The Numerical Simulation Study Of Superplastic Free Bulging Under The Typical Loading Paths

With the maturity of the superplastic theory and superplastic forming technology,superplastic forming has caused more and more attention by people, and its developmentand application prospect is also becoming more and more widely. Superplastic bulging isan effective process method which is used to make difficult complex components.Compared with the conventional technology, superplastic bulging can reduce componentsweight and manufacturing costs significantly. It has been widely used in aerospace andother fields. However, superplastic bulging needs a long time during the manufacturingprocess and has complex deformation under high temperature. Besides, it also has somedefects such as uneven thickness distribution and grain growth. So how to improve quality,shorten the forming time is the emphasis and difficulty in research of superplastic forming.Since most superplastic materials have the structural sensitivity, so their deformationand stress state will be influenced by loading path. Different loading paths will make thechange to strain rate sensitivity index, stress, strain, strain rate and thickness distribution,and then affect the quality of molding and forming time. The study about different loadingpaths will have important practical significance and influence to mechanical analysis,various parameters of superplastic and the finite element simulation, it will also provide thenecessary theoretical basis for further study and practical production.The article had a full knowledge and research to a kind of loading paths. On this basis,author simulated the superplastic bulging process of AZ31magnesium alloy under twotypical loading paths by using the finite element analysis software MSC.Marc. Thethickness, stress and strain distribution of superplastic air-bulging was analyzed underdifferent loading paths, which was used to predict the forming defects (neck, rupture, etc.)of workpiece. There is a contrast about the distribution of thickness, stress and strain underdifferent strain-rate sensitivity index, different forming height and pressure. The influence law of the strain-rate sensitivity index and the forming pressure to the superplasticair-bulging was determined. The superplastic forming process parameters were optimized.Moreover, there was a comparison about thickness and stress distribution under two kindsof loading paths.On the basis of successful and accurately simulation, this article has calculate andanalyze each to the stress, strain, equivalent stress, equivalent strain and bulging thicknessdistribution under two typical loading paths by the Song Yuquan analytical method andfinite element simulation. It made our mechanics analysis of bulging parts more accurateand intuitive. Moreover, it further illustrated the rationality of simulation parameters andthe accuracy of the simulation results by comparing the analytic results with the analogoutput.Theoretical analysis and simulation results showed that the free bulging can get thebest bulging parts when it remained constant strain rate in bulging vertices. So we obtainedthe pressure-time curve of bulging through the finite element simulation under thecondition of constant strain rate by software MSC.MARC. Then we determined the actualpressure-time curve of surplusplastic experiment by the simulation curve, which laid afoundation for superplastic bulging experimental research. Finally, on the basis of theresults of numerical simulation, I designed and retrofited the loading system of superplasticbulging experiment device, made it can realize various typical loading paths in theexperimental process, and expounds the detailed steps for the realization of various typicalloading paths.