月尘被动防护技术的最新研究进展

月球的特殊环境使月尘具有导电等特殊的性质,极易黏附在探测仪器上造成设备的失效,给探月工程带来极大的危害,因此国内外众多研究组针对月尘危害展开深入研究.本文从黏附机理、防护方法和实验测试几方面对月尘的被动防护技术进行综述和展望.首先,阐述了月尘对探测设备造成的不利影响及影响因素,进而具体论述月尘黏附的机理,详细介绍造成黏附的两种主要作用力的理论基础.然后,针对不同作用机理系统阐述了降低月尘颗粒黏附力的主要方法,对月尘被动防护技术的最新进展进行了总结.最后,结合防护方式的不同,总结了测试月尘黏附力的方法,从而为有效实现探测设备表面月尘防护奠定基础.     

原子力显微镜在轻敲模式下的动力学模型

基于Hamaker假设、Lennard-Jones势能定律及经典弹性理论建立了一种新型的球体与平面黏着接触的弹性模型，该模型显示黏着力在原子力显微镜(AFM)针尖趋近和撤离样品表面，即加载和卸载的两个过程中存在黏着滞后现象，表明了AFM在轻敲工作模式中存在能量耗散.同时，根据所建的黏着接触弹性模型，建立了AFM在轻敲工作模式下的动力学模型，研究了AFM在轻敲工作模式下的振动幅度、相位差及耗散功率随针尖与样品表面间距的变化规律，仿真结果与现有的实验结果相一致.     

Adhesive contact: from atomistic model to continuum model

Two types of Lennard-Jones potential are widely used in modeling adhesive contacts. However, the relationships between the parameters of the two types of Lennard-Jones potential are not well defined. This paper employs a self-consistent method to derive the Lennard-Jones surface force law from the interatomic Lennard-Jones potential with emphasis on the relationships between the parameters. The effect of using correct parameters in the adhesion models is demonstrated in single sphere-flat contact via continuum models and an atomistic model. Furthermore, the adhesion hysteresis behaviour is investigated, and the S-shaped force-distance relation is revealed by the atomistic model. It shows that the adhesion hysteresis loop is generated by the jump-to-contact and jump-off-contact, which are illustrated by the S-shaped force-distance curve.