【作者】 李大龙；

【导师】 于恩林；

【作者基本信息】 燕山大学 ， 重型装备设计理论及其数字化技术， 2014， 博士

【摘要】 电流所导致的金属在塑性变形过程中变形抗力下降，延伸率增加的现象被称为金属的电塑性效应。利用电塑性效应可大幅度地降低金属的加工硬化速率，减免常规塑性加工工艺中必须采用的软化退火、酸洗等工序，改善产品表面质量，提高成材率，电塑性效应有望在轧制、辊压、冷拔等金属的塑性加工中得到广泛的应用。但是，迄今为止人们对于金属电塑性效应的作用机理还不十分清楚，电塑性加工过程的理论分析和计算已经成为该技术推广的瓶颈。目前，国内外许多学者都在对金属的电塑性效应进行深入的研究，一旦能够在生产中应用电塑性效应，必将大大提高生产效率，降低生产成本，提高产品质量，这对于工业生产意义十分重大。因此，开展这方面的探索性工作对于加深电塑性效应的认识，促进相关工艺技术的发展和有效应用有着很强的理论意义。本文从位错滑移动力学、自由电子理论和量子理论三个方面深入研究电流导致金属流动应力降低的机理问题。以定向漂移的电子引起金属位错滑移所需激活能发生变化为出发点，研究定向漂移的电子与位错之间的能量交换量。基于位错热激活滑移速率公式，推导了电流作用下金属应变速率变化量的理论计算公式，得出了电流导致金属流动应力降低现象的本质为电流对金属的应变速率产生了影响的论断。利用实验数据回归了金属铜丝无电拉伸条件下的塑性变形过程的本构方程，综合考虑电流对该方程中应变速率和温度的影响，得出了金属铜丝电塑性拉伸条件下流动应力的理论计算公式，依据理论计算公式分析得出了电塑性效应中电流参数和物理参数对金属流动应力的影响规律。为了验证理论推导结果的准确性，进行了金属丝材的电塑性拉伸实验，将实验结果与理论计算结果进行了对比分析。本文的研究结果不仅为定量地分析电塑性效应中金属的流动应力提供了方法，而且为电塑性效应的工程应用奠定了理论基础。本文依据金属电塑性加工过程的实际需要，自行研制了脉冲电流发生装置，该装置采用了性能好、功率大的GTR模块控制电流回路的开启，利用多位波段开关控制并联的多路电路，从而在回路中实现了更大功率的脉冲电流。超低频示波器对脉冲电源输出电流的实测波形显示，该脉冲电流具有电流峰值大、波形好的特点，更好地满足了电塑性加工和理论研究对电源装置的要求。在电塑性效应机理研究的基础上，结合丝材带模拉拔的实际生产过程，建立金属丝材电塑性拉拔成型过程的数学模型，通过理论求解的方法对金属的电塑性拉拔变形过程进行了力学分析。最后，实验研究铜丝的电塑性拉拔过程，并将实验研究结果与理论计算结果进行了对比分析。更多还原

【Abstract】 It has been found that electrical current can reduce the metal flow stree and increaseforming limit. This additional component has been termed an electropalstic effect.Electroplastic forming can also dramatically reduces the metal work hardening rate,simplify annealing and pickling process, improve surface quality of product, and increasethe rate of finished products. Hence, the electroplastic manufacturing processing isexpected to be widespread used in rolling, drawing and other plastic procesing fields.However, the mechanism of electroplastic effect is unclear up to now and the analysis intheory of electroplastic forming process has become a bottleneck of the engineeringapplication of electroplastic technology. At present, the meatl electroplastic effct is furtherresearched all over the world. Once the electroplastc forming technology can besuccessfully used in actual production process, it will improve productivity, lower cost,and improved plasticity. This is very signigicant and important for industrial production.Therefore, to develop the exploring researchs in the mechanism of electroplastic effect andthe development in the computation methods are of great importance for the developmentand application of the related technial.In this paper, based on dislocation glide dynamics, free electron theory and quantumtheory, the mechanism of metallic electroplastic effect is studied. From the perspective ofenergy exchange between free electrons and metallic ions, the change in activation energyof dislocation is studied. According to the thermally activated strain rate equations, therelationship between electric current and strain rate could then be obtained, and it showsthat the flow stress reduction results from the effect of current on strain rate. A series ofcarefully designed experiments will be carried out to determine the constitutive law forforming of copper wire without electricity applied. Taking into account the influence ofcurrent on the constitutive law, the relational expression of the metal’s flow stress andelectroplastic deformed conditions is presented. Then based on the relational expression,the influences of electrical parameter and physical parameter on material flow stressduring forming process companied with electroplastic effct are analysed. In order to verifythe accuracy of the theoretical derivation results, the experimental researches on tensile tests of metal wire are carried out, and the comparative analysis between theoreticcalculation and experimental results is also made. The results of this paper not onlyoffered a quantitative analysis method for metal’s flow stress decreasing in electroplasticeffect but also formed the basis of practical application for electroplastic effect.According to the requirement of electroplastic manufacturing processing, the pulsecurrent generator is designed and fabricated. The design adopts powerful GTR module tocontrol current circuit on or off, thus generating pulse current. The pulse power generationcircuitry can output multichannel signals. The multichannel signals are linked togetherwith the monostable triggers to get a large current. The ultra-low frequency oscillographshows that the pulse current has the features of the larger summit current and perfect pulsewave, which will be more suitable for the practical application.On the basis of the research of mechanism of metal electroplastic effect andcombining with wire drawing production practic, the mathematical models of metal wireelectropalstic forming process was derived. Finally, the experimental research on metalwire electropalstic drawing was carried out, and a comparative analysis is made betweenthe experimental and theoretical results.更多还原