Influence of the surface geometry on the friction in adhesive contacts

接触体在粘着相互作用下的切向载荷和运动属于接触力学中最不了解的现象。与普通的粘合接触，即仅仅接触和脱离接触相比，没有通用的、基于能量的方法来解决这个问题。相反，耗散力量起着至关重要的作用。计划中的项目的主要目标是阐明粘性接触中摩擦力和能量耗散的微观和介观来源。在此基础上，提出了胶粘剂切向接触的建模和仿真概念，并在数值程序中实现，并进行了实验验证。我们的指导思想是，在微观尺度上的附着是无耗散的，只有由表面化学或地形的微观不均一性引起的不稳定性才会导致能量耗散(以及相应的摩擦力)。虽然这一概念在摩擦物理学(Prandtl-Tomlinson模型)中并不新鲜，但它还没有明确地应用于切向粘合接触。为了实现这一目标，在已开发的模拟可逆粘着的方法的基础上，对非均质接触进行了理论研究。这将与粘合切向接触的系统实验研究齐头并进。对胶粘剂接触中的耗散过程有充分的物理理解将在实际应用中指导胶粘剂相互作用的控制。特别是，将从理论和实验上考察形状、粗糙度、材料非均质性和其他尚未确定的系统参数的影响。

Tangential loading and movement of contacting bodies in the presence of adhesive interaction belongs to the least understood phenomena in contact mechanics. In contrast to normal adhesive contact, i.e. the mere approach and detachment of contacts, there is no universal, energy-based approach to this problem. Instead, dissipative forces play a crucial role. The main goal of the planned project is to clarify the microscopic and mesoscopic origin of the frictional forces and of the energy dissipation in an adhesive contact. Based on this, a concept for the modeling and simulation of adhesive tangential contacts should be developed, implemented in a numerical program and validated experimentally. We are guided by the idea that adhesion on the microscale is dissipation-free and that only instabilities - caused by microscopic heterogeneity of surface chemistry or topography - lead to energy dissipation (and corresponding frictional forces). While this idea is not new in friction physics (Prandtl-Tomlinson model), it has not yet been explicitly applied to tangential adhesive contacts. To achieve this goal, theoretical investigations of heterogeneous contacts are to be undertaken, based on the methods already developed to simulate reversible adhesion. This will go hand-in-hand with systematic experimental investigation of the adhesive tangential contact. A well-founded physical understanding of the dissipative processes in adhesive contacts will lead the way to control of adhesive interactions in practical applications. In particular, the influence of the shape, the roughness, the material heterogeneity and other system parameters that have yet to be determined will be examined theoretically and experimentally.