Adhesion effect analysis of ultra-fine lunar dust particles on the aluminum-based rough surface based on the fractal theory

Abstract

Investigation on the adhesion effect of lunar dust particles on contacting interface improves in lunar dust protection and prolongs the equipment service life. In this work, the contact mathematical adhesion model between an ultra-fine lunar dust particle and the aluminum-based rough surface is established based on the fractal theory. The research shows that the van der Waals force dominates adhesion force for ultra-fine lunar dust particles in space environment and is directly related to the rough surface fractal parameters, namely the fractal dimension parameter D , fractal roughness G as well as root-mean-square roughness(rms). Based on van der Waals adhesion model, the optimum rough surface fractal parameters are obtained through model optimization when the van der Waals force is minimal. The van der Waals forces reaches the minimum for lunar dust particle with diameters of 500 nm and 2.5 μm when the rms is 2.689 nm and 4.7 nm respectively. To validate the effectiveness of using fractal theory to the surface topography in van der Waals force calculation, the dust residual rates have been compared with the aluminum surfaces prepared using chemical etching method, electrochemical etching method, and combined chemical method. Based on the AFM topography of the surfaces, the van der Waals forces have been calculated between the lunar dust particles and the surfaces prepared using different etching methods. The centrifugal experiments suggest that van der Waals force is positively related to the dust residual rates. In summary, the fractal theory is effective in describing the surface roughness in lunar dust adhesion problems and it can be used in future lunar dust protection surface design and applications.