Quasicontinuum Simulations Research Articles

1819 Quasicontinuum法による転位パイルアップと粒界性格の関係(J06-3 マイクロ・ナノ構造解析法と応用,J06 計算マイクロ・ナノメカニクス)

1819 Quasicontinuum法による転位パイルアップと粒界性格の関係(J06-3 マイクロ・ナノ構造解析法と応用,J06 計算マイクロ・ナノメカニクス)

210 転位と粒界の相互作用に関するQuasicontinuumシミュレーション(OS1-1 解析・シミュレーション,オーガナイズドセッション1 計算固体力学の最新応用)

210 転位と粒界の相互作用に関するQuasicontinuumシミュレーション(OS1-1 解析・シミュレーション,オーガナイズドセッション1 計算固体力学の最新応用)

303 金属/セラミクス界面のマルチスケール強度解析(GS6 き裂3)

A limitation of empirical methodology on strength evaluation seems highlighted in problems of metal/ceramics interface fracture. This study is a trial to remove the limitation by means of computational science based on the atomistic simulation. A sort of multiscale simulation is successfully organized starting from ab initio to determine interatomic potentials for interface and concluding at quasicontinuum simulation to extend atomistic region. A simulation-based strength evaluation is proposed through numerical experiments related with fracture originated by interface crack. Inelastic phenomena associated with fracture are described in terms of their contribution to total potential energy.

Nucleation of dislocations beneath a plane strain indenter

We examine the conditions for dislocation nucleation beneath a plane strain rectangular indenter using atomistic simulations as well as analytic models, with the aim of (a) examining the validity of the analytic models and (b) extracting a nucleation criterion that can be used in mesoscopic dislocation dynamics models. Atomistic lattice statics calculations are performed using the quasicontinuum method, while the analytic analysis is carried out within the Rice–Thomson and Peierls–Nabarro frameworks. We find that both the atomistic and analytic models suggest a stress-based nucleation criterion. The features of the analytic models and quasicontinuum simulations are compared on the basis of the nucleation load and the incipient slip distribution. We find that the predictions of the analytical models are qualitatively borne out by the atomistic simulations, though quantitatively they are left wanting. Improvements to the analytical models to achieve quantitative agreement with the atomistic results are suggested.

The Energetics of Dislocation-Obstacle Interactions by 3-D Quasicontinuum Simulations

AbstractThe goal of this work is to study the interaction of dislocations with local obstacles to glide such as point defects, precipitates and other dislocations. The quasicontinuum method is used as the basis of this study. It is demonstrated that two types of boundary effects are of concern in the calculation of hardening parameters using finite sized simulation cells. A recently developed technique to incorporate periodic boundary conditions in the quasicontinuum method is used to eliminate surface effects which were present in earlier implementations and to simulate a dislocation of infinite extent interacting with an array of obstacles. The second type of boundary effect is due to the boundary conditions on the lateral boundaries. A method based on finite element calculations is proposed for quantifying the effect of lateral boundaries in these simulations. Preliminary results for the validation of the method are presented as well as a simulation of the interaction between a conventional edge dislocation in Al with an array of clusters of Ni atoms.

Quasicontinuum simulation of fracture at the atomic scale

We study the problem of atomic scale fracture using the recently developed quasicontinuum method in which there is a systematic thinning of the atomic-level degrees of freedom in regions where they are not needed. Fracture is considered in two distinct settings. First, a study is made of cracks in single crystals, and second, we consider a crack advancing towards a grain boundary (GB) in its path. In the investigation of single crystal fracture, we evaluate the competition between simple cleavage and crack-tip dislocation emission. In addition, we examine the ability of analytic models to correctly predict fracture behaviour, and find that the existing analytical treatments are too restrictive in their treatment of nonlinearity near the crack tip. In the study of GB-crack interactions, we have found a number of interesting deformation mechanisms which attend the advance of the crack. These include the migration of the GB, the emission of dislocations from the GB, and deflection of the crack front along the GB itself. In each case, these mechanisms are rationalized on the basis of continuum mechanics arguments.