球形压头与单晶铝材料纳米接触过程的多尺度分析

Multi-scale analysis of nanoscale contact process between spherical indenter and single crystal aluminium

采用准连续介质多尺度理论及排斥力场函数,建立了刚性球形压头与单晶铝材料表面纳米接触与脱离过程的跨尺度分析模型,得到载荷-位移响应曲线、原子变化状态图及位移云纹图.研究了接触与脱离过程中单晶铝材料微观变形时原子的排列情况以及压头形状对位错的形核和发射产生的影响.从微观角度分析了接触变形机理.结果表明,随着接触深度的增加,球形压头下部两侧的原子受力方向不断变化,使得载荷-位移响应曲线出现不同于方形压头的阶梯状.由于压头形状的影响,压头两侧的密排原子面实现部分滑移形成了肖克利不完全位错.脱离过程中,原子紧贴压头向上移动,实现部分弹性恢复,残余位移为0.3 nm,非常接近单晶铝单位位错的伯格斯矢量的模0.285 nm.

Based on the quasicontinuum method and repulsive force-field approach, a muti-scale modeling of nano-contact process between rigid spherical indenter and surface of single crystal aluminium is established. The corresponding load-depth, graph of atomic state, and moire pattern of displacement are obtained, from which the arrangement of atoms and the effects of the shape of indenter on the nucleation and emission of dislocations in the contact process are studied. Therefore micro-mechanisms of deformation are analyzed. The result shows that due （o the fact that the direction of force on atoms that contact the indenter is constantly changing with the increase of contact depth, the corresponding load-depth shows that step increases which is different from that of the square indenter with the response of the underlying crystal. Due to the indenter geometry, the close packed planes under both sides of indenter slip partially lead to Shockley partial dislocations. In the process of disengagement, the elastic recovery is accomplished as the atoms move up with indenter. The residual depth is 0.3 nm, which is close to the magnitude of the Burgers vector, 0.285 nm.