摘要
摆动辗压是一种连续的、局部加载的成形工艺。因其具有省力、节能、振动和噪音小、便于实现机械化和自动化等特点而得到高度重视,并在塑性加工领域得到了广泛应用。圆环件和圆盘件在摆辗工艺应用中占有重要比例。
摆辗的变形机理十分复杂,为用其来指导实践,国内外多位学者从最简单的圆环件和圆盘件的摆辗过程着手进行了大量分析,并得出了一些结论。这些结论大部分都是针对主动变形区,对被动变形区的研究较少,然而本文所要研究的塑性铰正好位于被动变形区。
塑性铰是圆环件和圆盘件摆辗过程中被动变形区发生塑性变形的状态,是摆辗工艺的非稳态因素之一。它的产生会引起内力的重新分布,影响摆辗工艺的稳定性,对其进行研究是非常必要的。摆辗过程中塑性铰的存在最早是由罗宾汉提出的,而后也有数位学者通过实验或理论研究的方法证明了塑性铰的存在,并提出了塑性铰模型；张猛教授通过理论推导给出了圆环件和圆盘件摆辗过程中产生塑性铰的条件。目前,摆辗塑性铰的相关理论是不完善的,并且对塑性铰状态没有形成统一的认识,对塑性铰的演化过程和状态等一些问题还有待进行深入研究。
本文首先在PRO/E中建立工件和模具的三维模型,以STL文件格式导入到DEFORM-3D软件中,进行参数设置后,对圆环件和圆盘件的摆辗过程进行模拟。通过对模拟结果进行分析,得出圆环件和圆盘件摆辗过程中塑性铰的演化过程及其状态、总结塑性铰区的等效应力和等效应变速率分布规律以及工件上的等效应变变化,分析塑性铰区的晶粒度变化规律,并比较圆环件和圆盘件塑性铰区域的异同点；另外,本文通过改变圆环件的大小、工件与摆头接触面的摩擦因子、摆头摆角以及下模进给量四个工艺参数对圆环件的摆辗过程进行研究,以此来分析这些参数对圆环件摆辗塑性铰的产生条件以及塑性铰演化进程产生的影响。本文的研究结果将有促进对摆辗塑性铰的认识和深化,也是对摆辗理论的重要补充。
Rotary forging is a continuous and incremental forming process. Because of its characteristics of labor and energy saving, little vibration and noise, easy to achieve mechanization and automation, it has been given serious attention, and widely applied in plastic forming process. Ring and disc parts occupy an important share in the application of rotary forging process.
Deformation mechanism of rotary forging is complex, and now a number of scholars at home and abroad had analyzed it from the most simple ring and disc parts to guide practice,and had got a number of conclusions. Most of these conclusions are for active deformation zone, and little for the passive deformation zone. Nevertheless, plastic hinge that this article just wants to study just lies in passive deformation zone.
Plastic hinge is a kind of status of passive deformation zone when it occurs plastic deformation and it is one of the non-steady-state factors in rotary forging ring and disc parts. It can cause the redistribution of internal forces, and affect the rotary forging process and properties of parts, so it is necessary to research it. The existence of plastic hinge in rotary forging was firstly put forward by Britain's Robin Hood, and then many scholars proved it by experiments or theory methods, and brought plastic hinge models, but the models was not same. Zhang Meng Professor obtained the generating conditions of plastic hinge in rotary forging ring and disc parts by theory derivation. At present, these conclusions about plastic hinge in rotary forging are not perfect and did not form a unified understanding on its state, so some problems of plastic hinges have yet to be studied, for example, its formation and status.
This article established the three dimensional models of work-piece and dies, and imported them to the DEFORM-3D software in the STL file format firstly, and then set parameters for simulating the process of rotary forging ring and disc parts. Base on analyzing the simulation results, this article got the evolution process and state of plastic hinges in rotary forging ring and disc parts, summarized the equivalent stress and strain-rate distribution of the plastic hinge area and the equivalent strain distribution in the whole parts, analyzed the variation of grain size of the plastic hinge area, and compared the similarities and differences between plastic hinges of ring and disc parts. In addition, this article also researched the impacts of the original ratio of height to diameter, the friction coefficient of contact surface between parts and cone die, the angle of cone die and the feed of low die on the produced conditions and evolution process of plastic hinges in rotary forging ring parts by changing the four technology parameters. The results will be helpful to gain a better understanding of plastic hinge, and are important supplements to the theories of rotary forging.
引文
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