Kesari Haneesh, Doll Joseph C, Pruitt Beth L, Cai Wei, Lew Adrian J
Department of Mechanical Engineering, Stanford University, Stanford, CA, 94305-4040.
Philos Mag Lett. 2010 Dec 1;90(12):891-902. doi: 10.1080/09500839.2010.521204.
In experiments that involve contact with adhesion between two surfaces, as found in atomic force microscopy or nanoindentation, two distinct contact force (P) vs. indentation-depth (h) curves are often measured depending on whether the indenter moves towards or away from the sample. The origin of this hysteresis is not well understood and is often attributed to moisture, plasticity or viscoelasticity. Here we report experiments that show that hysteresis can exist in the absence of these effects, and that its magnitude depends on surface roughness. We develop a theoretical model in which the hysteresis appears as the result of a series of surface instabilities, in which the contact area grows or recedes by a finite amount. The model can be used to estimate material properties from contact experiments even when the measured P-h curves are not unique.
在诸如原子力显微镜或纳米压痕等涉及两个表面间粘附接触的实验中，根据压头是朝着样品移动还是远离样品，常常会测量到两条不同的接触力（P）与压痕深度（h）曲线。这种滞后现象的起源尚未得到很好的理解，通常归因于水分、塑性或粘弹性。在此，我们报告的实验表明，在不存在这些效应的情况下也可能存在滞后现象，并且其大小取决于表面粗糙度。我们建立了一个理论模型，其中滞后现象表现为一系列表面不稳定性的结果，在这些不稳定性中，接触面积会有限地增大或减小。即使所测量的P - h曲线不唯一，该模型也可用于从接触实验中估算材料特性。
