Jülich Supercomputing Centre, FZ Jülich, 52428 Jülich, Germany.
Beilstein J Nanotechnol. 2014 Apr 8;5:419-37. doi: 10.3762/bjnano.5.50. eCollection 2014.
In this work, single-asperity contact mechanics is investigated for positive and negative work of adhesion Δγ. In the latter case, finite-range repulsion acts in addition to hard-wall constraints. This constitutes a continuum model for a contact immersed in a strongly wetting fluid, which can only be squeezed out in the center of the contact through a sufficiently large normal load F N. As for positive work of adhesion, two stable solutions can coexist in a finite range of normal loads. The competing solutions can be readily interpreted as contacts with either a load-bearing or a squeezed-out fluid. The possibility for coexistence and the subsequent discontinuous wetting and squeeze-out instabilities depend not only on the Tabor coefficient μT but also on the functional form of the finite-range repulsion. For example, coexistence and discontinuous wetting or squeeze-out do not occur when the repulsion decreases exponentially with distance. For positive work of adhesion, the normal displacement mainly depends on F N, Δγ, and μT but - unlike the contact area - barely on the functional form of the finite-range attraction. The results can benefit the interpretation of atomic force microscopy in liquid environments and the modeling of multi-asperity contacts.
在这项工作中，研究了单一粗糙峰接触力学在正粘附功和负粘附功 Δγ 的情况。在后一种情况下，除了硬壁约束外，还存在有限范围的排斥力。这构成了一种接触浸入强润湿流体的连续体模型，只有通过足够大的法向载荷 F N 才能在接触中心将其挤出。对于正粘附功，在有限的法向载荷范围内可以共存两个稳定的解。竞争的解决方案可以很容易地解释为具有承载流体或挤出流体的接触。共存以及随后的不连续润湿和挤出不稳定性不仅取决于 Tabor 系数 μT，还取决于有限范围排斥力的函数形式。例如，当排斥力随距离呈指数衰减时，共存和不连续润湿或挤出不会发生。对于正粘附功，法向位移主要取决于 F N、Δγ 和 μT，但与接触面积不同，它几乎不受有限范围吸引力的函数形式的影响。研究结果有助于解释原子力显微镜在液体环境中的应用以及多粗糙峰接触的建模。
