Corrosion environment adaptability assessment method for amphibious aircraft structure

Abstract

The invention discloses a corrosion environment adaptability assessment method for an amphibious aircraft structure. The method comprises the steps of assessment of the influence of a corrosion environment on fatigue, assessment of the influence of the corrosion environment on damage tolerance and assessment of the influence of the corrosion environment on residual strength. The method can be used for evaluating the influence of the corrosion environment on the fatigue life and damage tolerance of the aircraft structure.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft environmental adaptability verification, and in particular relates to a corrosion environment adaptability assessment method for amphibious aircraft structures. Background Art

[0002] The existing aircraft structure adaptability assessment for corrosion environments is to evaluate the impact of corrosion environments on structural fatigue life and damage tolerance through the ED assessment in the MSG-3 assessment method. The MSG-3 is revised through the corrosion control outline. This method belongs to the structural environmental adaptability assessment method for conventional aircraft and is not suitable for amphibious aircraft that are in harsh environments such as high temperature, high humidity and high salt spray for a long time. Summary of the invention

[0003] Purpose of the Invention

[0004] In order to evaluate the adaptability of an amphibious aircraft structure to a corrosion environment which is exposed to harsh environments such as high temperature, high humidity and high salt fog for a long time, the present invention provides an evaluation method for the adaptability of an amphibious aircraft structure to a corrosion environment.

[0005] Inventing technical solutions

[0006] A method for evaluating the adaptability of an amphibious aircraft structure to a corrosive environment, including the evaluation of the impact of the corrosive environment on fatigue, the evaluation of the impact of the corrosive environment on damage tolerance, and the evaluation of the impact of the corrosive environment on residual strength;

[0007] The method for evaluating the effect of the corrosion environment on fatigue is: conduct ground corrosion acceleration test, air accelerated corrosion test, fatigue test under normal environment in sequence and after several cycles, conduct DFR value test, compare the obtained DFR value with the DFR value under normal environment, and determine the effect coefficient of the corrosion environment on fatigue;

[0008] The method for evaluating the impact of the corrosion environment on damage tolerance is: conduct ground corrosion acceleration test, crack growth test under various single environments and cycle several times, then conduct crack growth test under each single environment to obtain the influence coefficient of typical materials under each single environment, and then obtain the influence coefficient of crack growth rate under the comprehensive environment according to the weighted percentage of each single environment in the structural area where different typical parts are located;

[0009] The method for evaluating the impact of the corrosive environment on the residual strength is as follows: after conducting a ground corrosion acceleration test for two maintenance cycles, a static strength test and a fracture toughness test are conducted under a conventional environment. The fracture toughness curve and static strength under the corrosive environment are compared with the fracture toughness curve and static strength under the conventional environment to obtain the influence coefficient of the corrosive environment on the fracture toughness and static strength.

[0010] Preferably, the ground corrosion accelerated test is performed according to the ground accelerated test environmental spectrum.

[0011] Preferably, the duration of the air accelerated corrosion test is the total flight hours of 1 year.

[0012] Preferably, the number of cycles of the ground corrosion acceleration test, the air accelerated corrosion test, and the fatigue test under a conventional environment in the method for evaluating the effect of the corrosion environment on fatigue is set according to the calendar life of the aircraft.

[0013] Preferably, when testing the DFR value in the method for evaluating the effect of a corrosive environment on fatigue, the number of fatigue loading times is included in the total number of cycles.

[0014] Preferably, the conventional environment refers to the normal atmospheric environment of a laboratory.

[0015] Preferably, the test pieces used in the method for evaluating the impact of corrosion environment on fatigue are divided into two categories: component level and assembly level. When testing component-level test pieces, it is necessary to consider two situations: repair and no repair after the protection system is damaged and fails in each overhaul cycle. When testing assembly-level test pieces, it is necessary to consider two situations: repair after the protection system is damaged and fails in each overhaul cycle.

[0016] Preferably, the number of cycles of the ground corrosion acceleration test and the crack growth test under various single environments in the method for evaluating the impact of the corrosion environment on the damage tolerance is set according to the aircraft overhaul cycle.

[0017] Advantages of the invention: The method can be used to evaluate the influence of the corrosive environment on the fatigue life and damage tolerance of the aircraft structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 To verify the effect of corrosive environment on fatigue (safe life).

[0019] Figure 2 To verify the effect of corrosion environment on crack growth rate.

[0020] Figure 3 To verify the idea of ​​the effect of corrosive environment on residual strength. DETAILED DESCRIPTION

[0021] The present invention is achieved through the following technical solutions.

[0022] The life assessment of the airframe structure under conventional environment is mainly carried out from two aspects: fatigue (safe life) and damage tolerance assessment. Therefore, the influence of the corrosive environment on the life of the airframe structure is also mainly verified from two aspects: fatigue (safe life) test and damage tolerance test under corrosive environment. The influence coefficient of the corrosive environment on fatigue life and damage tolerance is given, and the influence of the corrosive environment on the service life of the airframe structure is evaluated.

[0023] A corrosion environment adaptability assessment method for amphibious aircraft structures includes an assessment of the impact of the corrosion environment on fatigue (safety life) and an assessment of the impact of the corrosion environment on damage tolerance.

[0024] The influence of the corrosive environment on fatigue (safe life) includes the influence of the parking environment (pre-corrosion) and the influence of the operating environment (corrosion fatigue). Therefore, when testing the influence of the corrosive environment on fatigue (safe life), firstly, a one-year ground corrosion acceleration test is carried out according to the ground accelerated test environment spectrum, and then a one-year air accelerated corrosion test is carried out according to the air operating environment. The air accelerated corrosion test time is the total flight hours of one year. After the air accelerated corrosion test, 1000 fatigue tests are carried out in a conventional environment. The number of fatigue tests can be set according to needs. The above three tests are one cycle. After 30 cycles, the DFR value test is carried out in a conventional environment (normal laboratory atmosphere environment). The obtained DFR value (the number of fatigue loadings in the previous 30 cycles is included in the total number of cycles) is compared with the DFR value in the conventional environment to determine the influence coefficient of the corrosive environment on fatigue (safe life). The test pieces are divided into two categories: component level and component level. When testing the component-level test pieces, it is necessary to consider the two situations of repair and non-repair after the protection system is damaged and failed in each overhaul cycle. The component-level test pieces are repaired after the protection system is damaged and failed in each overhaul cycle. The verification idea is as follows Figure 1 shown.

[0025] The influence of corrosion environment on damage tolerance includes the influence of corrosion environment on crack propagation and residual strength.

[0026] The influence of the corrosion environment on crack growth is mainly the impact on the crack growth rate, including the impact of the parking environment (pre-corrosion) and the impact of the operating environment (corrosion fatigue). Therefore, when testing the impact of the corrosion environment on crack growth, we first conduct a 1-year ground corrosion acceleration test, and then conduct a 1-year crack growth test in various single environments, and repeat it 6 times (aircraft overhaul cycle) to study the adverse effects of the service environment on crack growth within an overhaul cycle. After 6 cycles, continue to carry out crack growth tests in each single environment to obtain the influence coefficient of typical materials in each single environment, and then obtain the influence coefficient of the crack growth rate in the comprehensive environment based on the weighted percentage of each single environment in the structural area where different typical parts are located. Ideas for the effect of the corrosion environment on crack growth are as follows: Figure 2 shown.

[0027] The effects of the corrosive environment on the residual strength include static strength and fracture toughness. The residual strength is the maximum load and stress that a damaged aircraft structure can withstand. It is the maximum load / stress that the structure can withstand during a maintenance cycle when the aircraft structure is damaged but uninspectable. Therefore, the effect of the corrosive environment on the residual strength mainly assesses the impact within a maintenance cycle. Since the impact of the air corrosion environment has been considered in the crack propagation stage, it will not be considered again here. Since there is a possibility of missed inspection during overhaul, the impact of the ground corrosion environment on the residual strength also needs to consider two maintenance cycles. That is, after conducting ground corrosion acceleration tests for two maintenance cycles, static strength tests and fracture toughness tests are carried out under conventional environments. The fracture toughness curve and static strength under the corrosive environment are compared with the fracture toughness curve and static strength under the conventional environment to obtain the influence coefficient of the corrosive environment on the fracture toughness and static strength. The verification idea is as follows: Figure 3 shown.

[0028] The protection scope of the present invention is not limited to the above-mentioned embodiments. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the scope of the present invention. If these changes and modifications fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include these changes and modifications.

Claims

1. A method for evaluating the adaptability of an amphibious aircraft structure to a corrosive environment, characterized in that: Including the assessment of the impact of the corrosive environment on fatigue, the impact of the corrosive environment on damage tolerance, and the impact of the corrosive environment on residual strength; The method for evaluating the effect of the corrosion environment on fatigue is: conduct ground corrosion acceleration test, air accelerated corrosion test, fatigue test under normal environment in sequence and after several cycles, conduct DFR value test, compare the obtained DFR value with the DFR value under normal environment, and determine the effect coefficient of the corrosion environment on fatigue; The method for evaluating the impact of the corrosion environment on damage tolerance is: conduct ground corrosion acceleration test, crack growth test under various single environments and cycle several times, then conduct crack growth test under each single environment to obtain the influence coefficient of typical materials under each single environment, and then obtain the influence coefficient of crack growth rate under the comprehensive environment according to the weighted percentage of each single environment in the structural area where different typical parts are located; The method for evaluating the impact of the corrosive environment on the residual strength is as follows: after conducting a ground corrosion acceleration test for two maintenance cycles, a static strength test and a fracture toughness test are conducted under a conventional environment. The fracture toughness curve and static strength under the corrosive environment are compared with the fracture toughness curve and static strength under the conventional environment to obtain the influence coefficient of the corrosive environment on the fracture toughness and static strength.

2. The method for evaluating the adaptability of an amphibious aircraft structure to a corrosive environment as claimed in claim 1, characterized in that: The ground corrosion accelerated test is carried out according to the ground accelerated test environment spectrum.

3. The method for evaluating the adaptability of an amphibious aircraft structure to a corrosive environment as claimed in claim 1, characterized in that: The duration of the air accelerated corrosion test is the total flight hours in 1 year.

4. The method for evaluating the adaptability of an amphibious aircraft structure to a corrosive environment as claimed in claim 1, characterized in that: The number of cycles of the ground corrosion acceleration test, the air accelerated corrosion test, and the fatigue test under normal environment in the evaluation method of the impact of the corrosion environment on fatigue is set according to the calendar life of the aircraft.

5. The method for evaluating the adaptability of an amphibious aircraft structure to a corrosive environment as claimed in claim 1, characterized in that: When testing the DFR value in the method for evaluating the impact of corrosive environment on fatigue, the number of fatigue loading times is included in the total number of cycles.

6. The method for evaluating the adaptability of an amphibious aircraft structure to a corrosive environment as claimed in claim 1, characterized in that: Conventional environment refers to the normal atmospheric environment in the laboratory.

7. The method for evaluating the adaptability of an amphibious aircraft structure to a corrosive environment as claimed in claim 1, characterized in that: The test pieces used in the evaluation method of the impact of corrosion environment on fatigue are divided into two categories: component level and assembly level. When testing component-level test pieces, it is necessary to consider the two situations of repair and no repair after the protection system is damaged and fails in each overhaul cycle. The assembly-level test pieces need to be repaired after the protection system is damaged and fails in each overhaul cycle.

8. The method for evaluating the adaptability of an amphibious aircraft structure to a corrosive environment as claimed in claim 1, characterized in that: In the method for evaluating the impact of corrosion environment on damage tolerance, the number of cycles of ground corrosion acceleration test and crack growth test under various single environments is set according to the aircraft overhaul cycle.

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