Analyses On Strain Distributions In Axisymmetric Deepdrawing Process And Researches On Wrinkling And Rupture Of Conical Part

Axisymmetric sheet forming process is one of the basic ways of sheet forming processes. It is not only a common manufacturing technique, but also a main technology in measuring sheet forming properties. Although various kinds of complex sheet forming problems can be analyzed by FEM and experiments, the researches on the common problems of sheets is still based on the analyses of basic sheet forming technologies including axisymmetric sheet forming processes. Conical part is a typical curved part. In the conical part forming process, wrinkling may occurs in the flange and conical wall regions and rupture may takes place in dangerous end surface. Therefore, the researches on wrinkling and rupture in conical sheet forming process have a practical an theoretical influence.For axisymmetric sheet forming process, researches on the direct integral method solving stress and strain are conducted. On this basis, wrinkling and rupture are analyzed under the energy method and the rupture instability criteria. The conical forming process using radial segmental blank holding technology is studied taking FE simulations and experiment.First, under the assumption of plane stress, proportional loading and so on, the strain and stress distributions of axisymmetric sheet forming processes are obtained adopting the direct integral method. Taking cylindrical cup deep drawing process using AA5754 and ST16 as examples, the solving processes of stress and strain in the flange area of axisymmetric deep drawing are given under plane stress, plane strain and inversely proportional assumptions respectively. And the comparison of stress and strain distributions in flange is made, by the analytical methods under the three assumptions, FE simulations and experiments for cylindrical cup drawing process.Then, the direct integral method is extended to solve curved part forming problems. The equation, containing strain, first-order partial derivative of strain and parameters, and the solving process are given with an explanation of the convergence of the solution. Meanwhile, stress and strain distributions along the die arc and the conical wall regions in axisymmetric forming process using ST16 are obtained. To extend the direct integral method into analyzing axisymmetric curved part sheet forming process lay a foundation for further studies of this kind of parts.On this basis, for conical deep drawing process using SPCC, the wrinkling critical BHF curve is obtained using the energy method to analyze wrinkling problems in flange and conical wall regions and the rupture critical BHF curve is obtained using the rupture instability criteria to analyze rupture problems. And the wrinkling and rupture critical curves are drawn by FEM.Finally, the comparison of the effects of conical deep drawing parts using SPCC is made using the radial segmental blank holder technology and the whole blank holder technology respectively in FEM. The moulds for conical deep drawing are designed and made. The FE results are validated with the experimental results. It is shown that the forming properties of conical deep drawing parts can be improved by the radial segmental blank holder technology.