The temperature of electronic components, automotive parts, aerospace and industrial products is often subject to change. These changes may cause stresses to materials and assemblies that cause cracks, deformation, electrical failure or lowered service life. Environmental testing is therefore an important aspect of the product development and quality control process.
Thermal shock testing and thermal cycling testing are two popular testing methods. Both present products to differing temperatures, but are used for testing different forms of thermal stress. A knowledge of the difference allows engineers to choose the correct test to be used on a particular application.
What Is Thermal Shock Testing?
Thermal shock testing is for testing a product for rapid and large temperature changes from hot to cold environments. The temperature change is very rapid, resulting in a large temperature gradient in the test specimen.
This quick change may lead to variations of expansion or contraction of materials used in an assembly. This means that mechanical stress might arise at sensitive places such as joints, coatings, solder joints, seals, and more.
The objective is to find out if a product will remain structurally and/or functionally intact after sudden temperature changes. Thermal Shock vs Thermal Cycling Testing can keep engineers abreast of the differences between these and let them know where each method is best suited.
What Is Thermal Cycling Testing?
Thermal cycling testing also involves multiple temperature changes as products are tested, but in general, the temperature changes are a bit more gradual. Product is held at a range of temperatures for a set period of time with a test chamber being moved between a specified range of temperatures.
The repeated expansion and contraction can highlight weaknesses which may not be seen in one transition of temperature. Typical causes of failure include material fatigue, cracking, seal degradation and connection failures.
When engineers are interested in exposing the engineering component to various environments over a period of time, thermal cycling is helpful. It can give useful data on the durability and reliability in the long term.
Key Differences Between the Two Tests
The most significant difference is the rate at which the temperature changes and the stress that is generated. Thermal shock is concerned with rapid change of temperature, and thermal cycling is a concern with repeated exposures to extremes of temperature.
Thermal shock is a common test to be used when the product could be subjected to sudden changes in the environment in its use. Thermal cycling is more appropriate for situations where products are cycled between hot and cold environments over long durations and/or frequent cycles.
Other test requirements include the chamber design, transition rates, dwell periods and temperature ranges. The conditions chosen should be selected by the engineer, considering the product and the industry in which it operates.
Choosing the Right Testing Approach
The appropriate test to use is dependent on the product, materials, operating conditions and failure potential. Ideally, both methods can be beneficial in some development programs as they will reveal different weaknesses.
Consistent and meaningful results can only be achieved by using reliable testing equipment. Equipment for controlled environmental testing or for the reliability evaluation of products is offered, for example, by companies like OTS Technik.
Care should also be taken to carefully set test parameters by the engineers. Depending on the specimen configuration, the results can vary with the temperature, exposure time, cycle number, transition speed and specimen geometry. The useful information from a well planned test can be used to enhance product design.
Conclusion
Thermal shock and thermal cycling testing can be helpful methods to test the reliability of the product under temperature stress conditions. But they should not be considered to be interchangeable. Thermal shock studies the consequences of changes in temperature and thermal cycling studies repeated exposure to temperature and fatigue it may cause over time.
The right method can assist manufacturers in determining weaknesses in the product early, enhance product longevity and minimize field failures. Environmental testing will continue to be a key element of the process for developing reliable products, as products continue to become more advanced and are used in more demanding environments. Therefore, it is important to grasp the difference between these two methods, in order to make more informed engineering decisions.
