纳米接触行为的三维多尺度数值模拟

Multiscale Modeling of Three-dimensional Contacts

应用分子动力学与有限元耦合的桥域多尺度算法,模拟三维刚性球形压头与光滑基体表面的纳米尺度接触行为,并与全原子分子模拟结果比较.考察在一定载荷下的系统弛豫行为、两种模型桥接区位移和应力的连续性、法向力和接触面积随压头位移变化等,结果表明:一定外载荷下,桥域多尺度算法能较快达到平衡状态,且压头的振荡幅度更小,系统初始温度为0 K时该算法的相对误差最小.在准静态加载过程中,该算法能够将原子区的位移、应力等连续的过渡到连续介质区,具有较好的耦合效果;法向力-压头位移和接触半径-压头位移曲线几乎与分子模拟结果重合,表明算法具有较高的计算精度.

A bridging domain method, in which molecular models and continuum models are coupled, is performed to study three- dimensional contact of a rigid spherical tip and a smooth flat substrate. It is compared with full-atom molecular simulations. We focus on relaxation behavior under a given load, continuity of displacement and stress at bridging domain, normal force and contact radius. It shows that the bridging domain method quickly reaches equilibrium and has weaker oscillations under a given external load. It has small relative errors as initial temperature of system is at 0 K. The bridging domain method can transmit continuously displacement and stress from molecular domain to continuum domain, and has good coupling effect. Normal force-displacement and contact radius-displacement are nearly coincide with molecular simulations. Its computational accuracy is high.