Environmental test design method for sealing structure of near space aircraft

Abstract

The invention discloses a near space aircraft sealing structure environment test design method which comprises the following steps: (1) determining an acceleration test environment module which is composed of an ultraviolet aging test and a low-temperature test; (2) determining test parameters, wherein the test parameters of the ultraviolet aging test comprise temperature, ultraviolet radiation intensity and ultraviolet radiation time; test parameters of the low-temperature test comprise temperature and temperature action time; and (3) sequentially carrying out an ultraviolet aging test and a low-temperature test. The test cost can be saved, the environmental adaptability verification or material screening speed of the sealing structure of the near space aircraft is accelerated, the development progress of the near space aircraft is guaranteed, and the environmental adaptability level is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft environmental adaptability verification, and in particular relates to a near-space aircraft sealing structure environmental test design method. Background Art

[0002] Near-space vehicles are used for a long time within the range of (20 to 100) km, and are mainly affected by low temperatures (as low as -100°C) and strong ultraviolet radiation. The sealing structural materials such as aircraft sealants and gaskets are easily aged and failed, resulting in reduced sealing performance, affecting the life and safety of the aircraft. It is necessary to evaluate and verify the environmental adaptability of the sealing structure through tests. At present, there are generally two methods for environmental adaptability evaluation and verification, namely natural environment tests and laboratory accelerated environmental tests. Since near-space vehicles work in extreme environmental conditions for a long time, especially low-temperature environmental conditions, which are quite different from the natural environmental conditions on the ground, and the test cycle is too long; if laboratory simulated environmental tests are used, the current laboratory standard low-temperature environmental test chamber has a low temperature range of no less than -70°C. When the temperature is lower than -70°C, a liquid nitrogen test chamber must be used. However, the liquid nitrogen test has the following problems. On the one hand, the effective volume of the liquid nitrogen test chamber is small, generally no more than 1m 3 , it cannot be used for testing larger structural parts or a large number of test pieces. On the other hand, liquid nitrogen needs to be purchased for each test, which is costly, unsafe to operate, and difficult to accurately control the temperature. Summary of the invention

[0003] Purpose of the Invention

[0004] In view of the problems that the existing liquid nitrogen test has high cost, unsafe operation, difficulty in precise temperature control and small effective volume of the liquid nitrogen test box, the present invention provides a method for designing an environmental test for a sealing structure of a near-space aircraft.

[0005] Inventing technical solutions

[0006] A method for designing an environmental test for a sealing structure of a near-space vehicle comprises the following steps:

[0007] (1) Determination of the accelerated test environment module, which consists of UV aging test and low temperature test;

[0008] (2) Determination of test parameters: The test parameters of the UV aging test include temperature, UV radiation intensity, and UV irradiation time; the test parameters of the low temperature test include temperature and temperature action time;

[0009] (3) Carry out UV aging test and low temperature test in sequence.

[0010] Preferably, the test is performed by means of an accelerated cycle test.

[0011] Preferably, the temperature of the UV aging test is the UV aging temperature value in a conventional aircraft accelerated corrosion test.

[0012] Preferably, when the UV aging test time needs to be reduced, the temperature of the UV aging test is adjusted according to the rule that the light aging reaction rate increases by about 1 times for every 10° C. increase in the temperature of the UV aging test.

[0013] Preferably, the UV irradiation intensity is set to (60±10) W / m 2 .

[0014] Preferably, the ultraviolet irradiation time t is calculated according to the following formula:

[0015]

[0016] Where: Q Z is the amount of ultraviolet radiation received by the test piece in one year; W is the radiation intensity of the ultraviolet radiation test chamber.

[0017] Preferably, for low temperature tests, when the ambient temperature of the rubber sealing material is lower than -70°C and the single low temperature exposure time is within 10 hours, the laboratory test temperature value is controlled within -70°C to -50°C, and the single low temperature test time should be within 20 hours; when the ambient temperature is higher than -70°C, the test is carried out according to the actual ambient temperature.

[0018] Preferably, the temperature of the UV aging test is 55°C.

[0019] Advantages of the present invention: The present invention can be used for environmental testing and assessment of sealing structures of near-space vehicles. By reasonably adjusting environmental test conditions and utilizing existing standard environmental equipment, long solar radiation and low temperature environmental tests can be completed, and the single cycle test time can be controlled within 30 days, thereby saving test costs, accelerating environmental adaptability verification or material screening of sealing structures of near-space vehicles, ensuring the development progress of near-space vehicles, and improving the level of environmental adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a cyclic test method for the sealing structure of a certain type of near-space vehicle. DETAILED DESCRIPTION

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

[0022] A design method for environmental test of sealing structure of near-space aircraft is based on the existing accelerated environmental test method of aircraft. Aiming at the characteristics of low temperature and long radiation time in near-space, a method for determining the parameters of accelerated environmental test module for rubber sealing structure is given, as well as the relationship between accelerated environmental test and actual environment.

[0023] Determination of accelerated test environment modules

[0024] In view of the environmental characteristics of near-space and taking into account that the aircraft sealing structure is mainly affected by solar radiation and low temperature, among which the ultraviolet radiation in the solar spectrum has a greater impact on the aging of the sealing material, the accelerated environmental test consists of two modules, namely ultraviolet aging test and low temperature test.

[0025] Determination of test parameters

[0026] 1) UV aging test

[0027] a) Temperature conditions

[0028] The temperature value in the accelerated corrosion test of general aircraft is taken as the benchmark, that is, T = 55°C. Considering that the solar radiation in near space is about twice that on the ground in the same period of time, if the near space aircraft flies at high altitude for a long time, the solar radiation intensity is several times higher than that of general aircraft. The accelerated test time is too long and it is difficult to accept in engineering. According to the Van't Hoff rule and actual experience data, the light aging reaction rate usually increases by about 1 times for every 10°C increase in temperature. When the aircraft flies in near space for a long time at a time, the test time can be reduced by increasing the test temperature.

[0029] b) UV radiation intensity

[0030] The parameters are the same as those for general aircraft UV radiation tests. The UV aging test chamber irradiation intensity is W = (60 ± 10) W / m 2 .

[0031] c) Calculation of UV exposure time

[0032] The ultraviolet irradiation time t is calculated according to the following formula:

[0033]

[0034] Where:

[0035] Q Z ——The amount of ultraviolet radiation received by the test piece in one year.

[0036] W——Radiation intensity of ultraviolet radiation test chamber.

[0037] 2) Low temperature test

[0038] Low temperature will mainly cause permanent deformation of rubber materials such as sealants. According to test results, within 20 hours of low temperature environment, the permanent deformation rate of materials will increase linearly with time. The lower the temperature, the faster the deformation rate of materials will increase. The deformation rate will double for every 10°C decrease, but after 20 hours in low temperature environment, the permanent deformation rate of materials will tend to be constant. Therefore, although the lowest temperature in near space can reach about -100°C, if the time in the extreme low temperature zone (-70°C to -120°C) is short (within 10 hours), the influence of actual low temperature conditions on materials can be realized by increasing the temperature (such as setting it to -70°C) and extending the low temperature test time.

[0039] According to tests, when the temperature is in the range of -20℃~120℃ and the temperature action time is within 20h, the permanent deformation rate of rubber sealing materials is proportional to time, and in the same time, the permanent deformation rate of rubber sealing materials will double for every 10℃ decrease in temperature. Therefore, when the ambient temperature of rubber sealing materials is lower than -70℃ and the single low temperature action time is short, the laboratory test temperature value can be controlled at -70℃~-50℃, and the corresponding test time needs to be extended, but the premise is that the final single test time should be within 20h.

[0040] When the ambient temperature is higher than -70℃, the test can be carried out according to the actual ambient temperature.

[0041] Since the permanent deformation rate of rubber materials tends to be constant when they are exposed to low temperature for more than 20 hours, the low temperature test time can be set to no more than 20 hours.

[0042] Cycle testing simulates the actual service history of aircraft:

[0043] In order to simulate the material performance attenuation process of rubber sealing materials under the coupling effects of ultraviolet aging and low-temperature environment, the test was carried out through accelerated cycle testing. One cycle is equivalent to the spacecraft working in near-space for one year.

[0044] Example

[0045] Take the development of accelerated environmental test methods for the upper surface sealing structure of a certain type of near-space vehicle as an example.

[0046] A certain type of near-space aircraft flies at an altitude of 20km to 30km in one cycle per day. At an altitude of 20km, the temperature reaches an extreme low temperature of -80℃ and lasts for 2h. At an altitude of 30km, the temperature reaches -36℃ and lasts for 22h. The specific plan for the accelerated environmental test method is as follows:

[0047] 1) UV aging test

[0048] a) UV radiation intensity

[0049] Take the UV aging test box irradiation intensity W = (60 ± 10) W / m 2 .

[0050] b) Ultraviolet irradiation time and test temperature

[0051] The annual solar radiation in the aircraft activity area is Q = 12000MJ / m 2 , one flight per year, duration of 3 months, i.e. Q'=12000 / 4=3000MJ / m 2 , conservatively taking the ratio of ultraviolet radiation to total solar radiation as δ = 6.53%, then:

[0052] Q Z -Q×δ-19.05MJ / m 2

[0053] Then the UV irradiation time of the upper surface of the aircraft is:

[0054]

[0055] The temperature value in the accelerated corrosion test of general aircraft is taken as the benchmark, that is, T = 55°C. In order to shorten the UV irradiation test time, the test temperature is increased by 10°C, and the light aging reaction rate can be increased by 1 times. Then the test temperature is set to 65°C, and the test time is conservatively set to 19 days, which is equivalent to the actual service of the sealing structure of the near-space vehicle for 1 year.

[0056] 2) Low temperature test

[0057] a) Test temperature

[0058] According to the lowest value of the temperature range of the general standard low temperature environment box in the laboratory, the test temperature is -70℃.

[0059] b) Test time

[0060] The aircraft will be kept at -80℃ for 2 hours every day. According to the relationship between the temperature of rubber sealing materials and the permanent deformation rate of the materials, the permanent deformation rate of rubber sealing materials will double for every 10℃ decrease in temperature. When the test temperature is set to -70℃ and the low temperature test time is set to 4h, the impact of -80℃ low temperature on rubber sealing materials can be characterized.

[0061] The aircraft is kept at -36℃ for 22 hours every day. Considering that the permanent deformation rate of the material tends to be constant after a single flight at -36℃ lasts for more than 20 hours, the temperature can be set at -36℃, and the test time can be conservatively taken as 22 hours.

[0062] c) Cyclic test method for sealing structure of near-space vehicle

[0063] The test is carried out through accelerated cycle testing, and one cycle is equivalent to the spacecraft operating in near-space for one year.

[0064] 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 designing environmental tests for sealing structures of near-space vehicles, characterized in that: The steps include: (1) Determination of the accelerated test environment module, which consists of UV aging test and low temperature test; (2) Determination of test parameters: The test parameters of the UV aging test include temperature, UV radiation intensity, and UV irradiation time; the test parameters of the low temperature test include temperature and temperature action time; (3) Carry out UV aging test and low temperature test in sequence.

2. A method for designing environmental tests for sealing structures of near-space aircraft as claimed in claim 1, characterized in that: The test is carried out by means of accelerated cycle test.

3. A method for designing environmental tests for sealing structures of near-space vehicles as claimed in claim 1, characterized in that: The temperature of the UV aging test is the same as the UV aging temperature in the conventional aircraft accelerated corrosion test.

4. A method for designing environmental tests for a sealing structure of a near-space vehicle as claimed in claim 3, characterized in that: When it is necessary to reduce the UV aging test time, adjust the UV aging test temperature according to the rule that the light aging reaction rate increases by about 1 times for every 10°C increase in the UV aging test temperature.

5. A method for designing environmental tests for sealing structures of near-space vehicles as claimed in claim 1, characterized in that: The UV radiation intensity was set to (60±10)W / m 2 .

6. A method for designing environmental tests for a sealing structure of a near-space aircraft as claimed in claim 1, characterized in that: The ultraviolet irradiation time t is calculated according to the following formula: Where: Q Z is the amount of ultraviolet radiation received by the test piece in one year; W is the radiation intensity of the ultraviolet radiation test chamber.

7. A method for designing environmental tests for a sealing structure of a near-space aircraft as claimed in claim 1, characterized in that: For low temperature tests, when the ambient temperature of the rubber sealing material is lower than -70℃ and the single low temperature exposure time is less than 10 hours, the laboratory test temperature value shall be controlled within -70℃~-50℃, and the single low temperature test time shall be within 20h; when the ambient temperature is higher than -70℃, the test shall be carried out according to the actual ambient temperature.

8. A method for designing environmental tests for sealing structures of near-space vehicles as claimed in claim 3, characterized in that: The temperature of the UV aging test was 55°C.

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