Development of Material Strength Evaluation System Based on the Microscopic Discrete Model Using the Molecular Dynamics

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(1) For the simulation of the behavior of cracks at the interface of dissimilar materials, a potential between atoms, which describes macroscopic material properties such as the Young's modulus and the Poisson's ratio, was proposed. A model of atoms used in this project consists of a two-dimensional triangular lattice. In addition, using a singular solution obtained by the theory of linear elasticity as a boundary condition, we developed a program for molecular dynamics analysis, which is capable of computing the configuration of atoms under the quasi-static load. Considering Cu-Si3N4 adhesive as an example, the influence of the crack opening mode and the interface strength onto the propagation of the interface crack was parametrically investigated. (2) In an attempt to evaluate the mechanical reliance of Si, which is the main composition of electrical devices, a modified version of the above program was developed. This program allows us to analyze the dislocation gliding motion of Si … More single crystal. Tersoff-type potential was used for computing the forces between the atoms. Results of simulations showed that the critical shear stress and the Peierls force computed were similar to the results from the previous reports. When considering the manufacturing process of semi-conductor devices or the precision engineering technique of atomic level, the surface of crystals must be modelled. This was successfully achieved by DAS model. Moreover, indentation and removal processes were simulated, and the energy necessary for the manipulation of atoms was investigated. (3) By modelling the interface with continuum mechanics, a technique to incorporate the microscopic information into the continuum mechanics such as the finite element method was developed. In this technique, micro-cracks are first simulated by molecular dynamics method, and the effect of damage is evaluated by the change of the elastic constants, which are macroscopic quantities. The Budiansky and O'Connell's theory was used for the evaluation of damage. Less