Ultraviolet laser cleaning paint layer simulation method based on photo-thermal-photochemical effect

Abstract

The invention provides an ultraviolet laser cleaning paint layer simulation method based on a photo-thermal-photochemical effect. The method takes into account the photo-thermal and photochemical effects of the ultraviolet laser as well as plasma formation and plasma shielding effects during the laser cleaning process. According to the method, a photo-thermal model of ultraviolet laser, a photochemical model of ultraviolet laser and a photo-thermal-photochemical model of ultraviolet laser are established, and numerical simulation is carried out. And the light spot size, the corrosion depth and the temperature change effect of the ultraviolet laser cleaning paint layer under different energy densities of the ultraviolet laser are obtained.

Description

Technical Field

[0001] The invention relates to the technical field of laser cleaning, and in particular to a simulation method for cleaning a paint layer using ultraviolet laser based on photothermal-photochemical effects. Background Art

[0002] The paint layer on the surface of aircraft and ships is often subjected to the ravages of intense environments such as alternating hot and cold, and is hit by foreign objects and eroded by air (water) flow, causing various forms of damage such as cracking, aging, peeling and shedding, and then losing its original performance. In order to meet the stability, safety and aesthetics of aircraft and ships, the original paint layer surface of the damaged area must be removed first, and then new paint must be sprayed.

[0003] Conventional surface cleaning methods include mechanical cleaning, high-pressure water jets, and chemical cleaning. These methods have their own advantages and disadvantages. Mechanical cleaning mainly includes manual cleaning methods and mechanical cleaning methods such as shot blasting. Manual mechanical cleaning methods are labor-intensive, require multiple polishings, and have high technical requirements for workers. Mechanical methods such as shot blasting and sand blasting have a large impact on the surface and can cause secondary pollution to the environment. High-pressure water jets can also have a large impact on the surface of the substrate, damage instruments and equipment, and cause rust and other problems. Chemical cleaning can cause serious pollution to the environment, and the discharge of waste liquid is also a difficult problem.

[0004] Laser cleaning technology has the characteristics of non-contact, precise and easy to control, and high efficiency. It has unique advantages over other cleaning methods in cleaning the surfaces of aircraft and ships. Ultraviolet laser has a short wavelength and high photon energy. When it interacts with materials, it has both photothermal and photochemical effects. Using ultraviolet laser cleaning can not only achieve better cleaning effects, but also is not easy to damage the substrate.

[0005] At present, the mechanism of UV laser cleaning is still unclear and still in the exploration stage. Laser cleaning mainly focuses on the photothermal effect of laser. Therefore, clarifying the mechanism of UV laser cleaning and simulation methods and obtaining the mechanism of action of UV laser cleaning are important issues to be solved.

[0006] In previous studies, only the photothermal effect was considered in the laser cleaning research, and the photothermal and photochemical effects of the ultraviolet laser were not considered. Therefore, in the modeling and simulation process of laser cleaning, the state of laser cleaning cannot be truly reflected. Previous studies ignored the photochemical effect of ultraviolet lasers, making it difficult to obtain an accurate simulation of laser cleaning.

[0007] In addition, previous studies have not considered the formation of plasma and the plasma shielding effect during the laser cleaning process. This is a more important point in the UV laser cleaning process. Without considering the formation of plasma and the plasma shielding effect, there is a certain gap between the obtained laser energy density and the actual value, which will affect the accuracy of laser cleaning modeling and simulation. Therefore, how to comprehensively consider the physical process of laser cleaning, take into account the parameter variables that affect the simulation results, accurately establish the laser cleaning model, and conduct simulation analysis is an important issue that needs to be solved urgently. Summary of the invention

[0008] The purpose of the present invention is to address the problems existing in the existing laser cleaning technology: "in the laser cleaning process, only the photothermal effect is considered, and the photothermal and photochemical effects of the ultraviolet laser are not considered", and "the formation of plasma and the plasma shielding effect generated in the laser cleaning process are not considered". A simulation method for ultraviolet laser cleaning of paint layers based on photothermal-photochemical effects is proposed.

[0009] The present invention is implemented by the following technical scheme. The present invention proposes a UV laser paint layer cleaning simulation method based on photothermal-photochemical effect, and the method comprises the following steps:

[0010] Step 1: Construct a photothermal effect model for UV laser cleaning of paint layers; construct a surface heat transfer equation, establish a UV laser equation, and establish functions of energy, plasma expansion rate, and digestion coefficient based on plasma formation and shielding effects;

[0011] Step 2: Construct a photochemical effect model for UV laser cleaning of paint layers; establish an equation for the photochemical ablation rate during UV laser cleaning;

[0012] Step 3: Construct a photothermal-photochemical effect model for UV laser cleaning of paint layers; introduce weight coefficients R(J) and H(J) to establish a photothermal-photochemical ablation rate model;

[0013] Step 4: Based on the photothermal-photochemical effect, carry out UV laser cleaning paint layer simulation.

[0014] Furthermore, in step 1, during the laser cleaning process, the surface heat transfer equation is expressed as:

[0015]

[0016] Where ρ, C p , k1, h, ε and σ are density, specific heat capacity, thermal conductivity, heat transfer coefficient, emissivity and Boltzmann constant, respectively.

[0017] Furthermore, in step 1, the laser satisfies the Gaussian pulse, and its equation expression is:

[0018] G(t)=I0(t / t1) r exp[(1-t / t1)]

[0019] Where I0 is the maximum light intensity, β is the time factor, and t1 is the duration;

[0020] The maximum light intensity I0 is expressed as:

[0021] I0=P / (t0·f·A)

[0022] Where P is the average output power of the laser, f is the pulse frequency, and A is the area of ​​the spot;

[0023] The energy of the laser output is expressed as:

[0024] I0(x,y,t)=I0·G(t)·g(x,y).

[0025] Further, in step 1, according to the formation of plasma and the shielding effect, Q is expressed as:

[0026]

[0027] The plasma absorption energy is expressed as:

[0028] s=exp(-αΛ)

[0029] in,

[0030] Λ=C s t1

[0031]

[0032] Where R is the surface reflectivity, C s is the plasma expansion rate, k is the plasma extinction coefficient, and λ is the laser wavelength; the boundary conditions during laser cleaning are expressed as:

[0033] T(x,y,z,t)| t＝0 =T0

[0034] T ambient =T0

[0035] where T(x,y,z,t) is the temperature at any point in the model, T ambient is the ambient temperature;

[0036] In the photothermal cleaning process, the function of the digestion coefficient is expressed as:

[0037]

[0038] Where δ is the ablation rate, k0 is the coefficient factor, and α effis the absorption coefficient, F is the incident laser energy, and F T is the laser threshold.

[0039] Further, in step 2, according to the photochemical action during the laser cleaning process, the ablation rate equation is expressed as:

[0040]

[0041] Where δ is the ablation rate, α eff is the absorption coefficient, F is the incident laser energy, and F T is the laser threshold.

[0042] Further, in step 3, the photothermal-photochemical ablation rate model is expressed as:

[0043] δ 总 =δ 光热 +δ 光化学

[0044] in,

[0045]

[0046]

[0047] Where E is the effective activation energy.

[0048] Furthermore, considering that the photothermal and photochemical effects are constantly changing during the laser cleaning process, the weight coefficients R(J) and H(J) are introduced; at this time, the photothermal-photochemical ablation rate model is expressed as:

[0049] δ 总 =R(J)δ 光热 +H(J)δ 光化学 .

[0050] Furthermore, combining the photothermal and photochemical effects, the specific expression of the photothermal-photochemical ablation rate model is:

[0051]

[0052] The present invention also proposes an electronic device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the ultraviolet laser paint layer cleaning simulation method based on photothermal-photochemical effect are implemented.

[0053] The present invention also proposes a computer-readable storage medium for storing computer instructions, which, when executed by a processor, implement the steps of a simulation method for ultraviolet laser cleaning of paint layers based on photothermal-photochemical effects.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] The present invention proposes a simulation method for ultraviolet laser cleaning of paint layer based on photothermal-photochemical effect, which takes into account the photothermal and photochemical effects of ultraviolet laser as well as the plasma formation and plasma shielding effect during laser cleaning. The method establishes a photothermal model of ultraviolet laser, a photochemical model of ultraviolet laser and a photothermal-photochemical model of ultraviolet laser, and carries out numerical simulation. The spot size, ablation depth and temperature change effect of ultraviolet laser cleaning of paint layer under different energy densities of ultraviolet laser are obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0057] Figure 1 It is a flow chart of a UV laser cleaning simulation method based on photothermal-photochemical effect described in the present invention.

[0058] Figure 2 This is a graph showing the relationship between the depth of paint removal during UV laser cleaning and the temperature.

[0059] Figure 3 The laser energy density is 2J / cm 2 , 3D graph of spot size, ablation depth and temperature change of UV laser cleaning paint layer.

[0060] Figure 4 The laser energy density is 3J / cm 2 , 3D graph of spot size, ablation depth and temperature change of UV laser cleaning paint layer.

[0061] Figure 5 The laser energy density is 4J / cm 2 , 3D graph of spot size, ablation depth and temperature change of UV laser cleaning paint layer. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0063] Combination Figure 1-Figure 5 The present invention proposes a UV laser paint layer cleaning simulation method based on photothermal-photochemical effect, the method comprising the following steps:

[0064] Step 1: Construct a photothermal effect model for UV laser cleaning of paint layers; construct a surface heat transfer equation, establish a UV laser equation, and establish functions of energy, plasma expansion rate, and digestion coefficient based on plasma formation and shielding effects;

[0065] Step 2: Construct a photochemical effect model for UV laser cleaning of paint layers; establish an equation for the photochemical ablation rate during UV laser cleaning;

[0066] Step 3: Construct a photothermal-photochemical effect model for UV laser cleaning of paint layers; introduce weight coefficients R(J) and H(J) to establish a photothermal-photochemical ablation rate model;

[0067] Step 4: Based on the photothermal-photochemical effect, carry out UV laser cleaning paint layer simulation.

[0068] In step 1, during laser cleaning, the surface heat transfer equation is expressed as:

[0069]

[0070] Where ρ, C p , k1, h, ε and σ are density, specific heat capacity, thermal conductivity, heat transfer coefficient, emissivity and Boltzmann constant, respectively.

[0071] In step 1, the laser satisfies the Gaussian pulse, and its equation expression is:

[0072] G(t)=I0(t / t1) p exp[β(1-t / t1)]

[0073] Where I0 is the maximum light intensity, β is the time factor, and t1 is the duration;

[0074] The maximum light intensity I0 is expressed as:

[0075] I0=P / (t0·f·A)

[0076] Where P is the average output power of the laser, f is the pulse frequency, and A is the area of ​​the spot;

[0077] The energy of the laser output is expressed as:

[0078] I0(x,y,t)=I0·G(t)·g(x,y).

[0079] In step 1, based on the formation of plasma and the shielding effect, Q is expressed as:

[0080]

[0081] The plasma absorption energy is expressed as:

[0082] s=exp(-αΛ)

[0083] in,

[0084] Λ=C s t1

[0085]

[0086] Where R is the surface reflectivity, C s is the plasma expansion rate, k is the plasma extinction coefficient, and λ is the laser wavelength; the boundary conditions during laser cleaning are expressed as:

[0087] T(x,y,z,t)| t＝0 =T0

[0088] T ambient =T0

[0089] where T(x,y,z,t) is the temperature at any point in the model, T ambient is the ambient temperature;

[0090] In the photothermal cleaning process, the function of the digestion coefficient is expressed as:

[0091]

[0092] Where δ is the ablation rate, k0 is the coefficient factor, and α eff is the absorption coefficient, F is the incident laser energy, and F T is the laser threshold.

[0093] In step 2, based on the photochemical action during laser cleaning, the ablation rate equation is expressed as:

[0094]

[0095] Where δ is the ablation rate, α eff is the absorption coefficient, F is the incident laser energy, and F T is the laser threshold.

[0096] In step 3, the photothermal-photochemical ablation rate model is expressed as:

[0097] δ 总 =δ 光热 +δ 光化学

[0098] in,

[0099]

[0100]

[0101] Where E is the effective activation energy.

[0102] Considering that the photothermal and photochemical effects are constantly changing during the laser cleaning process, the weight coefficients R(J) and H(J) are introduced; at this time, the photothermal-photochemical ablation rate model is expressed as:

[0103] δ 总 =R(J)δ 光热 +H(J)δ 光化学 .

[0104] Combining the photothermal and photochemical effects, the specific expression of the photothermal-photochemical ablation rate model is:

[0105]

[0106] The present invention also proposes an electronic device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the ultraviolet laser paint layer cleaning simulation method based on photothermal-photochemical effect are implemented.

[0107] The present invention also proposes a computer-readable storage medium for storing computer instructions, which, when executed by a processor, implement the steps of a simulation method for ultraviolet laser cleaning of paint layers based on photothermal-photochemical effects.

[0108] The memory in the embodiments of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), and direct RAM bus RAM (DRRAM). It should be noted that the memory of the method described in the present invention is intended to include, but is not limited to, these and any other suitable types of memory.

[0109] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions may be transmitted from a website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (digital subscriber line, DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website site, computer, server or data center. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated. The available medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a high-density digital video disc (DVD)), or a semiconductor medium (eg, a solid state disc (SSD)).

[0110] In the implementation process, each step of the above method can be completed by an integrated logic circuit of hardware in a processor or an instruction in the form of software. The steps of the method disclosed in conjunction with the embodiment of the present application can be directly embodied as a hardware processor for execution, or a combination of hardware and software modules in a processor for execution. The software module can be located in a storage medium mature in the art such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. The storage medium is located in a memory, and the processor reads the information in the memory and completes the steps of the above method in conjunction with its hardware. To avoid repetition, it is not described in detail here.

[0111] It should be noted that the processor in the embodiment of the present application can be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method embodiment can be completed by an integrated logic circuit of hardware in the processor or an instruction in the form of software. The above processor can be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components. The methods, steps and logic block diagrams disclosed in the embodiments of the present application can be implemented or executed. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor, etc. The steps of the method disclosed in the embodiment of the present application can be directly embodied as a hardware decoding processor to perform, or the hardware and software modules in the decoding processor can be combined and performed. The software module can be located in a mature storage medium in the field such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. The storage medium is located in a memory, and the processor reads the information in the memory and completes the steps of the above method in combination with its hardware.

[0112] The above is a detailed introduction to the ultraviolet laser paint layer cleaning simulation method based on photothermal-photochemical effect proposed in the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for general technical personnel in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A UV laser paint cleaning simulation method based on photothermal-photochemical effect, characterized in that: The method comprises the following steps: Step 1: Construct a photothermal effect model for UV laser cleaning of paint layers; construct a surface heat transfer equation, establish a UV laser equation, and establish functions of energy, plasma expansion rate, and digestion coefficient based on plasma formation and shielding effects; Step 2: Construct a photochemical effect model for UV laser cleaning of paint layers; establish an equation for the photochemical ablation rate during UV laser cleaning; Step 3: Construct a photothermal-photochemical effect model for UV laser cleaning of paint layers; introduce weight coefficients R(J) and H(J) to establish a photothermal-photochemical ablation rate model; Step 4: Based on the photothermal-photochemical effect, carry out UV laser cleaning paint layer simulation.

2. The method according to claim 1, characterized in that In step 1, during laser cleaning, the surface heat transfer equation is expressed as: where ρ, Cp, k1, h, ε and σ are density, specific heat, thermal conductivity, heat transfer coefficient, emissivity and Boltzmann constant, respectively.

3. The method according to claim 2, characterized in that In step 1, the laser satisfies the Gaussian pulse, and its equation expression is: G(t)=I0(t / t1) p ·exp[β(1-t / t1)] Where I0 is the maximum light intensity, β is the time factor, and t1 is the duration; The maximum light intensity I0 is expressed as: I0=P / (t0·f·A) Where P is the average output power of the laser, f is the pulse frequency, and A is the area of ​​the spot; The energy of the laser output is expressed as: I0(x,y,t)=I0·G(t)·g(x,y).

4. The method according to claim 3, characterized in that In step 1, based on the formation of plasma and the shielding effect, Q is expressed as: The plasma absorption energy is expressed as: s=exp(-αΛ) in, Λ=C s t1 Where R is the surface reflectivity, C s is the plasma expansion rate, k is the plasma extinction coefficient, and λ is the laser wavelength; The boundary conditions during laser cleaning are expressed as: T(x,y,z,t)| t＝0 =T0 T ambient =T0 where T(x,y,z,t) is the temperature at any point in the model, T ambient is the ambient temperature; In the photothermal cleaning process, the function of the digestion coefficient is expressed as: Where δ is the ablation rate, k0 is the coefficient factor, and α eff is the absorption coefficient, F is the incident laser energy, and F T is the laser threshold.

5. The method according to claim 1, characterized in that In step 2, based on the photochemical action during laser cleaning, the ablation rate equation is expressed as: Where δ is the ablation rate, α eff is the absorption coefficient, F is the incident laser energy, and F T is the laser threshold.

6. The method according to claim 1, characterized in that In step 3, the photothermal-photochemical ablation rate model is expressed as: d 总 =d 光热 +d 光化学 in, Where E is the effective activation energy.

7. The method according to claim 6, characterized in that Considering that the photothermal and photochemical effects are constantly changing during the laser cleaning process, the weight coefficients R(J) and H(J) are introduced; at this time, the photothermal-photochemical ablation rate model is expressed as: d 总 =R(J)δ 光热 +H(J)δ 光化学 。 8. The method according to claim 7, characterized in that Combining the photothermal and photochemical effects, the specific expression of the photothermal-photochemical ablation rate model is:

9. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 8 are implemented.

10. A computer-readable storage medium for storing computer instructions, characterized in that: When the computer instructions are executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

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