微纳尺度下液桥的形成

大气环境下原子力显微镜测试中,毛细力在所有粘着力中占主导地位,毛细力与水膜厚度、相对湿度有关。在本报告中,我们发现,除了上述因素外,毛细力还与两个表面的接触时间有关。通过实验数据的分析,提出了一种液桥形成的模型。实验与模型对于理解大气环境下原子力显微镜的工作机理具有重要意义

粘着接触滞后模型

随着微电了机械系统(MEMS)和纳电子机械系统(NEMS)的发展,微纳尺度下的粘着接触问题变得越发重要。许多MEMS器件的制备和运行都表明粘着接触是引起失效的主要因素,同样粘着接触也足影响纳尺度物体力学行为的重要因素。在粘着接触中,接触滞后是一个普遍存在的现象。所谓接触滞后,就是在粘着接触中,使两个粘

Hysteresis effect in adhesive elastic contact

Adhesive forces in microscale or nanoscale contact play a significant role in microelectromechanical systems (MEMS); scanning probe microscope (SPM) and some other related fields. In this paper, the relationship between the pull-off force and the transition parameter as well as the variation of the pull-off radius with the transition parameter is given. When hysteresis effect is considered, hysteresis models are presented to describe the contact radius as a function of external load in loading and unloading processes. Among these models, we verified the hysteresis model from JKR, which is in a good agreement with experiment. The parameter α of dissipated elastic energy can be measured through experiment

Experimental Investigation of the Velocity Effect on Adhesion Forces with an Atomic Force Microscope Atomic Force Microscope

Capillary forces are significantly dominant in adhesive forces measured with an atomic force microscope (AFM) in ambient air, which are always thought to be dependent on water film thickness, relative humidity, and the free energy of water film. We study the nature of the pull-off force on a variety of surfaces as a function of tip velocity. It is found that the capillary forces are of relatively strong dependence on tip velocity. The present experiment is expected to provide a better understanding of the work mechanism of AFM in ambient air

AFM中恒定体积液桥的热力学分析

AFM(原子力显微镜 )自 1986年发明以来到现在得了科技界的普遍重视。AFM是利用探针尖和样品表面的相互作来获得形貌工具，在基础表面科学、表面粗糙度分析和从硅原子结构到活体细胞表面微米尺度研究中发挥着重要作用。 本文研究AFM中由于液桥引起的针尖与样品之间作用力，通过热力学分析和几个重要的近似关系得出毛细力的表达式并与国外同行实验与数值结果相对照，基本吻合，同时探讨在 AFM针尖拉伸液桥时体系的温度变化，并探索性的得出初步结论

原子力显微镜中液桥的热力学分析

原子力显微镜(AFM)自1986年发明以来到现在得到了科技界的普遍重视。AFM是利用探针针尖和样品表面的相互作用来获得表面形貌的工具,在基础表面科学、表面粗糙度分析和从硅原子结构到活体细胞表面微米尺度研究中发挥着重要作用。本文研究AFM中由于液桥引起的针尖与样品之间的作用力,通过热力学分析和几个重要的近似关系得出毛细力的表达式并与国外同行实验与数值结果相对照,基本吻合,同时探讨在AFM针尖拉伸液桥时体系的温度变化,并探索性的得出初步结论

高速受电弓下框架等效阻尼影响因素的实验研究

三质量块模型是弓网动力学分析对受电弓简化的常用模型,已有研究指出简化模型中下框架等效阻尼增加对改善受流质量有一定作用,但有关下框架等效阻尼的影响因素及不同因素贡献量目前没有明确结论。设置对照实验探究DSA380受电弓下框架等效阻尼的影响因素,并确定了不同影响因素的占比。研究发现摩擦影响对受电弓下框架等效阻尼的占比最大,阻尼器影响占比次之,气囊对下框架等效模型影响的占比最小。该结论对受电弓阻尼器的选用具有借鉴作用

The Effects of Roughness on Adhesion Hysteresis

Adhesion hysteresis is defined as the difference between the work needed to separate two surfaces and that originally gained on bringing them together. Adhesion hysteresis is a common phenomenon in most surface/interface interactions. This paper studies the effects of surface roughness on adhesion hysteresis. We assumed that the surface asperity height distribution is Gaussian. Numerical simulations based on Fuller's model showed that adhesion hysteresis depended upon a single dimensionless parameter, the adhesion parameter, which represents the statistical average of a competition between the compressive forces exerted by the higher asperities, which are trying to separate the surfaces, and the adhesion forces of the lower asperities which are trying to hold the surfaces together. (C) Koninklijke Brill NV, Leiden, 201