粘着接触界面接触分离中的失稳与缺陷形核研究

Interfaces in adhesive contact exist in almost all the engineering systems and play an important role in their behavior and performance. Revealing the physical processes during the attachment and detachment of such interfaces is critical to understand and solve the puzzles in the mechanisms of interfacial failure and tribology. Although various models for adhesive contact have been developed, there are many illusive puzzles such as the interfacial instability and interfacial defects induced during the separation beyond their capture whose thorough understanding nevertheless may have great potentials in characterizing the mechanical properties of nanostructures. Consequently, in the present project, surface instability due to the adhesive contact between atomic probes and thin films, the Saffman-Taylor like instability and crack nucleation within the contact area during the normal separation, and the defect nucleation and sliding onset due tangential forces will be studied both experimentally and theoretically. It is aimed to determine the critical conditions and the governing factors for occurrence of the instabilities and to reveal the effect of defects on the separation of adhesively contacting interfaces. The outcome is expected to be beneficiary for developing novel techniques for measurement of mechanical properties of nanostructures as well as to promote understanding of the mechanisms involved in interfacial failure and tribology.

粘着接触界面广泛存在微纳系统和其他很多工程结构中，并对相关行为或性能具有重要影响。揭示粘着接触界面的接触分离行为是理解认识界面失效以及摩擦磨损机理的关键。尽管过去已建立了各种粘着接触力学模型，但粘着接触界面在任意载荷下的接触分离过程还存在很多问题难以理解却可能具有很好的应用前景，如接触分离过程中的界面失稳以及界面缺陷行为。本项目围绕这些问题，拟从理论模型和实验两方面具体深入研究探针类压头与薄膜类材料接触后所引起的表面失稳问题、法向载荷下脱粘过程接触界面的Saffman-Taylor失稳和接触区内的缺陷形核问题以及切向载荷下界面缺陷形核等问题。旨在确定界面失稳出现的临界条件及其影响因素，揭示界面缺陷的形核和扩张对分离的影响。相关研究成果预计既有利于发展新的力学参量表征技术，也可促进对界面失效和摩擦磨损机理的认识理解。

粘着接触界面接触和分离中的一些物理力学过程与材料界面强度、微观摩擦定律等紧密相关，是以往研究中尚未充分考虑的课题。本项目针对这些，主要在以下方面取得成果：.1）以JKR粘着接触模型为基础，考虑接触物体间初始存在温度差，得到了相应接触力与压入深度或接触尺寸之间的关系以及剥离力，揭示了温度差与剥离力之间的关系。.2）对切向载荷下的粘着接触，基于JKR模型和Rice有关裂纹尖端位错发射模型，研究了接触界面的位错形核。得到了局部出现滑动的临界剪切力即静摩擦力以及切向载荷对接触尺寸的影响规律，与相关实验结果吻合很好。.3）针对黏着斜接触问题，建立了广义的双赫兹模型，适用于Tabor参数为任意值的情况，且所得结果与很多实验结果吻合，并可得到摩擦定律。