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摘要介绍了激光致铝靶产生热熔融破坏的基本特征及现有理论，采用数值方法对长脉冲激光致铝靶温升、相变等热破坏过程进行了模拟。对模拟的结果进行了分析，得到了铝靶在激光烧蚀作用下的各项数值。33728
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使用COMSOL软件建立了激光致铝靶产生热熔融破坏的轴对称模型，并利用有限元方法对温度场进行了求解，得到了靶材温度场分布和液体重铸厚度等参数。
通过改变物理模型中激光输入参数，分析了不同能量密度的激光照射下造成的热破坏结果，并总结了激光能量对熔深，温升，液体重铸厚度的影响。
结果显示，在入射激光的光斑半径和脉宽一定的情况下，随激光能量的增加，熔融深度随之增加。在较小激光能量下，熔液流动不明显，将激光能量增至一定数值后可计算得出熔液重铸厚度。
研究可使激光致金属熔融破坏方面的研究更加全面，使熔体模型更加精确符合实际需求，并可在以后的研究当中进行更加复杂的运算模拟，亦可为脉冲激光加工的最优参数研究提供参考。
关键词 毫秒激光 金属熔融 有限元法 数值模拟
毕业论文设计说明书外文摘要
Title The recast thickness of molten liquid aluminum induced by millisecond laser
Abstract
The theory and the basic features of the thermal damage on aluminum target induced by the millisecond laser are presented. A numerical study is conducted to simulate the process of the temperature increasing and the phase transition process . The results of simulation are analyzed and the numerical values of the aluminum target are obtained.
An axisymmetric model is established to simulate the thermal melting process in COMSOL and the finite element method is used to solve the temperature field , the temperature rising along radialand axial direction, melt depth and the recast thickness of molten liquid are obtained.
The thermal destruction results induced by pulsed laser with different energy density are analyzed by changing the laser parameters, and the effect of laser energy on the penetration depth , temperature , recast thickness of liquid is summarized.
The results show that in the case of the incident laser spot radius and pulse width , the melting depth increases with the increasing of laser pulse energy. The molten liquid flow is not obvious under the lowpulse energy , and the recast thickness can be calculated when the laser energy increased to a certain value.
The research will make the metal melting damage more comprehensive,and make the model more precise and fit for actual conditions. Moreover, more complex simulation can be made in the future research.The research can also provide references for the optimum parameters of laser processing.
Keywords Thermal melting，Finite element model,Numerical simulation
目 次
1 绪论 2
1.1 引言 2
1.2 激光与物质相互作用研究国内外现状 … 2
1.3 本文的主要研究目的及工作 … 4
2 激光与物质相互作用的理论基础 5
2.1 物质对激光的吸收与反射 5
2.2 激光对物质的熔融破坏作用 5
2.3 铝的特性参数 … 6
2.4 熔融液体重铸厚度计算理论 … 6
3 数值模拟与计算方法 8
3.1. 有限差分法 8
3.2 有限元法 … 8
3.3 计算方法 … 8
3.3.1 热传导方程的求解 8
3.3.2 固态温升阶段 9
3.3.3 熔融阶段 9
4 数值模拟结果与讨论 11
4.1 模型构建 11
4.2 瞬时温度场结果 … 12