Forming Process For Parts With A Variable Diameter By Viscous Core

Shell parts with a variable diameter is one of the typical construction components in aeronautics and astronautics, The traditional method to form this kind of part is forming each part separately and then assembling together by welding becouse it is difficult to be formed one-time, it is difficult to control the forming quality, and can not satisfy the increasing requirement of improving the properties of forming parts. In this paper, a new forming technique for parts with a variable diameter by viscous core is firstly proposed, which use viscous medium as a core, fully make use of its superiority, complete sheet metal forming as the principle of bulk forming, and apply this technique to other materials which is difficultly formed one-time such as on niobium sheet metal. This paper aim at finding a better integral forming way to improve the performance of parts and go on promoting this technique to other parts which have complex shape.Firstly, the feasibility of forming parts with a variable diameter by viscous core is analyzed by theoretical method. According to plasticity theory, the stress and the strain of the deformation zone are analyzed. On the basis of the above researches, give the condition of wall thickness unchanging and explain the reasons for thinning from the view of geometry point. Explain the rule how end feeding influence forming process and propose the way improve wall thickness distribution by useing rigid cylindrical and rigid conical mandrel.Secondly, the influence law on tube billet material flowing and thickness distribution of viscous core is studied by the finite element method, and explain the influence law by analysising the stress and strain of the deformation zone and geometric configuration changing in forming process. Some technical parameter influences are investigated, such as viscous properties, movable die, rigid cylindrical mandrel and rigid conical mandrel. The influence law of some shape parameters such as tube billet size and the length of forming zone on tube billet material flowing and thickness distribution are also investigated.On the basis of above researches, a preliminary experimental study is conducted, the advantage of viscous medium as core module is verified. Finite element analysis results are verified by analysising the geometries of specimen in forming process. Rapidly viscous force transmission of viscous medium have good effect on improving forming quality is also verified. The influence of axial feeding on forming is analyzed and the cause of the flaw are studied and corresponding regulatory measures are proposed, the experimental results are in accordance with FEA, feasibility of forming with viscous core is verified.