Views: 125 Author: Site Editor Publish Time: 2019-10-09 Origin: Site
What Is The Thermal Shock Testing
Thermal shock test, also known as temperature shock test or high temperature shock test, is used to assess the adaptability of products to the rapid change of ambient temperature. It is an indispensable test in the identification test of equipment design and the routine test in batch production stage. It can be said that the frequency of thermal shock test in verifying and improving the environmental adaptability of equipment is second only to vibration and high and low temperature test.
Common Performance Criteria for Thermal Shock Test
1. GJB 150-86 Environmental Test Method for Military Equipment
2. GB 2423 Basic Environmental Test Procedures for Electrical and Electronic Products
3. MIL－STD－810F Environmental Engineering Considerations and Laboratory Tests
Purpose of Thermal Shock Test
1. It can be used in the engineering development phase to discover the design and process defects of the product.
2. Provide basis for product setting or design qualification and acceptance decision in batch production stage.
3. Eliminate the early failure of the product.
Starting Temperature Requirement
Although the initial temperature of thermal shock test is not mentioned or rigid in the general thermal shock test standard, this is a problem that must be considered when the test is carried out, because it involves whether the test ends at low temperature or high temperature, which determines whether the product needs to be dried and the test time is prolonged.
If the product of the low temperature standard test is removed from the thermal shock test chamber at the end of the test, it should be restored under the normal test atmosphere until the arrival temperature of the sample is stable, this operation will inevitably cause condensation on the surface of the test sample and the influence of temperature on the product. Thus changing the nature of the test.
In the GBJ 150 implementation guide, it is proposed that in order to eliminate this effect and prolong the test implementation time, the sample can be recovered in a high temperature chamber of 50, and the temperature can be stable at room temperature after the condensation is dry. The implementation guide proposes that the initial shock temperature can be changed to start the test at low temperature so that the test results can avoid condensation in the product cooling and heat impact test chamber at high temperature. However, the two test methods subjected the samples to the effect of six extreme temperatures (three high temperatures, three low temperatures) and five temperature impact processes, but the number of times of different impact direction was different. The test results of the two tests were basically the same, but the latter test method shortened the cold and hot shock test time without adding drying time.
Test Time Requirement
1. GJB150.5 specifies the lower limit of 1h in the world, that is, if the temperature stability time is less than 1h, if it is greater than 1h, it should be used for more than 1 hour.
2. GB2423.22 gives 5 time levels from 10 min to 3 h. According to the temperature stability time of the product measured by the thermal shock test chamber, the nearest time or time grade is adopted, and the nearest time is used as the retention time.