Corrosion simulation analysis method for aircraft aluminum alloy connecting structure

Abstract

The invention belongs to the technical field of airplane aluminum alloy connecting structure corrosion analysis, and particularly relates to an airplane aluminum alloy connecting structure corrosion simulation analysis method which comprises the following steps: step 1, establishing a simulation model of a self-corrosion problem of an airplane aluminum alloy metal material; step 2, performing multi-working-condition analogue simulation by using the simulation model for the self-corrosion problem of the aircraft aluminum alloy metal material, analyzing an analogue simulation result, and correcting the simulation model; 3, based on the simulation model of the self-corrosion problem of the aircraft aluminum alloy metal material, establishing a corrosion simulation model of the aircraft aluminum alloy connecting structure; and 4, carrying out multi-working-condition corrosion simulation analysis on the aircraft aluminum alloy connecting structure by using the aircraft aluminum alloy connecting structure corrosion simulation model.

Description

Technical Field

[0001] The present application belongs to the technical field of corrosion analysis of aircraft aluminum alloy connection structures, and specifically relates to a corrosion simulation analysis method for aircraft aluminum alloy connection structures. Background Art

[0002] The aviation industry generally adds elements to smelt aluminum into aluminum alloys to improve the structural strength of aircraft. This will produce a non-uniform microstructure and induce local corrosion, especially pitting corrosion.

[0003] For many years, the understanding and prediction of the initiation and development of pitting corrosion in aluminum alloys has been a hot topic and difficulty in research. The corrosion rate obtained only by Faraday's law is not comprehensive enough and even inaccurate for aluminum alloy materials on aircraft.

[0004] Laboratory accelerated corrosion tests are carried out on key corrosion parts of aircraft, such as tensile plates of typical connection structures. The laboratory acceleration spectrum obtained by engineering equivalent is usually used and carried out in a cyclic infiltration manner. By comparing and analyzing the data from real long-term natural environment exposure tests, the accuracy of the laboratory acceleration spectrum is verified and the corrosion resistance of the aircraft aluminum alloy connection structure is obtained.

[0005] However, the typical environmental conditions of actual aircraft service are complex and changeable, with many critical corrosion areas. The time period for determining and verifying the engineering equivalent relationship of laboratory accelerated spectrum tests is long, the cost is high, and the economic efficiency is poor.

[0006] This application is proposed in view of the above-mentioned technical defects. Summary of the invention

[0007] The purpose of this application is to provide a corrosion simulation analysis method for aircraft aluminum alloy connection structures to overcome or alleviate at least one of the known technical defects.

[0008] The technical solution of this application is: A corrosion simulation analysis method for an aircraft aluminum alloy connection structure, comprising: Step 1: Establish a simulation model for the self-corrosion problem of aircraft aluminum alloy metal materials; Step 2: Using the simulation model of the self-corrosion problem of aircraft aluminum alloy metal materials, conduct multi-condition simulation, analyze the simulation results, and correct the simulation model; Step 3: Based on the simulation model of the self-corrosion problem of aircraft aluminum alloy metal materials, a simulation model of corrosion of aircraft aluminum alloy connection structure is established; Step 4: Use the aircraft aluminum alloy connection structure corrosion simulation model to perform multi-condition corrosion simulation analysis on the aircraft aluminum alloy connection structure.

[0009] Optionally, in the above-mentioned aircraft aluminum alloy connection structure corrosion simulation analysis method, in step 1, a simulation model for the self-corrosion problem of aircraft aluminum alloy metal materials is established, and basic assumptions are established: The oxygen reduction reaction occurs only on the surface of the second phase, and the active dissolution of the metal occurs only in the matrix; The electrolyte is an infinitely dilute solution; The passive film does not dissolve and does not consider Destructive effect on the passivation film; The influence of the double electric layer on the electrode surface is not considered. All the physical and chemical processes considered include electrode reaction, material transport and homogeneous reaction in the electrolyte, and deposition of surface corrosion products. Ignoring the adsorption and desorption process of ions at the interface, the interface ion concentration distribution is completely controlled by diffusion and electromigration; The mass transfer of electrolyte only considers diffusion and electromigration, and does not consider convection; Only the microscopic galvanic corrosion under open circuit conditions is considered, no external voltage is applied, and the electrode reaction is driven by the galvanic effect between IMPs and the substrate; Consider the changes of the electrode surface over time due to active dissolution, and consider the impact of its changes on corrosion expansion; Considering the passivation effect of corrosion product deposition on active reaction surfaces and its influence on subsequent corrosion processes, Once deposited, it will not dissolve.

[0010] Optionally, in the above-mentioned aircraft aluminum alloy connection structure corrosion simulation analysis method, in step 1, in establishing a simulation model for the self-corrosion problem of aircraft aluminum alloy metal materials, it is assumed that the thickness of the diffusion layer is 10 μm; The initial values ​​of the ion concentrations on the upper surface of the electrolyte domain are consistent with the ion concentrations of the electrolyte solution; The boundaries on both sides of the electrolyte domain are insulating boundaries, and the lower surface serves as the electrode surface.

[0011] Optionally, in the above-mentioned aircraft aluminum alloy connection structure corrosion simulation analysis method, in step 2, the simulation results are analyzed, including Single phase mixed, The simulation results of single-phase inclusions, multi-phase inclusions and aluminum alloy self-corrosion are analyzed.

[0012] Optionally, in the above-mentioned aircraft aluminum alloy connection structure corrosion simulation analysis method, step three is specifically: Based on the simulation model of the self-corrosion problem of aircraft aluminum alloy metal materials, a simulation model of galvanic corrosion at the specimen level of aircraft aluminum alloy connection structure is established. The coupling potential and galvanic current are obtained by simulation calculation, and compared and analyzed with the test results, and then the simulation model of galvanic corrosion at the specimen level of aircraft aluminum alloy connection structure is corrected. Based on the specimen-level galvanic corrosion simulation model of aircraft aluminum alloy connection structure, a component-level galvanic corrosion simulation model of aircraft aluminum alloy connection structure is established, and simulation calculations are performed to obtain the potential distribution, corrosion morphology and microstructure morphology. The results are compared and analyzed with the test results, and then the component-level galvanic corrosion simulation model of aircraft aluminum alloy connection structure is corrected to obtain the corrosion simulation model of aircraft aluminum alloy connection structure.

[0013] This application has at least the following beneficial technical effects: Provided is a corrosion simulation analysis method for an aircraft aluminum alloy connection structure. The method adopts simulation means and a corrosion simulation model of an aircraft aluminum alloy connection structure to perform multi-condition corrosion simulation analysis on the aircraft aluminum alloy connection structure. The method can quickly predict the potential distribution, corrosion rate, corrosion deformation, mass loss rate, etc. of the aircraft aluminum alloy connection structure, find the dangerous position of the structure, and has low cost. The method can effectively guide the design and improvement of the aircraft aluminum alloy connection structure, as well as guide the maintenance of the aircraft aluminum alloy connection structure in practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic diagram of a corrosion simulation analysis method for an aircraft aluminum alloy connection structure provided in an embodiment of the present application; Figure 2 It is a schematic diagram of a geometric model of micro-galvanic corrosion of aircraft aluminum alloy metal materials self-corrosion provided in an embodiment of the present application; Figure 3 It is a schematic diagram of a geometric model for constructing the normal direction of an aluminum alloy interface by introducing a level set function provided in an embodiment of the present application; Figure 4 yes Figure 3 A partial enlarged view of; Figure 5 yes Figure 3 B is a partial enlarged view; Figure 6 yes Figure 3 A partial enlarged view of C.

[0015] In order to better illustrate the present embodiment, some contents of the drawings may be omitted, enlarged or reduced, which is only used for illustrative purposes and should not be construed as limiting the present application. DETAILED DESCRIPTION

[0016] In order to make the technical solution and advantages of the present application clearer, the technical solution of the present application will be described in further detail in detail and in detail with reference to the accompanying drawings. It can be understood that the specific embodiments described here are only partial embodiments of the present application, which are only used to explain the present application, not to limit the present application. It should be noted that, for the convenience of description, only the parts related to the present application are shown in the accompanying drawings, and other related parts can refer to the general design.

[0017] In addition, unless otherwise defined, the technical terms or scientific terms used in the description of this application should be the common meanings understood by those skilled in the art in the field to which this application belongs. The term "include" used in the description of this application means that the concepts appearing before the term include the concepts listed after the term and their equivalents, without excluding other related concepts.

[0018] In addition, the words indicating orientation used in the description of this application are only used to indicate relative directions or positional relationships. When the absolute position of the object being described changes, its relative positional relationship may also change accordingly. It should also be noted that, unless otherwise clearly specified and limited, the words "installation", "connection" and other similar words used in the description of this application should be understood in a broad sense. For example, the connection can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. Technical personnel in the field can understand its specific meaning in this application according to the specific circumstances.

[0019] With the development and improvement of computer technology and corrosion electrochemical theory, corrosion simulation technology can accurately predict the corrosion degree of aircraft structures under different working conditions in a relatively short time. Therefore, the corrosion simulation analysis method can be used to analyze the corrosion resistance of aircraft aluminum alloy connection structures.

[0020] However, corrosion simulation analysis is still in its infancy and lacks effective tools and means. The adaptive design of aircraft corrosion environment mainly relies on the experience of designers and physical verification in the research and development stage. However, the simulation analysis cycle is long and the cost is high. In addition, the existing methods for calculating the self-corrosion problem of metal materials are only applicable to pure metals. For aluminum alloy materials on aircraft, they are not comprehensive and even inaccurate.

[0021] Based on the above, this application provides a corrosion simulation analysis method for aircraft aluminum alloy connection structure based on the numerical simulation theory of the corrosion simulation analysis method of the damage dynamics equation, and conducts comparative analysis on mainstream simulation tools, such as Figure 1 shown.

[0022] Step 1: Establish a simulation model for the self-corrosion problem of aircraft aluminum alloy metal materials.

[0023] For aluminum alloys, their self-corrosion behavior is mostly localized corrosion in the early stage, such as pitting. The corrosion rate obtained by Faraday's law is only applicable to pure metals, which is not comprehensive or even inaccurate for aluminum alloy materials. The present invention considers the self-corrosion problem of aircraft aluminum alloy metal materials from the perspective of the material's microstructure and comprehensively considers the influence of the second phase organization to establish the basic assumptions of the simulation model, as follows: The oxygen reduction reaction occurs only on the surface of the second phase, and the active dissolution of the metal occurs only in the matrix; The electrolyte is an infinitely dilute solution, that is, the substance in the solution Activity The concentration can be directly used to make a substitution; The passive film does not dissolve and does not consider Destructive effect on the passivation film; Without considering the influence of the double layer on the electrode surface, all physical and chemical processes considered include electrode reaction, material transport (diffusion and migration) in the electrolyte and homogeneous reaction ( Hydrolysis and Composite reaction between them) and deposition of surface corrosion products; Ignore the adsorption and desorption process of ions at the interface, and assume that the interface ion concentration distribution is completely controlled by diffusion and electromigration; The mass transfer of electrolyte only considers diffusion and electromigration, and does not consider convection; Only the microscopic galvanic corrosion under open circuit conditions is considered, no external voltage is applied, and the electrode reaction is driven by the galvanic effect between IMPs and the substrate; Consider the changes of the electrode surface over time due to active dissolution, and consider the impact of its changes on corrosion expansion; Considering the passivation effect of corrosion product deposition on active reaction surfaces and its influence on subsequent corrosion processes, Once deposited, it will not dissolve.

[0024] Based on the basic assumptions of the simulation model, the inclusion phase and Under the combined action, the aluminum alloy expands in the depth direction, and a mathematical characterization of the electrode reaction, homogeneous reaction and steric effect of corrosion products in microgalvanic corrosion is established.

[0025] Microgalvanic corrosion geometry model Figure 2 As shown, the electrolyte is a 0.1 mol / L NaCl neutral solution.

[0026] For the electrode reaction, it is assumed that the Al substrate covered by the passivation film is inactive, that is, neither active dissolution occurs nor oxygen reduction reaction is supported. In a neutral solution, oxygen reduction and active dissolution of aluminum are carried out through the following electrode reactions: ; .

[0027] For homogeneous reactions, the Nernst-Planck equation in the form of conservation of species in the entire electrolyte domain is used as the governing equation: ; in, For the Species ion concentration; For time; For the Species ion diffusion coefficient; For the The charge number of the ion; is the gas constant; is the absolute temperature; is the Faraday constant; is the potential gradient; For the The reaction The stoichiometric coefficient of the species ion; For the The forward reaction rate constant is the position coordinate; For the The reverse reaction rate constant of a reaction; is the number of homogeneous reactions; is the number of positive reaction ions; is the number of reverse reaction ions.

[0028] For the steric effect of corrosion products, it is assumed that Concentration greater than its solubility When the concentration is 100 times of that, the supersaturation state is reached. Crystals will precipitate, and The precipitation process is fast enough. The deposition rate is equal to The formation speed makes The concentration will not increase any further, as shown below: ; in, for The deposition rate; for The speed of formation; for concentration; for solubility.

[0029] In order to quantitatively describe the steric effect, the coverage of the deposited product is introduced to quantitatively describe The coverage of the electrode surface by the precipitate. Deposition only occurs at the boundary, so the boundary coverage is regarded as a boundary with no thickness. Its change over time is determined by the deposition rate, and the ordinary differential equation (ODE) is introduced as follows: ; ; in, for Coverage at the border; For time; To completely cover the active electrode surface Deposition thickness; for Molar mass; for density; / The volume of the sedimentation product generated in each unit grid can be converted into the thickness of the sedimentation layer, i.e., the grid size.

[0030] In order to characterize the influence of the steric effect of corrosion products on corrosion, the if condition function is introduced for correction when calculating the cathode and anode reaction rates on the electrode surface, as follows: .

[0031] Based on the existing research, considering the effect of multiphase coupling and the inactive state of the passivation film, a preprocessed geometric model of the normal direction of the aluminum alloy interface can be constructed. After verification, the initial values ​​of the diffusion layer thickness and mixed potential that are most suitable for the self-corrosion problem of aircraft alloy metal materials can be determined.

[0032] The level set structure function is introduced, and the effect of multiphase coupling plus the inactive state of the passivation film are considered, including , , In order to distinguish the influence of four different phases on the same interface, four constants -1, 0, 1, and 2 are used to represent the position of each phase in the model, as follows: .

[0033] In order to deal with the sudden changes in values ​​at the phase boundaries caused by the constant value between phases, the Heaviside function H(ξ) is introduced to judge the boundaries of each phase, and the Heaviside function H(ξ) is further processed and second-order smoothing is performed within the range of 0±0.05μm.

[0034] ; in, is the variable of the Heaviside function. Introducing the level set function , the geometric model of the aluminum alloy interface in the normal direction is constructed, such as Figure 3-Figure 6 shown.

[0035] ; in, is the Heaviside function operation; , is the position coordinate. (Geometric coordinate value, can be deleted) In order to characterize the influence of each phase on corrosion, the if condition function is introduced for correction when calculating the cathode and anode reaction rates on the electrode surface, as follows: .

[0036] It has been verified that the thickness of the electrolyte domain from 10μm to 200μm has little effect on the concentration calculation results. Therefore, it can be assumed that the thickness of the diffusion layer, i.e. the electrolyte domain, is 10μm, which can both ensure that the concentration gradient is sufficient to form in the domain and reduce the amount of calculation.

[0037] The initial values ​​of the ion concentrations on the upper surface of the electrolyte domain are consistent with the ion concentrations of the electrolyte solution, that is, 0.1 mol / L NaCl solution, and the dissolved oxygen concentration is 0.258 mol / m3.

[0038] The boundaries on both sides of the electrolyte domain are insulating boundaries, and the lower surface serves as the electrode surface.

[0039] For mixed potential, it has been verified that appropriately increasing the smoothing interval of the Heaviside function H(ξ) can effectively improve convergence. The mixed potential can be directly calculated based on the mixed potential theory without the need to set the corresponding initial value.

[0040] Step 2: Use the simulation model of the self-corrosion problem of aircraft aluminum alloy metal materials to perform multi-condition simulation, analyze the simulation results, and correct the simulation model.

[0041] Specifically including Single phase mixed, The simulation results of single-phase inclusions, multi-phase inclusions and aluminum alloy self-corrosion are analyzed.

[0042] Step 3: Based on the simulation model of the self-corrosion problem of aircraft aluminum alloy metal materials, a corrosion simulation model of aircraft aluminum alloy connection structure is established.

[0043] Based on the simulation model of the self-corrosion problem of aircraft aluminum alloy metal materials, a specimen-level galvanic corrosion simulation model of aircraft aluminum alloy connection structure is established. Simulation calculations are performed to obtain the coupling potential and galvanic current. The results are compared and analyzed with the test results, and then the specimen-level galvanic corrosion simulation model of aircraft aluminum alloy connection structure is corrected to ensure the reliability of the model.

[0044] Based on the specimen-level galvanic corrosion simulation model of aircraft aluminum alloy connection structures, a component-level galvanic corrosion simulation model of aircraft aluminum alloy connection structures was established, and simulation calculations were performed to obtain the potential distribution, corrosion morphology, and microstructural morphology. The results were compared and analyzed with the test results, and then the component-level galvanic corrosion simulation model of aircraft aluminum alloy connection structures was corrected to obtain the corrosion simulation model of aircraft aluminum alloy connection structures to ensure the accuracy of the model.

[0045] Step 4: Use the aircraft aluminum alloy connection structure corrosion simulation model to perform multi-condition corrosion simulation analysis on the aircraft aluminum alloy connection structure.

[0046] It can carry out corrosion simulation analysis under four working conditions, including immersion test of typical dissimilar metal connectors of unpainted wing frame, immersion test of typical dissimilar metal connectors of painted wing frame, immersion test of typical metal and composite connectors of unpainted wing frame, immersion test of typical metal and composite connectors of painted wing frame. It can predict the potential distribution, corrosion rate, corrosion deformation and mass loss rate of aircraft aluminum alloy connection structure and find the dangerous positions of the structure.

[0047] When conducting multi-condition corrosion simulation analysis on aircraft aluminum alloy connection structures, the protection system can be considered at the same time.

[0048] The aircraft aluminum alloy connection structure corrosion simulation analysis method disclosed in the above-mentioned embodiment adopts simulation means, and uses the aircraft aluminum alloy connection structure corrosion simulation model to perform multi-condition corrosion simulation analysis on the aircraft aluminum alloy connection structure. It can quickly realize the prediction of the potential distribution, corrosion rate, corrosion deformation and mass loss rate of the aircraft aluminum alloy connection structure, and find the dangerous positions of the structure. It has low cost and can effectively guide the design and improvement of the aircraft aluminum alloy connection structure, as well as guide the maintenance of the aircraft aluminum alloy connection structure in practice.

[0049] So far, the technical solution of the present application has been described in conjunction with the preferred embodiments shown in the accompanying drawings. Those skilled in the art should understand that the scope of protection of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the scope of protection of the present application.

Claims

1. A corrosion simulation analysis method for aircraft aluminum alloy connection structure, characterized in that: include: Step 1: Establish a simulation model for the self-corrosion problem of aircraft aluminum alloy metal materials; Step 2: Using the simulation model of the self-corrosion problem of aircraft aluminum alloy metal materials, conduct multi-condition simulation, analyze the simulation results, and correct the simulation model; Step 3: Based on the simulation model of the self-corrosion problem of aircraft aluminum alloy metal materials, a simulation model of corrosion of aircraft aluminum alloy connection structure is established; Step 4: Use the aircraft aluminum alloy connection structure corrosion simulation model to perform multi-condition corrosion simulation analysis on the aircraft aluminum alloy connection structure.

2. The corrosion simulation analysis method for aircraft aluminum alloy connection structure according to claim 1 is characterized in that: In step 1, a simulation model for the self-corrosion problem of aircraft aluminum alloy metal materials is established, and basic assumptions are established: The oxygen reduction reaction occurs only on the surface of the second phase, and the active dissolution of the metal occurs only in the matrix; The electrolyte is an infinitely dilute solution; The passive film does not dissolve and does not consider Destructive effect on the passivation film; The influence of the double electric layer on the electrode surface is not considered. All the physical and chemical processes considered include electrode reaction, material transport and homogeneous reaction in the electrolyte, and deposition of surface corrosion products. Ignoring the adsorption and desorption process of ions at the interface, the interface ion concentration distribution is completely controlled by diffusion and electromigration; The mass transfer of electrolyte only considers diffusion and electromigration, and does not consider convection; Only the microscopic galvanic corrosion under open circuit conditions is considered, no external voltage is applied, and the electrode reaction is driven by the galvanic effect between IMPs and the substrate; Consider the changes of the electrode surface over time due to active dissolution, and consider the impact of its changes on corrosion expansion; Considering the passivation effect of corrosion product deposition on active reaction surfaces and its influence on subsequent corrosion processes, Once deposited, it will not dissolve.

3. The corrosion simulation analysis method for aircraft aluminum alloy connection structure according to claim 2 is characterized in that: In step 1, a simulation model for the self-corrosion problem of aircraft aluminum alloy metal materials is established, assuming that the thickness of the diffusion layer is 10 μm; The initial values ​​of the ion concentrations on the upper surface of the electrolyte domain are consistent with the ion concentrations of the electrolyte solution; The boundaries on both sides of the electrolyte domain are insulating boundaries, and the lower surface serves as the electrode surface.

4. The corrosion simulation analysis method for aircraft aluminum alloy connection structure according to claim 3 is characterized in that: In step 2, the simulation results are analyzed, including Single phase mixed, The simulation results of single-phase inclusions, multi-phase inclusions and aluminum alloy self-corrosion are analyzed.

5. The corrosion simulation analysis method for aircraft aluminum alloy connection structure according to claim 4 is characterized in that: Step three is as follows: Based on the simulation model of the self-corrosion problem of aircraft aluminum alloy metal materials, a simulation model of galvanic corrosion at the specimen level of aircraft aluminum alloy connection structure is established. The coupling potential and galvanic current are obtained by simulation calculation, and compared and analyzed with the test results, and then the simulation model of galvanic corrosion at the specimen level of aircraft aluminum alloy connection structure is corrected. Based on the specimen-level galvanic corrosion simulation model of aircraft aluminum alloy connection structure, a component-level galvanic corrosion simulation model of aircraft aluminum alloy connection structure is established, and simulation calculations are performed to obtain the potential distribution, corrosion morphology and microstructure morphology. The results are compared and analyzed with the test results, and then the component-level galvanic corrosion simulation model of aircraft aluminum alloy connection structure is corrected to obtain the corrosion simulation model of aircraft aluminum alloy connection structure.

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