A composite laser-based method for cleaning aircraft skin

Abstract

This invention discloses a method for cleaning aircraft skin based on a composite laser, comprising: S1, constructing a composite laser paint removal device that outputs both continuous and pulsed lasers; S2, conducting a small-scale circular area cleaning simulation experiment on the aircraft skin using the composite laser paint removal device to determine the optimal paint removal parameters; S3, fitting a model of the relationship between the power density of the continuous laser and the cleaning depth based on the optimal paint removal parameters; and S4, performing aircraft skin cleaning according to the model. This invention uses a composite laser, combining continuous and pulsed lasers, for aircraft skin cleaning, effectively solving the problem of ablation residues adhering to the substrate and being difficult to remove when using continuous lasers for aircraft skin cleaning. By determining the relationship model between the power density and cleaning depth obtained by fitting the optimal paint removal parameters for composite laser cleaning, the laser parameters can be adjusted based on this model, providing a reference for laser cleaning of aircraft skin.

Description

Technical Field

[0001] This invention belongs to the field of laser paint removal technology, specifically relating to a method for cleaning aircraft skin based on composite lasers. Background Technology

[0002] In recent years, laser cleaning technology, as an emerging cleaning technology, has developed rapidly. Compared with traditional cleaning methods, laser cleaning has shown great development potential in many fields due to its advantages such as higher efficiency, no pollution, and no damage.

[0003] Existing research primarily focuses on cleaning using a single laser, while combined cleaning with various lasers is a relatively recent and innovative approach. Many objects requiring cleaning (such as airplanes and trains) have multi-layered paint layers with varying physical and chemical properties. Using a single continuous laser for paint cleaning can easily lead to paint ablation adhering to the substrate, causing damage. Conversely, using a single pulsed laser can result in excessive energy causing irreversible damage. Combining continuous and pulsed lasers into a composite laser for cleaning multi-layered paint structures offers a more effective solution, as the parameters can be adjusted to achieve layered paint removal and improve the cleaning results. While current research on paint removal primarily focuses on single-system methods, this forms the basis for multi-laser combined cleaning. Existing research, both domestic and international, generally improves cleaning performance by controlling parameters such as laser energy, frequency, and scanning speed, although parameter control for multi-laser combined paint removal has not been explored. Summary of the Invention

[0004] In view of the above-mentioned shortcomings in the prior art, the aircraft skin cleaning method based on composite laser provided by the present invention solves the problem that the existing composite laser paint removal methods do not take into account the paint removal parameters.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: a method for cleaning aircraft skin based on composite laser, comprising the following steps:

[0006] S1. Construct a composite laser paint removal device that outputs continuous laser and pulsed laser;

[0007] S2. A small-scale circular area cleaning simulation experiment was conducted on the aircraft skin using a composite laser paint removal device to determine the optimal paint removal parameters.

[0008] S3. Based on the optimal paint removal parameters, a model is fitted to obtain the relationship between the power density of the continuous laser and the cleaning depth during composite laser paint removal.

[0009] S4. Clean the aircraft skin according to the relational model.

[0010] Furthermore, in step S1, the composite laser paint removal device includes a continuous laser and a pulsed laser. The continuous laser and pulsed laser emitted by the continuous laser and the pulsed laser are respectively passed through a beam splitter and a reflector, and then act on the aircraft skin through a focusing lens.

[0011] Furthermore, in the composite laser paint removal device, the angle between the continuous laser and the pulsed laser incident on the focusing lens is 20°.

[0012] Furthermore, the transmission and reflection energy ratio of the corresponding split laser beams obtained by the continuous laser and pulsed laser beam splitter is 8:2.

[0013] Furthermore, the continuous laser comprises a flat-top beam and a Gaussian beam, with the Gaussian beam covering the center of the flat-top beam.

[0014] Furthermore, in step S2, the paint removal parameters include the power density of the flat-top beam and the power density of the Gaussian beam in the continuous laser, the energy density and frequency of the pulsed laser, and the cleaning time.

[0015] Further, step S2 specifically includes:

[0016] S21. Use a continuous laser with a preset power density to clean small circular areas of the aircraft skin.

[0017] S22. Using a pulsed laser with a preset energy density and frequency to act on the cleaning area of ​​the continuous laser, a composite laser cleaning is achieved.

[0018] S23. Analyze the cleaning effect of the aircraft skin in the composite laser cleaning area and set different paint removal parameters;

[0019] S24. Continuously adjust the paint removal parameters and perform aircraft skin cleaning;

[0020] S25. Analyze the aircraft skin cleaning effect under different paint removal parameters, and take the paint removal parameter corresponding to the best paint removal effect as the optimal paint removal parameter.

[0021] Further, step S3 specifically includes:

[0022] S31. Based on the corresponding cleaning experimental data of the optimal paint removal parameters, the relationship between cleaning depth and cleaning time is fitted using a power function.

[0023] S32. Set the magnitude variation ratio p1 of the power density of the flat-top beam and the magnitude variation ratio p2 of the power density of the Gaussian beam in the continuous laser respectively;

[0024] S33. Based on the relationship between cleaning depth and cleaning time, and the magnitude change ratios p1 and p2, a model relating the power density of continuous laser to cleaning depth is fitted.

[0025] The beneficial effects of this invention are as follows:

[0026] (1) The present invention uses a composite laser formed by the combination of continuous laser and pulsed laser to clean aircraft skin, which effectively solves the problem that the ablation products caused by the ablation of the paint layer during the cleaning of aircraft skin by continuous laser are difficult to remove from the substrate.

[0027] (2) The method of the present invention takes into account the effects of continuous laser and pulsed laser. Based on the small circular cleaning experiment, the optimal paint removal parameters for composite laser cleaning are determined, and the relationship model between power density and cleaning depth at a certain moment is obtained by fitting. The laser parameters can be adjusted based on the relationship model, which provides a reference for laser cleaning of aircraft skin. Attached Figure Description

[0028] Figure 1 The flowchart of the aircraft skin cleaning method based on composite laser provided by the present invention.

[0029] Figure 2 This is a schematic diagram of the composite laser paint removal device provided by the present invention.

[0030] Figure 3 This is a schematic diagram of an aircraft skin sample provided by the present invention.

[0031] Figure 4 This is a schematic diagram illustrating the Gaussian beam cleaning effect provided by the present invention.

[0032] Figure 5 A schematic diagram illustrating the combined laser effect provided by the present invention.

[0033] Figure 6 The diagram shows the effect of composite laser cleaning composed of continuous laser and pulsed laser with various parameters provided by the present invention.

[0034] Figure 7 This is a schematic diagram illustrating the effect of using composite lasers to further clean small circular areas of aircraft skin, as provided by the present invention.

[0035] Figure 8 This is a schematic diagram of the cleaning depth versus time curve provided by the present invention. Detailed Implementation

[0036] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0037] Example 1:

[0038] This invention provides a method for cleaning aircraft skin based on composite lasers, such as... Figure 1 As shown, it includes the following steps:

[0039] S1. Construct a composite laser paint removal device that outputs continuous laser and pulsed laser;

[0040] S2. A small-scale circular area cleaning simulation experiment was conducted on the aircraft skin using a composite laser paint removal device to determine the optimal paint removal parameters.

[0041] S3. Based on the optimal paint removal parameters, a model is fitted to obtain the relationship between the power density of the continuous laser and the cleaning depth during composite laser paint removal.

[0042] S4. Clean the aircraft skin according to the relational model.

[0043] In step S1 of this embodiment of the invention, the constructed composite laser paint removal device is as follows: Figure 2 As shown, it includes a continuous laser and a pulsed laser. The continuous laser and pulsed laser emitted by the continuous laser and the pulsed laser are respectively passed through a beam splitter and a reflector and then act on the aircraft skin through a focusing lens. The continuous laser includes a flat-top beam and a Gaussian beam, and the Gaussian beam covers the center of the flat-top beam.

[0044] In the composite laser paint removal device of this embodiment, the angle between the continuous laser and the pulsed laser incident on the focusing lens is 20°.

[0045] In this embodiment, the transmission and reflection energy ratio of the corresponding split laser beams obtained by the beam splitter for continuous laser and pulsed laser is 8:2.

[0046] Specifically, in this embodiment, the output beam of the continuous laser can be flat-topped or Gaussian-shaped, with an output energy between 50W and 2000W, a minimum irradiation time of 30ms, and an output spot diameter of 700μm to 1100μm; the pulsed laser outputs a pulsed laser with an energy range of 0.2J to 2J, an output frequency range of 1Hz to 20Hz, and an output spot diameter of 2mm.

[0047] When the composite laser paint removal device is working, a beam splitter separates the continuous laser and pulsed laser into two beams. 80% of the laser energy from both beams is applied to the aircraft skin at a 20° angle after passing through a 1064 reflector and a focusing lens (focal length 20cm). The remaining 20% ​​of the laser energy is used for energy monitoring. In this embodiment, the aircraft skin is placed on a computer-controlled 3D platform for precise adjustment of the laser cleaning process.

[0048] In step S2 of this embodiment of the invention, the paint removal parameters include the power density of the flat-top beam and the power density of the Gaussian beam in the continuous laser, the energy density and frequency of the pulsed laser, and the cleaning time. The cleaning time refers to the duration of the continuous laser's action; the pulsed laser operates within the duration of the continuous laser's action, meaning that when the continuous laser stops operating, the pulsed laser also stops operating.

[0049] Step S2 in this embodiment of the invention is specifically as follows:

[0050] S21. Use a continuous laser with a preset power density to clean small circular areas of the aircraft skin.

[0051] S22. Using a pulsed laser with a preset energy density and frequency to act on the cleaning area of ​​the continuous laser, a composite laser cleaning is achieved.

[0052] S23. Analyze the cleaning effect of the aircraft skin in the composite laser cleaning area and set different paint removal parameters;

[0053] S24. Continuously adjust the paint removal parameters and perform aircraft skin cleaning;

[0054] S25. Analyze the aircraft skin cleaning effect under different paint removal parameters, and take the paint removal parameter corresponding to the best paint removal effect as the optimal paint removal parameter.

[0055] In this embodiment, as shown Figure 3 Taking the Boeing 717 model aircraft skin sample shown as an example, a small circular area cleaning simulation experiment was conducted. The sample has a 1 mm bright silver aluminum alloy metal substrate. The surface of this aluminum alloy has three layers of materials: red polyurethane topcoat (thickness of about 79 μm), gray epoxy primer, and yellow-green chemical conversion coating (thickness of about 130 μm).

[0056] In step S21 of this embodiment, when cleaning the paint layer of the aircraft skin, the characteristics of each paint layer must be fully considered to keep the metal substrate undamaged as much as possible. In order to make up for the defects of single-mechanism laser cleaning, the Gaussian beam and the flat-top beam are combined into a continuous laser and combined with the pulsed laser to form a composite laser for further cleaning experiments, and the influence of composite laser under different parameter settings on the cleaning effect of aircraft skin is investigated.

[0057] The effects of Gaussian beams of different powers on cleaning aircraft skin are as follows: Figure 4 As shown, the cleaning area gradually increases with the increase of laser treatment time. The cleaning area includes a bright silver area (the metal substrate of the aircraft skin is bright silver) and a black area. The area of ​​the bright silver area gradually increases, while the area of ​​the black area in the center remains basically unchanged. Simultaneously, at the same treatment time, as the laser power increases from 50W to 100W, the cleaning area gradually increases. Furthermore, when using a Gaussian beam for cleaning, the cleaning range is largest when the power is 100W and the treatment time is 100ms.

[0058] While Gaussian beams can clean the paint layer on aircraft skin, black areas remain in the center after cleaning with 50W to 100W Gaussian beams. Due to the characteristic of Gaussian beams having "high energy at the center and low energy at the periphery," it can be preliminarily inferred that the formation of these black areas may be due to two scenarios: one is over-ablation of the paint layer, resulting in black oxide adhering to the substrate at the center; the other is that the paint layer at the center is instantly vaporized by high temperature, causing black ablation damage to the substrate. These black areas are clearly not what should remain after normal cleaning of aircraft skin. To further improve the paint removal effect, improvements to the cleaning light source will be considered in future work.

[0059] In step S22 of this embodiment, to compensate for the shortcomings of the Gaussian beam in aircraft skin cleaning, a flat-top beam is considered to be added, combining the Gaussian beams into a continuous laser. The aim is to ensure a more uniform temperature change on the aircraft skin surface during paint removal, preventing the central temperature from being significantly higher than the surrounding temperature. Simultaneously, the high energy of the Gaussian beam at the center of the cleaning area facilitates an ablation effect spreading outwards from the center, improving the cleaning effect. Furthermore, since the black areas may contain ablated paint residue, a pulsed laser is considered to be added, hoping that the resulting stress effect will remove residual ablation material. Figure 5 Preliminary experimental results for aircraft skin cleaning using a composite laser consisting of a continuous laser (Gaussian beam plus a flat-top beam) and a pulsed laser.

[0060] Because a large portion of the central black area was removed after the composite laser treatment, it is speculated that the black area is an ablation product formed by the ablation and oxidation of the topcoat and primer. Meanwhile, based on... Figure 2 The experimental materials shown indicate that the gray areas represent incompletely ablated primer, while the silvery areas represent the metal substrate. This experiment demonstrates that a composite laser consisting of continuous and pulsed lasers can effectively clean the paint layer on aircraft skin surfaces. The ablation effect of the continuous laser causes the paint layer to oxidize, while the stress effect of the pulsed laser removes the ablated oxides.

[0061] In step S23 of this embodiment, since the cleaned skin only exposed part of the metal substrate (silver-colored area) in the composite laser skin cleaning result, and the paint layer (gray area) and ablation material (black area) were not completely removed, it is planned to use a composite laser consisting of a continuous laser with higher power density and pulsed lasers with different energy densities to clean the skin and remove the paint, in order to find the optimal cleaning parameters. Four main parameters are considered: the power density of the Gaussian beam and the flat-top beam, the energy density of the pulsed laser, and the laser interaction time. In addition, each experiment ensures that the pulsed laser interacts at least once during the cleaning process.

[0062] like Figure 6 As shown, when the power density of the flat-top beam is 105.28 W / mm 2 The Gaussian beam power density is 113.23 W / mm². 2 The skin was cleaned by continuously increasing the energy density of the pulsed laser. While ensuring at least one pulsed laser treatment, black areas existed regardless of whether the laser treatment time was 50ms or 100ms. When the continuous laser treatment time was 50ms, the area of ​​the black area initially increased and then decreased with increasing pulsed laser energy density. However, when the treatment time was increased to 100ms, the area of ​​the black area initially decreased, then increased, and finally decreased again with increasing pulsed laser energy density. Simultaneously, scattered bright silver areas were distributed within the gray area.

[0063] When the power density of the flat-top beam is increased to 157.92 W / mm 2 Furthermore, while maintaining a constant Gaussian beam power density, the energy density of the pulsed laser was continuously increased to clean the skin. Even with at least one pulsed laser treatment, black areas remained on the surface regardless of whether the cleaning time was 50ms or 100ms. Simultaneously, observations were made... Figure 6 (i)~ Figure 6 (p) reveals that the remaining black areas are roughly the same size, but compared to Figure 6 (a)~ Figure 6 (h) The difference between these experimental results is that the area of ​​the gray region is significantly reduced, while the distribution of the silvery bright region in the gray region is increased.

[0064] In addition, under the same continuous laser power density and ensuring at least one pulse laser action, regardless of whether the continuous laser action is 50ms or 100ms, the bright silver area of ​​the substrate is mixed with gray areas. Furthermore... Figure 6 Among all the cleaning results, the lowest cleaning depth was 225.0 μm (>220 μm). Combined with the observation of a bright silver area, this indicates that the composite laser did indeed clean the metal substrate.

[0065] Therefore, the stress effect of pulsed lasers does indeed have a removal effect on black areas (paint ablation). However, if... Figure 6 The experimental results show that black areas remain even after multiple adjustments to the energy density and duration of the pulsed laser. This indicates that the remaining black areas may not all be paint ablation material. Therefore, EDS analysis was performed on the black areas to determine if they are entirely paint ablation material, while EDS analysis was also performed on the other areas of various colors to determine their material composition.

[0066] Based on all the above experimental results and EDS analysis, the following experimental conclusions can be drawn:

[0067] ①The bright silver area obtained from cleaning is the metal substrate, the gray area is the primer, the black area is the oxide produced by paint layer ablation and the oxide produced by metal damage, and there are even unablated topcoat and primer.

[0068] ② In the composite laser skin cleaning experiment with different parameter settings, the overall power density of the continuous laser may be too high, which causes the metal substrate to undergo ablation and oxidation damage regardless of whether the continuous laser action time is 50ms or 100ms, turning it black. This black substance cannot be removed by the stress effect of the pulsed laser.

[0069] ③By Figure 6 Experiments show that although increasing the power density of the continuous laser is beneficial to reducing the gray area (primer), combined with the elemental content ratio of EDS analysis, increasing the power density of the continuous laser is very likely to cause the metal substrate to melt, resulting in a mixed distribution of gray and silvery areas.

[0070] Based on the above experiments, it is evident that a composite laser consisting of continuous and pulsed lasers can indeed clean the paint layer on the skin surface. However, excessively high power density of the continuous laser can lead to two undesirable cleaning scenarios: damage to the metal substrate and melting of the metal substrate, causing it to fuse with the primer. To avoid these negative consequences, subsequent experiments will consider reducing the power density of the continuous laser in the composite laser. Meanwhile... Figure 6 The experiment used 0.42 J / mm 2 ~1.05J / mm 2 While pulsed lasers were used, this series of pulsed lasers did not show significant differences in their effectiveness in removing black substances. Furthermore, high-energy-density pulsed lasers could potentially damage the substrate. Therefore, the pulsed laser energy density in subsequent experiments was set to 0.42 J / mm². 2 Furthermore, regardless of the total cleaning time, the duration of continuous laser application was gradually controlled while ensuring that the pulsed laser applied at least once in each experiment, in order to conduct further experiments. The experimental results are as follows: Figure 7 As shown.

[0071] Experiments show that by setting appropriate parameters and further controlling the action time, it is indeed possible to achieve non-destructive removal of the paint layer on the skin surface using composite lasers. Figure 7 This shows that when the power density of the flat-top beam is 52.64 W / mm² 2 The Gaussian beam power density is 56.62 W / mm². 2 Continuous laser with an energy density of 0.42 J / mm 2 Skin cleaning morphology images at various time points of a composite laser consisting of 10Hz pulsed lasers, compared to... Figure 6 The experiment reduced the overall energy of the continuous laser, further refined the control of the continuous laser action time, and ensured that the pulsed laser acted at least once before the cleaning ended.

[0072] When the continuous laser treatment time is very short (50ms), a predominantly red area is observed on the surface of the cleaned area, with a yellow central area. Increasing the continuous laser treatment time to 80ms results in a surface that is almost entirely silvery-white, with no black or gray areas, closely resembling the original morphology of the metal substrate; the cleaning result at this point is quite promising. To further investigate the effect of the composite laser on the skin under these parameters, the cleaning time is increased to 2000ms. At this point, a very small black area begins to remain on the surface of the cleaned area, but the rest remains largely silvery-white, still closely resembling the morphology of the metal substrate. Further increasing the cleaning time to 5000ms reveals a large area of ​​black on the surface of the cleaned area, indicating a significant decrease in cleaning effectiveness.

[0073] When the cleaning time is less than 80ms, the cleaning depth increases with time, indicating that the paint layer on the skin surface is removed by the composite laser. When the cleaning time reaches 2000ms, the substrate is slightly damaged, indicating that the temperature of the skin surface remains below the melting point of the substrate between 80ms and 2000ms. This also shows that the composite laser with this parameter setting has high controllability in keeping the aircraft skin undamaged.

[0074] Based on the results of the above series of skin cleaning experiments, the optimal paint removal parameters are set as follows: the power density of the flat-top beam in the continuous laser section is approximately 52.64 W / mm². 2 The Gaussian beam power density is approximately 56.62 W / mm². 2 The energy density of the pulsed laser portion is approximately 0.42 J / mm². 2 The frequency is approximately 10 Hz.

[0075] In this embodiment of the invention, step S3 specifically involves:

[0076] S31. Based on the corresponding cleaning experimental data of the optimal paint removal parameters, the relationship between cleaning depth and cleaning time is fitted using a power function.

[0077] S32. Set the magnitude variation ratio p1 of the power density of the flat-top beam and the magnitude variation ratio p2 of the power density of the Gaussian beam in the continuous laser respectively;

[0078] S33. Based on the relationship between cleaning depth and cleaning time, and the magnitude change ratios p1 and p2, a model relating the power density of continuous laser to cleaning depth is fitted.

[0079] In this embodiment, based on the aforementioned series of cleaning experiments and simulations, the mechanism of composite laser cleaning of aircraft skin can be clearly understood. The continuous laser portion of the composite laser ablates the topcoat and primer, transforming the paint layer into an ablated material that easily detaches from the skin surface. Simultaneously, the pulsed laser portion of the composite laser generates a stress effect on the ablated material, thus achieving thorough cleaning of the paint layer. Therefore, we must consider the skin cleaning process in two parts: first, ablate the paint layer, and then remove the ablated material. If the power density of the continuous laser is too high, although it will ablate all the topcoat and primer, superficially improving the paint removal efficiency, it may actually cause ablation defects in the metal substrate, thus reducing the cleaning effect. Furthermore, excessively high power density continuous lasers may also cause the metal substrate to melt and fuse with the primer, similarly damaging the substrate and reducing the cleaning effect. In addition, the continuous laser only plays a stress effect role in removing the ablated residue from the paint layer, and the removal efficiency of the ablated residue is not significantly related to the energy density of the pulsed laser itself. Moreover, to avoid stress damage to the substrate caused by the stress effect of the pulsed laser, it is best to avoid using a composite laser consisting of a high-energy-density pulsed laser and a continuous laser. Therefore, the removal of topcoat and primer from aircraft skin surfaces using composite lasers is primarily based on the ablation effect of continuous laser on the paint layer, while the stress effect of pulsed laser assists in the removal of ablated paint residue. The preceding analysis indicates that when using composite lasers to clean small, circular areas of aircraft skin, the optimal cleaning parameter settings are within the range of "52.64 W / mm² in the flat-top beam power density of the continuous laser portion." 2 ~73.7W / mm 2 The power density of the Gaussian beam is 56.62 W / mm². 2 ~79.26W / mm 2 The energy density of the pulsed laser portion is fixed at 0.42 J / mm². 2 The frequency is fixed at 10Hz.

[0080] In composite laser systems, the ablation effect of the continuous laser component is the primary factor, while the stress effect of the pulsed laser component is secondary. The ablation effect is mainly related to the parameter settings of the continuous laser, and since the criterion for non-destructive cleaning is the cleaning depth, this study focuses on the relationship between the cleaning depth and the power density of the continuous laser.

[0081] In step S21 of this embodiment, the relationship between cleaning depth and cleaning time is first investigated. Figure 8 Simulation curves showing the change in cleaning depth l over time (0–80 ms) under three composite laser parameter settings were generated. For two parameter settings, the cleaning depth l reached the substrate. Therefore, a power function of the following form was used to fit the simulation data for these two composite laser parameter settings:

[0082] l = a(bt) 2 +c

[0083] The following relation can be obtained:

[0084] When the power density of the flat-top beam in the continuous laser of the composite laser is 52.64 W / mm², and the power density of the Gaussian beam is 56.62 W / mm², the above power function becomes as follows:

[0085] l = 0.404 × (0.2564t) 2 +0.4991

[0086] In step S32 of this embodiment, the power density of the flat-top beam is 52.64 W / mm. 2 and a Gaussian beam power density of 56.62 W / mm 2 Based on this, when the power densities of the two beams change, let p1 be the proportion of the change in power density of the flat-top beam and p2 be the proportion of the change in power density of the Gaussian beam, as shown in the following two equations:

[0087]

[0088] Where α1 is the power density of the flat-top beam and α2 is the power density of the Gaussian beam.

[0089] In step S33 of this embodiment, by combining the above formula, the relationship model between power density and cleaning depth at a certain moment can be obtained as follows:

[0090] l=0.404[1.6×(p1-0.2)+2×(p2-0.3)](0.2564t) 2 +0.4991

[0091] In step S4 of this embodiment of the invention, when cleaning the aircraft skin, the aircraft skin is cleaned according to the above-mentioned relationship model based on the cleaning depth requirements, and according to the pulse energy density and frequency obtained when determining the optimal paint removal parameters.

[0092] Example 2:

[0093] In this embodiment, the reliability of the relational model obtained in Example 1 is tested. Specific data for the composite laser parameters are set and substituted into the aforementioned relational model to obtain the following result: Figure 8 The variation curves are shown, and the specific values ​​of the cleaning depth at 50ms and 80ms are shown in Table 1.

[0094] Table 1: Theoretically Obtained Cleaning Depth

[0095]

[0096] Table 1 shows that when α1 is 52.64 W / mm 2 α2 is 56.62 W / mm 2 At 80 ms, the theoretically calculated cleaning depth is 257.3242 μm, which is basically consistent with the cleaning depth at 80 ms in the EDS analysis. In addition, when α1 is 105.28 W / mm... 2 α2 is 113.23 W / mm 2 And α1 is 157.92 W / mm 2 α2 is 113.23 W / mm 2 At 50ms, the theoretically calculated cleaning depth already exceeded 220μm, which is greater than the combined thickness of the topcoat, primer, and composite coating. This indicates that the cleaning had reached the metal substrate and caused damage at 50ms. At 100ms, the theoretically calculated depth far exceeded 220μm, indicating even greater damage. This is consistent with... Figure 6 The experimental results obtained are consistent with the actual situation, which also verifies the objectivity and feasibility of the "relationship model between power density and cleaning depth at a certain moment" derived from this theory, and shows that it does have guiding value for actual laser paint removal.

[0097] Specific embodiments have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

[0098] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A method of composite laser based cleaning of aircraft skin, characterized in that, Includes the following steps: S1. Construct a composite laser paint removal device that outputs continuous laser and pulsed laser; S2. A small-scale circular area cleaning simulation experiment was conducted on the aircraft skin using a composite laser paint removal device to determine the optimal paint removal parameters. S3. Based on the optimal paint removal parameters, a model is fitted to obtain the relationship between the power density of the continuous laser and the cleaning depth during composite laser paint removal. S4. Clean the aircraft skin according to the relational model; In step S1, the composite laser paint removal device includes a continuous laser and a pulsed laser. The continuous laser and pulsed laser emitted by the continuous laser and the pulsed laser are respectively passed through a beam splitter and a reflector and then act on the aircraft skin through a focusing lens. The continuous laser includes a flat-top beam and a Gaussian beam, with the Gaussian beam covering the center of the flat-top beam; Step S2 specifically involves: S21. Use a continuous laser with a preset power density to clean small circular areas of the aircraft skin. S22. Using a pulsed laser with a preset energy density and frequency to act on the cleaning area of ​​the continuous laser, a composite laser cleaning is achieved. S23. Analyze the cleaning effect of aircraft skin in the composite laser cleaning area and set different paint removal parameters; S24. Continuously adjust the paint removal parameters and perform aircraft skin cleaning; S25. Analyze the aircraft skin cleaning effect under different paint removal parameters, and take the paint removal parameter corresponding to the best paint removal effect as the optimal paint removal parameter. Step S3 specifically involves: S31. Based on the corresponding cleaning experimental data of the optimal paint removal parameters, the relationship between cleaning depth and cleaning time is fitted using a power function. S32. Set the magnitude variation ratio p_1 of the power density of the flat-top beam and the magnitude variation ratio p_2 of the power density of the Gaussian beam in the continuous laser, respectively. S33. Based on the relationship between cleaning depth and cleaning time, and the magnitude change ratios p_1 and p_2, a model relating the power density of continuous laser to cleaning depth is fitted.

2. The composite laser-based method of cleaning an aircraft skin as claimed in claim 1, wherein, In the composite laser paint removal device, the angle between the continuous laser and the pulsed laser incident on the focusing lens is 20°.

3. The composite laser based method of cleaning an aircraft skin as claimed in claim 1, wherein, The transmission and reflection energy ratio of the corresponding split laser beams obtained by the beam splitter for the continuous laser and pulsed laser is 8:

2.

4. The composite laser based method of cleaning an aircraft skin as claimed in claim 1, wherein, In step S2, the paint removal parameters include the power density of the flat-top beam and the power density of the Gaussian beam in the continuous laser, the energy density and frequency of the pulsed laser, and the cleaning time.

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