CN116484508A

CN116484508A - Aircraft skin paint removal method, device, computer equipment and storage medium

Info

Publication number: CN116484508A
Application number: CN202310470822.5A
Authority: CN
Inventors: 韩敬华; 何长涛; 赵盛宇; 张松岭
Original assignee: Haimuxing Laser Intelligent Equipment Chengdu Co ltd
Current assignee: Haimuxing Laser Intelligent Equipment Chengdu Co ltd
Priority date: 2023-04-26
Filing date: 2023-04-26
Publication date: 2023-07-25

Abstract

The application relates to an aircraft skin paint removal method, an aircraft skin paint removal device, computer equipment and a storage medium, which are applied to the field of aviation, wherein the method comprises the following steps: obtaining finishing coat parameters and primer parameters of the aircraft skin; constructing a skin simulation model of the aircraft skin according to the finish paint parameters and the primer parameters; performing finish paint removal simulation on the skin simulation model through single pulses with different laser energy densities to obtain a first paint removal parameter for removing the finish paint of the aircraft skin; inputting the primer parameters into a predetermined primer removal model to obtain a second primer removal parameter for removing the primer of the aircraft skin; and after the finishing paint of the aircraft skin is removed through the first paint removal parameter, the primer of the aircraft skin is removed through the second paint removal parameter, and the paint-removed aircraft skin is obtained. The method can improve the paint removal effect on the aircraft skin.

Description

Aircraft skin paint removal method, device, computer equipment and storage medium

Technical Field

The present application relates to the field of aerospace technology, and in particular, to a method, apparatus, computer device, storage medium and computer program product for paint removal of an aircraft skin.

Background

When the aircraft is paint-removed, the time-saving and high-efficiency performance is required, the base material is not damaged, and the like. Thus, special attention must be paid to the cleaning process during the paint removal of the aircraft skin. The traditional paint removing method comprises a mechanical method and a chemical method, which are easy to damage the aircraft skin and cause secondary pollution to the environment, and the laser cleaning has been used for removing paint on the aircraft skin in recent years due to the advantages of greenness, high efficiency, wide applicability, non-contact and the like.

At present, when paint is removed by laser, if the energy density of the laser is too high, plasma breakdown and melting phenomena may occur to damage a substrate, and if the energy density of the laser is too low, paint may not be removed. Therefore, the current paint removal method requires that operators try to remove paint by adopting different laser energy densities, and the paint removal effect is difficult to be ensured.

Disclosure of Invention

Based on the foregoing, it is necessary to provide an aircraft skin paint removal method, an apparatus, a computer device, a computer readable storage medium and a computer program product for solving the technical problem that the paint removal effect of the paint removal method is difficult to be guaranteed.

In a first aspect, the present application provides a method for paint removal of an aircraft skin. The method comprises the following steps:

Obtaining finishing coat parameters and primer parameters of the aircraft skin;

constructing a skin simulation model of a corresponding aircraft skin according to the finish paint parameters and the primer parameters; performing finish paint removal simulation on the skin simulation model through single pulses with different laser energy densities to obtain a first paint removal parameter for removing the finish paint of the aircraft skin;

inputting the primer parameters into a predetermined primer removal model to obtain a second primer removal parameter for removing the primer of the aircraft skin;

and after the finishing paint of the aircraft skin is removed through the first paint removal parameter, the primer of the aircraft skin is removed through the second paint removal parameter, and the aircraft skin after paint removal corresponding to the aircraft skin is obtained.

In one embodiment, the performing, by using single pulses with different laser energy densities, a finish paint removal simulation on the skin simulation model to obtain a first paint removal parameter for removing the finish paint of the aircraft skin includes:

performing finish paint removal simulation on the skin simulation model through single pulses with different laser energy densities to obtain a temperature change curve chart and a thermal stress change curve chart of the skin simulation model in the corresponding finish paint removal process under the action of each laser energy density respectively; the thermal stress change curve graph represents a change rule diagram of thermal stress of the simulated finish paint along with the laser action depth;

Obtaining finishing paint removal mechanism information, and analyzing a temperature change curve chart and a thermal stress change curve chart which are obtained under each laser energy density based on the finishing paint removal mechanism information to obtain a laser energy density range for removing the finishing paint of the aircraft skin;

and in the laser energy density range, one of the laser energy densities is arbitrarily selected as a first removal parameter for removing the finishing paint of the aircraft skin.

In one embodiment, the obtaining topcoat removal mechanism information includes:

constructing a sample simulation model of an aircraft skin sample; performing finish paint removal simulation on the sample simulation model through single pulses with different laser energy densities to obtain a first surface topography of the finish paint of the sample simulation model;

carrying out energy spectrum analysis on the sample simulation model after the finish paint is removed to obtain a first energy spectrum of the finish paint of the sample simulation model after the laser action;

performing a plasma shock wave test on the finish paint of the sample simulation model to obtain a first stress distribution cloud picture of the shock wave, wherein the stress of the first stress distribution cloud picture changes with time in the finish paint transmission process of the sample simulation model;

and determining the finishing paint removal mechanism information based on the first surface topography map, the first energy spectrogram and the first stress distribution cloud map.

In one embodiment, the primer removal model is determined by:

acquiring primer removal mechanism information of an aircraft skin, and determining a first relational expression between the total removal depth of laser pulses on the primer and the total thickness of the primer according to the primer removal mechanism information;

acquiring a second relation between the laser energy density and the ablation depth and a third relation between the laser energy density and the thickness of the last primer layer in the primer removing process;

and carrying out fusion treatment on the first relational expression, the second relational expression and the third relational expression to obtain the primer removal model.

In one embodiment, the acquiring primer removal mechanism information of the aircraft skin includes:

constructing a sample simulation model of an aircraft skin sample; performing primer removal simulation on the sample simulation model through a plurality of groups of laser pulse parameters to obtain a second surface topography of the primer of the sample simulation model; the laser pulse parameters comprise laser energy density and laser pulse number;

carrying out energy spectrum analysis on the sample simulation model after the primer is removed to obtain a second energy spectrum of the primer of the sample simulation model after the laser action;

Performing a plasma shock wave test on the primer of the sample simulation model to obtain a second stress distribution cloud picture of the shock wave, wherein the second stress distribution cloud picture changes with time in the process of transmitting the stress inside the primer and the substrate of the sample simulation model;

and determining the primer removal mechanism information based on the second surface topography map, the second energy spectrum map and the second stress distribution cloud map.

In one embodiment, the obtaining a second relationship between laser energy density and ablation depth and a third relationship between laser energy density and thickness of the final primer layer during the primer removal process includes:

performing primer removal simulation on the sample simulation model after finishing coat removal by adopting different laser energy densities to obtain a relation diagram between the laser energy densities and the highest temperature and ablation depth of the primer surface;

fitting the simulation data in the relation graph to obtain a second relation between the laser energy density and the ablation depth and a third relation between the laser energy density and the thickness of the last primer layer under the action of single pulse.

In one embodiment, the primer removal model is a relationship with respect to the number of laser pulses and the laser energy density, and the laser energy density has a range of values;

Inputting the primer parameters into a predetermined primer removal model to obtain a second primer removal parameter for removing the primer of the aircraft skin, wherein the second primer removal parameter comprises the following steps:

inputting the primer parameters into the primer removal model, and determining the target laser pulse number and the target laser energy density of the primer for removing the aircraft skin in the range of the laser energy density as the second paint removal parameters.

In a second aspect, the present application also provides an aircraft skin paint removal device. The device comprises:

the parameter acquisition module is used for acquiring finishing coat parameters and primer parameters of the aircraft skin;

the first determining module is used for constructing a skin simulation model of the aircraft skin according to the finish paint parameters and the primer parameters; performing finish paint removal simulation on the skin simulation model through single pulses with different laser energy densities to obtain a first paint removal parameter for removing the finish paint of the aircraft skin;

the second determining module is used for inputting the primer parameters into a predetermined primer removing model to obtain a second primer removing parameter for removing the primer of the aircraft skin;

and the skin paint removal module is used for removing the top paint of the aircraft skin through the first paint removal parameter, and removing the primer of the aircraft skin through the second paint removal parameter to obtain the corresponding paint-removed aircraft skin of the aircraft skin.

In a third aspect, the present application also provides a computer device. The computer device comprises a memory storing a computer program and a processor which when executing the computer program performs the steps of:

obtaining finishing coat parameters and primer parameters of the aircraft skin;

and after the finishing paint of the aircraft skin is removed through the first paint removal parameter, the primer of the aircraft skin is removed through the second paint removal parameter, and the paint-removed aircraft skin is obtained.

In a fourth aspect, the present application also provides a computer-readable storage medium. The computer readable storage medium having stored thereon a computer program which when executed by a processor performs the steps of:

Obtaining finishing coat parameters and primer parameters of the aircraft skin;

constructing a skin simulation model of the aircraft skin according to the finish paint parameters and the primer parameters; performing finish paint removal simulation on the skin simulation model through single pulses with different laser energy densities to obtain a first paint removal parameter for removing the finish paint of the aircraft skin;

In a fifth aspect, the present application also provides a computer program product. The computer program product comprises a computer program which, when executed by a processor, implements the steps of:

obtaining finishing coat parameters and primer parameters of the aircraft skin;

According to the aircraft skin paint removal method, the device, the computer equipment, the storage medium and the computer program product, the surface coating of the aircraft skin is of a multi-layer structure, and the primer and the finish paint have different removal mechanisms, so that the first paint removal parameter of the finish paint and the second paint removal parameter of the primer are determined by adopting different methods, and the first paint removal parameter and the second paint removal parameter are sequentially removed from the finish paint of the aircraft skin to the primer according to the determined first paint removal parameter and the determined second paint removal parameter, so that the paint removal effect and the paint removal quality of the aircraft skin can be improved.

Drawings

FIG. 1 is a flow chart of a method of paint removal from an aircraft skin in one embodiment;

FIG. 2.1 is a graph of the variation of the laser radiation center at different depths at the end of a laser pulse for different laser energy densities, wherein (a) is a temperature variation graph and (b) is a thermal stress variation graph, according to one embodiment;

FIG. 2.2 shows an energy density of 6.37J/cm in one embodiment ² Wherein (a) is a temperature profile and (b) is a stress profile;

FIG. 3 is a side view of an aircraft skin sample in one embodiment;

FIG. 4 is a schematic illustration of a first surface topography of a topcoat under different laser energy densities in one embodiment;

FIG. 5.1 shows that the laser energy density is 0.64J/cm in one embodiment ² A finish appearance diagram;

FIG. 5.2 shows the laser energy density of 6.37J/cm in one embodiment ² A time finishing coat morphology map;

FIG. 5.3 shows that the laser energy density is 12.73J/cm in one embodiment ² A time finishing coat morphology map;

FIG. 6 is a first spectrum of the paint after paint removal according to one embodiment;

FIG. 7 is a first stress distribution cloud of time varying stress of a shock wave during topcoat delivery of a sample simulation model, in one embodiment;

FIG. 8 is a flow chart of a primer removal model determination step in one embodiment;

FIG. 9 is a graph of total depth of removal of a paint layer by laser pulses versus total thickness of a primer layer in one embodiment;

FIG. 10 is a graph of primer thickness versus pulse number for different laser energy densities in one embodiment;

FIG. 11.1 is a schematic illustration of a second surface topography of a primer under different laser pulse parameters in one embodiment;

FIG. 11.2 shows a laser energy density of 2.55J/cm in one embodiment ² When the pulse number is increased, a three-dimensional topography of laser ablation depth is formed;

FIG. 11.3 is a graph of the cleaning depth of the primer as a function of the number of laser pulses for different laser energy densities in one embodiment;

FIG. 11.4 is a graph of laser energy density versus laser pulse number and single pulse ablation depth for one embodiment;

FIG. 11.5 is a topography of one embodiment of a multi-pulse primer after exposure of a metal substrate;

FIG. 12 is a second spectrum obtained by performing a spectrum analysis after multi-pulse primer removal in one embodiment;

FIG. 13 is a second stress distribution cloud of stress over time during the transmission of shock waves inside the primer and substrate of the sample simulation model in one embodiment;

FIG. 14.1 is a graph of the temperature profile of a primer surface in one embodiment;

FIG. 14.2 is a graph of laser energy density versus primer surface peak temperature and ablation depth for one embodiment;

FIG. 15 is a graph of ablation depth of a primer under a single pulse at different laser energy densities in one embodiment;

FIG. 16.1 shows a laser energy density of 2.55J/cm in one embodiment ² The thickness of the residual paint layer is 25 mu m, and the temperature diagram and the thermal stress diagram of the primer and the substrate are shown when the last pulse is acted;

FIG. 16.2 is a graph of temperature and thermal stress versus depth at the center of a laser spot for one embodiment;

FIG. 17 is a block diagram of an aircraft skin paint removal device in one embodiment;

fig. 18 is an internal structural view of a computer device in one embodiment.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.

It should be noted that the terms "first," "second," and the like in the description and claims of the present application and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that embodiments of the present application described herein may be implemented in sequences other than those illustrated or otherwise described herein.

In one embodiment, as shown in fig. 1, an aircraft skin paint removal method is provided, and this embodiment is illustrated by applying the method to a terminal, it is understood that the method may also be applied to a server, and may also be applied to a system including a terminal and a server, and implemented through interaction between the terminal and the server. The terminal can be, but not limited to, various personal computers, notebook computers, smart phones, tablet computers, internet of things equipment and portable wearable equipment, and the internet of things equipment can be smart speakers, smart televisions, smart air conditioners, smart vehicle-mounted equipment and the like. The portable wearable device may be a smart watch, smart bracelet, headset, or the like. The server may be implemented as a stand-alone server or as a server cluster composed of a plurality of servers. In this embodiment, the method includes the steps of:

step S110, obtaining finishing coat parameters and primer parameters of the aircraft skin.

The top coat parameters and the primer parameters may specifically include physical attribute parameters and size parameters. Wherein the physical property parameters may include absorption rate, thermal conductivity, coefficient of thermal expansion, density, specific heat capacity, melting temperature, vaporization temperature, ionization temperature, and the like; the dimensional parameter may include the thickness of the paint.

In the specific implementation, before the aircraft skin to be subjected to paint removal is subjected to paint removal, the finish paint parameters and the primer parameters of the aircraft skin can be obtained first, so that the finish paint parameters and the primer parameters can be corresponding to each other when a skin simulation model is constructed later, and the paint removal parameters of the primer can be determined conveniently according to the primer parameters.

Step S120, constructing a skin simulation model of a corresponding aircraft skin according to the finish paint parameters and the primer parameters; and performing finishing paint removal simulation on the skin simulation model through single pulses with different laser energy densities to obtain a first paint removal parameter for removing the finishing paint of the aircraft skin.

Wherein the first paint removal parameter is in particular the laser energy density. Experiments show that the finishing paint can be removed under the action of a single pulse, so that the finishing paint can be removed by adopting the single pulse without determining the number of laser pulses, and the laser energy density is mainly determined.

In specific implementation, for removing the finishing paint, as finishing paint parameters of different aircraft skins can be different, and the optimal energy density range for removing the finishing paint can be influenced by the finishing paint parameters, for removing the finishing paint of a new aircraft skin, the finishing paint removing simulation is carried out on the finishing paint simulation model through constructing a skin simulation model of the aircraft skin again through single pulses of different laser energy densities, so that the optimal energy density range for removing the finishing paint of the aircraft skin is obtained, and one laser energy density is selected from the optimal energy density range to serve as a first finishing paint removing parameter. Wherein, although the optimal energy density range has a certain change according to the different parameters of the aircraft skin finish, the condition for obtaining the optimal energy density range is universal, namely, the optimal energy density range has a minimum value and a maximum value. The minimum laser energy density is determined under the condition that the thermal stress of the finish paint is larger than the adhesion force between the finish paint and the primer to remove, and the maximum laser energy density is determined under the condition that the finish paint generates a threshold value of plasma breakdown, namely that the cleaning process of the finish paint can not generate plasma.

In practical applications, the two-dimensional finite element model in the simulation program can be used to simulate the laser paint removal process, for example, the size of the top coat is 2mm×80 μm, the size of the primer is 2mm×100 μm, the physical parameters of the top coat and the primer are shown in table 1 below, since the energy is not conducted to the substrate when the top coat is cleaned by the laser, the substrate size can be set to 2mm×200 μm in order to shorten the calculation time, and a gaussian heat source is further loaded on the upper boundary surface of the skin to perform the top coat removal simulation.

Table 1 physical parameters of topcoats and primers

And step S130, inputting the primer parameters into a predetermined primer removal model to obtain a second primer removal parameter for removing the primer of the aircraft skin.

The second paint removal parameter refers in particular to the laser energy density and the number of laser pulses. It has been found through experimentation that when laser is applied to the primer, the laser energy is difficult to conduct on the substrate surface due to the large absorption coefficient of the primer, and therefore, a single pulse cannot achieve direct removal of the primer, requiring multiple pulses to act continuously, and therefore, the second amount of paint removal for removing the primer includes both the laser energy density and the number of laser pulses.

The primer removal model is a relational expression of the laser pulse number and the laser energy density, and the laser energy density has a value range.

In the specific implementation, a primer removing mechanism can be determined through analysis, a primer removing model is determined by combining the primer removing mechanism, after the primer parameters of the aircraft skin to be paint removed are obtained, the primer parameters are input into the determined primer removing model, and a second paint removing parameter for removing the primer of the aircraft skin is obtained.

And S140, removing the top paint of the aircraft skin through the first paint removal parameter, and removing the primer of the aircraft skin through the second paint removal parameter to obtain the paint-removed aircraft skin.

In the specific implementation, the surface coating of the aircraft skin is of a multilayer structure, and the mechanism of removing the top coating and the primer by laser is different, so that when the aircraft skin is subjected to paint removal, layered paint removal is required, and the top coating is removed first and then the primer is removed. Therefore, the paint of the aircraft skin can be removed through the first paint removal parameter, and then the primer of the aircraft skin can be removed through the second paint removal parameter, so that the paint-removed aircraft skin is obtained.

In the aircraft skin paint removal method, a skin simulation model of the aircraft skin is constructed according to the top paint parameters and the primer parameters of the aircraft skin before the top paint of the aircraft skin is removed, and then the top paint removal simulation is carried out on the skin simulation model through single pulses with different laser energy densities, so that a first paint removal parameter for removing the top paint of the aircraft skin is obtained; and then the finishing paint of the aircraft skin is removed through the first paint removal parameter. Before removing the primer of the aircraft skin, inputting primer parameters into a predetermined primer removing model to obtain a second primer removing parameter for removing the primer of the aircraft skin; and then, removing the primer of the aircraft skin through the second paint removal parameter to obtain the corresponding paint-removed aircraft skin. According to the method, the fact that the surface coating of the aircraft skin is of a multi-layer structure and the primer and the finish paint have different removal mechanisms is considered, so that the first paint removal parameter of the finish paint and the second paint removal parameter of the primer are determined by adopting different methods, and the first paint removal parameter and the second paint removal parameter are sequentially removed from the finish paint of the aircraft skin to the primer according to the determined first paint removal parameter and the determined second paint removal parameter, and therefore the paint removal effect and the paint removal quality of the aircraft skin can be improved.

In an exemplary embodiment, in the step S120, the finishing paint removal simulation is performed on the skin simulation model by using single pulses with different laser energy densities to obtain a first finishing paint removal parameter for removing the finishing paint of the aircraft skin, which may be specifically implemented by the following steps:

step S121, performing finishing coat removal simulation on the skin simulation model through single pulses with different laser energy densities to obtain a temperature change curve chart and a thermal stress change curve chart of the skin simulation model in the corresponding finishing coat removal process under the action of each laser energy density respectively; the temperature change curve graph represents a change rule diagram of the temperature of the simulated finish paint along with the action depth of the laser, and the thermal stress change curve graph represents a change rule diagram of the thermal stress of the simulated finish paint along with the action depth of the laser.

In the concrete implementation, the finish paint can be removed under the action of a single pulse, so that the change condition of various finish paints with different laser energy densities can be simulated by taking the laser energy density as an independent variable. In particular, the variation may include a temperature profile of the temperature field of the topcoat as a function of depth of laser action, and a thermal stress profile of the thermal stress of the topcoat as a function of depth of laser action.

For example, refer to (a) in FIG. 2.1, as being excitedAt the end of the light pulse, the temperature change curve graph of the laser radiation center at different depths under different laser energy densities, the applied laser energy density comprises 1.27J/cm ² 、1.91J/cm ² 、2.55J/cm ² 、6.37J/cm ² 、10.19J/cm ² 、12.73J/cm ² The method comprises the steps of carrying out a first treatment on the surface of the FIG. 2.1 (b) is a graph showing the thermal stress variation at different depths of the laser irradiation center at the end of the laser pulse at different laser energy densities, the applied laser energy density being 1.27J/cm ² 、1.91J/cm ² 、2.55J/cm ² 、6.37J/cm ² 、10.19J/cm ² 。

And S122, obtaining finishing coat removal mechanism information, and analyzing a temperature change curve chart and a thermal stress change curve chart which are obtained under each laser energy density based on the finishing coat removal mechanism information to obtain a laser energy density range of the finishing coat for removing the aircraft skin.

Specifically, the finishing coat removal mechanism information is: when the finishing paint is removed, the thermal stress effect is mainly used, the plasma impact effect is secondarily used, the plasma impact effect is avoided as much as possible, and the temperature change curve chart and the thermal stress change curve chart obtained in the step S121 are analyzed by combining finishing paint removal mechanism information, so that the laser energy density range of the finishing paint for removing the aircraft skin can be obtained.

For example, with respect to fig. 2.1, it can be seen from the figure that the maximum temperature and maximum thermal stress of the topcoat and primer gradually increase with increasing energy density. The temperature gradually decreases from the surface in the axial direction due to the gradual absorption of the laser by the topcoat. When the laser reaches the primer, the temperature is rapidly increased to the highest temperature due to the larger absorption coefficient and thermal expansion coefficient of the primer to the laser, and simultaneously falls to the room temperature within the range of 40 mu m, the thermal stress corresponding to the primer is also rapidly increased, and the energy density is higher than 1.91J/cm ² When the difference of thermal stress between the top coat and the primer is greater than 66MPa, the top coat starts to separate from the primer, and the vaporization point of the primer is not reached at this time. In the early stage, the higher laser energy has higher heating rate on the paint layer, the laser power is absorbed by the sample, the early temperature of the paint layer is continuously increased, the temperature of the finish paint in a small-range area of the light spot center reaches the melting point,from (d) in fig. 5.1, it can be seen that a small amount of fused particles are distributed in the middle of the topcoat. But when the energy density of the single pulse is increased to 12.73J/cm ² At this time, air near the topcoat is broken down and a portion of the energy is absorbed by the air while the temperature of the topcoat reaches 645K, above its boiling point. The higher the temperature is at the beginning of evaporation, the faster the evaporation rate, the plasma shielding effect will be generated near the paint layer surface, the heat energy generated by light will be absorbed by the plasma, the less the heat energy absorbed by the paint layer, the temperature reaching the center point of the paint layer will not always rise, therefore the paint layer removing effect will be greatly weakened, but the plasma impact force will become larger at this time, as shown in (g) - (i) in fig. 4, at this time the paint layer removing is mainly due to the plasma impact effect. Therefore, when the finishing paint is removed, the optimal energy density range is 1.91J/cm ² -12.73J/cm ² 。

FIG. 2.2 shows an energy density of 6.37J/cm ² The profile of the sample at the time of single pulse action of the topcoat, where (a) is the temperature profile and (b) is the stress profile. The graph shows that the temperature of the laser spot center is highest, the radial distribution is gradually reduced, the temperature field is in accordance with Gaussian distribution, the temperature of the primer is far higher than that of the finish paint, and the maximum difference of thermal stress at the contact surface of the primer and the finish paint is also the key of realizing the finish paint cleaning. At this energy density, the primer rapidly reached its vaporization point due to the large temperature rise, and a significant increase in the nanoparticle distribution of the primer was seen in fig. 5.2 (c). And at this time, the thermal stress of the contact surface of the top coat and the primer is 227MPa, which is greater than the adhesion force between the top coat and the primer, so that the top coat is peeled off from the surface of the primer, and the small-range ablation phenomenon of the top coat in the central area of the light spots can be seen in (d) of fig. 4, and the fracture marks exist in the edge area of the light spots.

Step S123, one of the laser energy densities is arbitrarily selected as a first removal parameter for removing the top-coat paint of the aircraft skin within the laser energy density range.

In specific implementation, after determining the optimal laser energy density range for removing the top coating of the aircraft skin, one laser energy density can be arbitrarily selected in the laser energy density range as a first removal parameter for removing the top coating of the aircraft skin.

In this embodiment, the skin simulation model is subjected to finish paint removal simulation through single pulses of different laser energy densities, the optimal laser energy density range for removing the aircraft skin finish paint is determined by combining the finish paint removal mechanism information based on a temperature change curve and a thermal stress change curve obtained by simulation, and further, the finish paint removal is performed by adopting a first removal parameter selected in the laser energy density range, so that the removal effect of the finish paint can be ensured.

In an exemplary embodiment, in the step S122, the step of obtaining the finishing coat removal mechanism information includes:

step S122a, constructing a sample simulation model of an aircraft skin sample; and carrying out finish paint removal simulation on the sample simulation model through single pulses with different laser energy densities to obtain a first surface topography of the finish paint of the sample simulation model.

For example, the aircraft skin samples used in the present application may be aluminum alloys with a metal substrate 1mm thick, and as shown in FIG. 3, the aluminum alloy surface has three layers of materials, namely a yellow-green chemical conversion coating, a red polyurethane top coat (80-90 μm in thickness) and a gray epoxy primer (100-110 μm in thickness).

Specifically, the method for constructing the sample simulation model is the same as the method for constructing the skin simulation model, and will not be described here again. After the sample simulation model is constructed, in order to determine the surface paint removal morphological characteristics, single pulses with different laser energy densities are loaded to the upper boundary of the skin of the sample simulation model, and surface paint removal simulation is performed, so that a first surface topography of the surface paint under the action of different laser energy densities is obtained.

Referring to FIG. 4, a schematic diagram of a first surface topography of a topcoat under different laser energy densities is shown, where it can be seen that the laser energy density is 0.64J/cm when the laser energy density is small ² When the laser action paint layer does not generate plasma light, only a weak sound is heard, the laser action area is small, the central area of the light spot is in an ablation shape, the paint layer in the annular area of the edge is blackened, and a small amount of carbonization marks are formed. When the laser energy is increased to 1.27J/cm ² During the laser actionThe generated plasma has weak intensity, the impact sound is slightly enhanced, the ablation area in the middle is slightly raised, and the paint layer around is black and deepened. The area I is an irradiation area of a pulse laser spot, the energy of the focused laser beam center is high, the heat is concentrated, and the area is subjected to the processes of melting, splashing and the like. The II area is a heat affected area irradiated by the pulse laser light spots. The heat conduction of the paint layer increases the temperature of the edge paint layer, but this region shows only a slight color change due to the low energy. The laser energy was 1.91J/cm ² And 2.55J/cm ² When the plasma brightness is slightly enhanced, a comparatively "clunk" impact sound can be heard. The area of laser removal is increased, ablation marks in the middle of the light spots are more obvious, but cracks start to appear at the periphery, and even the whole round finish paint directly breaks away from the primer. When the laser energy is continuously increased to 6.37J/cm ² During the cleaning process, a small amount of smoke dust is generated, the brightness of the plasma is further enhanced, and the sound generated by the laser acting paint layer starts to be sharp. The area of the laser removed finish paint is continuously increased, and the removed edge still presents a fracture mark. When the laser energy is higher than 12.73J/cm ² When the laser impact sound is very harsh, the plasma brightness is extremely harsh, however, the removal effect is greatly weakened, only a black ablation pit acts on the surface of the finish paint, the higher the energy is, the larger the pit area is, and the removal of the finish paint cannot be realized.

Further, the removal process of the topcoat may also be analyzed based on the topography of the topcoat, with reference to FIG. 5.1, to a laser energy density of 0.64J/cm ² The morphology of the finish paint, wherein (a) - (d) respectively represent that the laser energy density is 0.64J/cm ² An overall view, a low-power enlarged view, a side view and a high-power enlarged view of the finish appearance. At this time, the energy density is small, the laser only acts on a small range of the finish paint, and the finish paint cannot be completely removed by a single pulse. Fig. 5.1 (a) shows that the laser pit is not smooth as a whole, irregular fluctuation of the ablation pit is large, the paint layer slightly bulges at the edge area of the laser action (fig. 5.1 (c)), the fracture trace is obvious, and no melting phenomenon occurs. At the same time, many cracks exist on the surface, and the paint layer breaks into irregularly shaped blocks, as shown in (b) of FIG. 5.1 Shown. Enlarged detail fig. 5.1 (d) shows that the paint layer has a layering, with a small amount of fused particles distributed.

FIG. 5.2 shows the laser energy density increased to 6.37J/cm ² Topography of the primer remaining after removal of the topcoat in a single pulse, wherein (a) - (d) represent laser energy densities of 6.37J/cm, respectively ² An overall view, a low-power enlarged view, a side view and a high-power enlarged view of the finish appearance. The removed edge presents a clear incision, and the finish paint is completely removed in a mechanical stripping mode. At the moment, the surface relief of the primer etching pit after the laser action is smaller, the blocky appearance is more obvious in (b) and (c) in fig. 5.2, meanwhile, the number of nano particles is also obviously increased, the smooth surface of the paint layer can be seen after the amplification, the nano particles are adsorbed together, and part of nano particles are not completely formed and even just start to be exposed.

FIG. 5.3 shows the energy density increased to 12.73J/cm ² When the top coat is removed by a single pulse, the topography of the primer is left, wherein (a) - (d) respectively represent that the laser energy density is 12.73J/cm ² An overall view, a low-power enlarged view, a side view and a high-power enlarged view of the finish appearance. As shown in the figure, the single pulse laser can only remove a thin layer of the finish paint, the impact trace of the central area of the light spot is more obvious, a large crack exists, and the central paint layer is slightly convex, as shown in (a) in fig. 5.3. The paint layer in fig. 5.3 (c) has obvious edge fracture marks and no melting marks. The surface appearance is similar to that of fig. 5.1, a large number of cracks exist on the surface, the surface is in a block shape with different shapes and sizes, and the surface of the paint layer is almost free of nano particles.

And step S122b, carrying out energy spectrum analysis on the sample simulation model after the finish paint is removed to obtain a first energy spectrum of the finish paint of the sample simulation model after the laser action.

Referring to fig. 6, a first spectrum obtained by energy spectrum (EDS) analysis of the top-coat paint after paint removal is shown, wherein (a) and (b) in fig. 6 are ablation areas of the top-coat paint when the energy density is low. As can be seen from Table 2 below, the ratio of carbon (C) to oxygen (O) in the original topcoat was 3.92, and the atomic percentages of carbon and oxygen in the overall topcoat after laser exposure were 3.20 and 3.39, which were slightly reduced compared to the original topcoat. It was thus determined that slight ablation occurred during removal of the topcoat, but that thermal stress and vibration effects were dominant as a whole.

Surface 2 elemental duty ratio of the topcoat after laser action

And step S122c, performing a plasma shock wave test on the finish paint of the sample simulation model to obtain a first stress distribution cloud picture of the shock wave, wherein the stress of the first stress distribution cloud picture changes along with time in the finish paint transmission process of the sample simulation model.

Specifically, in addition to the laser ablation effect and thermal stress effect, there is also a plasma impingement effect during laser cleaning of the topcoat. Thus, this example also proposes a plasma shock wave test of the enamels. When the energy is smaller, the impact wave acts on the top paint to crack the surface of the paint layer, so that the uneven-size blocky distribution is formed, as shown in fig. 5.1; when the energy is increased to a certain value, the plasma shock wave effect is enhanced, the impact force is increased, but the energy reaching the paint layer is reduced at the moment, the thermal stress between the top paint and the primer is insufficient to remove the whole top paint, and because the paint layer is thicker, the impact force mainly removes a small part of the top paint, as shown in fig. 5.3. During the cleaning process, as the energy density increases, a popping sound is clearly perceived, and a flash of laser light loading onto the paint is also seen.

More specifically, when the laser energy density was 12.73J/cm at the time of the test ² At this time, the peak pressure of the shock wave was set to 352MPa. And loading the laser plasma impact crest value pressure to the upper boundary of the paint layer of the sample simulation model, and setting the side boundary as a low reflection boundary. Fig. 7 shows a transmission process of the shock wave in the sample simulation model, and propagation times corresponding to (a) - (i) in fig. 7 are respectively: (a) 28ns; (b) 46ns; (c) 65ns; (d) 130ns; (e) 169ns; (f) 194ns; (g) 205ns; (h) 229ns; (i) 300ns. Since the shock wave intensity color changes in the topcoats of (d) - (i) in FIG. 7 are not significant, the distribution cloud of stress over time in the topcoats is highlightedThe left side is a color legend for the topcoat layer and the right side is a color legend for the primer and substrate. As can be seen from the pressure distribution diagram of the shock wave, the pressure of the central area of the laser spot is maximum in the downward propagation process of the shock wave, and the pressure is sequentially reduced along the axial direction and the radial direction. In fig. 7, (a) - (f) are the impact waves first coupled from the air to the surface of the topcoat, then gradually propagating downwards, then continuously reflecting and superposing stress distribution in the topcoat, the tensile strength of the paint at room temperature is only 1.4-4MPa, and the tensile strength is reduced under the actions of combustion, thermal explosion and thermal stress. Thus, paint may crack or even fall off under the impact of the laser plasma.

Step S122d, determining finishing paint removal mechanism information based on the first surface topography map, the first energy spectrogram and the first stress distribution cloud image.

Specifically, based on the analysis, in combination with the topography map from which the topcoat is removed, the topcoat removal mechanism information can be determined as: the thermal stress effect should be dominant and the plasma impact effect should be subordinate when the topcoat is removed.

Based on the analysis, it can be determined that the removal of the top paint is mainly caused by the fact that laser acts on a sample, the absorption coefficient of the top paint and the primer to the laser and the thermal expansion coefficient of the two materials are different, so that the temperature rise and the thermal expansion of the two materials are different, the temperature rise of the primer is higher than that of the top paint, meanwhile, thermal stress difference can be generated at the contact surface of the top paint and the primer, the top paint can be directly cracked and removed by a single pulse, but when the energy density is too high, a plasma shielding effect can be generated on the surface of the top paint, and the removal effect of the top paint is greatly reduced. The laser removal of the topcoat is based on a thermal stress mechanism and plasma effects should be avoided.

In the embodiment, the surface topography map, the energy spectrogram and the stress distribution cloud map before and after paint removal are respectively obtained through an optical microscope, an energy spectrometer and a scanning electron microscope, so that the tests on the microscopic and macroscopic appearances and the element content of the aircraft skin paint layers before and after paint removal are realized, the determination of the laser paint removal is mainly based on a thermal stress mechanism, the plasma effect is avoided, and the basis is further provided for determining the optimal laser energy density removal range of the paint.

In an exemplary embodiment, as shown in fig. 8, the determining of the primer removal model includes:

step S810, acquiring primer removal mechanism information of the aircraft skin, and determining a first relation between the total removal depth of the laser pulse on the primer and the total thickness of the primer according to the primer removal mechanism information;

step S820, obtaining a second relation between the laser energy density and the ablation depth and a third relation between the laser energy density and the thickness of the last primer layer in the process of removing the primer;

in step S830, the first relational expression, the second relational expression and the third relational expression are fused to obtain a primer removal model.

In particular, for a primer such a paint layer requiring multiple pulse removal, a schematic diagram for the multiple pulse removal of the primer is depicted in fig. 9, since the last pulse is removed by the thermal stress effect after the paint layer is thinned by ablation of the multiple pulses.

Assuming a total number of laser pulses required for a primer of thickness l of n, the first n-1 pulses are based on the chemical ablation effect, corresponding to a removal depth of l ₁ The removal mechanism of the last pulse is due to thermal stress effects (corresponding paint removal depth of l ₂ ). As can be seen from fig. 8, the relationship between the total removal depth of the paint layer by the laser pulse and the total thickness of the primer layer can be expressed as the following first relationship:

l＝(n-1)l ₁ +l ₂ (1)

where n is an integer greater than 0 and for n=1 pertains to primer removal by a single laser pulse. According to relation (1) and fig. 8, the optimal laser pulse parameters for paint removal can be obtained given the thickness and thermodynamic parameters.

The energy density and the depth of single pulse ablation during primer removal are shown in fig. 11.4. The energy density is in the range of 0.71J/cm ² -1.91J/cm ² The depth of single pulse ablation becomes larger as the laser energy density increases, whereas when the energy density is higher than 1.91J/cm ² When the ablation effect is weakened, the plasma impact effect is enhanced, the substrate can be damaged, and the laser parameters are inconvenient to control, so that the energy density when the primer is removed is less than 1.91J/cm ² 。

To obtain the relationship between the paint layer thickness and the number of pulses, a logarithmic function is adopted to fit the simulation data of the energy density and the ablation depth in fig. 14.1 (b), and after the data are fitted, a second relationship between the laser energy density and the ablation depth under the action of a single pulse is as follows:

l ₁ ＝4.71+5.23ln(I ₀ -0.29)(2)

Wherein I is ₀ For the intensity of the laser incident light, when the thickness of the last primer layer is ablated to be l ₂ When the laser passes through the last layer of paint, the light intensity becomes:

I ₁ ＝A _bottom I ₀ exp(-α _Bottom l ₂ )

The simulation shows that when the primer is just removed from the substrate, the energy density of the final primer layer, namely the energy density irradiated on the surface of the substrate is 0.026J/cm ² When I ₁ ＝0.026J/cm ² At the time, the laser energy density and the thickness l of the final primer layer ₂ The third relation between:

wherein A is _Bottom An absorptivity of the primer, a _Bottom Is the absorption coefficient of the primer.

The first relation (1), the second relation (2) and the third relation (3) can be used to obtain a relation characterizing the primer removal model:

according to the parameters of the materials used in the experiment, the relationship between the paint layer thickness and the pulse number is shown in fig. 10 when different energy densities act after substituting the formula.

According to the method, a multi-pulse primer removal model is provided according to the primer removal morphology, the thermal stress effect between the primer and the substrate is used as a removal threshold value, the corresponding relation between the thickness of the primer and the optimal laser parameters is established, and the subsequent use is facilitated.

In this embodiment, a relation between the laser energy density and the number of laser pulses is obtained through experiments, and as a primer removal model, the thickness of the primer can be obtained, so that the thickness l of the primer can be obtained before the primer of the skin is removed, and the relation between the laser energy density and the required number of laser pulses is determined in advance, so that the primer can be removed while avoiding damaging the skin substrate.

In an exemplary embodiment, the step S810 of acquiring the primer removal mechanism information of the aircraft skin includes:

step S811, constructing a sample simulation model of the aircraft skin sample; performing primer removal simulation on the sample simulation model through a plurality of groups of laser pulse parameters to obtain a second surface topography of the primer of the sample simulation model; the laser pulse parameters include laser energy density and number of laser pulses.

In particular, the primer is difficult to completely remove under a single pulse, requiring multiple pulses. In order to determine the influence of the number of laser pulses and the laser energy density on the primer removal effect, the present embodiment performs primer removal simulation with the number of laser pulses and the laser energy density as arguments.

Referring to fig. 11.1, to remove the topcoat, the laser pit surface topography after paint removal was performed with different energy densities and different pulse numbers. It can be seen from the figure that the color of the primer is brighter as the number of pulses increases. Since the incident laser is a gaussian beam, the energy is highest at the center of the spot, so it can be seen from fig. 11.1 that the substrate emerges first in the center region of the spot. In FIG. 11.1, (a) after the top coat is removed with high energy, the energy density is 1.27J/cm ² The surface morphology of the laser pit after paint removal by 25 pulses, and the laser is applied to the substrate at the 20 th pulse. FIG. 11.1 (b) shows an energy density of 1.91J/cm ² Laser after paint removal by 20 pulsesPit surface topography. In the figure, none of the first 11 pulses breaks down the primer, and a small amount of clean substrate is exposed after the 12 th pulse. After the 12 th pulse, the laser removal range increases, but the metal substrate melts. FIG. 11.1 (c) shows an energy density of 2.55J/cm ² And (3) the surface morphology of the laser pit after paint removal by 20 pulses. At this energy density, the laser was cleaned to the substrate at 14 th pulse, and in 6 subsequent pulses, the laser was directly applied to the substrate, and most of the metal substrate was melted in the laser irradiation area. FIG. 11.1 (d) shows an energy density of 10.19J/cm ² And (3) cleaning the paint layer to a substrate by laser breakdown when the 20 th pulse acts on the surface morphology of the laser pit after paint removal by 25 pulses.

FIG. 11.2 shows a laser fluence of 2.55J/cm ² As the number of pulses increases, the laser ablates a three-dimensional topography of depth. Wherein (a) - (c) in fig. 11.2 are three-dimensional graphs after the first pulse, 13 th pulse, and 14 th pulse, respectively, specifically, the top coat falls off after the first pulse, and it can be seen from the depth graph, and the depth of the laser action is 86.99 μm, which is consistent with the measured thickness of the top coat. After 12 further pulses, only a thin layer of grey primer remained at pulse 13, exposing a small amount of chemical conversion coating, with a depth of 162.4 μm. After continuing to apply one pulse and applying the 14 th pulse, the clean metal substrate was exposed to a depth of 184.9 μm.

Fig. 11.3 is a graph of the cleaning depth of the primer as a function of the number of laser pulses for different laser energy densities. Under the same energy density, the cleaning depth gradually increases with increasing number of pulses, each pulse having an average cleaning depth of only a few microns, but the cleaning depth of the last pulse increases significantly. The trend of the depth profile is similar, although the energy density is different.

Fig. 11.4 (a) is a graph of laser energy density versus the number of laser pulses, and fig. 11.4 (b) is a graph of laser energy density versus single pulse ablation depth. As can be seen from the figure, the paint layer with the same thickness is removed in a certain energy range, and the higher the energy density is, the single pulse ablation isThe greater the depth, the smaller the number of pulses required, but when the energy density is higher than 1.91J/cm ² As the ablation depth of the single pulse gradually decreases, the number of pulses required to clean the substrate gradually increases, and as can be seen from FIG. 11.4, the optimum removal energy density is 1.91J/cm if the minimum pulse is to be used to remove the primer ² 。

Fig. 11.5 is a topography of the multi-pulse primer after exposing the metal substrate, specifically, a topography of the residual paint layer after the last pulse, wherein the corresponding schematic diagrams (a) - (i) are respectively: (a) optical microscopy images; (b) SEM images; (c) a side view; (d) primer pattern; (e) primer magnification; (f) high magnification; (g) a chemical conversion coating; (h) high magnification; (i) crack enlargement. In fig. 11.5 (a) it can be seen that after the last pulse, part of the primer monolith separated from the substrate but has not yet completely fallen off. Fig. 11.5 (b) is a laser pit edge topography, with the remaining primer layer exhibiting "terrace" topography along the direction of pulsed laser irradiation, indicating that the primer was cleaned layer by layer. The enlarged primer showed a large number of ablation pits and coagulated nanoparticles on the surface of the laser-applied primer, and the ablation marks were significantly heavier than those of the primer left after single pulse removal of the topcoat (fig. 5.2 (c)). At the same time, the chemical conversion coating in contact with the substrate after the last pulse is applied remains relatively intact, many irregular cracks exist on the surface, and the enlarged SEM (scanning electron microscope) image shows that the surface has almost no ablation mark.

And step S812, carrying out energy spectrum analysis on the sample simulation model after the primer is removed to obtain a second energy spectrum of the primer of the sample simulation model after the laser action.

Referring to fig. 12 (a) and (b), a second spectrum obtained by performing spectrum analysis after removing the primer for multiple pulses. As can be seen from the following table 3, the atomic percentage of carbon (C) atoms and oxygen (O) atoms of the original primer was 3.57. The atomic ratio of primer C, O after laser action was 1.92 and 1.42, respectively. The atomic percentage of C becomes significantly smaller and the atomic percentage of O increases. Under the action of multiple pulses, the temp. of primer quickly reaches its vaporization point, so generating violent ablation reaction, and the C element in paint layer is combined with oxygen in air to generate dioxygenCarbon CO conversion ₂ The content of the remaining C element is reduced. It can thus be determined initially that the primary ablation effect is that of the removal of the primer and that the mechanical vibration effect is that of the secondary effect.

TABLE 3 elemental ratios of primers after laser action

Step S813, performing a plasma shock wave test on the primer of the sample simulation model to obtain a second stress distribution cloud image of the shock wave with time change in the internal transmission process of the primer and the substrate of the sample simulation model.

Specifically, in addition to the laser ablation effect, there is also a plasma impingement effect during laser cleaning of the primer. Thus, this example also proposes a plasma shock wave test of the primer. As shown in fig. 11.5, the impact wave acts on the primer to crack the surface of the paint layer, and the paint layer is distributed in a block shape with different sizes.

The size of the simulated primer is set to be 2mm multiplied by 100 mu m, the size of the substrate is set to be 2mm multiplied by 1mm, the peak pressure of the laser plasma shock wave is loaded on the upper boundary of the paint layer, the bottom surface of the constraint model is fixed, the side surface is set to be a reflection-free boundary, and when the laser energy density is 2.55J/cm < 2 >, the peak pressure of the shock wave is set to be 114MPa. FIG. 13 shows the evolution of the stress distribution of the shock wave over time during the internal transmission of the primer and the aluminum substrate, with the corresponding propagation times (a) - (i) being: (a) 28ns; (b) 46ns; (c) 65ns; (d) 78ns; (e) 86ns; (f) 94ns; (g) 106ns; (h) 120ns; (i) 300ns, the cloud of stress over time in the primers of (d) - (i) in fig. 13 is highlighted, with the left side of the figure being the color legend for the primer layer and the right side being the color legend for the primer and substrate. As can be seen from the pressure distribution diagram of the shock wave, the pressure of the central area of the laser spot is maximum in the downward propagation process of the shock wave, and the pressure is sequentially reduced along the axial direction and the radial direction. Fig. 13 (a) - (f) show the stress distribution of shock waves coupled from the air to the primer surface, propagating gradually downward, and then continuously reflected and superimposed within the primer. Therefore, paint may crack or even fall off under the impact of laser plasma, but the intensity of shock waves transmitted to the substrate may be increased, possibly causing damage to the substrate.

Step S814, determining primer removal mechanism information based on the second surface topography map, the second energy spectrum map, and the second stress distribution cloud map.

Specifically, based on the analysis, in combination with the primer removal profile, it can be determined that during laser primer removal, ablation effects predominate, plasma impingement effects predominate, and plasma impingement effects should be avoided to reduce substrate damage.

In the embodiment, the surface topography map, the energy spectrogram and the stress distribution cloud map before and after the primer removal are respectively obtained through an optical microscope, an energy spectrometer and a scanning electron microscope, so that the micro and macro topography and the element content of the aircraft skin paint layers before and after the paint removal are tested, the mechanism of removing the top paint by laser is determined, and a basis is further provided for determining a primer removal model.

In an exemplary embodiment, in step S820, a second relation between the laser energy density and ablation depth and a third relation between the laser energy density and the thickness of the last layer of primer during the primer removal process are obtained, including:

and step S821, performing primer removal simulation on the sample simulation model after finishing coat removal by adopting different laser energy densities to obtain a relation diagram between the laser energy density and the highest temperature and ablation depth of the primer surface.

Step S822, fitting the simulation data in the relation diagram to obtain a second relation between the laser energy density and the ablation depth and a third relation between the laser energy density and the thickness of the last primer layer under the action of single pulse.

Specifically, fig. 14.1 is a graph showing the temperature distribution of the primer surface after removal of the topcoat by laser light, using a single pulse and different laser energy densities, specifically, the temperature distribution of the primer surface when laser light is irradiated at time t=12ns, in the X-axis direction, wherein the X-axis represents the radial distribution dimension of the laser beamThe laser pulse light intensity (energy density) exhibits a gaussian distribution. At a laser energy density of 1.91J/cm ² When the primer surface temperature reaches the threshold of laser plasma generation. Fig. 14.2 is a graph of the highest temperature and ablation depth of laser loading on the primer surface at different energy densities, and in order to obtain the relationship between the thickness of the paint layer and the number of pulses, the simulation data of the laser energy density and the ablation depth in fig. 14.2 are fitted by adopting a logarithmic function, and after the data are fitted, a second relationship between the laser energy density and the ablation depth and a third relationship between the laser energy density and the thickness of the last primer layer can be obtained under the action of a single pulse.

In the embodiment, primer removal simulation is performed on the sample simulation model after finishing coat removal through different laser energy densities, and the obtained simulation data are fitted to obtain a second relation between the laser energy density and ablation depth and a third relation between the laser energy density and the thickness of the last primer layer under the single pulse action, so that quantification of the relation between the laser energy density and ablation depth and the thickness of the primer is realized, and a foundation is provided for determination of a subsequent primer removal model.

Further, thermodynamic effects upon primer removal can be further analyzed based on fig. 14.1 and 14.2.

As can be seen from the experimental topography shown in fig. 11.5, the top coat is mainly due to the higher primer temperature, and a larger difference in thermal stress is finally generated than the crack removal after the adhesion between the top coat and the primer. In the case of primer application, the laser energy is difficult to be conducted on the surface of the substrate due to the large absorption coefficient of the primer, and a single pulse cannot directly remove the primer, so that multiple pulses are required to continuously act, and the edge of the primer removed is in a layered trapezoid distribution as can be seen in (c) in fig. 11.5, which shows that the primer removal is the result of multiple pulses.

As can be seen from FIG. 14.1, the temperature of the primer surface is also Gaussian, and as the energy density increases, the highest temperature of the primer surface increases linearly, and the ablation depth increases slowly, indicating that the fewer pulses are required, as shown in FIG. 14.2, in combination with the experiment, due to the greater energy density than1.91J/cm ² At this time, the primer removal efficiency slows down, and therefore, the application discusses primarily energy densities less than 1.91J/cm ² Is the case in (a). When the energy density is greater than 0.71J/cm ² At this time, the primer begins to ablate. The depth of absorption of laser energy is shallow as is known from lambert's law due to the large absorption coefficient of the primer. When the laser energy density is more than 1.91J/cm ² At this time, the primer surface temperature was 624K, and as is clear from fig. 11.4 (a), the number of pulses required for removing the primer at this time was increased, and at this time, the laser was blown through the air, and a part of energy was lost by the air, and at this time, a plasma shielding effect was also generated, so that the energy reaching the paint layer was reduced.

After the paint layer above the primer vaporization point 415K is filtered, the primer pits after laser cleaning are displayed, so that the ablation depth of the primer under different energies can be displayed, as shown in fig. 15, specifically, the laser energy densities corresponding to (a) - (d) in fig. 15 are respectively (a) 0.76J/cm ² ；(b)0.89J/cm ² ；(c)1.27J/cm ² ；(d)1.91J/cm ² . The removed pit morphology presents a bowl shape with a wide upper part and a narrow lower part, which corresponds to the Gaussian light source used in the experiment. It can be seen from fig. 11.5 (e) that numerous nano-particles and smooth pits are distributed on the paint layer, because the paint layer has a small thermal conductivity, and the incident laser energy is accumulated on the surface of the paint layer, so that the temperature of the surface of the paint layer is instantaneously raised to reach or even exceed the melting point and vaporization point of the paint layer. Thus, droplets generated by the instantaneous vaporization and volatilization of the primer undergo collisions, coalescence and agglomeration, forming nanoparticles of different sizes. The size of these particles is related to their rate of coagulation, and when the laser energy absorbed by the particles is high, there is sufficient time for the particles to develop larger, and for some particles that absorb less laser energy, the resolidification time is short, there is insufficient time for the particles to grow, and therefore the particles are smaller. The primer is then mainly removed by the ablative effect.

The initial laser pulse mainly thins the coating by ablation effect, and when the coating is thinned to a certain thickness, as can be seen from fig. 11.3, the depth of the removal of the last pulse is larger than that of the previous single pulse, and as can be seen from (a) in the topography fig. 11.5, the primer in the central area of the light spot is matched with the primer in the central area of the light spot after the last pulse The chemical conversion coating is in a fracture-separated form from the substrate. In FIG. 16.1, (a) and (b) are respectively laser energy densities of 2.55J/cm ² The thickness of the residual paint layer is 25 μm, the temperature diagram and the thermal stress diagram of the primer and the substrate are obtained when the last pulse is applied, and fig. 16.2 is a diagram showing the change of the temperature and the thermal stress with the depth at the center of the laser spot. At this time, the temperature of the surface of the primer reaches the vaporization point, meanwhile, the temperature is slightly raised after the laser is transmitted to the substrate due to the larger absorption coefficient of the substrate, and a larger thermal stress difference is generated at the contact surface of the substrate and the primer due to the larger thermal expansion coefficient and elastic modulus of the substrate, at this time, 168MPa is higher than the adhesion force (148 MPa) between the substrate and the primer, so that the paint layer is cracked and separated from the substrate, as shown in (h) in fig. 11.5. The paint layer is then no longer mainly ablated, but the last pulse is removed to a greater depth than the preceding pulse due to the stress removal.

By the above embodiment, it can be determined that the primer is deposited by multiple pulses, the thickness of the paint layer is gradually reduced by ablation effect, and when the thickness of the paint layer is reduced to be far smaller than the thermal diffusion depth, part of laser energy is absorbed by the substrate through the residual primer layer, the residual primer layer is removed by thermal stress effect, and the optimal removal energy density is 1.91J/cm ² 。

In an exemplary embodiment, the primer removal model is a relationship with respect to the number of laser pulses and the laser energy density, and the laser energy density has a range of values; step S140, inputting primer parameters into a predetermined primer removal model to obtain a second primer removal parameter for removing the primer of the aircraft skin, which specifically includes: inputting primer parameters into a primer removal model, and determining the target laser pulse number and the target laser energy density of the primer for removing the aircraft skin in the range of the laser energy density, wherein the target laser pulse number and the target laser energy density are used as second paint removal parameters.

The range of the laser energy density is the energy density range of the laser action on the top coat and the primer, and can be divided into two: the minimum is the laser energy density corresponding to this exceeding the melting point or thermal stress break threshold of the paint; the maximum value is the threshold at which paint ionizes and laser plasma is generated.

In specific implementation, the primer parameters input into the primer removal model are specifically the primer thickness l and the primer absorptivity A _Bottom And absorption coefficient a of primer _Bottom The following relation is a primer removal model, the three primer parameters are input into the following relation, the relation is changed into the relation about the laser pulse number and the laser energy density, further, a target laser energy density can be determined in the range of the laser energy density, and the target laser energy density is substituted into the following relation, and then the target laser pulse number I can be obtained by solving ₀ And taking the obtained target laser pulse number and target laser energy density as second paint removal parameters.

In this embodiment, the rationality and the paint removal effect of the determined second paint removal parameter can be ensured by determining the value range of the laser energy density, and for any skin to be removed of the primer, the second paint removal parameter can be determined in advance by the primer removal model as long as the thickness of the primer, the absorption rate of the primer and the absorption coefficient of the primer are known, so that the paint removal efficiency can be improved on the basis of ensuring the paint removal effect.

It should be understood that, although the steps in the flowcharts related to the embodiments described above are sequentially shown as indicated by arrows, these steps are not necessarily sequentially performed in the order indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps in the flowcharts described in the above embodiments may include a plurality of steps or a plurality of stages, which are not necessarily performed at the same time, but may be performed at different times, and the order of the steps or stages is not necessarily performed sequentially, but may be performed alternately or alternately with at least some of the other steps or stages.

Based on the same inventive concept, the embodiment of the application also provides an aircraft skin paint removal device for realizing the aircraft skin paint removal method. The implementation of the solution provided by the device is similar to that described in the above method, so the specific limitations in one or more embodiments of the aircraft skin paint removal device provided below may be referred to above as limitations on the aircraft skin paint removal method, and will not be described in detail herein.

In one embodiment, as shown in fig. 17, there is provided an aircraft skin paint removal device comprising: a parameter acquisition module 1710, a first determination module 1720, a second determination module 1730, and a skin paint removal module 1740, wherein:

a parameter obtaining module 1710, configured to obtain a finish parameter and a primer parameter of the aircraft skin;

a first determining module 1720, configured to construct a skin simulation model of the aircraft skin according to the topcoat parameters and the primer parameters; performing finishing paint removal simulation on the skin simulation model through single pulses with different laser energy densities to obtain a first paint removal parameter for removing the finishing paint of the aircraft skin;

a second determining module 1730, configured to input primer parameters into a predetermined primer removal model, to obtain a second paint removal parameter for removing the primer of the aircraft skin;

The skin paint removal module 1740 is configured to remove the top coat of the aircraft skin by using the first paint removal parameter, and remove the primer of the aircraft skin by using the second paint removal parameter, so as to obtain the paint-removed aircraft skin.

In one embodiment, the first determining module 1720 is further configured to perform a finishing coat removal simulation on the skin simulation model through single pulses with different laser energy densities, so as to obtain a temperature change curve graph and a thermal stress change curve graph of the skin simulation model in the corresponding finishing coat removal process under the action of each laser energy density respectively; the thermal stress change curve graph represents the change rule diagram of the thermal stress of the simulated finish paint along with the laser action depth; the method comprises the steps of obtaining finishing coat removal mechanism information, and analyzing a temperature change curve graph and a thermal stress change curve graph which are obtained under each laser energy density based on the finishing coat removal mechanism information to obtain a laser energy density range of finishing coats for removing aircraft skins; one of the laser energy densities is arbitrarily selected within the laser energy density range as a first removal parameter for removing a top-coat of an aircraft skin.

In one embodiment, the first determination module 1720 is further configured to construct a sample simulation model of the aircraft skin sample; performing finish paint removal simulation on the sample simulation model through single pulses with different laser energy densities to obtain a first surface topography of the finish paint of the sample simulation model; carrying out energy spectrum analysis on the sample simulation model after the finish paint is removed to obtain a first energy spectrum of the finish paint of the sample simulation model after the laser action; performing a plasma shock wave test on the finish paint of the sample simulation model to obtain a first stress distribution cloud picture of the shock wave, wherein the stress of the first stress distribution cloud picture changes along with time in the process of transmitting the finish paint of the sample simulation model; and determining finishing paint removal mechanism information based on the first surface topography map, the first energy spectrogram and the first stress distribution cloud map.

In one embodiment, the apparatus further includes a model determining module configured to obtain primer removal mechanism information of the aircraft skin, and determine a first relation between a total removal depth of the primer by the laser pulse and a total thickness of the primer according to the primer removal mechanism information; acquiring a second relation between the laser energy density and the ablation depth and a third relation between the laser energy density and the thickness of the last primer layer in the primer removing process; and carrying out fusion treatment on the first relational expression, the second relational expression and the third relational expression to obtain a primer removal model.

In one embodiment, the model determination module is further configured to construct a sample simulation model of the aircraft skin sample; performing primer removal simulation on the sample simulation model through a plurality of groups of laser pulse parameters to obtain a second surface topography of the primer of the sample simulation model; the laser pulse parameters include laser energy density and laser pulse number; carrying out energy spectrum analysis on the sample simulation model after the primer is removed to obtain a second energy spectrum of the primer of the sample simulation model after the laser action; performing a plasma shock wave test on the primer of the sample simulation model to obtain a second stress distribution cloud picture of the shock wave, wherein the second stress distribution cloud picture changes with time in the internal transmission process of the primer and the substrate of the sample simulation model; and determining primer removal mechanism information based on the second surface topography map, the second energy spectrogram and the second stress distribution cloud map.

In one embodiment, the model determining module is further used for performing primer removal simulation on the sample simulation model after finishing coat removal by adopting different laser energy densities to obtain a relation diagram between the laser energy densities and the highest temperature and ablation depth of the primer surface; fitting the simulation data in the relation graph to obtain a second relation between the laser energy density and the ablation depth and a third relation between the laser energy density and the thickness of the last primer layer under the action of single pulse.

In one embodiment, the primer removal model is a relationship with respect to the number of laser pulses and the laser energy density, and the laser energy density has a range of values; the second determining module 1730 is further configured to input primer parameters into a primer removal model, and determine, within a range of values of the laser energy density, a target laser pulse number and a target laser energy density for removing the primer of the aircraft skin, as a second paint removal parameter.

The various modules in the aircraft skin paint removal device described above may be implemented in whole or in part by software, hardware, and combinations thereof. The above modules may be embedded in hardware or may be independent of a processor in the computer device, or may be stored in software in a memory in the computer device, so that the processor may call and execute operations corresponding to the above modules.

In one embodiment, a computer device is provided, which may be a terminal, and the internal structure thereof may be as shown in fig. 18. The computer device includes a processor, a memory, a communication interface, a display screen, and an input device connected by a system bus. Wherein the processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The communication interface of the computer device is used for carrying out wired or wireless communication with an external terminal, and the wireless mode can be realized through WIFI, a mobile cellular network, NFC (near field communication) or other technologies. The computer program is executed by a processor to implement an aircraft skin paint removal method. The display screen of the computer equipment can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer equipment can be a touch layer covered on the display screen, can also be keys, a track ball or a touch pad arranged on the shell of the computer equipment, and can also be an external keyboard, a touch pad or a mouse and the like.

It will be appreciated by those skilled in the art that the structure shown in fig. 18 is merely a block diagram of a portion of the structure associated with the present application and is not limiting of the computer device to which the present application is applied, and that a particular computer device may include more or fewer components than shown, or may combine certain components, or have a different arrangement of components.

In an embodiment, there is also provided a computer device comprising a memory and a processor, the memory having stored therein a computer program, the processor implementing the steps of the method embodiments described above when the computer program is executed.

In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored which, when executed by a processor, carries out the steps of the method embodiments described above.

In an embodiment, a computer program product is provided, comprising a computer program which, when executed by a processor, implements the steps of the method embodiments described above.

It should be noted that, the user information (including, but not limited to, user equipment information, user personal information, etc.) and the data (including, but not limited to, data for analysis, stored data, presented data, etc.) referred to in the present application are information and data authorized by the user or sufficiently authorized by each party, and the collection, use and processing of the related data are required to comply with the related laws and regulations and standards of the related countries and regions.

Those skilled in the art will appreciate that implementing all or part of the above described methods may be accomplished by way of a computer program stored on a non-transitory computer readable storage medium, which when executed, may comprise the steps of the embodiments of the methods described above. Any reference to memory, database, or other medium used in the various embodiments provided herein may include at least one of non-volatile and volatile memory. The nonvolatile Memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash Memory, optical Memory, high density embedded nonvolatile Memory, resistive random access Memory (ReRAM), magnetic random access Memory (Magnetoresistive Random Access Memory, MRAM), ferroelectric Memory (Ferroelectric Random Access Memory, FRAM), phase change Memory (Phase Change Memory, PCM), graphene Memory, and the like. Volatile memory can include random access memory (Random Access Memory, RAM) or external cache memory, and the like. By way of illustration, and not limitation, RAM can be in the form of a variety of forms, such as static random access memory (Static Random Access Memory, SRAM) or dynamic random access memory (Dynamic Random Access Memory, DRAM), and the like. The databases referred to in the various embodiments provided herein may include at least one of relational databases and non-relational databases. The non-relational database may include, but is not limited to, a blockchain-based distributed database, and the like. The processors referred to in the embodiments provided herein may be general purpose processors, central processing units, graphics processors, digital signal processors, programmable logic units, quantum computing-based data processing logic units, etc., without being limited thereto.

The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples only represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the present application. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application shall be subject to the appended claims.

Claims

1. A method of paint removal for an aircraft skin, the method comprising:

obtaining finishing coat parameters and primer parameters of the aircraft skin;

2. The method of claim 1, wherein the performing a topcoat-removal simulation on the skin simulation model with single pulses of different laser energy densities to obtain a first paint-removal parameter for removing the topcoat of the aircraft skin comprises:

3. The method of claim 2, wherein the obtaining topcoat removal mechanism information comprises:

4. The method of claim 1, wherein the primer removal model is determined by:

5. The method of claim 4, wherein the obtaining primer removal mechanism information for the aircraft skin comprises:

6. The method of claim 5, wherein the obtaining a second relationship between laser energy density and ablation depth and a third relationship between laser energy density and thickness of the final primer layer during the removing of the primer comprises:

7. The method of claim 1, wherein the primer removal model is a relationship with respect to a number of laser pulses and a laser energy density, and the laser energy density has a range of values;

8. An aircraft skin paint removal device, the device comprising:

the first determining module is used for constructing a skin simulation model of the corresponding aircraft skin according to the finish paint parameters and the primer parameters; performing finish paint removal simulation on the skin simulation model through single pulses with different laser energy densities to obtain a first paint removal parameter for removing the finish paint of the aircraft skin;

9. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor, when executing the computer program, carries out the steps of the aircraft skin paint removal method according to any one of claims 1 to 7.

10. A computer-readable storage medium, on which a computer program is stored, characterized in that the computer program, when being executed by a processor, carries out the steps of the aircraft skin paint removal method according to any one of claims 1 to 7.

11. A computer program product comprising a computer program, characterized in that the computer program, when executed by a processor, implements the steps of the aircraft skin paint removal method according to any one of claims 1 to 7.