Simulation Of The Micro Deep Drawing Process And Analysis Of The Size Effect

Recent years, with the development of MST (Micro-system technology) and MEMS (Micro-electro-mechanical systems), and the needs of mechanical products greatly promote the microforming technique, the increasing trend of more and micro-parts products. When the size of mechanical parts is scaled down to microscale, the so-called size effect comes up which significantly affects the microforming process. It makes the know-how, empirical and analytical methods in traditional macroscale forming processes cannot be directly used in microforming fields. Therefore, in-depth understanding of material deforming behavior and process characteristics is critical in design and development of microforming. In this thesis, the micro deep drawing forming of copper sheet is conducted, to investigate the size effect.Firstly, based on the surface model, the copper sheet can be classified into surface grain and inner grain. Therefore the whole deformation behavior consists of surface grain deformation and inner grain deformation. The material constitutive model is established by introducing the scale effect factor, which is used to depict the surface grains ratio to inner grains. Moreover the constitutive model is verified by some experimental results cited from literatures to validate the material model.Furthermore, the simulation is conducted to reveal the entire deep drawing process. Comparison of the results from simulation and experiment proves that the simulation result is feasibility. It is found that the deep drawing process is affected by the size effect obviously, the deformation load decreases with the increase of grain size. The addition simulation is carried out with different relative die corner radius and relative punch corner radius, it indicates that the process is affected by relative die corner radius more obviously, especially when the grain size is similar to thickness.Ultimately, T-Shape friction test on the macros was modified to obtain the friction coefficient of microforming and friction calibration curves of under different conditions are determined through simulation. In addition simulation of analyzing effect of the material properties and die size, it was shown that variations in workpiece mechanical properties of up to 15% and the tolerance of 0.01 mm do not significantly influence the friction test results. But when the tolerance reaches to 0.05 mm, the friction calibration curves volatile. This conclusion has some guidance to the practical application.This paper uses the method combining theoretical research and simulation to study the size effect of micro deep drawing process and establishes the constitutive model considering the size effect of the material. Besides, simulation and analysis of micro deep drawing process and test method of micro forming friction are carried out to provide references for further research of micro forming technology.