What are the time-related test standards for high and low temperature impact test chambers?

What are the time-related test standards for high and low temperature impact test chambers?

    High and low temperature impact test chamber is also known as temperature shock test box, hot and cold shock test box, three-box temperature shock test box, two-box high and low temperature impact test box, basket type hot and cold shock test box, test box, testing machine and other aliases.

GJB150, GB/T2423 and MIL-STD-8lOF hot and cold shock test chamber are also slightly different in the three standards, and in principle, they are the time required for the test product to reach temperature stability at the test temperature.

GJB150.5 specifies the lower limit of 1h, that is, if the temperature stabilization time is less than 1h, it must be 1h; if it is greater than 1h, the time greater than 1h is used;

GB/T2423.22 gives 5 time levels from 10min to 3h, and the user uses a time similar to the product temperature stabilization time as the holding time;

The 810F method 503.4 does not specify the specific time or optional time level, directly using the time when the product reaches temperature stability or the real exposure time of the product in the environment, in the high and low temperature hot and cold shock test chamber test, the more critical is to establish the stress caused by the inconsistency of thermal expansion and contraction of different materials.

The actual thermal shock is more likely to occur on the outside of the test product, and the relevant information points out that it is not necessary to achieve the temperature stability of the entire product, but as long as the temperature of the outer surface of the test product is consistent with the test temperature. Although this opinion has some truth, it is also difficult to implement, because it is impossible to install many sensors on the surface of the product, in addition, the heat transfer capacity of each part of the product is inconsistent, and the heat capacity of the adjacent parts inside the test product is also inconsistent, so it is difficult to determine.