| Superplastic forming/diffusion bonding（SPF/DB）is a groundbreaking technology of the modernaviation and space industry, due to its unique advantages of increase structural integrity and weightreduction. With the improvement of application requirements, more layer, bigger size and morecomplex hollow sandwich structure is needed. There are much effort have been made in three-sheetand four-sheet SPF/DB structures research, however there is still a large gap between the developedcountry and ours.The defects in the forming of multilayer SPF/DB structures including face sheet of three-sheetstructure often produce groove defect，the core sheet of four-sheet structure existing the phenomenonthat SPF forming and diffusion bonding is not completely and the distribution of thickness is uneven.In this paper, forming of three-sheet and four-sheet SPF/DB structure of TC4titanium alloy isinvestigated using the numerical simulation and experimental method.Results show that thickness ratio λ between face sheet and core sheet and the angle α betweencore stiffener and face sheet has an important impact on the phenomenon of groove to the three-sheetSPF/DB structure, face sheet grooves almost completely eliminated when the efficient λ=3and α=30°;Strain rateε and strain rate sensitivity coefficient m has an important influence on the formingdefects of four-sheet structure. With the increasing of m value and reduction ofε value, core sheetforming situation will be improved. |
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