Structural Optimization Design Of Cold Extrusion Die Based On Small Elastic-plastic Deformation

In this paper, the structural design of extrusion die based on small elastic-plastic deformation is studied by means of finite element simulation and elastic-plastic theoretical.First of all, by virtue of finite element software Marc, the stress distribution rule and the deformation characteristics of simple die are analyzed under two different conditions. One is under different load rang length, and the other is under different load rang position. Hereby the design of stiffening ring in accordance with the length and position of load range is put forward. In addition, strength check expression of simple die under local load is also derived. Then the structural optimization design of three-layer combined die subjected to local load is performed by numerical simulation technology, artificial neural networks and genetic algorithm. Secondly, on the basis of elastic design idea, the die design idea based on small elastic-plastic deformation is brought forward, and the concept of autofrettage design is introduced into the extrusion die design. Moreover, the fundamental theoretical formula of autofrettage design of simple die is deduced and established. Though finite element method, the stress and deformation characteristics in the process of autofrettage are analyzed. Finally, on the basis of single-layer autofrettage die, autofrettage technology is introduced into the structure design of double-layer combined die by way of combining autofrettage technology and interference fit method. Two process scheme is proposed, that is shrunk-on method after autofrettage of the inner die and autofrettage method of interference fit combined die, and their feasibility is analyzed.The stress and deformation analysis of simple die under local uniform load and the structural optimization design of three-layer combined die shows that according to loading on the whole height, the die structure size is slightly larger. This means that the potential bearing capacity of die is not brought into full play, and the material of die is wasted. The stress and deformation analysis of single-layer autofrettage extrusion die shows that on the premise of satisfying the dimensional precision requirements, simple die can reach the same strength requirement as the combined die which has the same structure size. The structural analysis of double-layer autofrettage combined die shows that autofrettage technology after interference fit is in favor of further improving carrying capacity and die dimensional precision, so it is an effective design method. Therefore, in the traditional design of extrusion die, it is not good for giving full play of die materials when the stress is limited in the elastic range.The results and design method of autofrettage extrusion die proposed in this paper have practical guiding significance on the improvement of die design.