Software Development And Applications Of Beam Oscillation Patterns For Laser Welding

Laser oscillating welding can improve weld formation and performance by changing the metallurgical behavior of molten pool through beam oscillation in special small area,which reduces the clamping accuracy and make it more suitable for modern industry.However,the oscillating patterns are limited to horizontal straight line,vertical straight line,and circular shape.It limits the advantages of this new laser welding technology.In current thesis,a new software for customized design of oscillating patterns was developed,and verified by three typical applications.The main research results are as follows.Firstly,the software to design the beam oscillation patterns in laser welding was developed,which uses custom numerical code to divide a two-dimensional pattern into lines and arcs.It can achieve the customized design of beam oscillation patterns.The software interface displays the actual patterns after the oscillating pattern and the welding speed are synthetized in real time.In addition,the software integrates the function module based on the gaussian distribution model,which can display the energy distribution characteristics of the oscillating patterns in real time.This model can assist the design more conveniently.An inscribed double circle pattern was designed to solve the easily formed concave defect of laser welded magnesium(Mg)alloys.The surface concave could be completely suppressed when the oscillating frequency increased to 100 Hz.The suppression is attributed to two reasons.Firstly,the beam oscillation of inner circle improved the low internal energy of the single circle,which makes the energy distribution of whole molten pool more uniform.Secondly,the whole melt flow became smoother because the melt flow induced by inner circle is opposite to that driven by outer circle.The effects of the new inscribed double circle on the porosity of laser welded aluminum(Al)alloys were studied.Better ability to suppress the porosity was achieved in comparison of the single circle.For inscribed double circle,no pores were observed in the weld by X-ray test when the oscillating frequency was 150 Hz.However,for circle oscillation,the porosity kept 7% even when the frequency was 300 Hz.The improvement of porosity suppression is achieved by the combination of two reasons.Firstly,the Reynold number of melt flow of inscribed double circle at 150 Hz is same with that of single circle at 300 Hz.It means they have the same ability to escape the bubble into the air.Secondly,the track repetition rate of inscribed double circle is 1.33 times higher than that of single circle,suggesting that the formed bubbles are easier to be captured and exhausted via keyhole.An eight-shaped pattern was inversely designed to homogenize the interface of laser lap welded dissimilar Al/Mg alloys.The oscillating velocity of eight-shape was smoother than that of single circle,so the eight shape could form a more uniform energy distribution at interface,and thus a more uniform interface layer.The effective connection length at interface was increased by 4 times than that of single circle,enhancing the shear load and strength up to 4.363 k N and 121 MPa,393% and 23% higher than single circle,respectively.