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MIL-STD 202 Thermal Shock Testing

MIL-202 temperature shock testing helps determine the resistance of material to extremes of high and low temperatures. This test also evaluates the ability of material to withstand the shock of alternate exposures to these extremes. This might be experienced when equipment or parts are transferred to and from heated shelters in arctic areas. These conditions may also be encountered in equipment operated non-continuously in low-temperature areas or during transportation.

It is better for the specimen to reach thermal stability during the exposure specified. However, to save time, parts may be tested at the minimum exposure durations, which will approach, but not ensure thermal stability. Permanent changes in operation and physical damage caused variations in dimensions and other physical properties, may result.

Effects of MIL-STD 202 thermal shock include cracking and delamination of finishes. Cracking and crazing of embedding and encapsulating compounds may be an effect. Opening of thermal seals and case seams may occur. Materials may experience leakage of filling materials, rupturing, or cracking of hermetic seals and vacuum glass to metal seals. Changes in electrical characteristics may result from mechanical displacement or rupture of conductors or of insulating materials.

Keystone Compliance is a temperature shock testing lab, with significant MIL-202 thermal shock experience. Our experienced test engineers understand the requirements of MIL-STD 202 temperature shock compliance. The following information is extremely technical as it provides a summary of the MIL-STD-202 temperature shock testing requirements.

What Procedure Provides the Best Thermal Shock Testing?

All testing must be done in a thermal shock laboratory. Procedures may include environmental testing chambers and/or liquid baths. Materials are placed in the chambers so that there is no obstruction to the flow of air across and around it. When special mounting is required, it will be specified.

The first five cycles are run continuously, after this the test may be interrupted after the completion of any full cycle. Allow the specimens to return to room ambient temperature before resuming testing. One cycle consists of steps 1 through 4 of the applicable test condition.

Specimens should not be subjected to forced circulating air while being transferred from one chamber to another. Total transfer time from low to high temperature chambers, or vica-versa, should not exceed 5 minutes. The transfer time is the time between withdrawal from low temperature, and introduction into high temperature or visa versa.

Specimens may be immersed in a suitable liquid approved by the qualifying activity. The bath should be at the temperature in step 1 of the specified test condition, for the time specified. Immediately after step 1, the device is transferred to a suitable liquid at the temperature specified in step 2.

These two steps, step 1 and 2, constitute one cycle of the applicable test condition. Repeat the required number of cycles without interruption as specified. Transfer time from low to high temperature and from high to low temperature should be less than 10 seconds.

Specified measurements shall be made prior to the first cycle and upon completion of the final cycle. However, failures are based on measurements made after the specimen has stabilized at room temperature following the final cycle.

What Physical and Chemical Effects Does Temperature Shock Have on Material?

Several physical and chemical problems may occur when materials are exposed to the environments of the thermal shock testing lab. The lubricants could evaporate and gases or fluids could leak from gasket-sealed enclosures. Hermeneutic seals may fail, and  material may experience overheating due to reduced heat transfer.

The physical and chemical properties of low-density materials may experience a change. Sealed containers could deforme, rupture, or explode. Engines could experience erratic starting and operation problems. Any of these problems would indicate that material should not receive thermal shock certification.

What Temperature Shock Laboratory Provides the Best Temperature Shock Testing?

Keystone Compliance has been recognized as one of the best thermal shock labs in the country. Our test engineers understand the requirements of thermal shock compliance testing. We are equipped to provide temperature shock certifications for commercial, military, and aerospace products. Contact us to learn why Keystone Compliance is the best temperature shock lab to meet your compliance testing needs.

Looking for other MIL-STD-202 compliance tests? Click on a link below to learn more about the other test methods.