The Influence Of Contact States On Tribology Behaviour In Micro Sheet Forming

Due to the exitancen of tribology size effect , there is negative influence on micro forming. Tribology size effect was systematically studied in this paper, moreover by introducing a scale factor, friction model are established;Micro deep drawing of Au thin sheet was studied using the mould with DLC coating and the structure and composition of DLC which was weared were studied.Friction coefficient of specimens in different sizes were got by the strip drawing device in liquid lubricants and the influence of different contact stades on tribology size effect were studied. The results showed that the increment rate which of friction coefficient was increased with the increase of the specimens size was increased with the increase of the real contact rate, decreased with the increased of the mould surface roughness , normal pressure and forming velocity.A friction model was established based on the Coulomb theory and considering the ratio of the lubricants and no- lubricants zone.The real contact area rate was increase with the decrease of scale factor. The friction coefficient obtained from the experiment was in accord with the friction model. Besides,A correction which was used into the bulk forming was studied based on the friction model and the Wanheim/Bay general model.The simulation for deep drawing was done using the friction model which have been established abow by the FEM software.The result shows that the micro cup was broken more easily due to the high friction coefficient in the smaller scale factor.Micro deep drawing of copper T2 and Au thin sheet was studied using a micro blanking-deep drawing multiple operation mould with DLC coating. And compered the results with the micro deep drawing under the lubricants of PE films. The results showed that the DLC coated mould keep the forming quality stable. Structure and composition of DLC which was weared were studied by AFM and Raman spectrum.It indicated that there were phase transformation and the increase of hydrogen content during the wear process.