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The accumulation of dislocations, which are atomic defects in materials subjected to plastic deformation, can cause structural failures. Early detection of such dislocation-related damage is essential to prevent these failures. The acoustic nonlinearity parameter β has been shown to be sensitive to the nonlinearity of dislocation motions, and prior research has shown a relationship between β and dislocation parameters in various damage mechanisms. While most work thus far reports that β generally increases with increased plastic deformation, recent research showed that β can decrease during monotonic tensile loading in stainless steel 316L characterized by in situ nonlinear ultrasonic measurements. The objective of this research is to examine the correlation between the decrease of β with plastic strain as reported in this recent study, and the initial microstructure and strain hardening rate. The initial microstructure, characterized with electron backscatter diffraction (EBSD), shows an increase in dislocation density and a reduction of grain area, which can possibly result in a decrease in β. Further, it is shown that the decrease rate of β monotonically decreases with hardening rate, providing a evidence that the decrease in β may relate to the shift from planar slip to wavy slip. These results help interpret the underlying mechanisms for the decrease in β during tensile loading.
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Prediction of yield surface of single crystal copper from discrete dislocation dynamics and geometric learning
The yield surface of a material is a criterion at which macroscopic plastic deformation begins. For crystalline solids, plastic deformation occurs through the motion of dislocations, which can be captured by discrete dislocation dynamics (DDD) simulations. In this paper, we predict the yield surfaces and strain-hardening behaviors using DDD simulations and a geometric manifold learning approach. The yield surfaces in the three-dimensional space of plane stress are constructed for single-crystal copper subjected to uniaxial loading along the [100] and [110] directions, respectively. With increasing plastic deformation under loading, the yield surface expands nearly uniformly in all directions, corresponding to isotropic hardening. In contrast, under [110] loading, latent hardening is observed, where the yield surface remains nearly unchanged in the orientations in the vicinity of the loading direction itself but expands in other directions, resulting in an asymmetric shape. This difference in hardening behaviors is attributed to the different dislocation multiplication behaviors on various slip systems under the two loading conditions.
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- PAR ID:
- 10574842
- Editor(s):
- Deshpande, Vikram
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Journal of the Mechanics and Physics of Solids
- Volume:
- 186
- Issue:
- C
- ISSN:
- 0022-5096
- Page Range / eLocation ID:
- 105577
- Subject(s) / Keyword(s):
- Yield surface Discrete dislocation dynamics Geometric manifold learning Strain hardening Crystal plasticity
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1016/j.jmps.2024.105577
