Study On The Micro Plastic Deformation Behavior Of 304 Stainless Steel

With the development of modern industry,the demand for micro parts is increasing,and micro-plastic forming technology is widely applied because of its high efficiency and high accuracy.With the miniaturization of the size of the parts,the size effect appears,and the traditional plastic processing technology is no longer suitable for the micro plastic forming.In this paper,in order to provide the experimental basis for the future theoretical research,the plastic forming properties of 304 stainless steel sheet are studied by the experiments.First,the main research contents and research status of micro plastic forming are summarized in this paper.The physical mechanism of size effect in micro plastic forming and the corresponding theoretical models of two kinds of size effects are introduced.Then,the heat treatment experiments of sheets with different thickness are carried out.Under the same thickness,the grain size increases with the increase of heat treatment temperature.Then the uniaxial tensile test is carried out with the sample.Because the passive film formed on the surface of the sample has a strengthening effect on the sheet,the yield stress increases with the sheet thickness decreasing,which shows the size effect “thinner is stronger”.The experimental results are well predicted by the modified Hall-Petch formula.Second,the micro bending experiment is carried out with the heat treated sheets.The results show that the springback angle increases with the sheet thickness decreasing with the same heat treatment condition,which shows the size effect “thinner is stronger”.The springback angle increases with the heat treatment temperature decreasing with the same sheet thickness.The springback angle decreases with the grain size increasing with the same sheet thickness.Finally,the micro deep drawing experiment is carried out with the heat treated sheets,and drawing curves are analyzed.The results show that the influence of sheet thickness and heat treatment temperature on the variation rate of drawing force with stroke is obvious,and the diameter of punch has little influence on it,and the three factors have a certain influence on the amount of stroke corresponding to the maximum drawing force.