Study On Factors Influencing FLD Of Aluminum Alloy And Application Under Warm/Hot Stamping Conditions

In recent years, with the increase of domestic automobile productions, sales andownership, the problems of exhaust pollution, energy shortages have become increasinglyserious. Lightweight of automobile is one of efficient measures to realize energyconservation and emission reduction and solve the problems of exhaust pollution and energyshortage. With the proposing of automobile lightening, the research of lightweight materialshas become the hot topic in recent years. Aluminum alloys have become ideal lightweightmaterials in the automotive industry because of their excellent properties. It is howeverobvious that the poor formability of aluminum alloys at room temperature substantiallylimits their usage in the automotive industry. One practical solution to this problem islogically the use of the warm/hot stamping process, which can considerably improve theformability of aluminum alloys.The forming limit diagram(FLD) is widely used in sheet metal forming for determiningthe likely occurrence of failure. It plays a safety-judging role in sheet metal formabilitysimulation. It is necessary to use FLD to judge the forming property of aluminum alloysunder warm/hot stamping conditions. However, it is difficult to obtain accurate FLD underwarm/hot stamping conditions by the reason of temperature and experiment conditions. Thismeans that there are errors between the experimental FLD and the theoretical FLD.Therefore, it is necessary to study on factors influencing FLD of aluminum alloy andapplication for obtaining accurate FLD under warm/hot stamping conditions.First of all, experiments for obtaining the FLD of the AA5754are conducted underwarm/hot stamping conditions. Then, FE models are created and validated on the basis ofexperimental results, the focus is on choosing the material model of AA5754and FE modelof drawbead. Secondly, a number of FE simulations are carried out to investigate the factors influencingFLD. The study emphatically analyzes the two factors influencing FLD and quantizes errors,including the factors influencing the whole FLD, the plane strain state, the biaxial tensionstate, the uniaxial tension state and the necking location of the test-piece. The conclusionsfrom the study provide more accurate standard for the forming of aluminum alloy underwarm/hot stamping conditions.Finally, based on the analysis of FLD under different friction coefficients, the ideal FLDof AA5754under warm/hot stamping conditions had been chosen. Then, analyze the formingproperty of outerdoor using the accurate FLD under warm/hot stamping conditions. Basedon the analysis, it can be concluded that1) Simulating using the drawbead model canimprove the wrinkling during the forming process, it is an effective method to improve theforming property;2) The proper range of virtual stamping speed is10times to50times ofactual stamping speed, selecting a higher virtual speed can improve calculating efficiency,and the accuracy of simulation should not be affected.