| With the rapid development of the automobile industry and the aggravation of the energy crisis,more and more requirements are put forward for the goal of automobile lightweight.In recent years,automobile lightweight has become one of the main trends in the development of automobile industry.Aluminum alloy has the advantages of high specific strength,good corrosion resistance,good recyclability,good formability and so on.At present,it has become one of the most ideal materials in automobile lightweight technology.It is widely used in the design and manufacturing of automobile body structure.For the production of such body structure parts,stamping is generally used for processing.In this paper,5052 aluminum alloy square box is taken as the research object.Firstly,the properties and parameters of 5052 aluminum alloy material are obtained by tensile test,the stress-strain curve is drawn,the anisotropy of the material is considered,and the constitutive model(Hollomon model,Johnson-Cook model and Swift model)of the material at room temperature is established,and the model is verified.Through comparative analysis,it can be seen that Swift model can better fit the test data.Secondly,the paper analyzes the stamping process of square box and the defects of square box,and carries out stamping experiments.The experimental results show that when the blank holder force is less than 15 KN,wrinkle defects are easy to occur,and when the blank holder force is more than 35 KN,fracture defects will occur.The numerical simulation model of 5052 aluminum alloy square box stamping is established by using the professional stamping numerical simulation software Dynaform.The validity of the model is verified by experiments.Then,taking the thinning rate,thickness distribution and forming limit diagram as the evaluation indexes,the influence of different process parameters on the stamping process of square box is studied.Among them,with the increase of punch fillet radius,the fracture trend of square box will slow down and the wrinkle trend will increase;with the increase of blank holder force,the value of thinning rate will increase and the value of thickening rate will decrease,and the optimal value of blank holder force is 15.932KN;with the increase of friction coefficient,the fracture trend will increase and the wrinkle trend will slow down,and the optimal value of friction coefficient is 0.175;with the increase of stamping speed,the thickness will decrease.The overall rate shows a downward trend,thethickening rate has both an upward trend and a downward trend,and the optimal stamping speed is 1313mm/s;with the increase of sheet metal thickness,the thinning rate and thickening rate both show an upward trend,and the thinning rate rises faster;the larger the stamping stroke,the greater the possibility of rupture of square box parts,and the increasing wrinkle trend.On this basis,the formability of square box under variable blank holder force is further studied,and the simulation results are compared with the experimental results.The results show that the forming quality can be improved and the formability of sheet metal can be improved by applying Λ type variable blank holder force loading mode under the conventional variable blank holder force loading mode.Under Λ type variable blank holder force loading mode,the forming effect is the best when the upper limit value of variable blank holder force is 70 KN and the initial value is 12 KN.Finally,a curve type variable blank holder force loading mode is proposed.Through simulation analysis,it can be seen that under the concave curve variable blank holder force loading mode,the square box will not produce crack defects,and the thinning rate is only 14.264% when the forming effect is optimal. |
PDF Full Text Request