Research On Ultrasonic Micro Deep Drawing Process Of Flexible Punch Thin Sheetmetal Forming With Instantaneous Viscous Medium

The instantaneous viscous medium of flexible punch sheet metal ultrasonic micro forming process is a new type of micro forming process.The forming process using the flexible punch formed by molten plastic instead of the traditional rigid punch,which avoids the disadvantage that the rigid punch is not easy to be processed and is difficult to be matched with the concave die.At the same time,the forming process combines the ultrasonic vibration with the viscous medium,which makes the process have the advantages of viscous medium forming and ultrasonic forming.On the one hand,the viscous medium of flexible punch transfer pressure more evenly,can delay necking,improve the forming limit of materials;on the other hand,ultrasonic vibration to the billet and die by flexible punch,reduces the friction between blanks and die,reduce the blanks flow stress.On the basis of the previous work of the experimental group,the influence of the process parameters on the formability of the product was studied.The main contents of this paper include:(1)In the previous study,a set of experimental device for fixing the blank holder gap is designed to solve the problem of the blank forming.As the clearance value of the original experimental device is not adjustable,resulting in deep drawing parts are still asymmetric,broken or low degree of replication defects,so in the early research on the basis of the redesign and processing of a set of experimental devices.The experimental device can realize the balance and size adjustment of the blank holder gap,which lays the foundation for the further study of the influence of the blank holder factor on the drawing forming.(2)A new method is proposed to accurately measure the blank holder gap of the device.The plastic powder subjected to ultrasonic vibration under a certain pressure being heated under the excitation of ultrasonic vibration to melt into a viscous medium having flow properties and fill the entire gap cavity,and then measure the shape of the cooled medium to indirectly obtain the clearance value of the original Using this method to measure the experimental device to adjust the blank holder gap clearance range of 0~35?m,comparedwith the calculated results show that the average error of measurement is ±0.6?m,the local error is ±1.5?m.(3)The micro deep drawing experiments were carried out on the annealed T2 copper sheet.The influence of the parameters such as cylinder pressure,blank holder gap and ultrasonic amplitude on the forming quality was analyzed.The experimental results show that under certain experimental conditions,the degree of replication is proportional to the cylinder pressure and ultrasonic amplitude.The higher cylinder pressure and ultrasonic amplitude,the higher replication.When the cylinder pressure is 0.1MPa,the ultrasonic amplitude is 30?m,the replication of the work piece can reach to 84.6%;Through the study of the variation law of the wall thickness of the drawing parts,it is found that dueing to the particularity of the flexible punch of the viscous medium the stress in the upper part of the wall of the workpiece is the smallest.The central position is the most stress in the drawing process,causing upper part of the side wall parts increase the most,about 17.6%,in the vicinity of the central position of the bottom part of minimum thickness,the thickness is reduced by about 14.4%,so the center position is near the dangerous parts drawing most easily pull broken.