What is Thermal Shock Testing

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Update time : 2026-06-08

Definition of Thermal Shock Testing

Thermal Shock Testing involves alternately exposing test specimens to low-temperature and high-temperature air (or suitable inert gases) to subject them to the effects of rapid temperature changes. It is used to determine the ability of components, equipment, and other products to withstand rapid changes in ambient temperature.

It is designed to assess the product's adaptability to drastic changes in the surrounding environmental temperature and is an indispensable test in the qualification testing for equipment design finalization and routine testing during the batch production phase. In some cases, it can also be used for environmental stress screening tests. It can be said that the frequency of using thermal shock test chambers in verifying and improving the environmental adaptability of equipment is second only to vibration and high/low-temperature testing.

Purpose of Thermal Shock Testing

In fact, as a tool, the thermal shock test chamber serves different purposes when applied at various stages of product development:

2.1. In the engineering development phase, it can be used to discover design and manufacturing process defects in products.
2.2. It provides a basis for acceptance decisions during the product finalization or design qualification and batch production phases.
2.3. When applied as an environmental stress screening tool, the purpose is to eliminate early failures of the product.

Therefore, when compiling environmental test outlines, screening outlines, test reports, or screening reports at different stages of the development process, the test purpose of thermal shock testing should be clearly specified and should not be expressed vaguely or generally.

Requirements for Thermal Shock Testing

Starting Temperature Requirements

Although general thermal shock testing standards do not mention or strictly regulate the starting temperature of the test, this is an issue that must be considered when conducting the test. This is because it involves whether the test ends in a low-temperature or high-temperature state, which determines whether the product needs to be dried, thereby potentially extending the testing time.

If the test ends at a low temperature, after the tested product is removed from the thermal shock test chamber (room), it should be allowed to recover under normal testing atmospheric conditions until the specimen reaches temperature stability. This operation inevitably causes condensation on the surface of the test specimen, introducing the influence of temperature on the product and thereby changing the nature of the test.

In the implementation guidelines of GJB 150, it is proposed that to eliminate this effect and avoid prolonging the test implementation time due to a long recovery period, the specimen can be recovered in a high-temperature chamber at 50°C. After the condensation dries, it can then reach temperature stability at room temperature.

The implementation guidelines also suggest that the starting shock temperature can be changed to begin the test from a low temperature, so that the test ends at a high temperature, preventing condensation when the product is removed from the chamber. Both test methods subject the test specimen to six extreme temperature exposures (three high temperatures, three low temperatures) and five temperature shock processes; only the number of times in different shock directions differs. The test effects achievable by these two methods are basically the same, but the latter method requires no additional drying time, significantly shortening the thermal shock testing time.

Test Time Requirements

3.2.1. GJB 150.5 specifies a lower limit of 1 hour; that is, if the temperature stabilization time is less than 1 hour, the duration must be 1 hour. If it is greater than 1 hour, the actual time greater than 1 hour is used.
3.2.2. GB/T 2423.22 provides 5 time grades ranging from 10 minutes to 3 hours. Based on the product temperature stabilization time measured by the thermal shock test chamber, the closest time or a selectable time grade from the table is adopted, directly using the closest time as the holding time.
3.2.3. MIL-STD-810F Method 503.4 does not specify a concrete time or selectable time grade; it directly adopts the time required for the product to reach temperature stability or the actual exposure time of the product in the environment.

In thermal shock testing, the most critical aspect is to establish the stress caused by the inconsistent thermal expansion and contraction of different materials. Actual thermal shock is most likely to occur on the exterior of the tested product. Relevant data points out that it is not necessary to achieve temperature stability for the entire product, as long as the exterior temperature of the tested product is consistent with the test temperature. Although this opinion has a certain rationale, it is difficult to implement in practice because it is impossible to install numerous sensors on the surface of the product. Furthermore, the heat transfer capacity of various parts of the product is inconsistent, and the heat capacities of adjacent internal components within the tested product are also inconsistent, making it difficult to determine precisely.