大口径管材弯曲成形技术仿真研究

发布时间：2018-02-28 12:18

本文关键词： 中频感应加热弯管机热传导有限元分析非均匀壁厚管材　出处：《吉林大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着我国油气管道项目的不断增多,大口径弯管的需求量急剧增加。大口径弯管通常由中频感应加热弯管机弯制而成,其成形机理复杂,且精度不易控制。我国大口径弯管生产技术还低于世界先进水平,部分型号弯管仍依赖国外进口。因此,为了提高大口径弯管的成形质量,减少对国外进口的依赖,研究大口径管材弯曲成形技术具有重要意义。大口径弯管的主要质量缺陷有截面扁平化程度过大、弯管内侧起皱以及弯管壁厚变化率不均或过大等。目前,学者的研究多集中于管材在纯弯矩作用下弯曲成形的质量缺陷问题。中频感应加热弯管机的弯管方式属于热推弯加工,鉴于此,本文将着重分析推力对弯管中性层偏移及截面扁平化的影响,并探究弯管壁厚变化率的控制方法。具体研究内容及成果如下:(1)根据热传导理论,计算出待弯曲管材上的温度场。结合弹塑性弯曲理论及弯管成形过程的力学模型,计算出管材在热推弯过程中,所受推力的理论值。根据模型简化规则及力学等效理论,建立弯管机及管材的有限元模型。借助有限元分析软件,探究施温区宽度对弯管内侧起皱的影响,分析推力对弯管中性层偏移和截面扁平化的影响。(2)引入中性层偏移及截面扁平化对弯管壁厚减薄的影响,修正弯管壁厚减薄率计算公式,提高了弯管壁厚减薄率计算公式的精度。目前,最具代表性的壁厚控制法是阻力法,本文将探究施加阻力大小对弯管壁厚减薄率的影响。(3)提出非均匀壁厚管材弯曲成形法,介绍非均匀壁厚管材的加工制造工艺,并根据均匀壁厚弯管的目标壁厚推导出非均匀壁厚管材的初始壁厚。非均匀壁厚管材弯曲成形法使成形后的弯管壁厚均匀,避免了传统弯管外侧壁厚减薄问题。与阻力法相比,非均匀壁厚管材弯曲成形法也大大降低了弯管机各主要结构的受力峰值。
[Abstract]:With the increasing number of oil and gas pipeline projects in China, the demand for large-caliber bends is increasing rapidly. The large-caliber bends are usually made of medium frequency induction heating pipe benders, and the forming mechanism is complex. And the precision is not easy to control. The production technology of large diameter bend pipe in our country is still lower than the advanced level in the world, and some types of bend pipe still rely on foreign imports. Therefore, in order to improve the forming quality of large diameter bend pipe and reduce its dependence on foreign imports, It is of great significance to study the bending forming technology of large-caliber pipes. The main quality defects of large-caliber bends include the excessive flattening of sections, the wrinkling inside of the bends and the uneven or excessive change rate of the wall thickness of the bends. Most of the researches of scholars focus on the quality defects of pipe bending under the action of pure bending moment. The pipe bending mode of intermediate frequency induction heating pipe bending machine belongs to hot pushing bending process, in view of this, In this paper, the influence of thrust on neutral layer offset and flat section of bend tube is analyzed, and the control method of wall thickness change rate is explored. The concrete research contents and results are as follows: 1) according to the theory of heat conduction, The temperature field on the tube to be bent is calculated. The theoretical value of the thrust of the tube during the hot pushing bending process is calculated by combining the elastic-plastic bending theory and the mechanical model of the tube bending process. According to the simplified rules of the model and the mechanics equivalent theory, The finite element model of pipe bender and pipe is established. With the help of finite element analysis software, the influence of the width of the heating zone on the wrinkling of the inside of the bend is explored. The influence of thrust on neutral layer migration and section flattening of curved pipe is analyzed. (2) the influence of neutral layer migration and section flattening on wall thickness reduction of bend pipe is introduced, and the formula for calculating wall thickness thinning rate of bend pipe is revised. At present, the most representative method of wall thickness control is the resistance method. In this paper, the influence of applying resistance on the wall thickness thinning rate of curved pipe is studied, and a non-uniform wall thickness bending forming method is put forward. This paper introduces the processing and manufacturing technology of non-uniform wall thick pipe, and deduces the initial wall thickness of non-uniform wall thickness pipe according to the target wall thickness of uniform wall thickness bend tube. Compared with the resistance method, the bending forming method of non-uniform wall thickness pipe also greatly reduces the stress peak value of the main structure of the pipe bender.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE973

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