Investigations On The Law Of Ultrasonic-Assisted Hydroforming Of Microtubes

Ultrasonic vibration tube hydroforming technology is carried out on the basis of tube hydroforming technology combined with ultrasonic vibration.It has the characteristics of low forming load,good filling and moldability,uniform wall thickness,and high forming quality.At present,the law of ultrasonic vibration tube hydroforming is not clear.Research on the forming law can effectively describe the forming process of the tube,analyze the forming principle of the tube,and then can reasonably select the process parameters,effectively suppress or eliminate the forming defects,and improve the formability of tube.It has important theoretical significance and application value.In this paper,by combining experiment with simulation,the research on the law of ultrasonic-assisted tube hydroforming has been studied.Combining the principle of hydroforming with axial feeding,the characteristics of ultrasonic vibration,and the requirement that vibration directly acts on the tube,the ultrasonic vibration tube hydroforming device was designed and developed,and the experiment system was built with this device.The simulation model was constructed through the ABAQUS software,and the accuracy of model was verified by comparing the experiment results.Compared with conventional experiment,the T2 copper tube was used to study the influence of ultrasonic vibration on the fluctuation amplitude of liquid pressure,maximum axial force,maximum bulging height,minimum wall thickness and position under different the moment of vibration application,the length of tube,the speed of axial feeding and ultrasonic amplitude.The deviation of liquid pressure fluctuation amplitude,the deviation rate of maximum axial pressure,the deviation of maximum bulging height and wall thickness distribution uniformity have been analyzed.The influence of ultrasonic frequency on the tube bulging profile is studied by means of simulation.Experiments were carried out on TP2 seamless internally threaded copper tube,and the effect of ultrasonic vibration on the bulging profile of tube with different structures was studied.The results show that:(1)Ultrasonic vibration increases the hydraulic pressure,within0.5 MPa,reduces the axial force,with time-sensitive,increases the maximum bulging height,and within 0.4 mm,enhances the formability of the tube and reduces the minimum wall thickness of the tube,and the uniformity of the wall thickness is reduced.(2)The position of the maximum bulging height and the minimum wall thickness is changed from being close to the axial feeding(vibration application)end in the convention experiment state to far away from the axial feeding(vibration application)end when the ultrasonic is applied.(3)When the moment of vibration application is delayed,the increase in hydraulic pressure gradually decreases,and the formability gradually increases.The uniformity of the wall thickness first weakens and then increases.When vibration is applied in the last 15 s,the wall thickness is the most uniform.(4)When length of the tube increases,vibration has little effect on the increments in hydraulic pressure,and the effect of axial force reduction is gradually weakened,which reduces the uniformity of the wall thickness.The formability is first strengthened and then weakened.when the length of tube is 31mm,the formability is the best.(5)When the speed of axial feeding increases,the hydraulic pressure is increased,vibration has little effect on the increase of hydraulic pressure.The effect of axial force reduction is first strengthened and then weakened.The speed is 2 mm·min^-1,the effect of axial force reduction is the best.The formability is first weakened and then strengthened.The speed of axial speeding is 3 mm·min^-1,The formability is the best,and enhances the uniformity of the wall thickness.(6)When the amplitude increases,the increase in hydraulic pressure gradually increases,and the effect of axial force reduction is first strengthened and then weakened.When the amplitude is 22?m,it is best,and the formability is the first it weakens after enhancement,the best is when the amplitude is 20?m.The uniformity of the wall thickness is first weakened and then strengthened.When the amplitude is 16?m,the wall thickness is the most uniform.(7)When the frequency increases,the formability first strengthens and then weakens,and the formability is the best at a frequency of 20 k Hz.(8)The structure of the tube has no effect on the position of the maximum bulging height.