The 9th International Conference on Multiscale Materials Modeling

講演情報

Symposium

K. Multiscale Simulations of Catastrophic Phenomena: Toward Bridging between Materials Fracture and Earthquake

[SY-K1] Symposium K-1

2018年11月1日(木) 11:15 〜 12:30 Room5

Chairs: Momoji Kubo(Institute for Materials Research, Tohoku University, Japan), Tomoaki Niiyama(Kanazawa Univ., Japan)

[SY-K1] System-spanning shear avalanches induced by thermal structural relaxation in metallic glasses

Tomoaki Niiyama1, Masato Wakeda2, Tomotsugu Shimokawa4, Shigenobu Ogata3 (1.College of Science and Engineering, Kanazawa Univ., Japan, 2.Research Center for Structural Materials, National Institute for Materials Science, Japan, 3.Department of Mechanical Science and Bioengineering, Osaka University, Japan, 4.Faculty of Mechanical Engineering, Kanazawa University, Japan)

Metallic glasses (MGs) are one of the most attractive materials because of their excellent properties [1]. However, brittle fractures are an obstacle for MGs to be applied as structural materials. This brittleness originating from shear band nucleation is determined by structural relaxation using thermal annealing [2]. Thus, the influence of structural relaxation upon the nucleation of shear banding that can induce catastrophic failure in MGs is a significant challenge in material science.
For this challenge, we focus on the avalanche behavior that provides sudden massive deformations and spatiotemporal correlation in solid plasticity [3]. Thus, this avalanche behavior is deeply connected to the localization of plastic deformation and catastrophic failure in MGs.
In this study [4], we investigate the geometry of the shear transformation avalanches that exhibit the power-law statistics using molecular dynamics simulations of shear deformation in two thermally processed MG models that are based on a less-relaxed glass and a well-relaxed glass. The simulation showed a shear-band like heterogeneous pattern in the well-relaxed glass model, whereas the less-relaxed model exhibits homogeneous deformation patterns. Considering the spatial correlation functions of the non-affine least square displacements of atoms during each each avalanche event, we reveal that the regions an avalanche developed in well-relaxed glasses tend to be anisotropic whereas those in less-relaxed glasses are isotropic. Moreover, a temporal clustering feature of the direction of avalanche propagations and a considerable correlation between the anisotropy and size of an avalanche in the well-relaxed glass model are demonstrated.

[1] A. L. Greer, Science 267, 1947 (1995).
[2] G. Kumar, et al., Acta Mater. 57, 3572 (2009).
[3] M. C. Miguel, et al., Nature 410, 667 (2001).
[4] T. Niiyama, et al., arXiv:1804.00852 (2108).