Research On Ultrasonic Vibration Assisted Pure Copper Microforming

Some results about ultrasonic vibration in macroscopic metal forming processing technology have published.The advantage of ultrasonic vibration was reduction in forming force,a decrease in friction,improvement in quality of surface.So it attracted more and more attentions of researchers from home and abroad.Ultrasonic vibration assisted microforming technology was a potential compound forming technology,which was expected to be an ideal process for solving the problems of poor filling performance and low surface precision in microforming.It will be a new way for microforming in the future.Research on material deformation behavior by pure copper ultrasonic vibration assisted microforming had a significant impact on the application and development of ultrasonic vibration.It also had important theoretical significance and engineering application value.This paper focused on experiment and numerical simulation of ultrasonic vibration assisted micro-column forming and micro-upsetting of pure copper,and studied the vibration effects on material flow stress,microscopical structure,surface roughness and the grain size effect using finite element method.This paper also studied the forming mechanism of ultrasonic vibration in the microforming process and the influence on the plastic formability of the material.The main work of this paper is as follow:A die was designed in order to carry on micro-column forming experiment facilitated with ultrasonic vibration.A series of ultrasonic vibration assisted micro-column forming experiment were carried out using a high frequency of 15 kHz and five amplitudes,the max value of which is 15 ?m.The influence of the height of the specimen,the diameter of the micropore of the die,the grain size was studied.In addition,the influence of ultrasonic vibration parameters on the height of micro-cylinder,microstructure,surface quality of micro,column,roughness and so on were researched to reveal the mechanism of volume effect.The effect of ultrasonic vibration on the forming process was analyzed,and the mechanism of ultrasonic vibration on the material deformation behavior was revealed.The FEA model of ultrasonic vibration assisted micro-column forming was established.,and the numerical simulation of the forming process was realized.The distribution and evolution of physical field quantities under different conditions were obtained,and the distribution of stress and strain was studied.The effect of ultrasonic vibration and its different vibration parameters on the micro-column forming was clarified through compare the different effect of the contact pressure,friction force,and nodal velocity between the tool/specimen.The non-vibration and ultrasonic vibration micro-upsetting experiments with a frequency of 28 kHz and a maximum amplitude of 4.3 ?m were performed.The effect of ultrasonic vibration on the forming load,compressive strength,microstructure of workpiece,surface quality was investigated to explain the surface effect.Through these upsetting forging experiments,the influence of ultrasonic vibration on different grain size was revealed.The ultrasonic vibration parameter's influences on grain size effect during microforming process was also analyzed.The FEA model of ultrasonic vibration assisted micro-upsetting was established.By analyzing the results of numerical simulation,the ultrasonic vibration's effects on sample internal strain-stress distribution,deformation velocity,surface friction and contact pressure was studied.The simulation results were also compared with experimental results,the effect of ultrasonic vibration on the surface effect and volume effects is obtained and verified.