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通过优化激光清洗工艺参数(如激光波长、脉冲宽度、脉冲频率、功率、离焦量、扫描速度以及路径等)可以保证在不损伤基体的前提下实现精确除漆,是提高清洗效率和保证清洗效果的关键因素。除漆过程中是多种效应共同作用的结果,单调的考虑某一参数对激光除漆的影响是不够准确的,参数之间存在耦合作用。
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激光除漆的烧蚀效应与激光波长息息相关,飞机蒙皮常用漆层对激光的吸收率与激光波长呈正相关。当入射光子有足够的能量克服带隙时,就会发生单光子吸收,导致电子从价带向导带跃迁。被激发的电子与晶格声子碰撞,将吸收的能量转移到晶格,导致晶格紊乱、化学键断裂,随后漆层发生烧蚀。波长较短时,光子能量高、穿透能力强、光吸收深度小于热扩散长度,此时漆层吸收的热量较少,光化学烧蚀效应起主导作用。波长较长时,光子能量较低,热扩散长度大于光吸收深度,光热烧蚀效应起主导作用[10,21]。对于皮秒和飞秒脉冲激光,电子能量不能立即转化为热能,热弹性应力效应起主导作用[22]。
在其他激光清洗参数一定的情况下,激光波长越短,漆层吸收激光能量后迅速升温(但未到漆层烧蚀效应温度),由于漆层热传导率较低易在漆层内部形成大温差界面从而产生热弹性应力;由于飞机蒙皮漆层内部不可避免的存在缺陷,所以漆层实际强度较低,能在较低的热弹性应力下被机械式去除。当激光作用到漆层与金属基体界面时,漆层与基体在线膨胀系数、热扩散系数以及吸收率等物理性质方面具有很大差异,在该界面处会形成更大的热弹性应力,使漆层被机械式去除。笔者所在研究团队在使用纳秒脉冲激光器对飞机金属蒙皮逐层除漆过程中,当激光平均功率为270 W时,观察到部分漆层呈片状的脱离而未发生明显的烧蚀现象。在飞机金属蒙皮除漆时,激光束在金属表面的反射率随波长的增加而升高,选择金属基体吸收较弱的激光波长段(短波长)有利于提升清洗效率。对于飞秒激光,多光子吸收过程的相互作用仅限于表层,在飞机蒙皮一次性完全除漆过程中可忽略波长对清洗的影响[23]。而飞机复合材料蒙皮除漆时,激光波长越短,基体损伤阈值越高。除调控激光波长外,通过调整激光脉冲持续时间也可在不损伤基体的前提下,进行精准清洗。
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不同激光脉冲宽度的激光除漆机制有所不同,如图4所示。激光脉冲宽度越大,激光与表面漆层的作用时间越长易产生热积累,烧蚀效应是长脉冲宽度激光除漆的主要机理[20]。此外,脉冲宽度越大,激光能量产生的热和冲击力在材料内部的扩散更深。因此,使用长脉冲宽度激光在去除较厚漆层时可提高清洗效率[21-23]。然而,长脉冲激光作用深度较深可能会损伤基体,并对精确控制除漆深度带来不便。
短脉冲(纳秒范围内)与表面漆层的作用时间短,造成表面漆层温升比长脉冲更高,在快速加热和冷却循环中产生较强的热应力,形成的热冲击有利于去除表面漆层而不损伤基体,在工程化除漆中获得更多运用[24-25]。当脉冲宽度在微秒范围内时,形成的冲击力可以忽略不计。在皮秒脉冲宽度以下时,脉冲过程中只有电子被激发,材料晶格在时间尺度上不受影响[26]。即在激光能量通过电子-声子耦合和热传导传递到基体之前,已积累的电子能量被漆层吸收。因此,激光能量还来不及通过热传导或冲击波等形式传递到基体上,导致漆层被清洗时而基体几乎不受影响,这种清洗机制被称为冷烧蚀[27]。由于在激光除漆过程中基体温升不明显,皮秒激光特别适合于飞机复合材料蒙皮的激光清洗。
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激光功率固定时,脉冲频率越低,单脉冲激光能量越高,单次清洗深度越大。在工程化除漆过程中,单脉冲清洗深度有限(μm级别),一般需要多脉冲作用才能够完全清洗,如图5所示。在一定范围内提高脉冲频率,虽然单脉冲激光能量下降,但单位时间内作用于漆层的脉冲个数增多[18,20];由于蒙皮漆层导热系数较低会产生明显的热累积效应,有利于去除漆层。除热积累效应外,还存在热应力效应;提高脉冲频率,虽然峰值热应力个数增加,但产生的冲击应力小于漆层-基体结合力时,除漆效果下降[28]。脉冲频率过高时,单脉冲能量过小导致除漆效果下降,甚至激光能量密度小于清洗阈值时,漆层不能被去除。
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在工程化激光除漆过程中,使用激光能量密度可同时耦合激光功率、脉冲宽度、脉冲频率以及光斑尺寸等参数,任一参数变化都会影响着最终的除漆效果。在其他参数不变的前提下,激光功率与激光能量密度呈正相关。
在低激光功率条件下可能需要多激光脉冲作用才能获得良好的除漆效果,此时的除漆机制是激光烧蚀引起的漆层蒸发和“相爆炸”[29]。在一定程度上提高激光功率,有助于加强烧蚀效应和热应力效应,且清洗深度与激光功率呈线性关系。但激光功率过高时,容易引发等离子体效应,会消耗大量激光能量而使真实作用到漆层的激光能量大幅度减少,从而减弱清洗效果;此外,激发等离子冲击效应后,激光功率与除漆宽度和深度间不存在函数关系,为实现精准除漆带来不利影响。因此,在工程化激光清洗过程中通常选择在相对较低的激光功率下进行,以尽量减少对基材产生损坏的风险。
在光斑尺寸为定值时,适当地提高激光功率、增加脉冲宽度、减小脉冲频率都能提升激光能量密度,有利于提高清洗深度和工作效率[30]。在其他参数相同时,光斑面积与激光能量密度成反比。因此,在工程化应用中,高激光功率配合大的光斑面积,有利于提高清洗效率,而光斑面积可通过光学透镜加以控制。
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激光束的离焦量决定了光斑面积,从而能够调控激光能量密度[31]。工程化用脉冲激光器发出的是空间分布呈双曲线规律从焦点向外扩展(光斑尺寸变大)的高斯光束。假设为圆光斑,则远场光束为渐近的圆锥[32]。不同离焦量处(z)光斑直径(Rz)的示意图,如图6所示。在其他参数相同时,激光能量密度在焦点处最高,由焦点向外扩展激光能量密度逐渐降低。
在一般工业应用中的高功率激光器输出光束的发散角都控制在毫弧度量级范围内,在常见飞机蒙皮漆层厚度(60~180 μm)范围内,激光能量密度区别不大。朱映瑞[31]等计算结果表明离焦点位置±4 mm处光斑尺寸变化不大,激光除漆机理和效果未出现明显差异。因此,在工业化激光除漆过程中,漆层与光束距离较大时,需要及时调整光斑焦距,保证足够的激光能量密度。
除激光能量参数外,实际作用在漆层表面的激光能量密度还与扫描速度和路径有关。
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在工程化激光除漆过程中,高功率脉冲激光器发出的是一系列非连续点脉冲,而后通过调整扫描振镜的偏转来获得激光扫描线,从而提高除漆效率。在激光能量密度高于除漆阈值时,扫描速度决定了激光束和清洗表面作用时间的长短,影响着激光实际作用与清洗表面的能量密度,对清洗深度具有重要影响[9,33]。
扫描速度过小时,激光与漆层作用时间长,前激光脉冲产生的能量还未扩散造成热累积严重,甚至出现烧蚀基体现象;当扫描速度过大时,激光束能量作用于漆层的时间过短,漆层吸收能量较少,除漆效果减弱甚至出现不能除漆现象[34]。Yang[17]等在其他参数不变时模拟和实测验证了不同扫描速度下的除漆过程,研究发现:在激光能量密度为50 J/cm2、脉冲频率为100 kHz条件下,随着扫描速度增加,实际作用与漆层的能量密度下降,除漆深度减小,如图7(a)所示;扫描速度增加至一定程度后(大于7000 m/s),漆层热累积效应极弱相当于单脉冲除漆效果,如图7(b)所示;扫描速度为4000 mm/s、5000 mm/s和6000 mm/s时,实际单道除漆平均深度分别为31.29 μm、42.43 μm和64.94 μm,与模拟结果相吻合,如图7(c)所示。
图 7 不同扫描速度对激光除漆影响[17]:(a) 除漆深度;(b) 模拟结果;(c) 实测除漆形貌
Figure 7. Influence of different scanning speed on laser paint removal:(a) Ablation depth; (b) Simulation results; (c) Measured paint removal morphology
Manoj[35]等认为在激光能量密度较高时,最佳扫描速度可用下式来估算:
$$v=\frac{W f \ln \left({ }E / E_{\mathrm{th}}\right)}{\alpha t} $$ 式中:W为沿扫描方向的宽度;f为激光脉冲频率;E激光能量密度;Eth除漆阈值;t为需移除漆层厚度。Manoj等人根据上式设计了相应的除漆参数,在除去厚度为250 μm的环氧树脂漆时获得了较好的除漆效果,为工程化除漆扫描速度的设计缩小了选择范围。Zhang[20]等通过控制扫描速度,根据去除漆层所需的脉冲个数,实现了三层油漆的逐层去除。因此,扫描速度的提升,需要激光能量密度和脉冲频率的协同提高,才能实现快速除漆,提升工作效率。
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除扫描速度外,工程化激光除漆过程中对激光束的扫描路径进行合理规划,可获得更好的清洗效果[36-37]。在激光束完成横向扫描后,通过计算机严格控制纵向进给量,形成“弓”字形路径,纵向搭接量(dy)与扫描速度(vx)无关,如图8(a)所示;在激光束做横向水平扫描的同时,辅助平台带动飞机蒙皮做纵向进给,形成“之”字形扫描,如图8(b)所示。此时,光斑的横向搭接量(dx)和dy与vx、纵向供给速度(vy)和扫描宽度(L)有关。
图 8 脉冲激光扫描路径:(a) “弓”字形光斑行走路线;(b) “之”字形光斑行走路线;(c) 最小搭接量示意图
Figure 8. Pulse laser scanning path:(a) “Bow” shaped spot walking route;(b) “Zigzag” shaped spot walking route;(c) Schematic diagram of minimum overlap
在光斑直径(D)和脉冲频率固定时,dx与vx成反比关系。在dx和dy满足一定关系的前提下,可实现漆层的完全清除并减小搭接量对蒙皮基体的影响,提高清洗效率[37]。当θ=30°时,dxmin=0.134D、dymin=0.25D,能获得最小的光斑重叠面积,此时脉冲激光能量在除漆表面分布均匀,散热条件好,除漆效率更高[38],如图8(c)所示。
在工程化激光工艺参数设计时,可从最小搭接量的限定作用开始,反推缩小扫描速度选择范围;而后借助扫描速度与激光能量密度的函数关系缩小激光功率选择范围,再结合脉冲频率与扫描速度(如除漆所需脉冲个数)的耦合作用进一步缩小脉冲频率选择范围。脉冲宽度主要与单脉冲除漆深度有关,在精确单层除漆时(如飞机蒙皮首翻中,只去除面漆而保留底漆)需要注意。设计好的工艺参数先在飞机蒙皮对标样上进行试验验证,然后根据除漆效果和正交试验法,选出最优的工艺参数组合,再对飞机蒙皮进行激光除漆操作。
综上所述可知,激光能量参数和扫描参数协同调控才能取得较好的除漆效果。扫描速度较快时,必须同步提升激光能量密度,确保实际作用激光能量密度高于清洗阈值。当激光能量密度低于某临界值时,即使延长激光除漆时间,也没有任何的清洗效果,该临界值称为清洗阈值;当激光能量密度高于某临界值,漆层被完全去除但基体受损,该临界值称为损伤阈值[39]。因此,在激光除漆过程中必须保证实际作用在蒙皮漆层的激光能量密度处于清洗阈值和损伤阈值之间。
笔者课题组根据上述的研究经验,通过调整激光能量参数、扫描速度和蒙皮供给速度调控实际作用激光能量密度,结合一系列的微观组织观察和性能测试,获得了某型飞机金属蒙皮对标样的最佳激光除漆工艺参数,确定了激光能量密度控制范围,为后续整机蒙皮在首翻(只除去面漆而保留底漆)和大修(去除漆层不伤基体)过程中的工艺设计提供了实验参考,如图9所示。
Current status and prospect of engineering application of laser paint removal technology for aircraft skin (invited)
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摘要: 激光除漆技术具有高效环保、安全性高、可实时监测和易实现自动化除漆等优势,有望成为飞机整机除漆的主要途径之一。文中首先对激光除漆技术的主要方法和机理进行了分析。其次,总结了各工艺参数对飞机蒙皮激光除漆效果的影响规律,提出了工程化激光除漆工艺参数的设计思路,借助某型飞机金属蒙皮除漆结果验证了设计思路的效用性;并对激光除漆效果评价方法和现有技术标准情况进行了介绍。最后,归纳了飞机整机蒙皮激光除漆的应用实例,展望了激光除漆技术未来的研究方向和重点。Abstract: Laser paint removal technology has the advantages of high efficiency, environmental protection, high safety, real-time monitoring and easy automation, and has become one of the main ways of aircraft paint removal. In this paper, the main methods and mechanisms of laser paint removal technology were analyzed. Secondly, the influence of process parameters on the laser paint removal effect of aircraft skin was summarized, and the design idea of engineering laser paint removal process parameters was proposed. The effectiveness of the design idea was verified by the result of the paint removal of the metal skin of an aircraft. The evaluation methods of laser paint removal effect and the existing technical standards were introduced. Finally, the application examples of laser paint removal for aircraft skin were summarized, and the future research direction and emphasis of laser paint removal technology were prospected.
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图 7 不同扫描速度对激光除漆影响[17]:(a) 除漆深度;(b) 模拟结果;(c) 实测除漆形貌
Figure 7. Influence of different scanning speed on laser paint removal:(a) Ablation depth; (b) Simulation results; (c) Measured paint removal morphology
图 11 某型飞机金属蒙皮激光除漆时不同烧伤程度基体的组织和性能测试结果:(a)显微组织图;(b)扫描组织图;(c)电导率、硬度和拉伸强度测试结果
Figure 11. Mechanical property test results of microstructure and properties of substrates with different burn degrees during laser paint removal of metal skin of an aircraft: (a) Microstructure chart; (b) Scan organization chart; (c) Conductivity, hardness and tensile strength test results
图 12 典型的飞机整机激光除漆系统[49]:(a) LR Systems公司的大型激光除漆机器人;(b) General Laser tronics公司的直升机旋翼叶片激光除漆系统;(c)、(d)用于去除F-16战斗机漆层的ARLCRS系统
Figure 12. Typical laser paint removal system for aircraft[49]: (a) LCR of the LR Systems; (b) Laser paint removal system for helicopter rotor blades of the General Laser tronics; (c),(d) ARLCRS system for removing paint layer of F-16 fighter
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[1] Xia R, Zhao J, Zhang T, et al. Detection method of manufacturing defects on aircraft surface based on fringe projection [J]. Optik, 2020, 280: 164332. [2] Li X Y, Wang H Y, Yu W J, et al. Laser paint stripping strategy in engineering application: A systematic review [J]. Optik, 2021, 241: 167036. doi: 10.1016/j.ijleo.2021.167036 [3] 高辽远. 纳秒脉冲激光清洗铝合金表面漆层数值模拟与实验研究[D]. 江苏大学, 2020. Gao Liaoyuan. Numerical simulation and experimental study on nanosecond pulse laser cleaning of paint layer on aluminum alloy surface[D]. Zhenjiang: Jiangsu University, 2020. (in Chinese) [4] Yang H, Liu H X, Gao R X, et al. Numerical simulation of paint stripping on CFRP by pulsed laser [J]. Optics and Laser Technology, 2022, 145: 107450. doi: 10.1016/j.optlastec.2021.107450 [5] Xuan Shanyong. Influence of laser paint stripping process on mechanical property of CFRP laminate [J]. New Chemical Materials, 2020, 48(7): 124-128. (in Chinese) doi: 10.19817/j.cnki.issn1006-3536.2020.07.029 [6] Jia Baoshen, Tang Hongping, Shu Chunzhou, et al. Removal of surface coating of resin matrix composites by pulsed laser [J]. Chinese Journal of Lasers, 2019, 46(12): 1202010. (in Chinese) doi: 10.3788/CJL201946.1202010 [7] Ding M, Wu B, Xu J, et al. Visual inspection of aircraft skin: Automated pixel-level defect detection by instance segmentation [J]. Chinese Journal of Aeronautics, 2022, 35(10): 254-264. doi: 10.1016/j.cja.2022.05.002 [8] Moira B, Capucine K. Successes and challenges in laser cleaning metal artefacts: A review [J]. Journal of Cultural Heritage, 2022, 53: 100-117. doi: 10.1016/j.culher.2021.10.010 [9] Li X K, Zhang Q H, Zhou X Z, et al. The influence of nanosecond laser pulse energy density for paint removal [J]. Optik, 2018, 156: 841-846. doi: 10.1016/j.ijleo.2017.11.010 [10] Zhu G D, Xu Z H, Jin Y, et al. Mechanism and application of laser cleaning: A review [J]. Optics and Lasers in Engineering, 2022, 157: 107130. doi: 10.1016/j.optlaseng.2022.107130 [11] Cao Z H, Qiao H C, Zhang Y N, et al. Study on reducing burrs of super alloy through structures in water jet guided laser ablation [J]. Journal of Manufacturing Processes, 2022, 77: 809-818. doi: 10.1016/j.jmapro.2022.04.005 [12] Madhukar Y K, Mullick S, Chakraborty S S, et al. Effect of water-jet on laser paint removal behaviour [J]. Procedia Engineering, 2013, 64: 467-472. doi: 10.1016/j.proeng.2013.09.120 [13] Selen Ü, Kosmas P, Alexandre R, et al. Towards selective laser paint stripping using shock waves produced by laser-plasma interaction for aeronautical applications on AA 2024 based substrates [J]. Optics & Laser Technology, 2021, 141: 107095. [14] Wang W, Shen J, Liu W J, et al. Effect of laser energy density on surface physical characteristics and corrosion resistance of 7075 aluminum alloy in laser cleaning [J]. Optics & Laser Technology, 2022, 148: 107742. [15] Lu Y, Yang L J, Wang M L, et al. Simulation of nanosecond laser cleaning the paint based on the thermal stress [J]. Optik, 2020, 227(3): 165589. [16] 朱映瑞. 铝合金基体表面漆层激光清除机理及工艺[D]. 兰州: 兰州理工大学, 2020. Zhu Yingrui. Study on the mechanism and technology of paint laser cleaning on aluminum substrate[D]. Lanzhou: Lanzhou University of Technology, 2020. (in Chinese) [17] Yang J N, Zhou J Z, Sun Q, et al. Digital analysis and prediction of the topography after pulsed laser paint stripping [J]. Journal of Manufacturing Processes, 2021, 62: 685-694. doi: 10.1016/j.jmapro.2020.12.069 [18] Han J H, Cui X D, Wang S, et al. Laser effects based optimal laser parameter identifications for paint removal from metal substrate at 1064 nm: a multi-pulse model [J]. Journal of Modern Optics, 2017, 64(19): 1947-1959. doi: 10.1080/09500340.2017.1330433 [19] 孙浩然. 铝合金表面油漆涂层激光复合清洗工艺及去除机制研究[D]. 哈尔滨: 哈尔滨工业大学, 2020. Sun Haoran. Research on laser composite cleaning process and removal mechanism of paint coating on aluminum alloy surface[D]. Harbin: Harbin Institute of Technology, 2020. (in Chinese) [20] Zhang Z Y, Zhang J Y, Wang Y B, et al. Removal of paint layer by layer using a 20 kHz 140 ns quasi-continuous wave laser [J]. Optik, 2018, 174: 46-55. doi: 10.1016/j.ijleo.2018.08.057 [21] Coutouly J F, Deprez P, Florin B, et al. Optimisation of a paint coating ablation process by CO2 TEA laser: Thermal field modelling and real-time monitoring of the process [J]. Journal of Materials Processing Technology, 2009, 209(17): 5730-5735. doi: 10.1016/j.jmatprotec.2009.06.001 [22] Alicia M, Ana J L, Javier L, et al. Femtosecond pulsed laser ablation for paint removal at oblique illumination: Effect of the incidence angle [J]. Optik, 2022, 264: 169428. doi: 10.1016/j.ijleo.2022.169428 [23] Leng B Y, Tang E L, Luo H W, et al. Research on thermal and mechanical effects of Al/PTFE reactive materials irradiated by femtosecond pulsed laser [J]. Infrared Physics & Technology, 2021, 119: 103961. doi: 10.1016/j.infrared.2021.103961 [24] Brygo F, Dutouquet C, Guern F L, et al. Laser fluence, repetition rate and pulse duration effects on paint ablation [J]. Applied Surface Science, 2006, 252(6): 2131-2138. doi: 10.1016/j.apsusc.2005.02.143 [25] Zhang Zhiyan, Wang Yibo, Liang Hao, et al. Removal of low thermal conductivity paint by high repetition rate pulsed laser [J]. Chinese Journal of Lasers, 2019, 46(1): 0102009. (in Chinese) [26] Pentzien S, Conradi A, Koter R, et al. Cleaning of artificially soiled paper using nanosecond, picosecond and femtosecond laser pulses [J]. Applied Physics A, 2010, 101: 441-446. doi: 10.1007/s00339-010-5809-7 [27] Zhao W Q, Yu Z S. Self-cleaning effect in high quality percussion ablating of cooling hole by picosecond ultra-short pulse laser [J]. Optics and Lasers in Engineering, 2018, 105: 125-131. doi: 10.1016/j.optlaseng.2018.01.011 [28] Tong Ci, Qiu Taiwen, Yi Junlan, et al. Effect of pulse frequency on laser cleaning mechanism of paint coating [J]. Laser & Optoelectronics Progress, 2021, 58(19): 1914009. (in Chinese) [29] Zhang G X, Hua X M, Huang Y, et al. Investigation on mechanism of oxide removal and plasma behavior during laser cleaning on aluminum alloy [J]. Applied Surface Science, 2020, 506: 144666. doi: 10.1016/j.apsusc.2019.144666 [30] Tian Z, Lei Z L, Chen X, et al. Nanosecond pulsed fiber laser cleaning of natural marine micro-biofoulings from the surface of aluminum alloy [J]. Journal of Cleaner Production, 2020, 244: 118724. doi: 10.1016/j.jclepro.2019.118724 [31] Zhu Yingrui, Zhu Ming, Shi Yu, et al. Effect of laser defocus on removal mechanism of metallic paint [J]. Electric Welding Machine, 2020, 50(1): 29-36. (in Chinese) doi: 10.7512/j.issn.1001-2303.2020.01.04 [32] Yang Wenfeng, Fu Chanyuan, Qian Ziran, et al. Effect of defocus on damage characteristics of laser paint removal on aluminum alloy surface [J]. Laser and Infrared, 2022, 52(6): 849-855. (in Chinese) doi: 10.3969/j.issn.1001-5078.2022.06.009 [33] Li Z C, Xu J, Zhang D H, et al. Nanosecond pulsed laser cleaning of titanium alloy oxide films: Modeling and experiments [J]. Journal of Manufacturing Processes, 2022, 82: 665-677. doi: 10.1016/j.jmapro.2022.08.033 [34] Zhao Haichao, Qiao Yulin, Du Xian, et al. Research on paint removal technology for aluminum alloy using pulsed laser [J]. Chinese Journal of Lasers, 2021, 48(6): 0602121. (in Chinese) [35] Manoj K, Bhargava P, Biswas A K, et al. Epoxy-paint stripping using TEA CO2 laser: Determination of threshold fluence and the process parameters [J]. Optics & Laser Technology, 2013, 46: 29-36. [36] Jiang Yilan, Ye Yayun, Zhou Guorui, et al. Research on laser paint removing of aircraft surface [J]. Infrared and Laser Engineering, 2018, 47(12): 1206003. (in Chinese) doi: 10.3788/IRLA201847.1206003 [37] Zhang D H, Xu J, Li Z C, et al. Removal mechanism of blue paint on aluminum alloy substrate during surface cleaning using nanosecond pulsed laser [J]. Optics and Laser Technology, 2022, 149: 107882. doi: 10.1016/j.optlastec.2022.107882 [38] Song Y H, Zhang T F, Fan W J, et al. Effect of the overlap ratio on surface properties of 7B04 aluminum alloy for aviation during laser derusting [J]. Journal of Materials Research and Technology, 2022, 20: 1495-1511. doi: 10.1016/j.jmrt.2022.07.129 [39] Zhang Tiangang, Huang Jiahao, Hou Xiaoyun, et al. Research on mechanism for composite paint layer on aluminum alloy surface cleaned by laser [J]. Acta Aeronautica et Astronautica Sinica, 2023, 44(16): 427656. (in Chinese) [40] Hu Q C, Wei X L, Liang X Q, et al. In-process vision monitoring methods for aircraft coating laser cleaning based on deep learning [J]. Optics and Lasers in Engineering, 2023, 160: 107291. doi: 10.1016/j.optlaseng.2022.107291 [41] Hu Jiu, Ma Lu, Wang Wenquan, et al. In fluence of laser paint removal andsolvent paint removal on aircraft skin parts [J]. Metal World, 2017, 6: 6-10. (in Chinese) doi: 10.3969/j.issn.1000-6826.2017.06.02 [42] Liu Zhenming, Cheng Jian, Li Ziwen, et al. Removal of composite coating from 2024 aluminum alloy surface by CO2 laser cleaning [J]. Electroplating & Finishing, 2021, 40(12): 974-979. (in Chinese) [43] Zhu G D, Wang S R, Cheng W, et al. Corrosion and wear performance of aircraft skin after laser cleaning [J]. Optics & Laser Technology, 2020, 132(8): 106475. [44] Chen Yun, Huang Haipeng, Ye Shaowei. Research on acoustic monitoring technology of laser paint removal process [J]. Applied Laser, 2020, 40(6): 1153-1159. (in Chinese) doi: 10.14128/j.cnki.al.20204006.1153 [45] Zou W F, Song F, Luo Y. Characteristics of audible acoustic signal in the process of laser cleaning [J]. Optics and Laser Technology, 2021, 144: 107388. doi: 10.1016/j.optlastec.2021.107388 [46] Wang W J, Sun L X, Ying L, et al. Laser induced breakdown spectroscopy online monitoring of laser cleaning quality on carbon fiber reinforced plastic [J]. Optics and Laser Technology, 2022, 145: 107481. doi: 10.1016/j.optlastec.2021.107481 [47] Chen Lin, Deng Guoliang, Feng Guoying, et al. Study on laser paint removal mechanism based on LIBS and time-resolved characteristic peak [J]. Spectroscopy and Spectral Analysis, 2018, 38(2): 367-371. (in Chinese) [48] Yang Wenfeng, Qian Ziran, Cao Yu, et al. Study on controllability of laser paint removal of aircraft skin based on LIBS spectrum and component analysis [J]. Spectroscopy and Spectral Analysis, 2021, 41(10): 3233-3239. (in Chinese) [49] Schlett J. Laser paint removal takes off in aerospace[EB/OL]. (2018–03–11)[2022–11-03]. http://www.photonics.com/Articles/Laser_Paint_Removal_Takes_Off_in_Aerospace/a61353. [50] Angel R, AnaJ L, Javier L, et al. Robot-assisted laser ablation for 3D surfaces. Application for paint removal with ultrashort pulse laser [J]. Optics and Lasers in Engineering, 2023, 160: 107284. doi: 10.1016/j.optlaseng.2022.107284