A product temperature cycle and constant humidity step temperature combined test life evaluation method and system

Abstract

The application provides a product temperature cycle and constant humidity step temperature fusion test life evaluation method and system, and the steps comprise: carrying out an accelerated test according to a preset test profile, obtaining a likelihood function of a test sample, maximizing the obtained likelihood function, and estimating the product life; and the system adopts a computer control system to evaluate the test life. According to the scheme of the application, the storage life of a complex natural environment storage product under the influence of multiple environmental factors and multiple failure modes can be evaluated, the evaluation method uniformly fuses the temperature cycle into the constant humidity step temperature test, the actual storage conditions of the product can be better simulated, and the test result can be ensured to be more accurate.

Description

Technical Field

[0001] This invention belongs to the field of product life assessment technology, specifically relating to a product life assessment method and system for a fusion test of temperature cycling and constant humidity step temperature. Background Technology

[0002] Products are subject to temperature aging, temperature cycling fatigue, and humidity during natural storage. Temperature cycling and constant temperature step-humidity combined tests can effectively simulate these environmental effects. Currently, GJB 5103-2004 "Accelerated Life Test Method for Ammunition Components" provides data processing methods for temperature step-humidity tests, and GJB 736.13-1991 "Test Methods for Pyrotechnics: Accelerated Life Test - Constant Temperature Stress Test Method" provides data processing methods for constant temperature stress tests. While these methods are applicable to product life test data processing based on thermal oxidative aging failure mechanisms, products are also affected by temperature cycling fatigue and humidity during actual storage. Therefore, the aforementioned methods cannot accurately assess product lifespan. Summary of the Invention

[0003] In order to solve the technical problems mentioned in the background art, the present invention aims to provide a method and system for evaluating the life of a product through a fusion test of temperature cycling and constant humidity step temperature.

[0004] The present invention adopts the following technical solution.

[0005] A method for evaluating the lifespan of a product through a combined temperature cycling and constant humidity temperature test, comprising the following steps: Step 1, Sample preparation; Step 2: Conduct accelerated testing according to the preset test profile; Step 3: Obtain the likelihood function (VIII) of the test sample; ………… (VIII) in: …… (VII) In the formula: a, b, m — unknown parameters; T i —No. i Test temperature at each stress level ( i =1,2,…, k, k (Round to the integer, representing the total number of constant temperature and humidity stress levels). t —Test time, t≥0， At the i-th stress level, we have t i-1 <t<ti ; —No. i Failure distribution function under each stress level; —No. i Number of sample tests at each stress level k is the number of test stress levels; —No. i Under the stress level, the first j The test duration of the sample during the second test. ; —No. i Under the stress level, the first j The total number of samples tested in each test; —No. i Under the stress level, the first j Number of failed samples during the second test; —No. i Characteristic lifetime at each stress level ; —No. i Characteristic lifetime at each stress level ; —Product normal temperature stress level The characteristic lifetime below; —Storage environment at room temperature (temperature difference is) )middle Storage time corresponding to each temperature cycle; —Product under stress The constant temperature and humidity test time under these conditions; Step 4: Maximize the obtained likelihood function to obtain the maximum likelihood estimates of a, b, and m. And estimate the product lifespan according to formula (IX); ………………………… (IX) In the formula: T 0 —Normal temperature stress level e= 2.72.

[0006] To more accurately assess product lifespan, the test profiles are shown in the table below. .

[0007] As a preferred option, the temperature cycling test conditions are as follows: Temperature change rate 10℃ / min, high temperature 71℃ (80%RH), low temperature -54℃, temperature control deviation ±2℃; Each cycle lasts 4 hours: heating time 12.5 min, high temperature holding time 155 min, cooling time 12.5 min, and low temperature holding time 60 min.

[0008] A product temperature cycling and constant humidity step-temperature fusion test life assessment system includes a computer control system. The computer control system includes a memory, a processor, and a program stored in the memory and executable on the processor. The system is characterized in that the processor executes the program to perform the following steps: S1, read the input / selected test sample information, match the preset test profile and carry out accelerated testing; S2, read the input / recorded accelerated test result data and obtain the likelihood function (VIII) of the test sample; ………… (VIII) in:

[0009] In the formula: a, b, m — unknown parameters; T i —No. i Test temperature at each stress level ( i =1,2,…, k, k (Round to the integer, representing the total number of constant temperature and humidity stress levels). t —Test time, t≥0， At the i-th stress level, we have t i-1 <t<t i ; —No. i Failure distribution function under each stress level; —No. i Number of sample tests at each stress level k is the number of test stress levels; —No. i Under the stress level, the first j The test duration of the sample during the second test. ; —No. i Under the stress level, the firstj The total number of samples tested in each test; —No. i Under the stress level, the first j Number of failed samples during the second test; —No. i Characteristic lifetime at each stress level ; —No. i Characteristic lifetime at each stress level ; —Product normal temperature stress level The characteristic lifetime below; —Storage environment at room temperature (temperature difference is) )middle Storage time corresponding to each temperature cycle; —Product under stress The constant temperature and humidity test time under these conditions; S3, maximize the likelihood function to obtain the maximum likelihood estimates of a, b, and m. And estimate the product lifespan according to formula (IX); ………………………… (IX) In the formula: T 0 —Normal temperature stress level e= 2.72; S4 outputs the result data.

[0010] Beneficial Effects: The present invention provides a method to assess the storage life of products stored in complex natural environments under multiple environmental influences and multiple failure modes. The assessment method uniformly integrates the number of temperature cycles and temperature differences into the constant humidity and temperature step test, converting them to the actual number of temperature cycles and temperature differences in storage. It then calculates the corresponding storage time using the temperature operating extreme value method, further converting it to the constant humidity and temperature step test time. Finally, it extrapolates the storage life under actual storage conditions based on the number of failures at each temperature. The method uniformly integrates temperature cycles into the constant humidity and temperature step test, better simulating actual product storage conditions and ensuring more accurate test results. Furthermore, the invention uses the high-temperature and low-temperature operating extreme values ​​of the actual product storage environment to determine the annual number of temperature cycles and temperature differences, which better reflects actual storage conditions and effectively improves the accuracy of the assessment results. Attached Figure Description

[0011] Figure 1This is a schematic diagram of the temperature cycling test conditions in Example 1; Figure 2 This is a cross-sectional view of the combined "temperature cycling and constant humidity step temperature fusion test" in Example 1. Detailed Implementation

[0012] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0013] First, the life evaluation model of the temperature cycling and constant humidity step temperature fusion test in this invention will be explained.

[0014] The basic assumptions are as follows: Assumption 1, under stress underwater T i Under these conditions, the product lifetime follows a Weibull distribution. ; Assumption 2, various stress levels T i The shape parameters below m i Equal, that is ; Assumption 3, the characteristic lifespan of the product η i With the applied stress level T i The acceleration equation (Ⅰ) is satisfied: …………………… (I) In the formula: a, b For parameters to be estimated (unknown); Assumption 4: The remaining life of the product depends only on the accumulated failure portion and the stress level at that time, and is independent of the accumulation method (Nelson cumulative failure assumption). Assumption 5: Fatigue caused by temperature cycling satisfies the following Coffin-Manson model, Equation (II): ………………….. (II) In the formula, N a —Number of cycles in the temperature-accelerated cycling test; N 0 —Number of temperature cycles during actual storage; △T a —Temperature difference in temperature-accelerated cycling test; △T 0 —Temperature difference during actual storage; n >1 and is an integer. n It is the average value of the results of multiple tests.

[0015] Temperature accelerates the number of cycle tests N a ( △T a This can calculate the number of temperature cycles during actual storage. N 0 ( △T 0 The number of temperature cycles per year can be obtained by analyzing the actual number of temperature cycles in the storage environment. N 0 The corresponding room temperature storage time is t N0 Based on assumption one, the storage time at room temperature can be calculated. t N0 Corresponding temperature stress T i The following test time t Ni See equation (Ⅲ): …………………………….... (III) In the formula: η i —Product Stress T i The characteristic lifetime below; η 0 —Product at room temperature T 0 The characteristic lifetime below; t N0 —Storage at room temperature N 0 ( △T 0 Storage time corresponding to each temperature cycle; t Ni — t N0 Converted to temperature stress T i The test time below; Step stress T i The constant temperature and humidity test time is recorded as follows: t BiThen, according to assumption four, we get equation (Ⅳ):

[0016] ………………………… (IV) ……

[0017] In the formula: —Product under stress The constant temperature and humidity test time, ; t 1 、t 2 、t i —Step stress of temperature cycling test time conversion (1st and 2nd steps) i The time it takes for a temperature stress test to end.

[0018] Storage environment at room temperature △T 0 and N 0 The temperature range is determined by those skilled in the art based on the extreme values ​​of high-temperature and low-temperature operating conditions of the risk rate of the storage environment over a certain period of time; the temperature differences experienced by products such as ammunition when stored in a natural environment include annual temperature difference, monthly temperature difference, diurnal temperature difference, and short-term temperature difference. Determine the temperature difference of the storage environment △T 0 Then, the number of cycles the product will undergo per year under this storage environment can be determined based on the adopted time risk rate. N 0 Using the temperatures recorded at the Wanning meteorological station from 2016 to 2020 as the statistical object, the average high and low temperature extreme values ​​under a 10% time risk rate in the Wanning area over the past 5 years were 32.28℃ and 14.74℃, respectively. Therefore, taking the temperature difference as 18℃, the number of temperature cycles in a year is 37.

[0019] Assumption 3: ln η 0 = a+b / T 0， i =0, 1, ... k， The test was converted from a temperature cycling and constant humidity step-temperature fusion test to a test in T i ( i =1, 2, ... k A step temperature test was conducted at a temperature of ) temperature. The sample was first subjected to T 1Temperature test, test time t 1 Then at temperature T 2 （T 2 ＞T 1 ） The following experiment, the experiment time t 2 -t 1 Then at temperature T 3 （T 3 ＞T 2 ） The following experiment, the experiment time t 3 -t 2 Finally in T 4 （T 4 ＞T 3 ） Temperature test t 4 -t 3 Parameter estimation follows the parameter estimation method described above for the step temperature test, i.e., the product at (0, ... t The cumulative failure function on the [ ] is, i.e., equation (V): (V) In the above formula (Ⅳ) t i ( i =1, 2, ... k -1) Substituting into equation (V) respectively, we obtain equation (VI):

[0020] ………(VI)

[0021]

[0022] Then, the general formula for the cumulative failure function is equation (VII): … (VII) Further, the likelihood function (VIII) of the test sample (sample) can be obtained; …………… (VIII) In the formula: a, b, m — unknown parameters; T i —No. i Test temperature at each stress level ( i =1,2,…, k, k (Round to the integer, representing the total number of constant temperature and humidity stress levels). t —Test time, t≥0， At the i-th stress level, we have t i-1 <t<t i ; —No. i Failure distribution function under each stress level; —No. i Number of sample tests at each stress level k is the number of test stress levels; —No. i Under the stress level, the first j The test duration of the sample during the second test. ; —No. i Under the stress level, the first j The total number of samples tested in each test; —No. i Under the stress level, the first j Number of failed samples during the second test; —No. i Characteristic lifetime at each stress level ; —No. i Characteristic lifetime at each stress level ; —Product normal temperature stress level The characteristic lifetime below; —Storage environment at room temperature (temperature difference is) )middle Storage time corresponding to each temperature cycle; —Product under stress The constant temperature and humidity test time.

[0023] Maximize the resulting likelihood function to obtain the maximum likelihood estimates of a, b, and m. And estimate the product lifespan according to formula (IX); ………………………… (IX) In the formula: T 0 —Normal temperature stress level e= 2.72.

[0024] Example 1 A method for evaluating the lifespan of a product through a combined temperature cycling and constant humidity temperature test, comprising the following steps: Step 1, Sample preparation; The tested products (test samples) were of a certain type, randomly selected from the same batch of qualified products with intact packaging and clear markings. The total number of samples was 300 pieces, with 20 pieces for initial performance testing, and 20 pieces tested per cycle during the test, totaling 240 pieces over 12 cycles. 40 pieces were reserved. The testing process for the test samples is shown in Table 1. The samples were conditioned before and after the test. Before the test, the test samples were placed at (21±6)℃ for at least 12 hours. Performance testing and failure determination of the test samples were conducted according to the product acceptance technical conditions and product manufacturing and acceptance specifications.

[0025] Step 2: Conduct accelerated testing according to the preset test profile; First, determine the test conditions for the temperature cycling and constant humidity temperature fusion test based on the test samples. The specific conditions for the temperature cycling test are as follows: (Combined with...) Figure 1 As shown, the temperature change rate was 10℃ / min, the high temperature was 71℃ (80%RH), the low temperature was -54℃, and the temperature control deviation was ±2℃; each cycle was 4 hours: heating time 12.5min, high temperature holding time 155min, cooling time 12.5min, and low temperature holding time 60min; the total time for the temperature cycling test was 30 cycles (5 days). The specific conditions for the constant humidity-step temperature test are as follows: the temperature stress level should be determined based on the product type, characteristics, and structure, with four stress levels; the highest stress level is determined after analyzing the failure mechanism of the product, its components, and materials; the minimum test temperature for typical products is 326K (53℃), with a temperature interval of 9K; the total test time for the constant humidity-step temperature test is tentatively set at 90 days. According to the step stress sequence, the stress levels for the product tests are as follows: a) First stress level T1: 326K (53℃), 36d; b) Second stress level T2: 335K (62℃), 27d; c) Third stress level T3: 344K (71℃), 18d; d) Fourth stress level T4: 353K (80℃), 9d.

[0026] The test was conducted three times at each stress level. The relative humidity stress level was based on the highest relative humidity of the product stored in the standard warehouse. In this test, the relative humidity was 80%.

[0027] Then, the experimental profile combining the "temperature cycling and constant humidity temperature step-by-step test" was determined, see... Figure 2 As shown in Table 2, the relative humidity during the high-temperature phase was 80%, and the specific details are shown in Table 1. Table 1 Test profiles and quantity allocation of test samples .

[0028] The number of failed samples obtained after the test is shown in Table 2.

[0029] Table 2 Failure Sample Information .

[0030] Step 3: Based on the obtained failed samples and the detection results, obtain the likelihood function (VIII) of the test sample. ………… (VIII) In the formula: a, b, m — unknown parameters; T i —No. i Test temperature at each stress level ( i =1,2,…, k, k (Round to the integer, representing the total number of constant temperature and humidity stress levels). t —Test time, t≥0， At the i-th stress level, we have t i-1 <t<t i ; —No. i Failure distribution function under each stress level; —No. i Number of sample tests at each stress level k is the number of test stress levels; —No. i Under the stress level, the first j The test duration of the sample during the second test. ; —No. iUnder the stress level, the first j The total number of samples tested in each test; —No. i Under the stress level, the first j Number of failed samples during the second test; —No. i Characteristic lifetime at each stress level ; —No. i Characteristic lifetime at each stress level ; —Product normal temperature stress level The characteristic lifetime below; —Storage environment at room temperature (temperature difference is) )middle Storage time corresponding to each temperature cycle; —Product under stress The constant temperature and humidity test time under these conditions; Step 4: Maximize the obtained likelihood function to obtain the maximum likelihood estimates of a, b, and m. And estimate the product lifespan according to formula (IX); ………………………… (IX) In the formula: T 0 —Normal temperature stress level e= 2.72.

[0031] Based on the aforementioned testing time and the number of failed samples, the following calculations can be made: Storage life It is 10.41 years.

[0032] Example 2 A product temperature cycling and constant humidity step-temperature fusion test life assessment system includes a computer control system. The computer control system includes a memory, a processor, and a program stored in the memory and executable on the processor. The system is characterized in that the processor executes the program to perform the following steps: S1, read the input / selected test sample information, match the preset test profile and carry out accelerated testing; S2, read the input / recorded accelerated test result data and obtain the likelihood function (VIII) of the test sample; …… (VIII) in: …… (VII) In the formula: a, b, m — unknown parameters; T i —No. i Test temperature at each stress level ( i =1,2,…, k, k (Round to the integer, representing the total number of constant temperature and humidity stress levels). t —Test time, t≥0， At the i-th stress level, we have t i-1 <t<t i ; —No. i Failure distribution function under each stress level; —No. i Number of sample tests at each stress level k is the number of test stress levels; —No. i Under the stress level, the first j The test duration of the sample during the second test. ; —No. i Under the stress level, the first j The total number of samples tested in each test; —No. i Under the stress level, the first j Number of failed samples during the second test; —No. i Characteristic lifetime at each stress level ; —No. i Characteristic lifetime at each stress level ; —Product normal temperature stress level The characteristic lifetime below; —Storage environment at room temperature (temperature difference is) )middle Storage time corresponding to each temperature cycle; —Product under stress The constant temperature and humidity test time under these conditions; S3, maximize the likelihood function to obtain the maximum likelihood estimates of a, b, and m. And estimate the product lifespan according to formula (IX); ………………………… (IX) In the formula: T 0 —Normal temperature stress level e= 2.72; S4 outputs the result data.

[0033] The present invention provides a method to assess the storage life of products stored in complex natural environments under multiple environmental influences and multiple failure modes. The assessment method uniformly integrates the number of temperature cycles and temperature differences into the constant humidity and temperature step test, converting them to the actual number of temperature cycles and temperature differences in storage. It then calculates the corresponding storage time using the temperature operating extreme value method, further converting it to the constant humidity and temperature step test time. Finally, it extrapolates the storage life under actual storage conditions based on the number of failures at each temperature. The method uniformly integrates temperature cycles into the constant humidity and temperature step test, better simulating actual product storage conditions and ensuring more accurate test results. Furthermore, the present invention uses the high-temperature and low-temperature operating extreme values ​​of the actual product storage environment to determine the number of temperature cycles and temperature differences per year, which better reflects actual storage conditions and effectively improves the accuracy of the assessment results.

Claims

1. A method for evaluating the lifespan of a product through a combined temperature cycling and constant humidity temperature test, characterized in that the steps include... include: Step 1, Sample preparation; Step 2: Conduct accelerated testing according to the preset test profile; Step 3: Obtain the likelihood function (VIII) of the test sample; ………… （Ⅷ） in: ……… （Ⅶ） In the formula: a, b, m — unknown parameters; T i —No. i Test temperature at each stress level, i =1,2,…, k, k Round to the integer, representing the total number of constant temperature and humidity stress levels; t —Test time, t≥0， At the i-th stress level, we have t i-1 <t<t i ; —No. i Failure distribution function under each stress level; —No. i Number of sample tests at each stress level k is the number of test stress levels; —No. i Under the stress level, the first j The test duration of the sample during the second test. ; —No. i Under the stress level, the first j The total number of samples tested in each test; —No. i Under the stress level, the first j Number of failed samples during the second test; —No. i Characteristic lifetime at each stress level ; —No. i Characteristic lifetime at each stress level ; —Product normal temperature stress level The characteristic lifetime below; —Storage at room temperature The storage time corresponding to each temperature cycle, and the temperature difference of the ambient temperature storage environment are: ; —Product under stress The constant temperature and humidity test time under these conditions; Step 4: Maximize the obtained likelihood function to obtain the maximum likelihood estimates of a, b, and m. And estimate the product lifespan according to formula (IX); ………………………… （Ⅸ） In the formula: T 0 —Normal temperature stress level e= 2.

72.

2. The method according to claim 1, characterized in that: The experimental profiles are shown in the table below. 。 3. The method according to claim 2, characterized in that, The temperature cycling test conditions are as follows: Temperature change rate 10℃ / min, high temperature 71℃, humidity 80%RH, low temperature -54℃, temperature control deviation ±2℃; Each cycle lasts 4 hours: heating time 12.5 min, high temperature holding time 155 min, cooling time 12.5 min, and low temperature holding time 60 min.

4. A product temperature cycling and constant humidity step-temperature fusion test life assessment system, comprising a computer control system, wherein the computer control system includes a memory, a processor, and a program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it performs the following steps: S1, read the input / selected test sample information, match the preset test profile and carry out accelerated testing; S2, read the input / recorded accelerated test result data and obtain the likelihood function (VIII) of the test sample; ………… （Ⅷ） in: …… （Ⅶ） In the formula: a, b, m — unknown parameters; T i —No. i Test temperature at each stress level, i =1,2,…, k, k Round to the integer, representing the total number of constant temperature and humidity stress levels; t —Test time, t≥0， At the i-th stress level, we have t i-1 <t<t i ; —No. i Failure distribution function under each stress level; —No. i Number of sample tests at each stress level k is the number of test stress levels; —No. i Under the stress level, the first j The test duration of the sample during the second test. ; —No. i Under the stress level, the first j The total number of samples tested in each test; —No. i Under the stress level, the first j Number of failed samples during the second test; —No. i Characteristic lifetime at each stress level ; —No. i Characteristic lifetime at each stress level ; —Product normal temperature stress level The characteristic lifetime below; —Storage at room temperature The storage time corresponding to each temperature cycle, and the temperature difference of the ambient temperature storage environment are: ; —Product under stress The constant temperature and humidity test time under these conditions; S3, maximize the likelihood function to obtain the maximum likelihood estimates of a, b, and m. And estimate the product lifespan according to formula (IX); ………………………… （Ⅸ） In the formula: T 0 —Normal temperature stress level e= 2.72; S4 outputs the result data.

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