Recently, Dr. Yang Xu, a Research Professor from the School of Mechanical Engineering at Hefei University of Technology has made a breakthrough in the field of rough surface contact.His research paper entitled “An Asperity-based Statistical Model for the Adhesive Friction of Elastic Nominally Flat Rough Contact Interfaces” was published in the Journal of the Mechanics and Physics of Solids, a prestigious journal in solid mechanics.
Fig. 1 In 2018, Sahli et al. (PNAS. 2018, 115: 471 – 476) precisely measured the evolution of the contact areabetween a rough PDMS surface and a rigid glass with the friction. They found,for the first time, that the real contact area decreased parabolically with the increase of friction force right before the slip inception.Their experimental results are shown in the solid line in Fig. 2.
Fig. 2: The real contact area decreases parabolically with the increase of the friction force
In the present study, Xu et al. proposed an asperity-based statistical model for the rough surface interaction, see Fig. 2. The model qualitatively reproduces both the macroscopic shear-induced contact area reduction and, remarkably, the static friction peak. The parabolic drop of the real contact area against the friction force is due to the competition between the adhesive contact over the asperities in stick and slip stages. It also demonstrates that the static peak force (coefficient of static friction) is not an intrinsic material property, instead it depends on the normal load and certain key microscale interface properties such assurface energy, mode mixity and frictional shear strength. The present work can be served as a theoretical tool for those cross-disciplinary areas involving adhesive rough surface contact, e.g., wearable VR tactile devices, earthquakes, triboelectric nanogenerator.
Fig. 3: Schematic Diagram of AsperityContact
Dr. Yang Xu is the first and the corresponding author of this paper. Other authors include Dr. Daniel Mulvihill, Associate Professor at the University of Glasgow (co-corresponding author);Dr. Julien Scheibert, Scientist a CRNS Researcher at the Tribology and System Dynamics Laboratory (LTDS); Dr. Nikolaj Gadegaard, Professor at the University of Glasgow. This study is funded by the “Huangshan Scholar” Outstanding Young Scholar start-up funding of Hefei University of Technology, Leverhulme Trust, and the National Natural Science Foundation of China.
