Forming Limit Prediction And Loading Path Optimization Of Tube Hydro-forming

Hydraulic bulging processing is widely used in aerospace,automobile and pipe industry for the production of hollow parts.The prediction of the formability of the hydraulic forming parts and the determination of the bulging optimal loading path based on the predicted results are the key to the successful development of such parts.The development of the hydraulic bulging process technology at home and abroad is Investigated,and the shortcomings of the present forming limit prediction criterion is analyzed,the thesis proposed a new method to predict the forming limit of sheet metal.Using ABAQUS software,the pipe forming under complex strain paths in the loading process is simulated,the simulation results are substituted into the selfmade MATLAB program criterion to predict the rupture point.A set of hydraulic bulging die to form the round tube to a tube with square section is designed and developed.The hydraulic forming test of a pipe which has the same loading pass with the simulation process is implemented,the accuracy of the proposed theory is verified by comparing the experimental results with the simulation results.The detail work is as below.Firstly,the finite element software ABAQUS is used to simulate the local bifurcation deformation of the sheet metal and the bulge forming of tube,the starting point of the local bifurcation of the sheet metal and the deformation,stress and strain distribution of circular tube bulging square tube under different loading paths were obtained,the datum are the original data for the forming limit prediction criterion.Secondly,the constitutive equation for local bifurcation analysis is determined,and a forming limit prediction criterion is propoded.By the use of MATLAB program to link the bifurcation deformation criterion and finite element simulation results,and all nodes stress and strain and coordinate of finite element simulation in each incremental step are substituted to criterion formula,and all nodes taking place local bifurcation deformation are obtained,the deformed mesh is drawn and bifurcation nodes(crack point)are marked on the mesh with MATLAB program,material rupture location is clearly shown.Finally,a set of tube hydraulic forming mold is designed and manufactured,and the tube bulging experiment under different loading path are implemented.The reliability of the proposed theory method is proved by comparing the experimental results with the simulation results.The results of this study are significant for the design and forming process optimization of tube bulging forming parts.