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The high temperature and low temperature alternating test chamber temperature cyclic stress test is an important means to check the quality of products, which is of great significance for evaluating the quality of products.
The following is an analysis and discussion of the causes of product failure by the Shanghai Huanqiu Test Technology Department through the temperature cycle stress test:
1. Basic parameters of temperature cycle stress:
There are six basic parameters of temperature cyclic stress: 1 upper limit temperature; 2 lower limit temperature; 3 temperature change rate; 4 upper limit temperature holding time; 5 lower limit temperature holding time; 6 cycles.
2. Analysis of temperature cycle stress characteristics:
In the environmental reliability test, when the temperature cycle changes, high temperature stress, low temperature stress and thermal fatigue interact on the product.
The material will show different degrees of thermal expansion and contraction. It is characterized in that increasing the temperature variation range and the temperature change rate can strengthen the process.
Therefore, increasing the thermal stress and increasing the number of cycles will directly affect the excited stress.
In the temperature cycle test, the uniformity of the gas flow in the high and low temperature alternating test chamber is an important parameter that will affect the rate of temperature change of the product. This requires that when multiple test products are tested simultaneously, there should be appropriate spacing between the test products and between the test product and the test chamber wall so that the air flow can freely circulate between the test products and between the test product and the tank wall. .
In the temperature cycle test, when the low temperature and high humidity conditions are changed to high temperature and high humidity conditions, since the air temperature rises faster than the product temperature, when a certain temperature difference is reached, condensation occurs on the product. The greater the temperature difference, the more obvious the condensation phenomenon, and the condensation water cannot be discharged in time, which increases the probability of corrosion of the product and reduces the insulation strength. For the whole machine, it will lead to sensitivity reduction, frequency drift, etc.
Serious will affect product quality.
3. The mechanism of temperature cycle stress induced failure and the temperature cycling of sensitive components make different materials with different expansion coefficients expand differently, resulting in peeling, cracking, and sensitive components such as paint coating;
The temperature cycle makes the screw connection or riveted joint loose, its sensitive components such as screws, riveted parts, etc.; temperature cycling makes the press fittings with insufficient mechanical tension loose; high temperature and low temperature alternating test chamber temperature cycle makes the material poor brazing The contact resistance of the solder increases or induces an open circuit, and its sensitive components such as resistive components; temperature cycling causes contact corrosion and contamination, and its sensitive components such as alloy materials.
Create a harmonious unity of energy and the environment. ——Shanghai Huanjing Test Equipment Factory
Discussion on Failure Mode of Temperature Cyclic Stress Test in High and Low Temperature Alternating Test Chamber