Adhesive Mechanics Of Rough Cylindrical Surfaces And Contact Analysis Of Micro Gears

Micro gear is a very important component in MEMS, and the transmissionperformance of micro gear plays a vital role to overall performance of MEMS. Incomparison to macro gear the surface force, which is caused by scale effects, will havesignificant effect on the contact between micro gears. At the same time, the tribologyand wear problems caused by surface effects in the micro gear are a prominent problem.However, the current research of micro gear mainly focus on manufacture and the toothcontact analyses of micro gear are relatively few studies. For the special of micro gear,theories which applied to macro gear are not suit for micro gear. Hence, for consideringthe role of surface force, the tooth contact analyses of micro gear are extremelyimportant.The contact between teeth of micro gear is equivalent to the contact betweencylinders. For considering the effect of surface roughness on the adhesive force in themicroscale, the adhesive contact between rough cylindrical surfaces is first establishedin this research. Equivalent pressure of cylindrical surface is calculated by utilizingnumerical method. The tooth contact of micro gear is established by using this adhesivecontact model. All of these provide a theoretical basis for micro gear. The main work isas follow:â‘ The relationships among external load, contact radius and elastic displacementfor the JKR and DMT adhesive contact models are analyzed. In the meantime, the roughsurface and GW model are also analyzed.â‘¡Surface asperities summits have been supposed as spherical, all with the sameradius. The high of asperities summits is assumed to Gaussian distribution. The contactbetween asperities and flat respectively adopt the JKR and DMT model. For consideringdeformation of the whole surface, the adhesive contacts for soft and hard materialsbetween rough cylindrical surfaces are respectively set up.â‘¢Discretization pressure and separation equations is calculated by using themodified Newton-Raphson iteration. The effective pressure distribution of cylindricalsurfaces, the relationship curves between dimensionless contact half-width and theexternal load and the pull-off forces are also calculated. These results are applied tocompare with the traditional contact model. The effect of surface roughness, elasticity modulus and cylindrical radius on the adhesive force is also analyzed.â‘£Machining technology, surface characteristic of micro gear and the problem ofload distribution during meshing process are analyzed. The tooth contact model, for softand hard materials micro gear, is studied by using the adhesive contact model which isset up in the previous. Under the action of surface force, the tooth surface contactcondition of micro gear is obtained. The determination method of adhesion failure ofmicro gear and the method of decreasing adhesive force are proposed.