| Aluminum alloy forming process is widely used in automobile industry,which is used to manufacture many kinds of parts,such as automobile body,the panel of automobile and the chassis of automobile,etc.In order to avoid a large range of machining defects in the mass production of parts,it is necessary to study the bending forming process in depth.6061 aluminum alloy rolling plate is taken as the research object.The 6061 aluminum alloy plates were treated by solution treatment and artificial aging for 1 h,2 h,4 h and 8 h,and then quasi-static tensile and three-point bending tests were carried out by instron5966 electronic universal testing machine.The bending curvature distribution of 6061 aluminum alloy sheet during plastic deformation was obtained by using DIC(Digital Image Correlation,DIC)correlation equipment.The bending and springback process of 6061 aluminum alloy sheet was simulated by LS-DYNA software.The effects of material parameters such as hardening index n and hardening coefficient K on bending springback,stress distribution and section deformation of 6061 aluminum alloy sheet were discussed.The results show that solution heat treatment can significantly improve the plastic deformation ability and elongation of 6061 aluminum alloy sheet.The work hardening index n of T6 sheet after decreases rapidly,and the longer the artificial aging time is,the smaller the work hardening index n is.With the increase of artificial aging time,the strength of 6061 aluminum alloy sample is improved,the work hardening rate is gradually increased,and necking phenomenon is easy to appear in the deformation process.The equivalent compressive stress on the upper surface and the equivalent tensile stress on the lower surface of T6 aluminum alloy plate increase gradually with the increase of artificial aging time.And the difference of the equivalent stress increases gradually,which leads to the increase of springback.The increase of strain hardening coefficient K promotes the nonuniform distribution of thickness and the distortion of cross section.In order to simulate the real sheet metal forming process,the bending process of 6061 aluminum alloy sheet is stretched first and then bent at three points.The 6061 aluminum alloy samples were tested under quasi-static conditions by single pre-tension and cyclic pre-tension.The pre-stretching amounts were 2 mm,4 mm,6 mm and 8 mm respectively.Then the three-point bending test is carried out on the pre-loaded specimen.The mechanical properties of 6061 aluminum alloy sheet during the process of the loading and unloading were analyzed.The variation of elastic modulus with different plastic strain degree and its influence on bending properties were studied.According to the flow stress curves of the specimens with different pretensions,a constitutive model considering the pre-strain was obtained.The results show that with the increase of plastic deformation,the inelastic recovery behavior of 6061 aluminum alloy gradually increases,the value of elastic modulus E decreases,and the springback angle increases gradually. |
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