Viscoelasticity is well known to cause significant hysteresis of crack closure and opening when an elastomer is brought in and out of contact with a flat, rigid, adhesive counterface. A separate origin of adhesive hysteresis is small-scale, elastic multistability. Here, we study a system in which both mechanisms act concurrently. Specifically, we compare the simulated and experimentally measured time evolution of the interfacial force and the real contact area between a soft elastomer and a rigid, flat punch, to which small-scale, single-sinusoidal roughness is added. To this end, we further the Green’s function molecular dynamics method and extend recently developed imaging techniques to elucidate the rate- and preload-dependence of the pull-off process. Our results reveal that hysteresis is much enhanced when the saddle points of the topography come into contact, which, however, is impeded by viscoelastic forces and may require sufficiently large preloads. A similar coaction of viscous- and multistability effects is expected to occur in macroscopic polymer contacts and to be relevant, e.g., for pressure-sensitive adhesives and modern adhesive gripping devices.

众所周知，当弹性体与平坦、刚性、粘性的接触面接触和脱离接触时，粘弹性会导致裂纹闭合和张开的显着滞后。粘附滞后的另一个来源是小规模弹性多稳定性。在这里，我们研究了一个系统，其中两种机制同时起作用。具体来说，我们比较了模拟和实验测量的界面力的时间演变以及软弹性体和刚性平面冲头之间的真实接触面积，其中添加了小规模的单正弦粗糙度。为此，我们进一步发展了格林函数分子动力学方法，并扩展了最近开发的成像技术，以阐明拉断过程的速率和预载依赖性。我们的结果表明，当形貌的鞍点接触时，滞后会大大增强，但是，这会受到粘弹性力的阻碍，并且可能需要足够大的预紧力。预计在宏观聚合物接触中会发生类似的粘性和多稳定性效应的共同作用，并且与例如压敏粘合剂和现代粘合剂抓取装置相关。