In experiments that involve contact with adhesion between two surfaces, as found in atomic force microscopy or nanoindentation, two distinct contact force (P) versus 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 which 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.

中文翻译：

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表面粗糙度在粘合剂弹性接触过程中的滞后作用

在涉及两个表面之间的粘附接触的实验中，如在原子力显微镜或纳米压痕中发现的那样，通常根据压头是移向还是远离样品来测量两种不同的接触力 (P) 与压痕深度 (h) 曲线. 这种滞后的起源尚不清楚，通常归因于水分、可塑性或粘弹性。在这里，我们报告的实验表明，在没有这些影响的情况下可以存在滞后，并且其大小取决于表面粗糙度。我们开发了一个理论模型，其中滞后出现是一系列表面不稳定性的结果，其中接触面积以有限的量增长或后退。