Steinberg-Lund strength model simulations with new parameterizations. (Bottom image) 1D hydrodynamic simulation of the graded impactor striking an Al target depicting the process of quasi-isentropic wave being generated and applied to a target during impact.

Novel product development and fabrication require extensive use of continuum simulations. However, the fundamental quantities and constitutive models that compose these simulations need to be either completely developed or improved. To this end, we are incorporating calculated smaller-length scale quantities (e.g. yield stress, chemical reaction pathways, etc.) into continuum models.

This work becomes two fold in that we are assessing and refining our quantum and atomistic work on these integrated models and that we are guiding experimental design work to probe new high pressure regimes. Through the use of arbitrary Lagrange/Eulerian codes, we are then able to evaluate sensitivity and impact of these fundamental quantities at the continuum length scale.

Current Research

To examine the behavior of energetic materials under the stimulus of non-shock scenarios, such as low velocity impacts, friction and cutting motions during machining of high explosives (HEs), we employ continuum mechanics simulations for sensitivity tests of the constitutive models.
Constitutive strength models, that combine calculations from several length scales from robust first principles combined with quantum based atomistic for a complete thermoelastic description, a Green's function simulation for the onset dislocation flow, and dislocation dynamics simulations for work hardening, are being evaluated and validated in comparison with experiments using standard hydrodynamic codes.
Hydrodynamic simulations of novel gas-gun compression wave experiments using functionally graded material (FGM) impactors are being performed to compare and to understand the high pressure material response.
- Another aspect of study within the general context of high strain-rate, compression waves is the wave propagation in materials---currently investigating dissipative and dispersive effects with intent to relatively quantify that in high pressure dynamic experiments

Selected Publications

D. Orlikowski, J. H. Nquyen, J. R. Patterson, R. Minich, L. P. Martin and N. C. Holmes "New experimental capabilities and theoretical insights of high-pressure compression waves," Shock Comp. Cond. Matter-2007, eds. M. Elert, et al. American Inst. Phys.: New York (2007) p1186.
L. Peter Martin, J. Reed Patterson, Daniel Orlikowski, and Jeffrey H. Nguyen, "Application of tape-cast graded impedance impactors for light-gas gun experiments ," J. Appl. Phys. 102, 02357 (2007)
Christine J. Wu, Tom Piggot, Jack Yoh and Jack Reaugh, "Numerical Modeling of Impact Initiation of High Explosive", LLNL Report, May 2006, UCRL-TR-221760.
D. Orlikowski, P. Söderlind and J. A. Moriarty, " First-principles thermoelasticity of transition metals at high pressure: Tantalum prototype in the quasiharmonic limit ," Phys. Rev. B 74, 054109 (2006).
P. Söderlind and J. A. Moriarty, " First-principles theory of Ta up to 10 Mbar pressure: Structural and mechanical properties ," Phys. Rev. B 57, 10340 (1998).
J. H. Nguyen, D. Orlikowski, F. H. Streitz, J. A. Moriarty, and N. C. Holmes " High-pressure tailored compression: Controlled thermodynamic paths ," J. Appl. Physics 100, 023508 (2006).

Maintained by metals-alloys-web [at] llnl.gov (Lorin X. Benedict)