Calendar life evaluation method for multiple stress levels

Abstract

The invention discloses a calendar life evaluation method for multiple stress levels, and the method comprises the steps: 1, determining a task profile of airborne equipment, and determining a sensitive sample piece type related to the calendar life of the airborne equipment; 2, determining the type of stress mainly borne by each sensitive sample piece and the stress level under each stress type; 3, determining a calendar life-stress acceleration model of each sensitive sample piece through a laboratory test; step 4, determining a time proportion corresponding to each stress level of each sensitive sample piece under each stress type based on the mission profile; 5, calculating the corresponding calendar life of each sensitive sample piece under each stress level of each stress type based on the calendar life-stress acceleration model of each sensitive sample piece obtained in the step 3; and step 6, based on calculation results of the step 4 and the step 5, calculating the calendar life of each sensitive sample piece by adopting a pre-designed calendar life prediction model applied to multiple stress levels. According to the technical scheme provided by the invention, the problem of low credibility of an evaluation conclusion caused by the fact that the calendar life of the airborne equipment evaluated by adopting an existing constant stress level evaluation mode does not conform to the actual state of the airborne equipment for the calendar life evaluation of the airborne equipment is solved.

Description

Technical Field

[0001] The present invention relates to the field of life assessment technology, but is not limited to it, and in particular to a calendar life assessment method for multiple stress levels. Background Art

[0002] The life index of airborne equipment is essentially a description of the durability of the product, which is mainly characterized by the working life and calendar life. During the product development and identification stage, it is necessary to verify and evaluate whether the design index requirements can be met in combination with the specified mission profile. The current verification and evaluation methods for the working life of airborne equipment are very mature and have been widely used in model development; the calendar life verification and evaluation methods are relatively weak and are still in the scientific research stage, and there are not many cases of model engineering application.

[0003] Considering that the calendar life of airborne equipment is generally very long, usually from more than ten years to several decades, the stress level it suffers during its entire life cycle varies greatly with the season, day and night, region, and different operating conditions. It is normal for it to serve under multiple stress levels rather than constant stress levels. At present, the life-stress acceleration model based on the regression of laboratory test results can calculate the calendar life of the product under a certain constant stress level. However, given that the calendar life sensitive stress (such as temperature) of most products, especially airborne equipment, is variable rather than constant during its entire life cycle. Using the current constant stress level to evaluate the calendar life of airborne equipment does not conform to the actual status of the airborne equipment, and the credibility of the evaluation conclusion is low. Summary of the invention

[0004] Purpose of the present invention: In order to solve the above technical problems, an embodiment of the present invention provides a calendar life assessment method for multiple stress levels to solve the problem that, in the calendar life evaluation of airborne equipment, the calendar life of the airborne equipment assessed by the existing constant stress level assessment method does not conform to the actual state of the airborne equipment, resulting in low credibility of the assessment conclusion.

[0005] Technical solution of the present invention: The embodiment of the present invention provides a calendar life assessment method for multiple stress levels, comprising:

[0006] Step 1: determine the mission profile of the airborne equipment and the types of sensitive samples related to the calendar life of the airborne equipment;

[0007] Step 2, determine the stress type that each sensitive sample is mainly subjected to and the stress level under each stress type;

[0008] Step 3, based on the task profile, determine the time proportion corresponding to each stress level of each sensitive sample under each stress type;

[0009] Step 4, based on the type of sensitive samples, determine the calendar life-stress acceleration model of each sensitive sample through laboratory testing;

[0010] Step 5, based on the calendar life-stress acceleration model of each sensitive sample obtained in step 4, calculate the calendar life corresponding to each sensitive sample at each stress level of each stress type;

[0011] Step 6: Based on the calculation results of steps 4 and 5, the calendar life of each sensitive sample is calculated using a pre-designed calendar life prediction model for multiple stress levels.

[0012] Optionally, in the calendar life assessment method for multiple stress levels as described above, step 3 comprises:

[0013] Based on the task profile, the stress levels of each sensitive sample under its various stress types are determined, and the time proportions corresponding to each stress level of each sensitive sample under its various stress types are obtained.

[0014] Optionally, in the calendar life assessment method for multiple stress levels as described above, step 4 comprises:

[0015] The calendar life-stress acceleration model type is selected according to the type of each sensitive sample; according to the calendar life-stress acceleration model type selected for each sensitive sample, the model parameters of the calendar life-stress acceleration model of each sensitive sample are confirmed through laboratory test regression method, that is, the calendar life-stress acceleration model of each sensitive sample is obtained.

[0016] Optionally, in the calendar life assessment method for multiple stress levels as described above, step 5 comprises:

[0017] For each sensitive sample, each stress level of each stress type is substituted into its respective calendar life-stress acceleration model to calculate the calendar life corresponding to each stress level in each stress type of each sensitive sample.

[0018] Optionally, in the calendar life assessment method for multiple stress levels as described above, before step 1, the method further includes:

[0019] Step a, establishing a calendar life prediction model, wherein the calendar life prediction model takes the calendar life corresponding to all stress levels of all stress types of all sensitive samples as input and takes the calendar life of the sensitive samples as output.

[0020] Optionally, in the calendar life assessment method for multiple stress levels as described above, the step a of establishing a calendar life prediction model comprises:

[0021] Based on the life-expiration mechanism of airborne equipment and the weight relationship between the calendar life and the calendar life of sensitive samples at various stress levels of various stress types, the calendar life prediction model is established as follows:

[0022]

[0023] Where, t is the calendar life of the sensitive sample;

[0024] is the time proportion of the kth stress level of the i-th stress type, determined by the task profile;

[0025] S l，k is the kth stress level of the i-th stress type;

[0026] N is the number of stress types of the sensitive sample;

[0027] i is 1, 2, 3, …, N;

[0028] M is the number of stress levels of the i-th stress type;

[0029] k is 1, 2, 3, …, M;

[0030] f(S l，k ) is the calendar life of the sensitive specimen at the kth stress level of the ith stress type, calculated by the calendar life-stress acceleration model.

[0031] Optionally, in the calendar life assessment method for multiple stress levels as described above,

[0032] The stress types include: temperature, humidity, chemical substances, microorganisms, deformation, and load;

[0033] The stress level of each stress type is based on all values ​​of the mission profile of the airborne equipment.

[0034] Optionally, in the calendar life assessment method for multiple stress levels as described above,

[0035] The stress level set formed by the stress type and stress level is expressed as:

[0036]

[0037] The calendar life for each stress level under each stress type is:

[0038]

[0039] The time proportion of each stress level under each stress type is:

[0040] in

[0041] Beneficial effects of the present invention: The embodiment of the present invention provides a calendar life assessment method for multiple stress levels. On the one hand, by determining the type of sensitive samples related to the calendar life of airborne equipment and determining the calendar life-stress acceleration model of each sensitive sample, the calendar life corresponding to each sensitive sample at each stress level of each stress type is calculated; on the other hand, by determining the main stress type and stress level of each stress type borne by each sensitive sample, and determining the time proportion corresponding to each stress level of each sensitive sample under each stress type based on the mission profile; based on the calculation results of the above two aspects, the calendar life of each sensitive sample is calculated using a pre-designed calendar life prediction model for multiple stress levels. The technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0042] 1) The application scope of the life-stress acceleration model established based on laboratory test data has been expanded, breaking through the limitations of the traditional life calculation method at a constant stress level, making the evaluation conclusion more consistent with the actual service scenario of the product and improving the credibility of the conclusion;

[0043] 2) A calendar life assessment scheme for multiple stress levels is given, the calendar life assessment elements and steps are standardized, and the operability of the calendar life calculation method for multiple stress levels is improved;

[0044] 3) Using the weight proportion principle, a cumulative damage modeling scheme was proposed, which provided new ideas and statistical analysis methods for the collection and analysis of environmental stress levels of airborne equipment during its life cycle, and promoted the equipment environmental engineering profession to better serve model engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0046] Figure 1 A flowchart of a calendar life assessment method for multiple stress levels is provided for an embodiment of the present invention;

[0047] Figure 2 A trend diagram of the life curve in the calendar life assessment method for multiple stress levels provided for an implementation example of the present invention. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present invention more clear, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other arbitrarily without conflict.

[0049] As explained in the above background technology, the life indicators of airborne equipment are usually characterized by working life and calendar life. The verification and evaluation methods of working life of airborne equipment are very mature, while the verification and evaluation methods of calendar life are relatively weak and are still in the scientific research stage. They mainly include:

[0050] 1) The evaluation is based on the life of calendar-sensitive samples (mainly including seals, cables, springs, etc.) selected for airborne equipment. The evaluation value directly adopts the life of calendar-sensitive samples, and does not fully consider factors such as assembly size, installation environment and stress level (temperature, humidity, chemicals, microorganisms, deformation, load, etc.);

[0051] 2) Calendar life sensitive samples are used as test objects. The actual working conditions of the aircraft are fitted as much as possible through the design of tooling and fixtures, and stress acceleration tests are carried out. The test process data is detected to establish a life-stress acceleration model, and then the life under actual stress conditions is reversed. The evaluation value obtained based on the life-stress acceleration model is the corresponding life index of the airborne equipment under constant stress, which causes the life assessment conclusion to deviate from the actual service life value of the equipment. The credibility of the assessment conclusion is poor and cannot support actual engineering applications.

[0052] Based on laboratory test data, a calendar life-stress acceleration model for airborne equipment can be established, and the calendar life under a specified stress level S can be calculated based on the acceleration model. Usually, during the service life of a product, the stress levels encountered may include one or more of temperature, humidity, chemicals, microorganisms, deformation, load, etc., and each stress level may change with changes in the environment, season, and operating conditions, rather than a constant stress S. Currently, there is a lack of calendar life assessment models and standardized assessment procedures under multiple stress levels. Using a constant stress level to assess the calendar life of a product does not conform to the actual status of the product, and the credibility of the assessment conclusion is low.

[0053] Based on the above analysis, it is very necessary to establish a calendar life assessment method for multiple stress levels rather than a constant level, and it is of great practical significance. In view of the above problems and the demand for calendar life assessment for multiple stress levels rather than a constant level, an embodiment of the present invention provides a calendar life assessment method for multiple stress levels.

[0054] The present invention provides the following specific embodiments which can be combined with each other. The same or similar concepts or processes may not be described in detail in some embodiments.

[0055] The embodiment of the present invention provides a calendar life assessment method for multiple stress levels, which is applicable to the case of a single stress type with different stress levels, and is also applicable to the case of multiple stress types and multiple stress levels. The technical solution provided by the embodiment of the present invention mainly involves two parts: a calendar life assessment model and a process of the calendar life assessment method.

[0056] The input of the calendar life assessment model is the calendar life corresponding to all stress levels of all stress types of each sensitive sample. Among them, the stress type mainly includes temperature, humidity, chemical substances, microorganisms, deformation, load, etc. The stress type is determined by the wear and degradation mechanism, working environment, working conditions, etc. corresponding to the calendar life sensitive sample; the stress level set S N×M Represents all stress levels of all stress types, and the calendar life f(S) of each stress level under each stress type N×M , time proportion (in ).

[0057] Among them, the stress level set S N×M , the proportion of each stress level under each stress type (in ) is determined by the corresponding mission profile on board, and the calendar life value f(S) for each stress level under each stress type is N×M The calendar life-stress acceleration model is used to solve the problem. The calendar life-stress acceleration model corresponding to calendar life-sensitive samples such as seals, cables, and springs can be constructed using existing mature methods. For example, the Arrhenius model is used for seals. The input data information of the calendar life assessment model is shown in Table 1.

[0058] Table 1 Inputs of calendar life prediction model for multiple stress levels

[0059]

[0060]

[0061] The calendar life assessment method for multiple stress levels provided by the present invention is described in two parts as follows.

[0062] 1. Establishing a calendar life prediction model

[0063] First, considering that calendar life loss is cumulative damage, when the total loss of calendar life caused by all stress levels of all stress types reaches the total calendar life (100%), the life is reached.

[0064] Secondly, based on the life-expiration mechanism of airborne equipment, and taking into account the weight relationship between the calendar life and the calendar life of sensitive samples at various stress levels of various stress types, a calendar life prediction model is established as shown in the following formula (1):

[0065]

[0066] Where, t is the calendar life of the sensitive sample;

[0067] is the time proportion of the kth stress level of the i-th stress type, determined by the task profile;

[0068] S i，k is the kth stress level of the i-th stress type;

[0069] N is the number of stress types of the sensitive sample;

[0070] i is 1, 2, 3, …, N;

[0071] M is the number of stress levels of the i-th stress type;

[0072] k is 1, 2, 3, …, M;

[0073] f(S i，k ) is the calendar life of the sensitive sample under the kth stress level of the ith stress type, calculated by the calendar life-stress acceleration model;

[0074] Finally, by transforming formula (1), we can get the calculation formula of the calendar life of sensitive samples, see formula (2):

[0075]

[0076] (II) Implementation process of calendar life assessment method for multiple stress levels:

[0077] like Figure 1 As shown, a flowchart of a calendar life assessment method for multiple stress levels is provided in an embodiment of the present invention. The method comprises the following steps:

[0078] Step 1: determine the mission profile of the airborne equipment and the types of sensitive samples related to the calendar life of the airborne equipment;

[0079] In this step, the mission profile of the airborne equipment is determined based on the design and service characteristics of the airborne equipment.

[0080] Step 2, determine the stress type that each sensitive sample is mainly subjected to and the stress level under each stress type;

[0081] In this step, the main stress type borne by each sensitive sample and the stress level under each stress type are determined based on the durability failure mechanism analysis.

[0082] Step 3, based on the task profile, determine the time proportion corresponding to each stress level of each sensitive sample under each stress type;

[0083] In this step, firstly, the stress levels of each sensitive sample under each stress type are determined based on the task profile, and secondly, the time proportion corresponding to each stress level of each sensitive sample under each stress type is obtained.

[0084] Step 4, determine the calendar life-stress acceleration model of each sensitive sample through laboratory tests;

[0085] In this step, the calendar life-stress acceleration model type is selected according to the type of each sensitive sample; for the calendar life-stress acceleration model type selected for each sensitive sample, the model parameters of the calendar life-stress acceleration model of each sensitive sample are confirmed through laboratory test regression, that is, the calendar life-stress acceleration model of each sensitive sample is obtained.

[0086] Step 5, based on the calendar life-stress acceleration model of each sensitive sample obtained in step 4, calculate the calendar life corresponding to each sensitive sample at each stress level of each stress type;

[0087] In step 5, for each sensitive sample, each stress level of each stress type is substituted into its respective calendar life-stress acceleration model to calculate the calendar life corresponding to each stress level in each stress type of each sensitive sample.

[0088] Step 6: Based on the calculation results of steps 4 and 5, the calendar life of each sensitive sample is calculated using a pre-designed calendar life prediction model for multiple stress levels.

[0089] The calendar life assessment method for multiple stress levels provided in the embodiment of the present invention, on the one hand, by determining the type of sensitive samples related to the calendar life of airborne equipment, and determining the calendar life-stress acceleration model of each sensitive sample, thereby calculating the corresponding calendar life of each sensitive sample at each stress level of each stress type; on the other hand, by determining the main stress type and stress level of each stress type borne by each sensitive sample, and determining the time proportion corresponding to each stress level of each sensitive sample under each stress type based on the mission profile; thus, based on the calculation results of the above two aspects, the calendar life of each sensitive sample is calculated using a pre-designed calendar life prediction model for multiple stress levels. The technical solution provided in the embodiment of the present invention has the following beneficial effects:

[0090] 1) The application scope of the life-stress acceleration model established based on laboratory test data has been expanded, breaking through the limitations of the traditional life calculation method at a constant stress level, making the evaluation conclusion more consistent with the actual service scenario of the product and improving the credibility of the conclusion;

[0091] 2) A calendar life assessment scheme for multiple stress levels is given, the calendar life assessment elements and steps are standardized, and the operability of the calendar life calculation method for multiple stress levels is improved;

[0092] 3) Using the weight proportion principle, a cumulative damage modeling scheme was proposed, which provided new ideas and statistical analysis methods for the collection and analysis of environmental stress levels of airborne equipment during its life cycle, and promoted the equipment environmental engineering profession to better serve model engineering.

[0093] Implementation Example

[0094] Taking the calendar life assessment of a certain airborne equipment as an example, the implementation process of the calendar life assessment method for multiple stress levels provided by the present invention is described in detail. The assessment process is as follows: Figure 1 In order to clearly illustrate the implementation process of this implementation example, the airborne equipment and its mission profile are simplified. It is assumed that the calendar life sensitive part of the airborne equipment has only one O-ring, and the mission profile only considers the environment during the day and night and working conditions throughout the year.

[0095] The first step is to determine the mission profile

[0096] Airborne equipment will encounter spring, summer, autumn, winter, day and night as well as operating conditions throughout its life cycle.

[0097] The second step is to determine the stress type of sensitive samples related to the calendar life of airborne equipment.

[0098] In this embodiment, it is determined that the sensitive sample is an O-ring, the main mechanism of calendar life loss of the O-ring is aging, and the stress type is temperature.

[0099] The third step is to determine the calendar life-stress acceleration model based on the test data

[0100] 1) Determine the calendar life-stress acceleration model

[0101] The O-ring calendar life-stress acceleration model is the Arrenius formula, and its basic form is shown in formula (3):

[0102]

[0103] Where: F is the reaction rate, and the reciprocal can be used as a measure of the life of the airborne equipment;

[0104] P is the state;

[0105] t is time;

[0106] A is a constant variable, greater than 0;

[0107] K is the Boltzmann constant;

[0108] T is the absolute temperature, +273 degrees Celsius;

[0109] Ea is the activation energy, and the activation energy of different failure modes is different.

[0110] 2) Linear transformation of calendar life-stress acceleration model

[0111] In order to better use the Arrhenius model in engineering, it is necessary to establish a linear relationship between time and temperature and transform the above formula as follows:

[0112]

[0113] make:

[0114]

[0115] but:

[0116]

[0117] The standard form is as follows:

[0118] logt=a+b / T (5)

[0119] 3) Determine the model parameters of the calendar life-stress acceleration model

[0120] Assume that the laboratory selected four temperature levels of 80℃, 120℃, 160℃ and 180℃ to carry out accelerated tests. The test results are shown in Table 2.

[0121] Table 2 Test results at four test temperatures

[0122]

[0123]

[0124] The regression formula is logt = a + b / T, and the trend is as follows Figure 2 As shown, it is a trend diagram of the life curve in the calendar life assessment method for multiple stress levels provided by the implementation example of the present invention. The formula is as follows:

[0125] logt=6.3897+2170.60757 / T; (6)

[0126] The fourth step is to determine the time proportion of each sensitive sample under each stress level of each stress type.

[0127] The life cycle of this airborne product includes seven usage scenarios, including spring and autumn nights, spring and autumn nights, spring and autumn daytime, summer nights, summer daytime, winter nights, winter daytime, and working hours. The corresponding stress levels are 8℃, 18℃, 30℃, 35℃, -12℃, -2℃, and 180℃, and the corresponding time proportions are 20%, 20%, 10%, 10%, 10%, 10%, 20%, respectively. The temperature and stress level and proportion of the product during its life cycle are shown in Table 3.

[0128] Table 3 Temperature and stress level and proportion

[0129]

[0130]

[0131] Step 5: Calculate the calendar life of each sensitive sample at each stress level of each stress type

[0132] Substituting the stress levels of each stress type in Table 3 into formula (6), the calendar life f(S) at each stress level of 8℃, 18℃, 30℃, 35℃, -12℃, -2℃, and 180℃ can be calculated respectively. i，k ), and the calculation results are shown in Table 4.

[0133] Table 4 Calendar life under various stress levels

[0134]

[0135] Step 6: Calculate the calendar life of sensitive samples using the calendar life prediction model for multiple stress levels

[0136] Calculation is performed according to formula (2), and the calculation results are shown in Table 5. Since the stress type of the O-ring in this example only includes temperature, there are 7 stress levels in total, that is, N=1 and M=7 in formula (2).

[0137] Table 5 Life calculation under multiple stress levels

[0138]

[0139] From the calculation results, it can be seen that the calendar life of the airborne equipment under the multi-stress level service environment described in Table 3 is about 32.6 years (285637h).

[0140] The calendar life assessment method for multiple stress levels provided in the embodiment of the present invention, on the one hand, determines the type of sensitive samples related to the calendar life of airborne equipment, and determines the calendar life-stress acceleration model of each sensitive sample, so as to calculate the corresponding calendar life of each sensitive sample under each stress level of each stress type; on the other hand, by determining the main stress type and stress level under each stress type of each sensitive sample, and determining the time proportion corresponding to each stress level of each sensitive sample under each stress type based on the mission profile; thus, based on the calculation results of the above two aspects, the calendar life of each sensitive sample is calculated using a pre-designed calendar life prediction model for multiple stress levels. The technical solution provided in the embodiment of the present invention has the following beneficial effects:

[0141] 1) The application scope of the life-stress acceleration model established based on laboratory test data has been expanded, breaking through the limitations of the traditional life calculation method at a constant stress level, making the evaluation conclusion more consistent with the actual service scenario of the product and improving the credibility of the conclusion;

[0142] 2) A calendar life assessment scheme for multiple stress levels is given, the calendar life assessment elements and steps are standardized, and the operability of the calendar life calculation method for multiple stress levels is improved;

[0143] 3) Using the weight proportion principle, a cumulative damage modeling scheme was proposed, which provided new ideas and statistical analysis methods for the collection and analysis of environmental stress levels of airborne equipment during its life cycle, and promoted the equipment environmental engineering profession to better serve model engineering.

[0144] Although the embodiments disclosed in the present invention are as above, the contents are only embodiments adopted to facilitate understanding of the present invention and are not intended to limit the present invention. Any technician in the field to which the present invention belongs can make any modifications and changes in the form and details of implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A calendar life assessment method for multiple stress levels, characterized in that: include: Step 1: determine the mission profile of the airborne equipment and the types of sensitive samples related to the calendar life of the airborne equipment; Step 2, determine the stress type that each sensitive sample is mainly subjected to and the stress level under each stress type; Step 3, based on the task profile, determine the time proportion corresponding to each stress level of each sensitive sample under each stress type; Step 4, based on the type of sensitive samples, determine the calendar life-stress acceleration model of each sensitive sample through laboratory testing; Step 5, based on the calendar life-stress acceleration model of each sensitive sample obtained in step 4, calculate the calendar life corresponding to each sensitive sample at each stress level of each stress type; Step 6: Based on the calculation results of steps 4 and 5, the calendar life of each sensitive sample is calculated using a pre-designed calendar life prediction model for multiple stress levels.

2. The calendar life assessment method for multiple stress levels according to claim 1, characterized in that: The step 3 comprises: Based on the task profile, the stress levels of each sensitive sample under its various stress types are determined, and the time proportions corresponding to each stress level of each sensitive sample under its various stress types are obtained.

3. The calendar life assessment method for multiple stress levels according to claim 2, characterized in that: The step 4 comprises: The calendar life-stress acceleration model type is selected according to the type of each sensitive sample; according to the calendar life-stress acceleration model type selected for each sensitive sample, the model parameters of the calendar life-stress acceleration model of each sensitive sample are confirmed through laboratory test regression method, that is, the calendar life-stress acceleration model of each sensitive sample is obtained.

4. The calendar life assessment method for multiple stress levels according to claim 3 is characterized in that: The step 5 comprises: For each sensitive sample, each stress level of each stress type is substituted into its respective calendar life-stress acceleration model to calculate the calendar life corresponding to each stress level in each stress type of each sensitive sample.

5. The calendar life assessment method for multiple stress levels according to any one of claims 1 to 4, characterized in that: Before step 1, the method further includes: Step a, establishing a calendar life prediction model, wherein the calendar life prediction model takes the calendar life corresponding to all stress levels of all stress types of all sensitive samples as input and takes the calendar life of the sensitive samples as output.

6. The calendar life assessment method for multiple stress levels according to claim 5, characterized in that: The step a) of establishing a calendar life prediction model includes: Based on the life-expiration mechanism of airborne equipment and the weight relationship between the calendar life and the calendar life of sensitive samples at various stress levels of various stress types, the calendar life prediction model is established as follows: Where, t is the calendar life of the sensitive sample; is the time proportion of the kth stress level of the i-th stress type, determined by the task profile; S i，k is the kth stress level of the i-th stress type; N is the number of stress types of the sensitive sample; i is 1, 2, 3, …, N; M is the number of stress levels of the i-th stress type; k is 1, 2, 3, …, M; f(S i，k ) is the calendar life of the sensitive specimen at the kth stress level of the ith stress type, calculated by the calendar life-stress acceleration model.

7. The calendar life assessment method for multiple stress levels according to any one of claims 1 to 4, characterized in that: The stress types include: temperature, humidity, chemical substances, microorganisms, deformation, and load; The stress level of each stress type is based on all values ​​of the mission profile of the airborne equipment.

8. The calendar life assessment method for multiple stress levels according to claim 7, characterized in that: The stress level set formed by the stress type and stress level is expressed as: The calendar life for each stress level under each stress type is: The time proportion of each stress level under each stress type is:

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