Wear is a gradual removal of the material of the bodies during their interaction. The process appears in many mechanical systems, ranging from large scales, as in wind mills, to nanoscales, as in the AFM tip – substrate contact. The macroscale wear is a relatively well developed field of tribology, whereas, the wear at the nanoscale has become a forefront of the scientific interest only recently. Since the behavior of many phenomena qualitatively change at the nanoscale, the macro scale methods has to be adapted to be applicable in the nanoscale.
Researchers from University of California Merced adapted abrasive and adhesive macroscopic wear models by redefining classical wear coefficients and explored the process at nanoscale. They characterized wear between Si AFM tip and Cu substrate using molecular dynamic simulations. By varying the applied load and roughness of the tip and using the macroscale wear models, they were able to separate the adhesive and abrasive wear components in the total wear and find their relative importance. It was found, that the relative input of the adhesive wear decreases with the increase of roughness, whereas the abrasive component increases.
Further, they applied the developed model to find the roughness of the tip, which minimizes wear. The optimum was found to be dependent on the load. This model can be used to control and optimize the behavior of nanoscale devices.
Further details of the research can be found in the original article by Zhijiang Ye and Ashlie Martini, “Atomistic simulation of the effect of roughness on nanoscale wear”, doi:10.1016/j.commatsci.2015.02.036.
Credit for the image: Zhijiang Ye and Ashlie Martini