Simulation And Experimental Study Of Pulsed Laser Etching Of Aluminum Alloys

A pulsed laser is the common light source in laser etching technology.Studying the thermal effects of the interaction between lasers with different pulse widths and materials can help the researchers to reveal the law and mechanism of the influence of pulsed laser parameters on the etching results,to broaden the application of pulsed lasers in laser etching,and to improve the efficiency of etching.However,it is difficult to observe the transient process of the interaction between pulsed laser and material completely and accurately through experiments.Therefore,in this paper,the finite element simulation model of millisecond and picosecond laser etching of aluminum alloy is established,the influence of different laser parameters on the temperature field and etching results are explored,and the picosecond laser etching experiment and simulation analysis is carried out.The major contents and conclusions are exhibited as follows:(1)The basic theory of laser-material interaction was studied.Based on the Fourier heat conduction theory,the theoretical model of temperature field of laser aluminum alloy interaction was analyzed;The dynamic laser absorptivity was especially considered,and the equivalent specific heat capacity was used to treat the transformation process of aluminum alloy.(2)By establishing the finite element simulation model of millisecond laser etching aluminum alloy,the effects of single pulse energy and repetition rate on the temperature change,radial and longitudinal temperature distribution and vaporization time threshold of laser center point were studied.The results show that the highest temperature is 2510 K with the repetition rate of 500 Hz,single pulse energy of 7.2 J and 50 laser pulses;increasing the repetition rate and single pulse energy can effectively promote the heat accumulation effect;the thermal effect is obvious in the area of 1 mm radially on the surface and 0.6 mm longitudinally inside;when the repetition frequency is greater than 300 Hz,the threshold of vaporization time is less than 0.013 s under the single pulse energy of 10 J.(3)By establishing the finite element simulation model of picosecond laser etching aluminum alloy,the influence of single pulse energy and scanning speed on the etching results was studied,and the laser focus fixed and focus following processing methods were simulated and analyzed.The results show that under the given parameters,when the single pulse energy increases from 9.7 ?J to 43.2 ?J,the simulated etching depth increases from2.05 ?m to 2.64 ?m;when the scanning speed increases from 200 mm/s to 460 mm/s,the simulated etching depth increases from 3.21 ?m to 1.12 ?m;the simulated etching depth of laser focus following method is 3.31 ?m under the defocusing of 50 ?m,100 ?m and 150?m,it can effectively correct the influence of defocus amount.(4)The experiment and simulation analysis of picosecond laser etching are carried out.The experimental and simulated etching results under different single pulse energy and scanning speed are compared to verify the effectiveness of the simulation model;laser focus fixing and focus following etching experiments were carried out;Based on the simulation results,the mechanism of surface roughness change caused by laser parameters is analyzed.The results show that the experimental and simulated etching results are in good agreement;in the process of laser etching,the focus is more accurately focused on the surface of the etching area,so the etching depth remains stable;in the case of given parameters,when the single pulse energy increases from 9.7 ?J to 45 ?J,the surface roughness decreases from 3.2?m to 1.6 ?m;when the etching interval increases from 7.5 ?m to 15 ?m,the surface roughness increases from 1.1 ?m to 3.1 ?m;when the scanning speed increases from 220mm/s to 380 mm/s,the surface roughness increases from 1.5 ?m to 3.3 ?m;according to the simulated etched surface topography under the corresponding laser parameters,the change of peak valley height difference in the etched area causes the change of surface roughness.