Simulations of an Interface Crack Nucleation During Nanoindentaion : Molecular Dynamics and Finite Element Coupling Appr
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1086-U08-29
Simulations of an Interface Crack Nucleation During Nanoindentaion : Molecular Dynamics and Finite Element Coupling Approach Shotaro Hara1, Satoshi Izumi1, Shinsuke Sakai1, Yoshiyuki Eguchi2, and Tomio Iwasaki3 1 Mechanical Engineering, The University of Tokyo, Hongo7-3-1, Bunkyo-ku, Tokyo, Japan 2 Hitachi East Japan Solutions, Ltd, Ibaraki, Japan 3 Hitach, Ltd, Ibaraki, Japan ABSTRACT We carried out the nanoindentation simulations for the Ru (superlayer) / Cu (film) / SiO2 (substrate) system using the finite temperature MD-FEM coupling method. The calculations are performed for the different adhesion energies of Cu/SiO2 ranging from 0.2 to 0.6 J/m2. During loading, it was found that the interfacial crack nucleation occurs at three to four times the contact radius, driven by the tensile stress acted on the Cu/SiO2 interface. We also show that the asymmetric defect behavior have a great effect on giving birth to the crack nucleation. The observation of our simulation indicates that the mechanism of the crack nucleation strongly depends on the interfacial bonding energy.
INTRODUCTION Delamination of the thin metallic film on the dielectric substrate is one of the critical issues in the technological applications [1]. Experimentally, much effort has been devoted to measure a quantitative value of the interfacial adhesion energy [2]. One of the common adhesion tests is a superlayer nanoindentation technique recently developed by Kriese et. al [3]. This technique has a great advantage in that it can induce the interfacial crack accurately without the need of the complex sample preparation. However, the critical conditions at which a crack nucleate at the interface and the deformation mechanism involved are still unclear. Molecular dynamics (MD) is the powerful computational tool to provide a great insight of the defect behavior such as a dislocation motion during indentation loading. But, due to its heavy computational burden, most of the MD simulations have been limited to track the homogeneous dislocation nucleation event which occurs in the early stage of the indentation [4]. The interest of this study is the crack nucleation at interface, which is the further subsequent event during the indentation process. Therefore, we need to incorporate the more sophisticated modeling approach. The approach we develop here is the coupling method of the molecular dynamics and the continuum calculation based on a finite element method (FEM). In this multiscale framework, the atomistic level description is only applied to the highly deformed inelastic region, which results in the considerable decrease in the degree of the freedom. We modified the coupling approach originally developed by Kohlhoff [5]. In addition, to consider the dynamic effects of the defect motion, the original static algorithm has been extended to the finite temperature coupling scheme [6]. The above coupling approach is applied to the nanoindentation simulations in the Ru (superlayer) / Cu (film) / SiO2 (substrate) system. In this study, we report
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