| Because of the high specific strength, good thermal conductivity, aluminum alloy is widely applied in industry such as the field of aerospace, transportation, communications electronics and so on. So aluminum alloy is research hotspot in materials. Aluminum alloy sheet parts are high precision parts and asked for higher quality. The way of laser cutting can overcome the defects cutting by tradition machining. At present, great achievements in studying of process parameters and mathematical model of laser cutting have been got. Which help us to understanding the mechanism of laser cutting more. The status and final form of melt during laser cutting and Its removal mode and mechanism directly have great influence upon laser cutting quality. Establishing the model of melt removal and the relationship with cutting quality has great applied value and theoretical meaning for high-precision laser cutting.The shape and characteristic parameters distribution of removal melt particles were obtained through the way of image processing of the microscopic images of removal melt particles with Image Pro-plus (IPP) software. And the removal melt particles were classified three kinds of shapes based on the metric rule, the spherical particles, the quasi-spherical particles and the tadpole-shape particles. The results show the percentage of spherical particles in removal melt particles increases with vaporization-melt ratio and the average size of particles reduces with vaporization-melt ratio. For example, the percentage of spherical particles in removal melt particles reaches up to69%, and the average diameter of spherical particles is smaller,88.96μm at high vaporization-melt ratio,0.6519. The percentage of tadpole-shape particles in removal melt particles increases sharply at high assist gas pressure. For example, The percentage of tadpole-shape particles in removal melt particles reaches up to60%.According to experiments data and theoretical research, the dynamical model of melt is developed, and the melt removal model is also established based on Kelvin-Helmholtz instability theory. Assist gas shear force, viscosity force and vapor recoil pressure decide the dynamic characteristic of melt, and the melt removal model is established based on aerodynamic action and surface tension through the Weber number. The average size of removal melt particles is predicted and airborne particles arc explained well by secondary breakup theory. This melt removal model explains well about the shape and characteristic parameters distribution of removal melt particles, also the cutting quality acted by vapor-melt ratio and assist gas.The culling quality of aluminum alloy sheet is studied based on vaporization-melt ralio and assist gas pressure controlled, including adhering slag and cutting width and so on. The results show the good culling quality can be easily obtained at high vaporization-melt ratio and high assist gas pressure. The good culling quality includes a small amount adhering slag and uniform cutting width and so on. The above-mentioned results prove the correctness of the model. Finally the high cutting quality with no adhering slag, Hal cutting wall, low roughness (Ra4.195) was achieved at high vaporization-melt ratio0.6519and high assist gas pressure0.6MPa. Also the high quality of aluminum alloy slot array antenna sheet was obtained. |
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