Research On Electrically-assisted Roll Forming Process Of Corrugated Microstructure Of T2 Copper Foil

Functional surface microstructures have attracted the attention of experts and scholars all over the world because of their good surface modification performance.They have great application space in drag reduction,hydrophobic,precise optical devices,heat and mass transfer and other fields.In this paper,the application of functional surface microstructures in different fields is introduced in detail,and the methods of fabricating surface microstructures by scholars in various countries are analyzed.Roll forming has become the most promising processing technology for replication of microstructural arrays because of its advantages of high efficiency and low cost.In this paper,an integral roll forming method for sinusoidal functional surface microstructures perpendicular to the roll axis is proposed.Electrically-assisted forming technology is introduced to improve the plastic forming ability of T2 copper foil,increase the forming limit of blank and optimize the roll forming process of corrugated surface microstructures.The stress-strain curves of samples were obtained by uniaxial micro-extension test of T2 copper foil.The effects of grain size,pulse power output parameters(voltage,frequency and pulse width)on flow stress and fracture strain of T2 copper foil were studied.The results show that only when the current density reaches a threshold,the mechanical properties of samples can be greatly changed.With the increase of current density,the flow stress decreases,the fracture strain of hard T2 copper increases greatly,while that of soft T2 copper decreases gradually.It was observed by infrared thermal imager that the temperature of the sample increased sharply after applying pulse current,then slowed down due to the increase of heat dissipation,and finally fused due to excessive temperature.ABAQUS was used to simulate the roll forming process.The distribution of stress,strain and thickness during the rolling process was studied.The effects of simulation parameters such as roll clearance and blank thickness on the stress,strain,thickness distribution of surface microstructures and rolling force were analyzed.The wrinkling of blank will occur during roll forming,which will result in the warping of surface microstructures.A new method of restraining the warping of surface microstructures by blank shape is proposed.It is found that the trapezoidal blank with bottom angle less than 70 degrees can basically eliminate the warping of surface microstructures.In this paper,the effects of roll clearance,blank thickness and roll speed on the forming accuracy and rolling force of surface microstructures are studied by rolling experiments.The results show that roll speed has little influence on roll forming,and the roll pressure increases linearly with the decrease of roll clearance and the increase of blank thickness.When the roll gap is small,the smaller the roll gap is,the larger the standard deviation of the forming height of surface microstructures is,that is,the uniformity of roll forming is poor.Under the same conditions,the standard deviation of forming height of surface microstructures decreases with the increase of thickness,and the consistency of roll forming of corrugated foils is improved.Based on the electrically-assisted micro-extension experiment,the effect of pulse current on the roll forming of T2 copper corrugated surface microstructures was studied.It was found that pulse current could improve the forming height of surface microstructures,but the thickness reduction rate increased.It is found that high peak current density and high frequency pulse can restrain the local thinning of surface microstructures and improve the uniformity of rolling forming,but the pulse current is not as large as possible.When the current density is too high,the hard T2 copper foil will break down during rolling forming.Therefore,it is necessary to combine the high temperature mechanical properties of the blank and the shape and size of the blank to comprehensively formulate the current parameters during the electrically-assisted roll forming process.