The temperature cycling test of the test piece will have a significant impact on the aging effect of the material on the material. In particular, under the high and low temperature cycle changes, the performance and life of the material will be greatly affected. This test is to experience 5 mechanical shocks. Test samples were tried. The test chamber is a high-low temperature test chamber (-70°C~150°C) produced by Wuhan Shangchen Test Equipment Co., Ltd.
The specified change rate of the temperature cycling test and the specified changeover time for rapid temperature change are two test methods, and the temperature change ranges from the low temperature k. (up to -40°C) to high temperature Tx (up to 160°C). Among them, the temperature cycling test that stipulates the change rate has the requirements of live working in the regulations of Part 4 of the standard. Both tests are from normal temperature to low temperature to high temperature and return to normal temperature to form a temperature cycle.
First, the damage in the low temperature test is mainly:
1. Material embrittlement: may appear on plastic materials and some alloy materials;
2. Physical shrinkage: direct mechanical damage due to shrinkage;
3, structural damage: due to material embrittlement caused by cracks, strength weakening and cracking.
Second, the damage in high temperature test is mainly:
1. Material aging, softening and soft-melting decomposition and sublimation: may occur in plastic materials and synthesis;
2, physical expansion: due to direct mechanical damage caused by expansion;
3, structural damage: due to aging and expansion of the material caused by cracks, strength weakening and cracking;
4, oxidation or chemical reactions occur.
In the temperature cycle test, due to the heat transfer process of the temperature cycle test, partial condensation occurs alternately in the test sample and the high-low temperature test chamber. These condensation waters may accumulate within the structural gaps or penetrate into the microscopic fractures through capillary phenomena, and may also enter the interior of the test product or component due to "breathing" effects caused by temperature changes. The retained water will also freeze and expand when it enters a low temperature, which will generate or expand cracks, reduce the structural strength, and even directly cause damage and failure. Water or water molecules that enter the interior may also cause significant damage such as electrical failure or reduced electrical performance, and may even cause hidden damage such as corrosion and electrical corrosion.
In the two temperature cycle tests, the temperature cycle test of the specified rate of change of the test sample charged with power obviously has the characteristics of the aging test; the rapid temperature change test without charge work more accelerating the properties of the test.
For samples undergoing free drop test and mechanical impact test, in the temperature change test, the dominant failure caused by the structure of the test sample, such as the loss of function or obvious decline, will exit the test. If there is a hidden damage, it will be aggravated. .
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