脉冲激光加工金属表面典型效应的理论和实验研究

发布时间：2018-06-15 09:15

本文选题：脉冲激光 + COMSOL　；参考：《江苏大学》2017年硕士论文

【摘要】：脉冲激光作用于金属表面,获得特定的表面形貌,在工业领域有广泛应用。特定表面形貌的形成,是光与靶材相互作用复杂物理过程的作用结果,该过程与激光脉冲宽度密切相关。当脉冲宽度大于材料的热弛豫时间(纳秒、微秒或者毫秒激光),热力效应在表面形貌形成过程中起关键作用;而当脉冲宽度小于材料热弛豫时间(皮秒或者飞秒激光),靶材中光致热力效应较小,表面形貌形成机制与长脉冲激光迥然不同。本文选择飞秒激光和百微秒激光为加工源,从实验和数值研究两方面,细致研究了长脉冲与超短脉冲激光与金属材料作用后,表面形貌的形成结果、形成机制和相关规律。主要工作内容如下:(1)基于COMSOL Multiphysics仿真软件,数值研究了超短脉冲激光作用金属表面后的能量分布以及长脉冲激光作用金属材料表面后温度场分布;研究了金属表面形貌以及不同金属材料对超短脉冲激光在金属表面能量分布的影响;长脉冲激光作用金属表面能量分布。数值研究结果表明:表面微结构越密集,激光能量会越往微结构尖峰移动;由于长脉冲激光热效应的存在,热影响区域大于光斑辐照区域。(2)进行超短脉冲激光金属表面微加工实验,研究了金属材料、靶材表面粗糙度以及单脉冲激光能量等对表面形貌变化的影响规律。实验结果发现:超短脉冲激光作用后,由于激光和表面波干涉,金属表面形成共振周期性结构;不同金属材料形成周期性表面结构的难易不同,对激光能量吸收更多的材料更易形成周期性表面结构;单脉冲能量大的超短脉冲激光加工形成的表面周期性结构的轮廓更加明显,但是由于高斯光束使得激光能量分布不均匀,光斑中心的热效应也更加明显。(3)进行长脉冲激光辐照裂纹金属表面实验,研究了输出功率和离焦量对不同金属材料表面裂纹弥合的影响。实验结果发现:硬度低的材料更易利用微熔凝的方法弥合金属表面裂纹;当输出功率选择合适时,可以通过适当调整离焦量,在获得裂纹修复结果的同时改善金属表面的质量。
[Abstract]:Pulsed laser acts on metal surface and obtains specific surface morphology, which is widely used in industrial field. The formation of specific surface morphology is the result of the complex physical process of the interaction between light and target, which is closely related to the laser pulse width. When the pulse width is larger than the thermal relaxation time (nanosecond, microsecond or millisecond laser), the thermal effect plays a key role in the formation of surface morphology. However, when the pulse width is smaller than the thermal relaxation time (picosecond or femtosecond laser), the photoinduced thermal effect in the target is small, and the mechanism of surface morphology formation is very different from that of long pulse laser. In this paper, femtosecond laser and femtosecond laser are selected as the processing source. The formation of surface morphology, formation mechanism and related laws of the surface after the interaction of long pulse and ultrashort pulse laser with metal materials are studied in detail from both experimental and numerical aspects. The main work is as follows: (1) based on COMSOL Multiphysics simulation software, the energy distribution of metal surface and the temperature field distribution after long pulse laser acting on metal surface are numerically studied. The influence of metal surface morphology and different metal materials on the energy distribution of ultrashort pulsed laser on metal surface and the energy distribution on metal surface by long pulse laser were studied. The numerical results show that the denser the surface microstructures, the more the laser energy moves to the peak of the microstructures, due to the existence of long pulse laser thermal effects. The influence of metal materials, target surface roughness and single pulse laser energy on the surface morphology was studied. The experimental results show that the metal surface has resonant periodic structure due to the interference of laser and surface wave after ultrashort pulse laser, and different metal materials are difficult to form periodic surface structure. It is easier to form periodic surface structure for more materials absorbing laser energy, and the surface periodic structure formed by ultrashort pulse laser processing with large monopulse energy is more obvious, but the laser energy distribution is not uniform due to the Gao Si beam. The thermal effect at the center of the spot is also more obvious. (3) the effects of output power and defocus on the crack healing of different metal materials have been studied by long pulse laser irradiation on the metal surface. The experimental results show that it is easier for the materials with low hardness to use the method of micro-melting to close the crack on the metal surface, and when the output power is selected properly, the quality of the metal surface can be improved by adjusting the amount of defocusing properly.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG665

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