A multiscale strength model for tantalum over an extended range of strain rates

Abstract

Strain hardening and large tensile elongation in ultrahigh-strength nano-twinned copper Appl. Phys. Lett. 85, 4932 (2004); 10.1063/1.1814431Modeling of the high strain and high strain rate behavior of tantalum-Application to the dynamic expansion of a spherical shell AIP Conf.

Grain-Size-Independent Plastic Flow at Ultrahigh Pressures and Strain Rates

“…The 2-D ARES hydrodynamics simulation [32] was then used to predict the ripple GFs shown in the plot assuming various models of flow stress. The conventional constitutive models of Preston-TonksWallace (PTW) [33], Steinberg-Guinan (SG) [34] and Steinberg-Lund (SL) [35] are seen to under-predict the Ta flow stress at these pressures and strain rates whereas the predictions of the Livermore Multiscale Strength (LMS) model [13,14] match the data well. The LMS model connects atomistic level behavior to the continuum level plastic flow by linking density functional theory, molecular dynamics, dislocation dynamics and continuum simu- lations to model flow stress as a function of P, T, , and˙ .…”

“…We now compare the magnitudes of ρ sat and ρ GN D . The ρ sat can be expressed as ≈ ρ s0˙ n where ρ s0 is the initial dislocation density,˙ is the strain rate and n is 0.59 for Ta [13,14]. The ρ GN D can be expressed as ≈ /(4bD), where is the plastic strain, and b is Burgers vector, and D is the grain size.…”

“…It was recently realized for high pressure, high strain rate conditions, that the macroscopic plastic flow stress of a material can be expressed explicitly in terms of phenomena coupled across a wide range of physical scales, including the quantum-based atomic interactions, the crystal lattice structure, dislocation mobilities on the nanoscale, and the character of the dislocation network at the mesoscale. Multiscale plasticity simulations incorporating these multiple length scales have been developed [13,14], and differ significantly from simulations utilizing conventional models of flow stress [8], when the flow occurs at extreme pressures and strain rates. These new theoretical results offer the potential to tie the experimental observables directly to fundamental properties of the crystal and its lattice dynamics, and need to be experimentally tested and verified.…”

Using high energy diffraction microscopy to assess a model for microstructural sensitivity in spall response

“…The dislocation kinetics are adjusted for the high rate loading conditions, especially to capture the release portion of the wave profiles. As highlighted in several recent works [15,6,16] details of the microstructural evolution, particularly dislocation network arrangements and their kinetics, may play a significant role in the material response upon release. Here we use a model that tracks only a single scalar dislocation density state variable.…”

“…The crystal mechanics framework builds from that presented in [4], with some of the kinetics informed by observations from multi-scale modeling [5,6]. We deliberately keep the forms relatively simple, and do not include effects such as dislocation nucleation [7].…”