Research On Laser Shock Micro Forming Technology Of Metal Foil In Water Environment

Micro plastic forming is an important technology for manufacturing micro metal parts.With the development of science and technology,the requirements for small,precise and accurate micro / nano devices are higher and higher.The common process characteristic of conventional micro plastic forming is the need of die.The difficulties of mold manufacturing before forming,the strict requirements of mold assembly and adjustment during forming,and the difficulty of demolding after forming have all become the bottleneck of the development of micro plastic forming with molds.In this paper,a method of fabricating microstructure on metal foil by underwater dieless laser shock forming is proposed.The main research contents and conclusions are as follows:(1)Study on the mechanical effect induced by nanosecond laser breakdown in water.Based on the theory of interaction between laser and water,combined with experiment and simulation,the mechanical effect induced by laser breakdown in water is studied.The results show that when the laser peak power density is higher than the breakdown threshold of water,three kinds of mechanical effects will be induced,namely,the shock wave radiated by the laser when it breaks through water;The shock wave radiated during bubble pulsation;The micro jet produced by bubble collapse.The results show that the initial peak value of shock wave is high,and the metal foil can still undergo plastic deformation after a certain distance of underwater transmission.The bubble induced by laser breakdown water collapses near the wall,and the micro jet velocity is faster.When it acts on the foil surface,the pressure generated exceeds the yield strength of the material.(2)The study on the forming mechanism of metal foil under water by nanosecond laser.The forming mechanism of laser induced foil was studied by confocal microscope and high speed camera monitoring.The results are as follows: the distance between the laser breakdown point and the target(H)influences the dominant forming mechanism.When H is about 0.76 mm,the impact wave caused by the water breakdown and bubble pulse will act together;when H is about 0.51 mm,the shock wave caused by laser breakdown will work with bubble pulse and micro jet;when H is about 0.45 mm and0.39 mm,the shock wave produced by laser breakdown water will be in common with micro jet The same effect.The different mechanical effects constitute different forming mechanism of target.(3)Study on the influence of parameters of metal foil induced by nanosecond laser underwater.The influence of key experimental parameters on the forming results of foil was studied.The results show that: the increase of laser energy density will lead to the increase of the maximum radius of the cavity,resulting in the increase of the range and depth of the formed target;increasing the processing times can also increase the range and depth of the formed target.