Effects Of Fractal Rough Surface On Tribology In MEMS

Recently MEMS is a hotspot of Micro-Nano Science and Technology. As a result of the scale effect, contact, adhesion, wear and lubrication have been one of the most important research area in MEMS.Based on the fractal rough surface, tribological properties in MEMS such as contact, adhesion, wear and lubrication have been studied in this thesis. Finite Element Method is used in the research on contact and adhesion; numerical method is used in the research on wear; Finite Volume Method is used in the research on lubrication. The main research contents and conclusions are as follows:1. Fractal geometry theory is introduced to simulate the rough surface which is then measured by AFM. After that the polysilicon surface is simulated through fractal function. The result indicates that fractal dimension is the intrinsic parameter of rough surface. Besides, polysilicon surface is fractal.2. Contact, adhesion and wear in MEMS have been studied based on fractal rough surface. The results indicate that contact area and surface adhesive force will be reduced with the decrease of fractal dimension. Furthermore, when fractal dimension is between 1.45 and 1.55, the wear ratio is the minimum.3. Reynolds equation is modified based on roughness effect which is incorporated in the research on micro gas bearing. The results indicate that the pressure of gas will be decreased as a result of surface roughness which could also affect the load capacity gas bearing, slip velocity and Reynolds distribution of the gas.In a word, the methods and conclusions of this thesis will pave a way for Tribology in MEMS, showing great promise in both theoretical explorations and practical applications.