Research On Size Effects Of H80 Copper Foils Bend Forming

With the development of micro-electro-mechanical-system technology,the demanded quantities of micro-metal parts are daily on the increase.Micro-metal parts fabricating with forming method have the advantages of high efficiency low cost and suitable for mass production.However,the size effect has appeared with the miniaturization of metal parts.At present,the research on the size effect of microforming is still in the exploratory stage.In this paper,the size effect of H80 brass foil bending process has been studied through theoretical analysis and experimental research.Firstly,the mechanical properties of H80 brass foil were studied by uniaxial tensile test.According to the experimental data,the mechanical properties of H80 brass foil showed a strong size effect with the change of material size.The reason why the flow stress decreasing was that the percentages of the surface grain decreased with decreasing of the thickness and increasing of the grain size.In addition,the analysis results of micro-hardness indicated that the forming probability of easy forming areas increased with thickness decreasing and intensively deforming of easy forming areas were the main reason of the thin foil prematurely fracturing.Secondly,the three-point bending test of H80 brass foil was performed to study the influence of different process parameters on the bending springback.The experimental results showed that the springback angle and its coefficient of variation had different type size effects with the change of process parameters.Changing the thickness dimension,punch radius and bending angle could increase the proportion of plastic deformation in the sample,which was beneficial to reduce the springback angle In addition,refining grain or increasing the thickness were beneficial to improve the bending deformation distribution and the part quality.Lastly,Voronoi exact polycrystalline model and rough polycrystalline model were established in Abaqus software combining with polycrystalline theory,and the finite element simulation of metal foil bending was carried out.The results showed that the simulated deformation distribution and the springback law were in good agreement with the experimental results.These two models include the grain shape,mechanical properties and distribution of materials properties,which could describe the size effect well in the process of material forming.