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切向气流对激光辐照金属板熔融损伤效果影响

时间:2020-05-17 19:51来源:毕业论文
切向气流的对流换热作用使得金属板为达到相同温升所需要的激光功率密度会随气流速度的增大而增大,且气流每增大50m/s,激光功率需增加约 60W/cm2;对于薄金属板加载亚声速切向气流

摘要本文以薄板铝合金为对象, 从理论分析和有限元数值模拟研究了自然对流条件和亚声速切向气流条件下激光辐照金属板作用过程。分析了切向气流在激光辐照金属板过程中的主要效应,包括对流冷却、熔融物质移除、气动力及促进氧化反应等效应。通过有限元发数值计算铝合金受激光辐照的温度场、热应力场分布及形变量的变化规律。结果表明:在连续激光辐照下,金属板表面产生快速升温并产生热应力,随着入射激光能量增加,金属板受热力作用将产生熔融损伤;在亚声速气流条件下,激光辐照金属板,气流主要起到对流换热作用,在初始加载较小速度气流时温度的下降速率较快,随着气流速度的增加,对流换热量增大但温度下降速率趋于平缓;切向气流的对流换热作用使得金属板为达到相同温升所需要的激光功率密度会随气流速度的增大而增大,且气流每增大50m/s,激光功率需增加约 60W/cm2;对于薄金属板加载亚声速切向气流,将受到激光和切向气流的共同作用并导致金属板在未达到熔点时,由于板内应力大于初始屈服应力,从而出现应力屈服进而导致金属板的热力损伤;本文的研究可为激光与金属材料相互作用过程中切向气流的应用提供理论参考,并帮助对薄金属板的热力损伤研究。49145
毕业论文关键词 激光辐照 铝合金 切向气流 有限元法 热应力
Title Damage of Laser Irradiate Metal Plate Under theCondition Of Tangential Air Flow
Abstract Based on the theoretical analysis and finite element numerical simulation, theeffect of laser irradiation on the thin Aluminum alloy plate under the conditionof natural convection and sub sonic velocity was studied in this paper. The maineffects of the tangential flow in the process of laser irradiation on metal plateare analyzed, including the effect of convection cooling, the removal of the moltenmaterial, the power of the gas and the promotion of the oxidation reaction. Byusing the finite element method, the distributions of temperature field, thermalstress field and shape variable of aluminum alloy irradiated by laser arecalculated.The result shows that:the surface of the metal plate is rapidly heatedup with the increasing incident laser power density, and the thermal effect ofthe plate can be produced by the heat stress; In subsonic air flow condition, laserirradiates the metal plate, the airflow mainly leads to the convection heattransfer, in the initial loading of the low speed airflow makes temperature ratedecreased faster, with the increase of air velocity, convection heat transferincreases, but the temperature decreasing rate tends to slow down; the convectionheat transfer of the tangential airflow makes the metal plate required for higherlaser power density to reach the same temperature increase ,with the increase ofthe gas flow velocity, and the laser power is increased by about 50m/s per 60W/cm2;for thin metal plate loading of subsonic tangential flow,the metal plate isinfluenced by laser and tangential airflow, before reaching the meltingpoint,because the interplay stress is greater than the initial yield stress, whichappeared stress yield and lead to the thermal damage of metal plate. The researchof this paper provides a theoretical reference for the application of laser and metal materials in the process of the interaction under tangential flow, andstudies the thermal damage of thin metal plates.
Keywords Laser irradiation Aluminum alloy Airflow Finite elementmethods Thermal stress

目次

1绪论…1

1.1研究背景及意义1

1.2国内外研究发展1

1.2.1国外研究进展…1

1.2.2国内研究进展2

1.3本文的主要工作及结构安排…3

2激光辐照金属板切向气流的作用…4

2.1切向气流对流冷却…4

2.2切向气流加速熔融物质迁移…5 切向气流对激光辐照金属板熔融损伤效果影响:http://www.lwfree.com/wuli/lunwen_52062.html

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