| The wide application of laser drilling technology has promoted the research progress in many industries.Its higher efficiency,higher speed and lower cost drilling performance have established its irreplaceable position in micro holes array processing.However,for millisecond laser drilling,there are still some problem s,such as complex technological parameters,slag on the surface of the hole,recasting layer on the inner wall,and micro-cracks,which seriously affect the application of laser drilling technology in ultra-precision micro-hole processing.In addition,when the number of holes is high,the thermal deformation of materials will occur.In this paper,based on the level set method,after coupling heat transfer and fluid flow physical field,considering the effect of recoil pressure,surface tension,Marangoni force and gravity on fluid,a two-dimensional simulation model of laser drilling was established,and the enthalpy-pore method and the improved level set method were used to track the changes of solid-liquid interface and gas-liquid interface.And then,analyzed the temperature field distribution of laser drilling,the forming law of the hole and the flow state of the molten pool in the hole.Finally,the mechanism of laser drilling recast layer and the distribution of recast layer were discussed.The 1Cr18Ni9 Ti stainless steel with a thickness of 1mm was selected for experimental research.Orthogonal experiment and single factor experiment were adopted to study the influence of laser energy,pulse width,pulse number,pulse frequency,defocusing amount,auxiliary gas pressure and other process parameters on hole size and morphology.The results of experiment and simulation were compared to verify the correctness of simulation analysis.In order to improve the surface quality of laser drilling,the effects of laser parameters on slag and recast layer on the surface of the hole were discussed,and the best process method to reduce the slag and recast layer is put forward.The problem of sheet deformation caused by laser multi-hole processing will seriously affect the consistency of holes and the quality of workpiece processing.In this paper,a three-dimensional simulation model of sheet metal deformation in laser group hole processing was established by using finite element analysis method,and the thermal stress state of sheet metal under laser was analyzed.The effect of stress accumulation on the whole sheet metal deformation was discussed.The method of restraining sheet metal deformation is put forward theoretically.On the basis of theoretical analysis and experimental study,the effects of workpiece clamping mode,laser parameters and drilling path on sheet metal deformation in laser drilling were discussed.The accuracy of theoretical analysis was verified and the drilling strategy of minimum deformation is obtained. |
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