Research On Mechanical Properties And Bending Springback Of Pure Copper Foil Under Micro Scale

In recent years, with the rapid development of electronics industry and precision machinery, micro-parts are widely used in the field of electronics, communications, medical care, aerospace and the other fields. Plastic micro-forming technology becomes the first choice of mass production of micro-parts for its advantages including low material loss, low cost, high efficiency, high productivity and excellent mechanical properties. However, because of the miniaturization of specimen size, during the process of metal roil forming, the shaping mechanism and deformation rule of the material is different from macro-forming, and shows a strong size effect, which restricts the development of micro plastic forming. Therefore, the study of the size effect on the mechanical properties has important significance to promote the development of micro metal foil forming technology.T2 pure copper foil was selected as the exprimental material. Heat treatment experiments and single micro-tensile tests were performed to investigate the influence of rolling, stock thickness, grain size and oxidation film on the mechanical properties. The results show that, for the pure copper foil with rolling state, under the same material samping direction, yield ratio increases and the elongation decreases with the decrease of stock thickness; under the same stock thickness, the mechanical properties parallel to the rolling direction is superior to perpendicular to the rolling direction. For the pure copper through high temperature annealing process with protective atmosphere, the flow stress of material decreases with the increase of grain size as the stock thickness is constant; but the materials with different thickness exhibit two distinct size effect as the annealing temperature is identical. When the stock thickness is more than 0.05mm, it shows size effect phenomenon "the smaller the weaker", and when the stock thickness is less than 0.05mm, it shows "the smaller the stronger" phenomenon. For the pure copper through low temperature annealing process with different atmosphere, flaw stress of the material after oxidation annealing is higher than the material after vacuum annealing which shows that oxidation film at micro-forming has a significant influence on the mechanical properties of the materials.This paper constructed a finite element model of a V-shape free bending with ABAQUS. The pure copper micro bending and springback process were simulated based on the constitutive model of the material obtained by tensile test. This paper studied the influence law on bending springback by the material thickness, grain size, oxidation filmand’ radius. And the measures to reduce the bending springback were given. The simulation results show that:the springback of bending increases with the decrease of stock thickness. The thinner the blank is, the faster the springback increases which shows the size effect. The springback decreases with the increase of grain size, and it increases with the relative thickness. The springback increases when punch radius rises; the existence of the oxidation film also increases springback partly.