The Research On Multilayer Titanium Structure SPF/DB Based On Optimal Pressure Control With FEM

Superplastic Forming/Diffusion Bonding (SPF/DB) process is one of the most important research subjects in the aero-space engineering field. The titanium multilayer structure is an important application in SPF/DB because of its perfect frame, low weight and few components. However the titanium alloy SPF/DB process has been taken into applied use, the study on forming character and process parameters are not good enough. The research institute 306 and 625 both were confronted with some problems during forming process, such as the unstable forming quality and bad thickness distribution. Research on combination of theory and real forming is necessary yet.As an assistant tool of forming analysis, the finite element method can get rid of fussy experiments and come to conclusions that referred to real experiments directly. In this thesis, based on ABAQUS FEM software, the titanium multilayer SPF/DB process and experiment were extensively studied.Beginning with mechanism of SPF/DB, the factors influencing process, deforming path and microstructure were discussed. Then the process was studied and an experimental scheme was designed based on the sample in this thesis.ABAQUS/Standard was used to take into account of ε|. , m and P-t together. The algorithm controlled i at the optimal value, and through this method, gained optimal P-t curve that during the whole forming process. Both single-hole SPF/DB and four-layer SPF/DB were analyzed, the P-t curve, forming result and thickness distribution were derived from each of them. The result also showed 10^-3s^-1 was the best value of optimal ε|. .After getting numerical results, the optimal parameters were used into experiment. Then the results from numerical simulation and experiments were contrasted. The contrast showed that the forming result, thickness distribution and forming time were all consistent. The numerical result was correct. In the end, comparing optimal experiment result with old ones, it proved that the optimal parameters can improve product condition. The result of this thesis was advisable.