The constant temperature and humidity test chamber is also known as "high and low temperature humidity and heat alternating test chamber". It uses a touch screen intelligent instrument and can set a program cycle test. During the test, there is a cycle test failure. The following is the analysis of the cause of failure:
1. Basic parameters of temperature cycle stress: There are 6 basic parameters: ①upper limit temperature; ② lower limit temperature; ③ temperature change rate; ④ upper limit temperature holding time; ⑤ lower limit temperature holding time; ⑥ cycle number.
2. Analysis of temperature cycle stress characteristics: In the temperature cycle test, the airflow uniformity in the constant temperature and humidity test chamber is a very important parameter, which will affect the temperature change rate of the product. This requires that when multiple test products are tested at the same time, there should be appropriate intervals between the test products, between the test product and the test box wall, so that the airflow can circulate freely between the test products, between the test product and the box wall .
3. The mechanism of temperature cycle stress-induced failure and sensitive components: temperature cycling makes the expansion of different materials with different expansion coefficients different, causing peeling, cracking, and sensitive components such as paint coatings.
3.1 Temperature cycling makes loose joints that are screwed or riveted loose, and sensitive components such as screws and riveted parts;
3.2 The temperature cycle makes the pressure-matching joints with insufficient mechanical tension relax; the temperature cycle of the high and low temperature alternating test chamber makes the brazing contact resistance of poor materials increase or induces an open circuit, and its sensitive components such as resistance components;
3.3 Temperature cycle makes the contact corrosion and pollution, and its sensitive components such as alloy materials.
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