摘要:大塑性变形技术具有强烈的晶粒细化能力，可以直接将材料的内部组织细化到亚微米乃至纳米级。基于高压扭转塑性变形的思想，将管材正挤压与旋转剪切变形相结合，研究管材旋转挤压时的变形行为以及各因素对管材旋转挤压的影响，实现单道次变形即在材料内部累积大的应变，以解决高压扭转坯料尺寸有限、制备过程不连续等问题，为大塑性变形技术的工业化及高性能管材的连续制备提供一种新途径。

本文运用有限元软件Deform-3D模拟了管材旋转挤压的成形过程，针对四个不同的参数：摩擦系数、芯棒角速度、不同的挤压比和工作带的长度，分析了各个参数下旋转挤压过程中的管材应力应变的分布状态、凸模轴向应力载荷和芯棒扭矩大小。模拟结果表明：挤压比增大时，平均应变增大，凸模轴向应力载荷和芯棒扭矩也增大。当挤压比为7.22时，挤出的管材变形最均匀。芯棒旋转促进管材变形，旋转正挤压比传统正挤压能达到更大的应变。工作带长度是影响管材旋转挤压的一个重要因素。本文中工作带长度为8mm时，管材能积累的应变更大。模具与管材之间的摩擦系数增大，应变会增大，同时凸模轴向应力载荷和芯棒扭矩也增大。本文研究表明这种模具结构具有可观的细化晶粒的能力，而且不需要施加高压。对于管材的旋转挤压具有生产指导意义。

关键词：旋转挤压；管材；有限元；应变；载荷

Abstract:Large plastic deformation technology has a strong ability of grain refinement, it can directly refine the internal organization of fine material to submicron and even to nano-level, In this paper, based on the idea of high pressure torsional plastic deformation, combining the positive squeezing of the pipe with the rotation shear deformation, the deformation behavior of the pipe during the extrusion and the influence of the factors on the rotary extrusion of the pipe are studied. To let the internal material accumulate large strain in single pass deformation, to solve the problem of limited size of high-pressure torsional billet and discontinuous preparation process, which provides a new way for the industrialization of large plastic deformation technology and the continuous preparation of high performance pipe.

This paper uses the finite element software Deform-3D to simulate the forming process of tube rotary extrusion, for four different parameters: friction coefficient, mandrel angular velocity, different extrusion ratio and the length of work belt, analysis of the various parameters in the process of rotating extrusion pipe shall be the distribution of strain, the punch load and torque of the mandrel. The simulation results show that When the extrusion ratio is increased, the average strain increases, and the axial stress load and the mandrel torque increase. When the extrusion ratio is 7.22, the extruded tube is the most uniform. The mandrel rotates to promote the deformation of the tube, and the rotating positive extrusion achieves greater strain than the conventional positive extrusion. The length of the working belt is an important factor affecting the rotation of the pipe. In this paper, the length of the work belt is 8mm, the pipe can accumulate greater strain. The friction coefficient between the mold and the pipe increases, the strain will increase, and the axial stress load and the mandrel torque increase. This study shows that the mold structure has considerable capacity to refine grain and does not require high pressure. It has guiding significance for the rotary extrusion of tubes.

Keywords: rotary extrusion; pipe; finite element; strain; load

目录

第一章 绪 论 1

1.1课题背景