Theoretical And Experimental Study On Metal’s Flow Stress In Electroplastic Effect

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.