Predicting the process of porosity-based ductile damage in polycrystalline metallic materials
is an essential practical topic. Ductile damage and its precursors are represented by extreme
values in stress and material state quantities, the spatial probability density function (PDF)
of which are highly non-Gaussian with strong fat tails. Traditional deterministic forecasts
utilizing sophisticated continuum-based physical models generally lack in representing the
statistics of structural evolution during material deformation. Computational tools which do
represent complex structural evolution are typically expensive. The inevitable model error and
the lack of uncertainty quantification may also induce significant forecast biases, especially
in predicting the extreme events associated with ductile damage. In this paper, a data-driven
statistical reduced-order modeling framework is developed to provide a probabilistic forecast
of the deformation process of a polycrystal aggregate leading to porosity-based ductile damage
with uncertainty quantification. The framework starts with computing the time evolution of
the leading few moments of specific state variables from the spatiotemporal solution of full-
field polycrystal simulations. Then a sparse model identification algorithm based on causation
entropy, including essential physical constraints, is utilized to discover the governing equations
of these moments. An approximate solution of the time evolution of the PDF is obtained from
the predicted moments exploiting the maximum entropy principle. Numerical experiments based
on polycrystal realizations of a representative body-centered cubic (BCC) tantalum illustrate a
skillful reduced-order model in characterizing the time evolution of the non-Gaussian PDF of the
von Mises stress and quantifying the probability of extreme events. The learning process also
reveals that the mean stress is not simply an additive forcing to drive the higher-order moments
and extreme events. Instead, it interacts with the latter in a strongly nonlinear and multiplicative
fashion. In addition, the calibrated moment equations provide a reasonably accurate forecast
when applied to the realizations outside the training data set, indicating the robustness of the
model and the skill for extrapolation. Finally, an information-based measurement is employed
to quantitatively justify that the leading four moments are sufficient to characterize the crucial
highly non-Gaussian features throughout the entire deformation history considered.
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Deformation, dislocation evolution and the non-Schmid effect in body-centered-cubic single- and polycrystal tantalum
A physically-informed continuum crystal plasticity model is presented to elucidate deformation
mechanisms, dislocation evolution and the non-Schmid effect in body-centered-cubic (bcc)
tantalum widely used as a key structural material for mechanical and thermal extremes. We
show the unified structural modeling framework informed by mesoscopic dislocation dynamics
simulations is capable of capturing salient features of the large inelastic behavior of tantalum at
quasi-static (10−3 s−1) to extreme strain rates (5000 s−1) and at low (77 K) to high temperatures
(873 K) at both single- and polycrystal levels. We also present predictive capabilities of the
model for microstructural evolution in the material. To this end, we investigate the effects
of dislocation interactions on slip activities, instability and the non-Schmid behavior at the
single crystal level. Furthermore, ex situ measurements on crystallographic texture evolution
and dislocation density growth are carried out for polycrystal tantalum specimens at increasing
strains. Numerical simulation results also support that the modeling framework is capable of
capturing the main features of the polycrystal behavior over a wide range of strains, strain
rates and temperatures. The theoretical, experimental and numerical results at both single- and
polycrystal levels provide critical insight into the underlying physical pictures for micro- and
macroscopic responses and their relations in this important class of refractory bcc materials
undergoing large inelastic deformations.
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- Award ID(s):
- 2118399
- NSF-PAR ID:
- 10477049
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- International Journal of Plasticity
- Volume:
- 163
- Issue:
- C
- ISSN:
- 0749-6419
- Page Range / eLocation ID:
- 103529
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Single-phase solid-solution refractory high-entropy alloys (HEAs) show remarkable mechanical properties, such as their high yield strength and substantial softening resistance at elevated temperatures. Hence, the in-depth study of the deformation behavior for body-centered cubic (BCC) refractory HEAs is a critical issue to explore the uncovered/unique deformation mechanisms. We have investigated the elastic and plastic deformation behaviors of a single BCC NbTaTiV refractory HEA at elevated temperatures using integrated experimental efforts and theoretical calculations. The in situ neutron diffraction results reveal a temperature-dependent elastic anisotropic deformation behavior. The single-crystal elastic moduli and macroscopic Young’s, shear, and bulk moduli were determined from the in situ neutron diffraction, showing great agreement with first-principles calculations, machine learning, and resonant ultrasound spectroscopy results. Furthermore, the edge dislocation–dominant plastic deformation behaviors, which are different from conventional BCC alloys, were quantitatively described by the Williamson-Hall plot profile modeling and high-angle annular dark-field scanning transmission electron microscopy.more » « less
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.ijplas.2023.103529
