Prediction Of Aluminum Alloy Sheet Forming Limit And Numerical Simulation

In recent years, more and more lightweight aluminum alloy material have beenused in the aerospace and automobile industry, so it’s very important to study theformability of aluminum alloy sheet. The forming limit diagram (FLD) and theforming limit stress diagram (FLSD) are important criterion to judge the material’sperformance in the process of sheet metal forming. The experiment method to getthese two kinds of forming limit diagram existing many difficulties, such as theexperiment equipment is complex, the experimental cycle is long and themeasurement technology is imperfect. Based on the above matters, this paper takesthe5083aluminum alloy sheet as research object and uses the method of combiningthe theory and numerical simulation to study the FLD and FLSD access method, theinfluence factors, their application and other aspects.Firstly, the basic theory of plastic relating to the plate’s plastic deformationprocess is introduced in the theoretical part of the thesis. Analysis and comparison ofthe anisotropic yield criterion, hardening rule and flow rule. Moreover, summarizesthe scope of application of Swift diffuse instability theory and Hill localizedinstability theory and the method of using these two kinds of theory to get thecomplete FLD. Then，based on the above theory, using the Hill48and Hill79yieldcriterions deduced the limit strain formula, bring in the Mechanical propertyparameters of the5083aluminum alloy sheet metal into the formula to get FLD.Finally, use the incremental theory to get the FLSD under linear strain path.At first，in the numerical simulation part of the paper, the principle to get FLDand FLSD by using the finite element simulation is introduced. Through the analysis,using the maximum punch force criterion and the strain path change criterion as theinstability criterion is put forward. Then, the finite element simulation results andtheoretical results are compared and analyzed, the results show that the right part ofFLD obtained by using Swift diffuse instability theory calculation is not very accurate; the left part of FLD obtained by localized instability criterion was similar to thesimulation result. At last, the regularity of FLD changes with coefficient of friction,the stamping speed and blank holder force is discussed, The study shows that whenthe friction coefficient is0.12, the stamping speed is1000mm/s, the blank holderforce is20KN the result is more reasonable.In addition, by the use of preloading and bulging simulation in ABAQUS, thechanging rules of FLD and FLSD with the strain path is analyzed. The result showsthat the FLSD is independent of strain path and the FLD is associated with the strainpath. Finally, use FLSD and FLD as the ultimate criterion in the finite elementsimulation. The same result shows that the FLSD is a reliable limit criterion andFLSD can deal with complex loading path problem.This paper obtains the5083aluminum alloy sheet of FLD and FLSD by thetheory and method of finite element. They can be used as the failure criterion ofprocess of linear strain path problem in the finite element simulation. At the sametime this paper provides the method of theory and finite element access for obtainingforming limit of other types of material. At last, the foundation for the use of FLSD inmore complex loading path problem is laid.