Research On Ultrasonic Vibration Assisted Micro-forming Limit Of 5052 Aluminum Alloy Sheet

In the sheet microforming process,the material is easily to cause uneven deformation,strain concentration and forming limit reduction.The size effect makes the traditional prediction model and experimental method of sheet metal forming limit difficult to apply.Ultrasonic vibration assisted sheet micro-forming technology can improve the formability of the metal sheet and enhance the surface quality of forming parts At present,the research on ultrasonic vibration of the softening effect have achieved certain results,but there are few research on the scale effect of the ductility failure and forming limit of ultrasonic vibration,the vibration assisted soft mold forming limit and the vibration assisted microarray.In this paper,based on the traditional forming limit experimental method,established an experimental platform for ultrasonic vibration-assisted micro-forming limit of sheet metal,which is suitable for materials below 0.2mm;The effects of vibration on the forming limit and fracture of were studied by ultrasonic vibration-assisted microstretching and micro-bulging experiments.It is found that vibration has opposite effect on the extreme strain values in tension-compression zone and tension-tension zone.,The reason for the analysis is due to the difference of vibration loading mode and ultrasonic energy.With the increase of amplitude,the fracture mode gradually develops from microporous aggregation fracture to fatigue fracture.When the amplitude is small,vibration does not change the trend of forming limit curve with grain size and fracture mode.But it also has obvious size effect.The change of grain size and vibration have opposite effect on the number and size of fracture dimples.Appling the soft mold to the vibration auxiliary etc double bulging,.Made a discussion about the multiple influences of ultrasonic vibration,flexible punch and size effect.The ultimate bulging height of the soft mold is reduced,but the ultimate strain value is increased.After vibration,the ultimate bulging height increases gradually,and the change of ultimate strain is not obvious.With the change of grain size,the size effect of vibration assisted soft mold is obvious.The results show that vibration improves the fluidity of the soft die,makes the plastic deformation more uniform and increases the formability of the material.Carried out the ultrasonic vibration assisted soft mode micro-bulging array experiment,the influence of process parameters on surface quality and die-insertion of spherical crown micro-structure array parts is analyzed by changing the amplitude,vibration time and force.The results show that a certain degree of vibration-assisted soft die forming can improve the surface quality of spherical crown and die-bonding property,which is beneficial to ensure the accuracy of forming parts and improve the forming performance of sheet metal.The optimum technological route was obtained and spherical crown microstructural arrays with the same die size were formed.The results show that the vibration-assisted soft die bulging process is very suitable for manufacturing thin-walled microstructural arrays.