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激光加工技术在材料加工领域，以其独特的优越性， 成为制造业的重要加工手段。毫秒级脉冲激光具有激光能量密度大，作用时间长，功率密度低，与材料相互作用不易产生激光等离子体，因为与材料相互作用的耦合效率高。功率密度相对较低的毫秒脉冲激光对金属靶材的破坏多以熔融，汽化以及熔融喷溅为主，因此温度场的研究是激光和金属相互作用机理的一个重要方面，在激光精细加工、激光烧蚀等方面都具有一定的理论和实际意义。 本文针对塑性屈服、熔融及小孔成形过程进行了理论计算和实验研究。建立了半无限大的轴对称模型，利用物质守恒以及能量守恒，在流体力学模型下，分别模拟了不同能量、不同光斑半径的激光辐照条件下铝表面温度，得出材料表面温度随激光功率的增大而增加的结论。基于热传导理论及温度分布形式，得到了温度和“钻孔”速度的解析解，并利用实验研究获得的熔池形貌验证了解析计算结果。计算结果表明 ，尤其是在焊接和切割中，由于吸收的激光强度而产生的反冲压力作用，将会引起接触区域金属熔化并高速喷出。这些熔化喷出的金属将会从接触区域上削弱绝大部分的激光强度。因此，无论在计算在接触区域的能量平衡上还是在计算焊接池或者切割面附近的热区时，相关对流项都是不能忽略的。 本文研究结果可为进一步研究毫秒激光与金属相互作用中出现的温升、热应力、塑性屈服、熔融及小孔成形提供理论和实验研究依据，亦有助于毫秒激光在加工和军事中得到进一步的应用。59570
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毕业论文关键词：毫秒激光，反冲压力，熔体喷溅，熔融深度
Title The calculation of the temperature of aluminum interact with millisecond laser of different energy.
Abstract The laser processing technology in the field of materials processing, has become an important processing manufacturing means with its unique superiority. The metal target was damaged by the lower power density pulsed laser in the way of melting and vaporizing. One of the most important aspects to research the interaction between the laser and metal is temperature field. It is of definite theoretical and practical significance to research temperature field interaction between the laser and metal on laser precision machining and laser ablation. According to the plastic yield, melting and the process of keyhole forming, we has carried on the theoretical calculation and experimental study. Separately, the temperature field of aluminum was simulated after irradiated by different wavelengths, different radius and different axial depth of laser. A semi-infinite ax symmetric model is established for millisecond laser melting of a metal slab. The analytical solutions of the entire temperature filed and the melting depth are obtained based on the heat conduction theory and the distribution of temperature field，and come to the conclusion that material surface temperature increases with the increase of laser power. It is shown that, for the absorbed laser intensities typical in welding and cutting, the recoil pressure induces high-velocity melt-flow ejection from the interaction zone. This melt flow carries away from the interaction zone a significant portion of the absorbed laser intensity. Thus, convection-related terms can be ignored neither in calculations of the energy balance in the interaction zone nor in calculations of the thermal field in the vicinity of the weld pool or cutting front. The research consequences may offer theoretical and experimental references to the further study of the temperature rising, the thermal stress, the plastic damage, the melting and the formation of hole, and accelerate the application of millisecond laser in manufacturing and military.