Surface Roughness And Multi - Scale Rough Surface

With the development of science and technology, surface processing technology becomes more diverse. Thus, the surfaces processed become more and more smooth. In spite of this, when the surface is magnified to different scales, different degree of roughness can be observed. When rough surfaces are brought into contact under typical loads, only the peaks or asperities come into contact. The asperities exist on many different magnitudes of scales and can also vary in shape. The contacts between these asperities govern the friction, wear and the surface fatigue resistance, and also constrict the conduction of electricity and heat.In this work, the Dectek 150 profilometer from Vecco Company was used to measure the different surface roughness, all these measured surfaces were from a standard reference surface with various finishes. Then two different series--arithmetic series and geometric series, were implemented to analyze the surface profile. In describing the rough surfaces, the fractal dimension(D) is an important and widely used parameter, two different methods---the roughness length method and the box-counting method were used to calculate the value and the values from these two methods were then compared.Moreover, after performing the analysis on the contact area and contact pressure, the results that the linear relationship between the contact pressure and the real contact area can be obtained. This conclusion is different from the results that many traditional methods obtained. After the analysis of the relationship between the electrical contact resistance and the contact pressure, the multiscale roughness model can make a better prediction of the electrical contact resistance at some certain forces compared with some traditional methods was found. In analyzing the processed surfaces, a stacked multiscale contact model was applied. The results show that the multiscale roughness of surfaces, as described by the aspect ratio of each scale(B), can greatly influence the real contact area and the pressure by several orders of magnitude in both the elastic and elastic-plastic regimes. Furthermore, some certain types of machining processes can be chosen properly to control the roughness of equipment parts reasonably, so that the properties of seal, wear resistant and contact stiffness for the parts can be developed well and then the parts maybe better suited to the contact applications.