Study On The Size Effects Of 304 Stainless Steel Micro Drawing

With the rapid development of micro plastic forming technology,micro parts have been widely used in various industries,and the demand is greatly increased.The micro plastic forming has the characteristics of high efficiency and good strength,and is suitable for large scale production of micro and small metal parts.In micro plastic forming,the smaller the size of the micro parts,the less the number of internal grain,the yield stress,tensile strength and elongation rate of the materials are different from that of conventional plastic forming.With the majority of scholars in-depth study in micro plastic forming technology,surface layer model,crystal plasticity theory model and strain gradient hardening model of the size effect of micro forming process in the analysis,can explain some experimental phenomenon,but there are some limitations.In order to further explore the formation of micro parts,this paper has carried out the experiment and numerical simulation analysis of the 304 stainless steel sheet in the micro cylindrical part drawing.In this paper,304 stainless steel plate as the test material,different thickness of the specimen after different temperature heat treatment,the one-way tensile test,the test results show that the yield stress of the material with the thinning of the material and enhance.Considering the influence of thickness on the surface of the grain arrangement and dislocation slip,the Hall-Petch relation was added in relative thickness,the better prediction on the yield stress of different thickness of the material,the experimental results are consistent with the predicted results;because the material is thin,thick grain number is less,the grain is not easy to coordinate the deformation,the tensile strength and elongation increased with decreasing material.In the micro deep drawing experiment,obtain the drawing force displacement curve,under the same conditions of heat treatment,drawing force displacement curve is affected by the tube diameter and the thickness of the test,and the maximum drawing force with the thinning of the material decreases;the introduction of Nix-Gao strain gradient hardening correction model is used to calculate the maximum drawing force,comparison with the test results,the results are basically consistent.Using finite element analysis software DYNAFORM of 304 stainless steel tube micro deep drawing process was simulated and analyzed the distribution and variation of stress in the forming process,verify the cylinder numerical simulation of micro deep drawing forming feasibility.