金属壳体（封头）对胀成形工艺探究与数值模拟

发布时间：2018-06-20 23:09

本文选题：封头 + 内高压　；参考：《太原科技大学》2015年硕士论文

【摘要】：随着目前国内核电、化工等能源产业的快速发展,对压力容器的产品要求也在日益提高,针对现有封头生产工艺中出现的产品抗压稳定性差、加工制造困难等问题,本文提出了一种用于封头整体成形的新工艺。本文通过分析金属胀形的实验现象,结合封头在实际使用状况下的受力环境,拟定胀形工艺。将两块大小相同的圆形钢板重叠放置,周边满焊的同时,在钢板间隙中加入一定量的水作为膨胀介质。将试件放置到加热炉中,由于壳体内部完全封闭,随温度升高,水汽化成蒸气并对钢板内表面产生压强,钢板向两边凸起便形成一对的封头体。运用内高压整体对胀成形的工艺方法可以一次加工出两个形状大小相同的封头体。在成形过程中力能的来源是气体膨胀产生的压强,与封头的使用环境一致。成型后的封头应力分布均匀、结构稳定性强。为了避免在成形过程中因应力集中而出现失稳现象,导致发生不必要的安全隐患,需要确立工艺的可行性。首先对胀形过程中试件的几何模型进行受力分析,通过理论公式计算找到试件模型的受力薄弱点;选用水蒸气作为气体膨胀介质,运用热力学定律和水蒸气的气体性质推算出水蒸气在高温高压的密闭空间内所产生的胀形力。其次对“封头内高压整体对胀成形工艺”进行仿真模拟。在有限元模拟中无法直接设定水蒸气气化,需将水蒸气释放的内能转化为对金属壳体内表面施加的压强载荷,而数值会受到水蒸气温度变化、金属壳体内部体积变化以及初始加入的水量等因素的影响。本文利用MATLAB自编译程序对DEFORM有限元软件进行二次开发,实现数据的导出、外部计算以及数据的导入替换,经过迭代计算的方法解决了影响因素之间的相互制约。分析模拟胀形的应力-应变云图分布以及成形过程中影响因素的关系曲线,得出金属塑性变形规律。最后,依据模拟参数指定实验方案,分析实验结果并与模拟结果进行比较,得出相对误差。全文利用模拟和实验方法完成了金属壳体受内部气压作用的成形过程,得到了胀形过程的重要参数,为封头成形工艺提供了一定的参考。
[Abstract]:With the rapid development of domestic nuclear power, chemical and other energy industries, the product requirements for pressure vessels are also increasing day by day. In this paper, a new technology for integral forming of head is presented. By analyzing the experimental phenomenon of metal bulging and combining the stress environment of the head in actual use, the bulging process is worked out in this paper. Two circular steel plates of the same size were placed superimposed, and a certain amount of water was added to the gap of the steel plate as the expansion medium while the periphery was fully welded. When the specimen is placed in the heating furnace, because the shell is completely closed, with the increase of temperature, the water vaporizes into steam and produces pressure on the inner surface of the steel plate, and the steel plate protrudes to both sides to form a pair of sealing heads. Two head bodies with the same shape and size can be produced by using the internal high pressure monolithic bulging process. In the forming process, the source of force energy is the pressure produced by gas expansion, which is consistent with the use environment of the head. After forming, the stress distribution of the head is uniform and the structure is stable. In order to avoid the phenomenon of instability due to stress concentration in the forming process and lead to unnecessary hidden safety problems, it is necessary to establish the feasibility of the process. Firstly, the force of the geometric model of the specimen in the process of bulging is analyzed, and the weakness of the model is found through the calculation of the theoretical formula, and the steam is chosen as the gas expansion medium. By using the law of thermodynamics and the gas properties of water vapor, the bulging force produced by water vapor in the closed space of high temperature and high pressure is calculated. Secondly, the paper simulates the bulging process with high pressure inside the head. Water vapor gasification can not be directly set in finite element simulation. The internal energy released by water vapor should be converted into the pressure load applied on the surface of metal shell, and the value will be affected by the change of water vapor temperature. The influence of the internal volume change and the initial addition of water on the metal shell. In this paper, the deform finite element software is redeveloped by using MATLAB self-compiler, which realizes the data export, external calculation and data import and replacement, and solves the mutual restriction between the influencing factors through iterative calculation. The distribution of stress-strain cloud diagram of simulated bulging and the relationship curve of influencing factors in forming process are analyzed, and the rule of metal plastic deformation is obtained. Finally, according to the simulation parameters, the experimental results are analyzed and compared with the simulation results, and the relative errors are obtained. In this paper, the forming process of metal shell subjected to internal pressure is completed by means of simulation and experiment, and the important parameters of bulging process are obtained, which provides a certain reference for the forming process of head.
【学位授予单位】：太原科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG306

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