A method for determining the equivalent of laboratory environment acceleration spectrum based on corrosion simulation results

Abstract

The present application belongs to the technical field of aircraft structure corrosion testing, and specifically relates to a method for determining the equivalent of a laboratory environment acceleration spectrum based on corrosion simulation results. Only a small number of component corrosion tests are required to obtain an equivalent conversion coefficient for calculating the corrosion resistance of the test piece. The method has high accuracy, can shorten the test cycle and its cost, and is highly economical.

Description

Technical Field

[0001] The present application belongs to the technical field of aircraft structure corrosion testing, and specifically relates to a method for determining the equivalent of a laboratory environment acceleration spectrum based on corrosion simulation results. Background Art

[0002] Currently, when conducting laboratory accelerated corrosion tests on aircraft structures, the laboratory acceleration spectrum obtained by engineering equivalent is usually used and carried out in a cyclic immersion manner. By comparing and analyzing the test data with the actual long-term natural environment exposure test data, the accuracy of the laboratory acceleration spectrum is verified and the corrosion resistance of the aircraft structure is obtained.

[0003] 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 equivalence relationship of laboratory accelerated spectrum tests is long, the cost is high, and the economic efficiency is poor.

[0004] This application is proposed in view of the above-mentioned technical defects. Summary of the Invention

[0005] The purpose of this application is to provide a method for determining the equivalent of a laboratory environment acceleration spectrum based on corrosion simulation results, so as to quickly determine the equivalent conversion coefficient of the laboratory environment acceleration spectrum, derive the corrosion resistance of the aircraft structure, reduce the test cycle and its cost, and improve the economy of the test.

[0006] The technical solution of this application is:

[0007] A method for determining the equivalent of a laboratory environment acceleration spectrum based on corrosion simulation results, comprising:

[0008] Step 1: Establish a test piece corrosion simulation model construction process;

[0009] Step 2: Build a corrosion simulation model for the test piece based on the test piece corrosion simulation model construction process, expand the analysis of the corrosion current on the test piece under different temperature, relative humidity and salt spray corrosion related conditions, and obtain a test piece corrosion current database;

[0010] Step 3: Extract corresponding data from the corrosion current database of the test piece according to the service environment, and calculate the corrosion current of the test piece under the service environment;

[0011] Step 4: Select a laboratory benchmark environment to form a laboratory accelerated test environment spectrum, build a test piece corrosion simulation model using the test piece corrosion simulation model construction process, and simulate and calculate the corrosion charge of the test piece in the laboratory accelerated test environment;

[0012] Step 5: Calculate the equivalent conversion coefficient based on the corrosion electricity of the test piece in the service environment and the corrosion electricity of the test piece in the laboratory accelerated test environment.

[0013] Optionally, in the above-mentioned method for determining the laboratory environment acceleration spectrum equivalent based on corrosion simulation results, step 1 specifically includes:

[0014] S1. Establish a test piece-level corrosion simulation model and perform simulation calculations, specifically including:

[0015] S11. Conducting a specimen-level electrochemical test to obtain the material electrochemical dynamic parameters as boundary inputs and establishing a specimen-level corrosion simulation model;

[0016] S12, performing specimen-level corrosion simulation calculations to obtain the galvanic current and coupling potential of the galvanic pairs in the coupling system;

[0017] S13, adjusting the test piece specimen-level corrosion simulation model based on the test results until the galvanic current and coupling potential obtained by the simulation calculation are consistent with the test results;

[0018] S2. Establish a simulation model for the corrosion of the test piece flat plate and perform simulation calculations, specifically including:

[0019] S21. Based on the test piece-level corrosion simulation model, a test piece flat plate simulation piece-level corrosion simulation model is established;

[0020] S22, performing flat plate simulated component-level corrosion simulation calculation to obtain corrosion morphology, corrosion depth, and corrosion rate;

[0021] S23. Based on the test results, the simulation model of the test piece flat plate simulated component-level corrosion is adjusted to ensure that the corrosion morphology, corrosion depth, and corrosion rate obtained by simulation calculation are consistent with the test results, and the appropriate liquid film thickness is selected;

[0022] S3. Establish a test piece assembly-level corrosion simulation model and perform simulation calculations, specifically including:

[0023] S31. Establishing a test piece assembly-level corrosion simulation model based on the test piece flat plate simulated piece-level corrosion simulation model;

[0024] S32, performing assembly-level corrosion simulation calculations to obtain corrosion location, corrosion range, corrosion rate, and corrosion depth;

[0025] S33. Based on the test results, the test piece assembly-level corrosion simulation model is adjusted so that the corrosion position, corrosion range, corrosion rate, and corrosion depth obtained by simulation calculation are consistent with the test results, thereby obtaining the test piece corrosion simulation model.

[0026] Optionally, in the above-mentioned method for determining the laboratory environment acceleration spectrum equivalent based on corrosion simulation results, step three is specifically as follows:

[0027] ;

[0028] in, is the corrosion charge of the test piece in the service environment; For the the duration of the corrosion-related condition; is the corrosion current database of the test piece, where is the corrosion current of the test piece under various corrosion-related conditions; F is the Faraday constant; and k is the number of corrosion-related conditions.

[0029] Optionally, in the above-mentioned method for determining the laboratory environment acceleration spectrum equivalent based on corrosion simulation results, step 4 includes:

[0030] ;

[0031] in,

[0032] It is the corrosion charge of the test piece under the accelerated test environment in the laboratory; For test pieces in laboratory accelerated test environment The corrosion current at that moment.

[0033] Optionally, in the above-mentioned method for determining the laboratory environment acceleration spectrum equivalent based on corrosion simulation results, step five is specifically as follows:

[0034] ;

[0035] in, is the equivalent conversion factor.

[0036] This application has at least the following beneficial technical effects:

[0037] A method for determining the equivalent of a laboratory environment acceleration spectrum based on corrosion simulation results is provided. Only a small number of component corrosion tests are required to obtain an equivalent conversion coefficient for calculating the corrosion resistance of the test piece. The method has high accuracy, can shorten the test cycle and its cost, and is highly economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of a method for determining the equivalent of a laboratory environment acceleration spectrum based on corrosion simulation results provided in an embodiment of the present application;

[0039] Figure 2 It is a schematic diagram provided in an embodiment of the present application;

[0040] Figure 3 Schematic diagram of establishing a galvanic corrosion model of TC18 titanium alloy and 30CrMnSiNi2A high-strength steel provided in an embodiment of the present application;

[0041] Figure 4 This is a schematic diagram of the grid division near the electrode provided in an embodiment of the present application;

[0042] Figure 5 This is a schematic diagram of the coupled potential distribution of the galvanic system calculated using the galvanic corrosion model of TC18 titanium alloy and 30CrMnSiNi2A high-strength steel provided in the embodiments of the present application;

[0043] Figure 6 Schematic diagram of establishing a galvanic corrosion model of a lap joint based on a steady-state corrosion electric field provided in an embodiment of the present application;

[0044] Figure 7 Schematic diagram of the surface potential distribution of the bridge member provided by the simulation calculation of the embodiment of the present application;

[0045] Figure 8 Schematic diagram of the simulation calculation of the current density distribution on the surface of the joint provided in the embodiment of the present application;

[0046] Figure 9 is a schematic diagram of a galvanic corrosion model of dissimilar metal materials provided in an embodiment of the present application;

[0047] Figure 10 Schematic diagram of the anode current density distribution of the bridging member provided in an embodiment of the present application.

[0048] In order to better illustrate this embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product. In addition, the drawings are only used for illustrative purposes and should not be understood as limiting this application. DETAILED DESCRIPTION

[0049] To make the technical solution and its advantages of this application more clear, the technical solution of this application will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described here are only some of the embodiments of this application and are only used to explain this application, not to limit this application. It should be noted that for ease of description, only the parts relevant to this application are shown in the accompanying drawings, and other relevant parts can refer to the general design.

[0050] In addition, unless otherwise defined, the technical terms or scientific terms used in the description of this application should have the usual meanings understood by those skilled in the art in the field to which this application belongs. 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 described object changes, its relative positional relationship may also change accordingly. The word "include" used in the description of this application means that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, but does not exclude other elements or objects.

[0051] In addition, it should be noted that, unless otherwise clearly stipulated and limited, the words "installation", "connection" and similar terms 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.

[0052] The basis for converting the equivalent relationship of laboratory accelerated environmental spectra is the measurement of the corrosion current of the structure in both real and laboratory accelerated environments. However, measuring the corrosion current of the structure directly on the aircraft is difficult. Usually, the ground parking environmental spectrum is used as a benchmark, and the natural corrosive environment of the aircraft is reproduced in the laboratory environmental chamber, and the corresponding corrosion current is obtained using structural simulation parts. In order to fully obtain the corrosion current of each key corrosion part of the aircraft, a large number of tests are required, which is extremely costly and time-consuming. In addition, due to the limitations of laboratory equipment, the test environmental spectrum composition is relatively simple, which makes it difficult to truly reflect the impact of the natural corrosive environment.

[0053] 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 environmental conditions in a relatively short time. Therefore, the corrosion simulation results can be used to replace some corrosion tests, quickly and accurately obtain the equivalent conversion coefficient of the laboratory acceleration spectrum, and calculate the corrosion resistance of the aircraft structure.

[0054] This application provides a method for determining the equivalent of laboratory environment accelerated spectrum based on corrosion simulation results. By using the established specimen-plate simulation-assembly level corrosion simulation method, the corrosion current in the real environment and laboratory accelerated corrosion environment can be quickly obtained to determine the equivalent conversion coefficient, such as Figure 1 shown.

[0055] Step 1: Establish the test piece corrosion simulation model construction process.

[0056] This application establishes a corrosion simulation process at the test piece-flat plate simulation part-assembly level, based on the relationship between the various levels of the building block corrosion simulation and test design scheme, such as Figure 2 shown.

[0057] First, a specimen-level corrosion simulation model is established to perform simulation calculations. The specific process is as follows:

[0058] S11. Conducting a specimen-level electrochemical test to obtain the material electrochemical dynamic parameters as boundary inputs and establishing a specimen-level corrosion simulation model;

[0059] S12, performing specimen-level corrosion simulation calculations to obtain the galvanic current and coupling potential of the galvanic pairs in the coupling system;

[0060] S13. Based on the test results, the test piece specimen-level corrosion simulation model is adjusted until the galvanic current and coupling potential obtained by simulation calculation are consistent with the test results.

[0061] Secondly, a simulation model of the test piece’s flat plate-level corrosion simulation is established and simulation calculations are performed, taking into account structural details such as bolt holes. The specific process is as follows:

[0062] S21. Based on the test piece-level corrosion simulation model, a test piece flat plate simulation piece-level corrosion simulation model is established;

[0063] S22, performing flat plate simulated component-level corrosion simulation calculation to obtain corrosion morphology, corrosion depth, and corrosion rate;

[0064] S23. Based on the test results, the simulation model of the test piece flat plate simulated component-level corrosion is adjusted so that the corrosion morphology, corrosion depth, and corrosion rate obtained by simulation calculation are consistent with the test results, and the appropriate liquid film thickness is selected at the same time.

[0065] Finally, a test piece assembly-level corrosion simulation model is established to perform simulation calculations. The specific process is as follows:

[0066] S31. Establishing a test piece assembly-level corrosion simulation model based on the test piece flat plate simulated piece-level corrosion simulation model;

[0067] S32, performing assembly-level corrosion simulation calculations to obtain macro / micro morphologies such as corrosion location, corrosion range, corrosion rate, and corrosion depth, as well as detailed corrosion depth;

[0068] S33. Based on the test results, the test piece assembly-level corrosion simulation model is adjusted so that the corrosion position, corrosion range, corrosion rate, and corrosion depth obtained by simulation calculation are consistent with the test results, thereby obtaining the test piece corrosion simulation model.

[0069] Through the continuous debugging, verification and optimization of the early test piece-level → simulated component-level corrosion simulation model and the comparison of the application effect of the assembly-level corrosion simulation model, a test component corrosion simulation model with relatively ideal effect was obtained and applied to engineering applications of corrosion simulation.

[0070] Step 2: Use the test piece corrosion simulation model construction process to build a test piece corrosion simulation model, expand the analysis of the corrosion current on the test piece under different corrosion-related conditions such as temperature, relative humidity, and salt spray, and obtain the test piece corrosion current database.

[0071] Step 3: According to the service environment, extract the corresponding data from the test piece corrosion current database and calculate the corrosion current of the test piece in the service environment.

[0072] ;

[0073] in, is the corrosion charge of the test piece in the service environment; For the the duration of the corrosion-related condition; is the corrosion current database of the test piece, where is the corrosion current of the test piece under various corrosion-related conditions; F is the Faraday constant; and k is the number of corrosion-related conditions.

[0074] Step 4: Select the laboratory benchmark environment to form the laboratory accelerated test environment spectrum, build the test piece corrosion simulation model according to the test piece corrosion simulation model construction process, and simulate and calculate the corrosion quantity of the test piece in the laboratory accelerated test environment.

[0075] ;

[0076] in,

[0077] It is the corrosion charge of the test piece under the accelerated test environment in the laboratory; For test pieces in laboratory accelerated test environment The corrosion current at that moment.

[0078] Assume that the laboratory accelerated environment spectrum includes salt spray environment and temperature and humidity environment. The salt spray environment uses 5% NaCl solution with a small amount of dilute H2SO4 added to make the pH value 4.0~4.5 to simulate the effects of salt spray and acid gas; the temperature and humidity environment is set at 43±2℃ and relative humidity at 95%. One accelerated cycle is minutes, the salt spray environment and the temperature and humidity environment act for 、 , then the corrosion charge under one cycle of the laboratory accelerated environment spectrum is: + ,in, is the corrosion current of the test piece in salt spray environment; is the corrosion current of the test piece under temperature and humidity environment.

[0079] Step 5: Calculate the equivalent conversion coefficient based on the corrosion electricity of the test piece in the service environment and the corrosion electricity of the test piece in the laboratory accelerated test environment.

[0080] ;

[0081] in, is the equivalent conversion factor.

[0082] In a specific embodiment, the process of constructing a test piece corrosion simulation model is as follows:

[0083] First, the galvanic corrosion model of TC18 titanium alloy and 30CrMnSiNi2A high strength steel was established, such as Figure 3 As shown. The tetrahedral mesh is used to mesh the solution domain. The meshing situation near the electrode is as follows: Figure 4 shown.

[0084] The cathodic polarization curve of TC18 titanium alloy and the anodic polarization curve of 30CrMnSiNi2A steel were fitted respectively, and the electrochemical kinetic parameters obtained by fitting are shown in the following table:

[0085]

[0086] The electrochemical kinetic parameters obtained by fitting the cathodic polarization curve of TC18 titanium alloy and the anodic polarization curve of 30CrMnSiNi2A steel were introduced into the galvanic corrosion model of TC18 titanium alloy and 30CrMnSiNi2A high-strength steel as boundary conditions. The coupling potential of the galvanic system was calculated to be distributed between -564 and -562 mV. The average coupling potential was -563.39 mV, which was very close to the coupling potential obtained in the experiment. This proves the accuracy of the galvanic corrosion model of TC18 titanium alloy and 30CrMnSiNi2A high-strength steel. The calculation results are shown in Figure 5 .

[0087] The galvanic corrosion model of the lap joint is established based on the steady-state corrosion electric field, such as Figure 6 As shown, the boundary conditions can be selected from the electrochemical kinetic parameters fitted by Cview software, as shown in the following table:

[0088]

[0089] Simulate and calculate the surface potential distribution of the bonded test piece, such as Figure 7 As shown, the surface current density distribution is Figure 8 As shown in the figure, compared with the experimental test values, it is determined that the galvanic corrosion model of the lap joint has good consistency with the experimental reality in the early stage of corrosion.

[0090] Establish a galvanic corrosion model for dissimilar metal materials, such as Figure 9 As shown in the figure, the anode current density distribution of the lap joint is obtained by analysis, as shown in the figure. Figure 10 shown.

[0091] By comparing the accelerated corrosion test results and morphology with the corresponding simulation results, an equivalent relationship can be determined. The average corrosion depth can be used as a metric, and the equivalent relationship can be established by comparing the simulated accelerated corrosion test results with the simulated field exposure test results.

[0092] The method for determining the equivalent of the laboratory environment acceleration spectrum based on the corrosion simulation results disclosed in the above embodiment only requires a small number of component corrosion tests to obtain the equivalent conversion coefficient for calculating the corrosion resistance of the test piece. It has high accuracy, can shorten the test cycle and its cost, and is highly economical.

[0093] 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 replacements to the relevant technical features, and the technical solutions after these changes or replacements will fall within the scope of protection of the present application.

Claims

1. A method for determining the equivalent of laboratory environment acceleration spectrum based on corrosion simulation results, characterized in that: include: Step 1: Establish a test piece corrosion simulation model construction process; Step 2: Build a corrosion simulation model for the test piece based on the test piece corrosion simulation model construction process, expand the analysis of the corrosion current on the test piece under different temperature, relative humidity and salt spray corrosion related conditions, and obtain a test piece corrosion current database; Step 3: Extract corresponding data from the corrosion current database of the test piece according to the service environment, and calculate the corrosion current of the test piece under the service environment; Step 4: Select a laboratory benchmark environment to form a laboratory accelerated test environment spectrum, build a test piece corrosion simulation model using the test piece corrosion simulation model construction process, and simulate and calculate the corrosion charge of the test piece in the laboratory accelerated test environment; Step 5: Calculate the equivalent conversion coefficient based on the corrosion electricity of the test piece in the service environment and the corrosion electricity of the test piece in the laboratory accelerated test environment; Step three is as follows: Among them, Q C is the corrosion charge of the test piece in the service environment; t i is the duration of the i-th corrosion-related condition; I ci is the corrosion current of the test piece under the i-th corrosion-related condition in the test piece corrosion current database; F is the Faraday constant; k is the number of corrosion-related conditions In step 4: in, Q p I is the corrosion charge of the test piece under the accelerated test environment in the laboratory; p (t) is the corrosion current of the test piece at time t under the accelerated test environment in the laboratory.

2. The method for determining the laboratory environment acceleration spectrum equivalent based on corrosion simulation results according to claim 1, characterized in that: Step 1 specifically includes: S1. Establish a test piece-level corrosion simulation model and perform simulation calculations, specifically including: S11. Conducting a specimen-level electrochemical test to obtain the material electrochemical dynamic parameters as boundary inputs and establishing a specimen-level corrosion simulation model; S12, performing specimen-level corrosion simulation calculations to obtain the galvanic current and coupling potential of the galvanic pairs in the coupling system; S13, adjusting the test piece specimen-level corrosion simulation model based on the test results until the galvanic current and coupling potential obtained by the simulation calculation are consistent with the test results; S2. Establish a simulation model for the corrosion of the test piece flat plate and perform simulation calculations, specifically including: S21. Based on the test piece-level corrosion simulation model, a test piece flat plate simulation piece-level corrosion simulation model is established; S22, performing flat plate simulated component-level corrosion simulation calculation to obtain corrosion morphology, corrosion depth, and corrosion rate; S23. Based on the test results, the simulation model of the test piece flat plate simulated component-level corrosion is adjusted to ensure that the corrosion morphology, corrosion depth, and corrosion rate obtained by simulation calculation are consistent with the test results, and the appropriate liquid film thickness is selected; S3. Establish a test piece assembly-level corrosion simulation model and perform simulation calculations, specifically including: S31. Establishing a test piece assembly-level corrosion simulation model based on the test piece flat plate simulated piece-level corrosion simulation model; S32, performing assembly-level corrosion simulation calculations to obtain corrosion location, corrosion range, corrosion rate, and corrosion depth; S33. Based on the test results, the test piece assembly-level corrosion simulation model is adjusted so that the corrosion position, corrosion range, corrosion rate, and corrosion depth obtained by simulation calculation are consistent with the test results, thereby obtaining the test piece corrosion simulation model.

3. The method for determining the laboratory environment acceleration spectrum equivalent based on corrosion simulation results according to claim 2, characterized in that: Step 5 is as follows: Among them, α is the equivalent conversion coefficient.

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