The reliability test should be after the reliability design, but at present the reliability work in China is mainly in the test phase, where the test is placed first. In order to measure the reliability of the product (that is, to measure the MTBF of the product), we need to take a certain sample and do a long-term running test to find out the failure time of each sample, according to the formula in the first section. Out of MTBF, of course, the more samples, the more accurate the test results. However, such an ideal test is actually impossible, because for this test, it is necessary to wait until the last sample fails - the test time required is unimaginable, all samples fail - the cost required Unbelievably high. High and low temperature test chamber
In order to test the reliability, here is introduced: Accelerated testing (that is, increasing the stress*), so that the defects appear quickly; after a large number of experts, long-term statistics, some methods to increase the stress were found and converted into some test items. If the product has passed the test of these items, there are still no obvious defects, which means that the reliability of the product can reach at least a certain level. After conversion, the MTBF can be calculated (because the product can pass these tests, there is no obvious defect, indicating that it has not been reached. The ultimate capacity of the product, so the corresponding MTBF is the minimum value of the product). Other calculation methods are described below. (*stress: refers to the destructive power of various external environments on the product. For example, the stress of the product working at 85 °C is greater than the stress at 25 °C; when working under high stress, the possibility of product failure is greatly increased. increased);
First, environmental testing
During the use of the product, there are different environments (some installed outdoors, some carry-on, some are on board, etc.), which will be stressed by different environments (some are subject to wind and rain, some are subject to vibration and fall, some In order to confirm that the product can work normally in these environments, the national standard and the standard label require the product to simulate some test items in the environmental method. These test items include:
1. High temperature test (high temperature operation, high temperature storage);
2, low temperature test (low temperature operation, low temperature storage);
3. High and low temperature alternating test (temperature cycle test, thermal shock test);
4, high temperature and high humidity test (wet heat storage, wet heat cycle);
5. Mechanical vibration test (random vibration test, frequency sweep vibration test);
6. Automobile transportation test (simulated transportation test, collision test);
7. Mechanical impact test;
8, switch electrical test;
9, power supply bias test;
10. Cold start test;
11. Salt spray test;
12, rain test;
13. Dust sand test;
The relevant national standards for the above environmental tests are as follows (some tests may not have relevant national standards, or I have not found them yet):
1, low temperature test
According to GB/T2423.1-89 "Electrical and Electronic Products Environmental Test Part II: Test Method Low Temperature Test";
GB/T2423.22-87 "Environmental testing of electrical and electronic products - Part 2: Test methods for temperature change of test methods"
Perform low temperature test and temperature change test.
Temperature range: -70 ° C ~ 10 ° C.
2, high temperature test
According to GB/T2423.2-89 "Electrical and Electronic Products Environmental Test Part II: Test Method High Temperature Test";
GB/T2423.22-87 "Environmental testing of electrical and electronic products - Part 2: Test methods for temperature change of test methods"
Perform high temperature test and temperature change test.
Temperature range: 10 ° C ~ 210 ° C
3. Damp heat test
According to GB/T2423.3-93 "Electrical and Electronic Products Environmental Test Part II: Test Method Constant Damp Heat Test";
GB/T2423.4—93 Environmental Testing for Electrical and Electronic Products Part II: Test Method for Alternating Damp Heat Test
A constant damp heat test and an alternating damp heat test were performed.
Humidity range: 30% RH ~ 100% RH
4, mold test
The mold test is carried out according to GB/T2423.16-90 "Environmental Testing of Electrical and Electronic Products Part II: Test Method for Mildew Test".
5, salt spray test
According to GB/T2423.17-93 "Electrical and Electronic Products Environmental Test Part II: Test Method Salt Spray Test" for salt spray test.
6, low pressure test
According to GB/T2423.21—92 “Environmental Testing of Electrical and Electronic Products Part II: Test Method Low Air Pressure Testâ€;
GB/T2423.25—92 “Environmental Testing of Electrical and Electronic Products Part II: Test Methods Low Temperature/Low Pressure Testâ€;
GB/T2423.26—92 “Environmental Testing of Electrical and Electronic Products Part II: Test Methods for High Temperature/Low Pressure Testsâ€;
Perform low pressure test, high, low temperature / low pressure test. Test range: -70 ° C ~ 100 ° C 0 ~ 760 mm Hg 20% ​​~ 95% RH.
7, vibration test
According to GB/T2423.10—95 “Electrical and Electronic Products Environmental Test Part II: Test Method Vibration Testâ€, the vibration test is carried out.
Frequency range (mechanical vibration table): 5 to 60 Hz (fixed frequency vibration 5 to 80 Hz), maximum displacement amplitude 3.5 mm (full load). Frequency range (electromagnetic vibration table): 5 to 3000 Hz, maximum displacement 25 mmP-P.
8, impact test
According to GB/T2423.5-95 "Electrical and Electronic Products Environmental Test Part II: Test Method Impact Test", the impact test is carried out. Impact acceleration range: (50 ~ 1500) m / s2.
9. Crash test
Collision test shall be carried out according to GB/T2423.6-95 "Environmental Testing of Electrical and Electronic Products Part II: Test Method Collision Test".
10. Drop test
According to GB/T2423.7-95 "Electrical and Electronic Products Environmental Test Part II: Test Method Dumping and Turning to Test";
GB/T2423.8-95 "Electrical and Electronic Products Environmental Test Part II: Test Method Free Drop Test" for the drop test.
Note: The above 13 items comprehensively summarize the external environment encountered by the product in the process of its use; in actual test, because the properties of each product are far apart and the use environment is very different, each company can according to the characteristics of the product. Appropriately select and add some items to test (the required test items required in the country/line label of this product, of course, must be tested); you can also design some new test items according to the specific use environment and usage of the product. To verify that the product can work for a long time.
Test conditions: Different product test conditions are different; for high temperature test, some products require high temperature storage test, some require high temperature operation test, some products are tested at 85 ° C for high temperature, and 65 ° C for some products. °C to do the test. However, there is only one purpose, that is, at least meet the country/line standard. To test the reliability of a product, it is necessary to find the country/standard label of the product. According to the requirements and guidelines of the national/market standard, the necessary test items and test methods of each item are found to conduct environmental testing;
The same product, at different stages, the test conditions are different; in general, the product will undergo three stages of research and development, small batch trial production, mass production. In the research and development stage, the test conditions are the most severe (maximum stress), the test is the shortest; the small batch trial production stage, the test stress is moderate, the test time is moderate; the mass production stage, the test stress is the smallest, the test time is short; the three stages The main differences are as follows:
Stage experiment purpose experimental characteristics experimental requirements
R&D found design flaws, expanded design margin, high stress, and short-term trouble-free
The pilot test examines whether the product has reached the basic reliability level of stress, no significant failure for a long time.
Stability of mass production process conditions, low stress, short-term conditional allowable failure
Identification and identification of product reliability, calculation of MTBF low stress, no special requirements for a long time
Accelerated environmental testing technology
The traditional environmental test is a test method based on real environment simulation, called environmental simulation test. This test method is characterized by: simulating the real environment, plus design margins to ensure that the test passes. The drawback is that the efficiency of the test is not high, and the resources of the test are expensive.
Furniture Chair,Student Study Chair,Table And Chair Set,Adjustable School Table And Chair
AU-PINY FURNITURE CO., LTD , https://www.jmaupiny.com