Experimental And Numerical Research On Random Characteristics Of Flow Stress Distribution In Micro Scale

Micro-forming technology is mainly used in electronic industry, telecommunication and medical treatment. Micro parts of high precision, mechanical performance and stability are demanded. Traditional machining and other processing methods can provide high- precisioned micro parts; however, mass production cannot be applied due to high cost and low productivity. Therefore, mass production technology of micro parts of high precision and performance are in badly need, and micro forming technology can meet such requirements. This research was supported by National Natural Science Foundation of China, Doctoral Fund of Ministry of Education of China and Scientific Research initial fund of Young Teachers from Shanghai Jiao Tong University.Based on detailed analysis about current literature review of the micro-forming technology and its scale effects, this paper adopted micro upsetting with various conditions to study the fluctuation of flow stress as big strain was available in upsetting. By measuring micro hardness along diameter on the surfaces, random fluctuation of flow stress was study. Results showed that in small strain condition, smaller friction and bigger grain size did bad to uniform distribution of flow stress, however, in large strain condition, they do good to the uniform distribution of flow stress. This was useful for the further R&D of micro forming.Furthermore, based on the rate dependent crystal plasticity constitutive relation and Taylor polycrystal model, with the universal finite element software MSC.Marc2007 as the developing platform. Results show simulation and experiment were consistent, so crystal plasticity finite element simulation results can relatively truly reflect the stress and deformation situation of material in micro scale. This research provided necessary information to further simulation research.