Numerical Research On Sheet Metal Stretch Forming Based On Varying Forming Surface Of Multi-point Die

Multi-point stretch forming as a new sheet metal forming technology, still has a hugeforming potential for further research and exploit. In this background, this paper researchesthe multi-point stretch forming based on varying forming surface of multi-point die. TheMPSF based on fixed forming surface of multi-point die mainly according to controlling themovement of grippers to form work pieces, however, the MPSF based on varying formingsurface of multi-point die mainly according to regularly, progressively controlling themovement of elements to build up the needed MPD forming surface and forms work piecessimultaneously. Work pieces processed by the new method have a better performance infitting die-surface and a better uniformity in plastic deformation. This new technologymakes full use of the advantages of the multi-point die, whose surface is adjustable，so itcan be used in forming work pieces with a higher quality requirement. The main contentsand conclusions of this paper are summarized as follows:In this paper, finite element models corresponding to MPSF based on varying formingsurface of multi-point die and MPSF based on fixed forming surface of multi-point die arebuilt, and related contact, loading, meshing and element selection are stated as well, whichprovide accurate finite element models for the following researches. Then, the principle ofMPSF technology based on varying forming surface of multi-point die is proposed. And twovarying ways of the forming surface of multi-point die are researched and introduced:partial varying way and integral varying way.By comparing the stress, strain distributions and shape accuracy of three typical shape--cylinder, spherical and saddle shape work-pieces formed from the numerical simulation,the differences in forming effect between MPSF based on varying forming surface ofmulti-point die and MPSF based on fixed forming surface of multi-point die are analyzed, in this way, the superiority in sheet metal forming of MPSF based on varying formingsurface of multi-point die is proved. In addition, the selection discipline of the varying waysof the forming surface of multi-point die is stated.Furthermore, the paper also researches on four important process parameters of MPSFbased on varying forming surface of multi-point die: pre-stretching of sheet metal, initialrise value of the plane multi-point die, varying velocity of the forming surface of MPD, thethickness and the number of layers of the elastic cushion. In the end, related rational processparameters are determined.