摘要：激光应用的重要基础是激光与靶材的相互作用的应用。金属材料受到激光作用，吸收激光能量，引起金属靶材温度升高，可能产生融化、气化、喷溅、产生小孔，甚至产生等离子体等现象，而这些现象正是金属激光加工技术的基础（激光焊接、加工、表面改性、快速成型、激光细微加工技术等）。在激光深熔焊接过程中，当高功率密度的激光束照射工件表面时，工件材料吸收激光能量发生融化和气化，并在气化膨胀压力的作用下，在工件内部形成一个小孔，在小孔内部存在着两种激光能量的吸收机制:一种是菲涅尔吸收，另一种是反轫致辐射吸收。由于激光入射到小孔内部后，将会发生多次发射和吸收现象，具有多重菲涅尔吸收现象。因此，为了分析激光在小孔中的多重反射吸收，就必须了解小孔的形状。而关于光线在小孔内的多次反射和吸收现象，则与光线在小孔内的吸收系数有关，这就可以用几何光学的知识来解答。另一方面，激光与材料相互作用产生小孔，在小孔的尺度与激光波长相差不多的情况下，光线在入射进去小孔内部的时候，将会发生衍射现象，此时可以用物理光学的知识来理解。87514

毕业论文关键词  小孔模型 菲涅尔吸收 多重反射 激光深熔焊接

毕业设计说明书外文摘要

In the process of laser ablation hole wall numerical studies of multiple Fresnel absorption

Abstract Laser application is the important basis of the application of interaction of laser and target material。 Metal materials by laser effect, absorption of laser energy, causes the metal target temperature, melting, gasification, splash, produce holes may be produced, and even produce the phenomenon such as plasma, and these phenomena is the base of metal laser processing technology（laser welding, machining, surface modification, rapid prototyping, laser micro processing technology, etc。)。In deep penetration laser welding process, when the high power density laser irradiation surface, melting and gasification in the material absorption laser energy of components, and under the action of inflationary pressure gasification, a small hole, is formed within the workpiece inside the hole there are two kinds of laser energy absorption mechanisms: one is the Fresnel absorption, the other is a inverse bremsstrahlung absorption。 Due to the laser incident into the hole, will happen many times emission and absorption phenomenon, with multiple Fresnel absorption phenomenon。 Therefore, in order to analyze multiple reflection absorption of laser in the hole, you must understand the shape of the hole。 Laser application is the important basis of the application of interaction of laser and target material。 Metal materials by laser effect, absorption of laser energy, causes the metal target temperature, melting, gasification, splash, produce holes may be produced, and even produce the phenomenon such as plasma, and these phenomena is the base of metal laser processing technology, laser welding, machining, surface modification, rapid prototyping, laser micro processing technology, etc。)。In deep penetration laser welding process, when the high power density laser irradiation surface, melting and gasification in the material absorption laser energy of components, and under the action of inflationary pressure gasification, a small hole, is formed within the work-piece inside the hole there are two kinds of laser energy absorption mechanisms: one is the Fresnel absorption, the other is a inverse bremsstrahlung absorption。 Due to the laser incident into the hole, will happen many times emission and absorption phenomenon, with multiple Fresnel absorption phenomena。 Therefore, in order to analyze multiple reflection absorption of laser in the hole, you must understand the shape of the hole。 And about the light within the pores of multiple reflection and absorption phenomenon, is related to the light within the pores of absorption coefficient, which can use the knowledge to answer of geometrical optics, on the other hand, the interaction between laser and material to produce holes, the holes under the condition of similar in scale to the laser wavelength, the light in the incident in the inside of the hole, diffraction phenomena will happen, can use the knowledge of the physical optics to understand at this time。