If the test sample suddenly enters the low temperature environment from the high temperature environment, it is a cold and hot shock test.
There are three main ways of cold and hot impact testing machine:
1. Two box type cold and hot shock (gas): the test equipment has two boxes (high temperature area, low temperature area), the sample is placed in a basket, and the effect of cold and hot shock is achieved through the movement of the basket in the high temperature area and low temperature area. (the conversion time of two box type temperature shock is faster than that of three box type).
2. Two box type cold and hot shock (liquid): the test equipment has two boxes (high temperature area, low temperature area), the high temperature area and the low temperature area are respectively filled with silicone oil, the sample is placed in a basket, and the cold and hot shock effect is achieved through the movement of the high temperature area and the low temperature area of the basket. (the conversion rate of two box liquid impact is faster than that of two box gas impact).
3. three box type cold and hot shock (gaseous): the test equipment has three boxes (high temperature area, normal temperature area, low temperature area). During the test, the sample is in the normal temperature area and does not move. Only through the opening and closing of the damper in the high temperature area and normal temperature area, and the damper in the low temperature area and normal temperature area, the cold and hot shock effect is achieved. (the existing equipment in our laboratory is three box type)
How to dehumidify the cold and hot impact tester?
The cold and hot impact tester is used to test the material structure or composite material, which can endure the degree under the continuous environment of extremely high temperature and extremely low temperature in an instant, so as to detect the chemical change or physical damage caused by the expansion and contraction of the sample in a short time.
There are two dehumidification methods of the cold and heat impact testing machine: one is mechanical refrigeration dehumidification, the other is desiccator dehumidification. The dehumidification principle of mechanical refrigeration dehumidification is to cool the air below the dew point temperature, so that the water vapor with more than the saturated moisture content condenses out, thus reducing the humidity.
Desiccator dehumidification is to use air pump to extract the air in the cold and hot impact test machine, and inject the dry air. At the same time, send the wet air to the recyclable dryer for drying, and then send it to the cold and hot impact test machine after drying, so as to carry out dehumidification repeatedly.
At present, the former dehumidification method is used in most of the comprehensive cold and heat shock testing machines. The latter dehumidification method can make the dew point temperature below 0 ℃, which is suitable for occasions with special requirements, but the cost is relatively expensive.