Investigation On Mechanism Of Ultrasonic Vibration Assisted Plastic Deformation And Micro Blanking Process Of Copper Foil

Pursuing portability and miniaturization without losing the performance of the product has been a common trend in our industrial production and daily life.And this brings challenges to the manufacturing of micro parts.Microforming has advantages like high productivity,high efficiency and low cost.However,size effect decreases the quality and accuracy of micro parts and is always the bottleneck in microforming.Ultrasonic vibration assisted(UVA)forming can reduce the deformation resistance and friction by volume effect and surface effect,which is a promising way to deal with size effect.Mechanism of plastic deformation in UVA forming is still a topic on which no consensus has been reached,especially for the deformation behavior coupled with size effect.For now,few studies focus on this research.Supported by the National Natural of Science Foundation of China,the mechanism of UVA deformation behavior and UVA blanking process of T2 copper foil have been carried out experimentally and theoretically.Deformation behavior of copper foil under the coupling of ultrasonic vibration and size effect has been studied.Mechanism of softening effect under UVA forming has been specified.The forming of foil parts with high quality and high accuracy has been realized.Firstly,softening effect of T2 copper foil in UVA tension has been studied and the results show that softening effect increases with the increase of ultrasonic amplitude and the residual softening effect increases with increase of ultrasonic duration.Misorientation angle and KAM distribution are studied by Electron Backscattered Diffraction(EBSD)method.Both the misorientation angle and KAM value are reduced by ultrasonic vibration.The analysis indicates that the plastic deformation is more uniform with the assistance of ultrasonic vibration.According to the flow stress reduction under different ultrasonic energy density,theoretical model of softening effect has been established based on the crystallographic theory considering stress superposition and acoustic softening.Secondly,size effect in UVA tension has ben conducted.The grain size effect model based on ultrasonic energy has been developed.Micro mechanism of plastic deformation under ultrasonic vibration coupling with grain size effect is described by the change of Hall-Petch slope from the view point of dislocation emission.By curve fitting of exponential function,e exponential function of geometry size effect is modeled and the experimental results can be accurately predicted.Digital Image Correlation(DIC)full field strain measurement has been conducted to study the fracture behavior and results show that r value and formability of the material are improved.Limit strain is decreased because the process from necking to fracture is shortened by ultrasonic vibration.Based on the research above,mechanism of UVA shearing deformation is carried out.The influence of shearing clearance,grain size,and shearing speed on the maximum shearing strength are studied,as well as the accuracy and fracture appearance.Results show that maximum shearing strength is greatly decreased by ultrasonic vibration.Also,the smooth zone of the fracture surface is improved by delaying the initiation of shearing crack,and by reducing both the crack angle and shearing deformation area.Surface roughness is decreased by surface effect of ultrasonic vibration.Finally,UVA circular ring part blanking process has been carried out.The results of dimension measurement and fracture surface SEM observation show that concentricity and diameter of the circular ring part are satisfied by UVA blanking process.The rollover is reduced and ratio of smooth zone is increased.Both the surface roughness and flatness of the part are improved.This research indicates that the UVA micro blanking process is a promising way for the forming of micro foil parts with high quality and high accuracy.