| Tube hydroforming(THF)technology has low production cost,light quality,high strength,etc.The parts is the main way to realize lightweight structure.Found in the actual production application,however,THF high manufacturing costs,forming difficulty big,forming efficiency is low.Impact hydroforming(Liquid Impact Forming,LIF)is based on the hydraulic bulging and stamping Forming technology,developed a kind of new composite using press die closed up and down when the radial pressure pipe movement,makes the pressure inside the pipe internal Liquid spontaneously and rapid filling mold cavity,complete the bulging process,in order to get rid of complicated hydraulic system and greatly reduce the cost and period of pipe Forming.Accurate pipe plastic constitutive relations has important influence on the analysis of the pipe forming mechanism,and the results of finite element simulation precision is largely depends on accurate pipe plastic constitutive relation.Therefore,in this paper,the impact of hydraulic pipe plastic constitutive relation under loading study has important theoretical significance.In present paper,(1)the analysis of the constitutive relation theory and the strain rate response of materials,based on the stress condition of shock tube hydroforming,shape incremental theory,etc.,selected shock tube hydroforming dynamic plasticity constitutive model.(2)the SS304 stainless steel tube hydroforming test,determine the real-time online measurement tube bulging every moment of the transient wall thickness,axial strain and axial strain,maximum radius of bulging,processes of tubing axial curvature radius and relative fluid pressure data at all times.(3)based on the above test deformation data,using linear regression method and genetic algorithm respectively,to determine the pipeline under the action of hydraulic impact load dynamic plasticity constitutive relation.(4)based on DYNAFORM and ANSYS Workbench joint simulation,finite element models of shock tube hydroforming,respectively,the linear regression method and genetic algorithm for pipe plastic constitutive relation as the material model and finite element simulation was carried out on the shock tube hydroforming process,respectively,by comparing the test results and simulation results,to institute building shock tube hydroforming dynamic plastic hardening model precision.Research shows that:(1)in this paper,the dynamic plastic constitutive relation,the research from the Angle of strain rate under impact loading metal thin wall pipe precise plastic constitutive relation.By comparing simulation results with the test results,proving that this paper established the dynamic plastic constitutive relationship has high precision.(2)the biggest bulging height according to the simulation results compared with the results of experiment,the constitutive model can quantitatively get Johnson-cook within 7.43%,the maximum error range Fields-Backofen constitutive model within 8.65%,the maximum error range jaynes-cummings constitutive model is more suitable for describing shock tube hydraulic bulging plastic hardening.(3)according to the results of the validation of linear regression to determine the constitutive model of error were greater than the genetic algorithm to determine the constitutive model of error,show that genetic algorithm possesses the advantages of stable and fast convergence,to find out in the variable space contains the optimal solution and the extreme value of single peak area and search for the optimal solution,in fitting complex target function has obvious advantages.(4)with the improvement of impact velocity,the results of simulation error decreases,show this paper to determine the dynamic plastic constitutive relation for tube hydroforming of impact velocity is larger.Impact this topic research results provides a hydraulic load under the action of pipe method of dynamic plasticity constitutive relationship building,the other study of LIF and finite element simulation has a certain reference and guidance. |
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