Research On The Process And Theory Of Dieless Laser Shock Forming Of Micro Metal Parts

The rapid development of Micro-Electro-Mechanical System leads to the increasing demand for micro metal parts.The traditional micro manufacturing technology can not meet the large demand for micro metal parts in the near future.the high cost and difficulty of designing and manufacturing micro moulds are also seriously restricting the productivity of micro metal parts by traditional micro manufacturing technology.Because of its advantages of high processing efficiency,low cost and good flexibility,the dieless laser shock micro-forming has attracted the attention of the society in the field of the manufacture of micro metal parts.But the technology of the dieless laser shock micro-forming is still at the initial stage,and there will be great research prospects in the aspects of process plan,accuracy control and theoretical analysis.In this paper,the process of dieless laser shock micro-forming metal foils have been carried out by experiment and numerical simulation.The purpose was to explore the law of forming process and the precision control of deformation of metal foils.The main works and conclusions of the research were as follows:(1)The induced principle of the laser shock wave has been analyzed by the forming process of plasma and the basic equation of induced stress wave.The models for estimating the peak pressure of laser induced shock wave have been compared,and the reasons for using the Fabbro formula were clarified.Calculation method of strain rate of deep drawing model has be analysed,and adopted to research dieless laser shock micro-forming.(2)An ABAQUS finite element simulation model for multi-point laser shock micro-forming of copper foil was established to simulate the process of multi-point laser shock micro-forming.Using T2 copper foil with the thickness of 20?m as the target material to research the effects of single pulse energy,pulse width,and scanning sequence in the process of laser shock micro-forming.The results show that the concave pit morphology can be characterized by the pit depth,the inclination angle of pit wall,the inner diameter of pit and the outer diameter of pit.Theyincreased with the single pulse energy and pulse width increasing.Due to the large variable range and good controllability of laser energy,we can precisely control the topography of pits through adjusting laser energy during dieless laser deep drawing.On the other hand,the topography of pits can be roughly controlled through varying laser pulse width due to its small variable range and low flexibility.The inclination angle of the pit wall decreases with increasing single pulse energy and pulse width.The depth of the concave pit and the slope angle of the pit wall can be changed only through changing the scanning path of the laser.The farther the first scanning path is from the center of the pit,the inner diameter and outer diameter of the dent can be increased,which can be used for controlling the transverse dimensions of the pits.(3)Dieless multi-point nanosecond laser shock micro-forming was experimentally studied with copper foil as the research object.The transparent adhesive tape was used as the confinement layer.The experiment was carried out along the laser scanning path of three concentric circular tracks with the diameters of0.4mm,0.45 mm and 0.5mm.The pulse width of laser was 5ns.The variation of dynamic micro-deep drawing progressive forming of T2 copper foil was researched with single pulse energy,spot overlap rate and the changing sequence of laser scanning path.The results show that the depth of pits,the bottom plane diameter of pits and the inclination of pits' wall increase linearly with increasing the single-pulse energy and the spot overlap rate when the confinement layer is not damaged.The sequence of laser scanning inside and outside the circle has no effect on the depth of pits,but having impacts on the bottom plane diameter of pits.Laser scanning the outer circumference firstly will form a larger bottom plane diameter of pits.It is indicated that the shape of the pit is controllable without mold.This result is helpful for the further study on dieless laser micro-deep drawing progressive forming.