Environmental testing is not the same as reliability testing. Do you know this? Although environmental test and reliability test are closely related, they are very different in terms of test purpose, test time, magnitude of environmental stress used, test type, selection criteria of environmental force value, etc.
Environmental testing is to investigate the adaptability of the product to the environment, to determine whether the design of the product's environmental adaptability meets the contract requirements, and to provide decision-making basis for acceptance and rejection. The reliability test is to quantitatively evaluate the reliability of the product, that is, under the specified environmental conditions, the probability of the product to complete the specified function within the specified time.
In the environmental test, the time of each test basically depends on the selected test and the specific test procedure, but due to the different time required for the performance test at each stage, the test time is much shorter than that of the reliability test. The reliability test time depends on the reliability index value to be verified, the selected statistical test scheme and the quality of the product itself. The time can only be determined when the total unit hours of the product to be tested reaches the specified value or the acceptance fails.
In terms of environmental testing, the test items are specified, including environmental stress that has an important impact on the product, such as temperature, humidity, salt spray, vibration, shock, etc., pressure, solar radiation, sand, rain, etc. Test items should be selected based on future environmental conditions and impact levels. In general, more than 10 environmental stresses should be investigated. Due to the comprehensive simulation, the reliability test only considers the comprehensive environmental stress (temperature, humidity, vibration) and electrical stress.
Environmental tests usually use single-factor tests and multi-factor combination tests, which act on the product in a certain order. Comprehensive stress tests are often used in reliability tests. Applying multiple environmental stresses to the specimen in the same space and at the same time can more realistically simulate the effects of environmental conditions. In order to improve the accuracy and reliability of the test results, environmental testing has also begun to focus on the development of comprehensive testing, and actively develop large-scale multi-functional environmental testing equipment that can simultaneously apply stresses such as temperature, humidity, vibration, radiation, dust, wind, and rain.
Environmental tests basically use extreme conditions, and use harsh conditions instead of mild conditions, that is, take the extreme environmental conditions that may be encountered in the product life cycle as the test conditions. Many tests are destructive to a certain extent, and there is no need to simulate the working state of the product during the test. The reliability test adopts the actual effect test, which simulates the main environmental conditions and their dynamic changes during storage, transportation and use. Determine the environmental profile based on the mission profile, and then simplify the environmental profile to a test profile for long-term reliability evaluation of the product. Generally speaking, the reliability test will not cause damage to the product. It needs to simulate the working state of the product. Most of the test conditions are used to simulate mild stress environments often encountered in the work, and their values are much lower than environmental tests.