Establishment of friction model and calculation of size factor in micro/meso forming processes

Due to the so-called “size effect,” the tribological theory for traditional plastic forming processes cannot be applied directly to the micro/meso forming processes. Therefore, the friction behavior in micro/meso forming was systematically studied in this paper. Firstly, based on the open-close lubrication pockets model, a scale factor was introduced to modify the Wanheim/Bay friction model and a micro/meso forming friction model was established. The established friction model can be used in the numerical simulation of micro/meso forming processes. Secondly, the simulation and experiment of cylindrical upsetting without lubricant were carried out. Then, by comparing the simulation and experiment results, the calculation method of friction factor in Wanheim/Bay friction model was proposed. Finally, the simulation and experiment of cylindrical upsetting under the condition of liquid lubrication were also performed, and thus an approach to calculate the size factor in the established friction model for micro/meso forming was proposed. The friction model built in this paper and the methods to calculate the parameters in this model are of great importance for the quantitative study of size effect in micro/meso forming processes.