长脉冲与短脉冲激光联合作用铝合金靶材损伤特性研究

发布时间：2018-06-22 03:52

本文选题：长短脉冲联合激光 + 激光烧蚀效果　；参考：《长春理工大学》2017年硕士论文

【摘要】：激光加工作为现阶段常用的一种加工手段,其在汽车生产、器件制造以及航空航天等领域都有着重要应用。随着自动化水平的提高和科技的发展,如何进一步提升激光加工效率,已成为科研工作者的关注点之一。调查结果显示,当采用连续与长脉冲组合激光加工金属靶材时,可以有效提高光源的利用效率;同时发现在相同条件下,加工过程中产生的不利因素也有一定程度的降低。那么毫秒长脉冲激光与纳秒短脉冲激光组合,是否也可以对加工效率有所提高。针对这一问题,论文以铝合金靶材为研究对象,从理论和实验两方面,深入探讨了纳秒与毫秒双脉冲联合激光对铝合金材料的损伤机理与特性,为双脉冲组合激光加工的发展提供了一定的理论支持与依据。针对长短脉冲联合激光对铝合金靶材的作用机理,论文从激光与金属靶材相互作用过程出发,基于激光作用靶材引起的吸收率变化,重点探讨了激光诱导热作用机理。在讨论材料吸收率随靶材温度、电子层数及作用激光波长等因素的变化趋势的基础上,分析了金属相变情况下其性质的变化过程。基于热传导理论,建立了组合脉冲激光作用铝合金靶材烧蚀的物理模型,采用多物理场耦合有限元分析软件Comsol与数值计算软件Matlab,分别模拟分析了单脉冲激光作用靶材和双脉冲组合激光不同延时情况下作用靶材,其温度场和吸收率分布等的变化规律。研究结果表明:在双脉冲激光作用下,靶材温度相对单脉冲作用效果提升较高;同时发现延时时间将对靶材烧蚀形貌变化产生较大影响,这一结论为后续实验设计提供了理论计算依据。在理论研究的基础上,论文建立和完善了长短脉冲激光组合实验装置,开展了不同延时情况下组合激光对铝合金2024靶材的损伤特性研究。基于靶材的熔坑深度和半径等烧蚀形貌,分析了组合激光脉冲的损伤特性与规律。研究发现:在相同条件下,控制短脉冲激光相对于长脉冲激光的作用靶材的时刻,其烧蚀特性存在明显差异,在毫秒激光诱导靶材温度最高处纳秒激光开始作用,靶材烧蚀效果最佳,产生的等离子谱最强。结果表明长短脉冲组合激光在精确控制延时条件下,可有效提升靶材的烧蚀效果,这与理论的研究结果是一致的。这一结果可为激光加工领域的发展提供一定的理论依据和技术支撑。
[Abstract]:Laser processing, as a commonly used processing method at present, has important applications in the fields of automobile production, device manufacture, aerospace and so on. With the improvement of automation and the development of science and technology, how to further improve the efficiency of laser processing has become one of the concerns of researchers. The results show that the use efficiency of light source can be improved effectively when the metal target is processed by continuous and long pulse laser, and the unfavorable factors in the process are reduced to a certain extent under the same conditions. So millisecond long pulse laser and nanosecond short pulse laser combination can also improve the processing efficiency. In order to solve this problem, the damage mechanism and characteristics of nanosecond laser combined with millisecond double pulse laser on aluminum alloy materials are discussed in theory and experiment. It provides some theoretical support and basis for the development of double pulse laser processing. Based on the interaction between laser and metal target, the mechanism of laser induced thermal action is discussed based on the change of absorption rate caused by laser acting on aluminum alloy target. On the basis of discussing the changing trend of the material absorptivity with the target temperature, electron layer number and laser wavelength acting, the change process of the properties of the material under the condition of metal phase transition is analyzed. Based on the theory of heat conduction, a physical model of ablation of aluminum alloy target by combined pulse laser is established. By using the finite element analysis software Comsol and the numerical calculation software Matlab. the temperature field and the absorptivity distribution of the target acting on the target with single pulse laser and double pulse combination laser with different delay time are simulated and analyzed respectively. The results show that the temperature of the target is higher than that of the single pulse laser, and the delay time has a great influence on the ablation morphology of the target. This conclusion provides a theoretical basis for the subsequent experimental design. On the basis of theoretical research, this paper establishes and perfects the experimental equipment of long and short pulse laser combination, and studies the damage characteristics of aluminum alloy 2024 target under different delay conditions. The damage characteristics and rules of combined laser pulse are analyzed based on the ablation morphology of the target. It is found that under the same conditions, the ablation characteristics of short pulse laser is different from that of long pulse laser at the same time, and the nanosecond laser begins to act at the highest temperature of the target induced by millisecond laser. Target ablation is the best and the plasma spectrum is the strongest. The results show that the long and short pulse combination laser can effectively improve the ablation effect of the target under the condition of accurately controlling the delay, which is in agreement with the theoretical results. The results can provide some theoretical basis and technical support for the development of laser processing.
【学位授予单位】：长春理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG665;TN249

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