薄壁管壳体环矢挤压缩径工艺仿真分析与研究

目的 针对空心薄壁件在缩径成形工序中力学性质难以观测且缩径成形加工效率较低的问题，提出一种使用18瓣环矢挤压模具进行环矢挤压一次性成形的缩径工艺，并研究了该工艺下薄壁管壳体的弹塑性变形规律。方法 以外径6.3 mm、壁厚2 mm、颈缩宽度1 mm的小尺寸薄壁管壳体（Q255材料）为研究对象，基于Barlat''96屈服准则和M–K沟槽理论，结合L.H.Donnell理论，建立管壳体环矢挤压缩径的塑性微元应力模型，通过ANSYS软件建立环矢挤压缩径工艺有限元模型，并进行数值模拟分析，获得管壳体环矢挤压过程中内壁面和颈缩区厚度方向的应力分布规律；最后进行实验验证，利用千分尺测量外径，采用应力测定仪测量中心位点应力，验证了该工艺下仿真结果的准确性。结论 颈缩区域宽径比越大，缩径成形越远离弹性区；内壁面的应力整体呈凸状分布；卸载后，壁厚方向的残余应力呈从外壁到内壁逐渐增大的线性分布趋势，缩径区中心点最大残余等效应力为319.76 MPa，分布在挤压部位的内表面；经实验验证，内壁面中心位点的最大残余应力为183 MPa，其与仿真分析结果（202.5 MPa）的吻合度高达91.5%，验证了仿真结果的准确性。该环矢挤压模具能够有效进行空心薄壁管壳体的一次性缩径成形，提高制造效率，该研究结果可为薄壁管件环矢挤压缩径成形的工艺设计及工程应用提供参考。

Simulation Analysis and Study on Annual Vector Extrusion Reduction Process of Thin-walled Tube Shell

The work aims to propose an 18-flap annular vector extrusion die for one-time forming reduction process by annular vector extrusion to solve the problem that the mechanical properties of hollow thin-walled parts are difficult to observe in the reduction forming process and the reduction forming processing efficiency is low and study the elastic-plastic deformation law of thin-walled tube shells under this process. A small-sized thin-walled tube shell made of Q255, with an outer diameter of 6.3 mm, a wall thickness of 2 mm, and a necking width of 1 mm was used as the object of study. Based on Barlat''96 yield criterion and M-K groove theory, combined with L.H. Donnell''s theory, a plastic micro-element stress model was established for the annular vector extrusion reduction of the tube shell, and a finite element model of the annular vector extrusion reduction process was established by ANSYS software. Then, the numerical simulation was carried out to obtain the stress distribution variation law of the inner wall surface and the thickness direction of the necking zone during the annular vector extrusion of the tube shell. Finally, experiment was carried out to verify the accuracy of the simulation results under this process by measuring the outer diameter with micrometer and measuring the stress at the centre with stress measuring instrument. The larger the width to diameter ratio of the necking zone is, the further away from the elastic zone the reduction forming is. The overall stress on the inner wall surface is convexly distributed. After unloading, the residual stress in the wall thickness direction shows a linear distribution trend of gradually increasing from the outer wall to the inner wall, and the maximum residual equivalent stress at the centre of the necking zone is 319.76 MPa, which is distributed on the inner surface of the extruded part. The maximum residual stress at the centre of the inner wall surface at point E is verified to be 183 MPa, which is in good agreement with the simulation results (202.5 MPa) by 91.5%, verifying the accuracy of the simulation results. The annular vector extrusion die can effectively contribute to the one-time reduction forming of the hollow thin-walled tube shell, improving the manufacturing efficiency. The results of this study provide a reference for the process design and engineering application of annular vector extrusion reduction forming of thin-walled tube shells.