Thermal Shock Chamber-Three Zone

• The temperature conversion rate varies between tests. In the cold and thermal shock test, the temperature conversion rate is exceptionally rapid, with temperature changes occurring suddenly in the process. For instance, in the macro-zhan technology’s two-box basket-type cold and thermal shock test chamber, the temperature conversion time is less than or equal to 10 seconds. In contrast, general temperature cycle tests do not prioritize sudden temperature changes, and the temperature rises and falls at a rate of approximately 1 to 3 degrees Celsius per minute.
• Cold and heat shock tests do not include humidity testing, whereas temperature cycle tests offer the option to include humidity testing.
• The difference in stress loading mechanisms distinguishes temperature cycling tests from thermal shock tests. Thermal shock testing identifies sample failure resulting from fatigue damage and creep, while temperature cycling detects sample failure due to shear fatigue.
• It’s important to note that cold and thermal shock tests permit the use of two-tank-type testing equipment, while temperature cycling tests require the use of a single-tank-type testing equipment.

Exposure to extreme temperatures can have several adverse effects on materials:

• Rubber and Flexible Materials:

Elasticity is reduced, and rupture may occur.

• Plastics and Metals:

Increased brittleness may lead to breakage or cracking.

• Electronic Components:

Changes in temperature can alter electrical parameters, affecting the electrical properties of the product.

• Structural Damage:

Icing or frosting may cause structural damage or moisture-related issues.

• Lubricants:

Increased viscosity of lubricants, resulting in reduced flow capacity and diminished lubrication.

• Material Shrinkage:

Shrinkage of materials may cause changes in the mechanical structure of the product.

• During testing, exercise caution to prevent damage to the rubber edge on the door of the test chamber. Any harm to the rubber edge can impact the service life of the test chamber. To prevent dust from entering the equipment and compromising performance, ensure cleanliness around the bottom of the test chamber and the surrounding ground.
• Regularly inspect the refrigeration system, which is the machine’s core. Check all copper tubes for leakage every six months. If there is any oil leakage from the couplings and welded ports, promptly notify the company or address the issue directly.
• Maintain the high-current contacts in the switchboard and distribution room by cleaning them at least once a year. Loose contacts can lead to dangerous working conditions, ranging from burned components to fire hazards and personal injuries. Utilize a vacuum cleaner to remove dust from inside the room.
• Be cautious with the over-temperature protector settings in the switchboard box. Do not attempt to adjust them arbitrarily, as the factory has already set them. These protection switches are in place to safeguard against heating tube burnout and trigger alarms. The set point is equal to the temperature set point +20℃ to 30℃.
• When retrieving the test product at the end of the testing period, ensure the equipment is in a shutdown state. Staff members handling the product must wear dry, anti-electric, and temperature-resistant gloves.
• Regularly clean and maintain both the interior and exterior of the box. Remove internal impurities before operating the machine.
• Perform an annual cleaning of the distribution room to eliminate dust. Use a vacuum cleaner for interior cleaning, and wipe the exterior of the cabinets with soapy water.

Here are several methods available for conducting cold thermal shock tests:

• Cyclic test method
• Rapid temperature change test
• Temperature shock test
• Programmed temperature rise and fall
• Comprehensive temperature test

In summary, electronic product manufacturers have various options for cold thermal shock tests, and they can choose the method that best suits their specific needs. To ensure the accuracy and reliability of these tests, manufacturers should pay attention to factors such as equipment selection, equipment calibration, and the scientific nature of the testing procedures.

The impact test is influenced by dynamic forces, leading to various factors that affect the accuracy and dispersion of the test results. The primary influencing factors include material factors, sample processing and preparation factors, and other considerations in the testing environment.

1. Material Factors:
   • Chemical composition, metallurgical microstructure, particle size, presence of segregation, white spots, cracks, and non-metallic inclusions exceeding standards impact the sample’s metallurgical defects.
   • Overheating, overcooking, tempering cellular, and other thermal defects in the material influence the impact properties, leading to greater dispersion in impact test results.
2. Sample Processing and Preparation Factors:
   • (1) Sampling Direction: Sampling along the rolling direction with a notch perpendicular to it results in higher impact values, while sampling perpendicular to the rolling direction with a notch along it yields lower impact values.
   • (2) Notch Processing Quality: The size and surface quality of the specimen’s notch significantly affect its impact performance. Rough notch roots, low notch roots, and machining traces parallel to the notch axis can decrease impact performance.
   • (3) Specimen Size: Increasing the width or height of the specimen increases the volume of plastic deformation during impact, resulting in higher absorbed energy. The specimen’s notch size determines the concentration of stress near the notch, affecting the specimen’s impact energy absorption.

• Reduced elasticity of flexible materials, such as rubber, and rupture;
• Increased brittleness of metals and plastics, leading to rupture or cracks;
• Changes in the electrical parameters of components affect the product’s electrical properties.
• Icing or frosting causing structural damage to the product or exposure to moisture;
• Increased viscosity of lubricants, reduced flow capacity, and reduced lubrication;
• Changes in mechanical structure caused by material shrinkage.

A thermal shock test chamber is a testing equipment. It can instantly switch from high to low temperature. It is generally used to test material structures or composite materials. Tests how well a material can withstand an environment of extremely high and low temperatures. At the same time, thermal expansion and contraction can cause chemical changes or physical damage. They can be detected quickly in the specimen.

In practice, you can specify the cold and thermal shock test’s duration based on these factors:

(1) The use conditions of the material:

Different materials are subject to different temperature changes under different use conditions. So, when doing the thermal shock test, specify the test’s duration based on how the material will be used.

(2) Practical needs:

The test’s duration should also be set based on practical needs. For example, if we need to test how durable a material is at extreme temperatures, we should increase the test’s duration.

(3) Test standards and industry specifications:

Different test standards and industry specifications have different rules. They vary for the duration of thermal shock testing. So, refer to the test standards and codes. They will tell you how long the thermal shock test should be.

Thermal shock is the result of a sharp heating or cooling of an object, which produces a large amount of heat exchange in a relatively short period of time, leading to a drastic change in temperature, thus generating shock thermal stresses. This phenomenon is commonly found in metallic materials. When a metallic material is subjected to rapid heating and cooling, a large temperature difference occurs within it, causing a large shock thermal stress. For example, in steam turbines, the main causes of thermal shock include the mismatch between the steam temperature and the metal during start-up, the thermal stresses generated during start-up in the extremely hot state due to the steam temperature being lower than the metal temperature of the cylinder and the rotor, and the sharp change in the temperature of the metal in the through-flow part when the load changes drastically.

1. Physical factors

(1) Glass vials and optical instruments broken.
(2) Clamping or loosening of moving parts.
(3) Different contraction/expansion rates of materials or inconsistent induced strain rates.
(4) Cracking of surface coatings, deformation or rupture of parts.
(5) Leakage from sealed compartments.
(6) Failure of insulation protection.

2. Chemical factors

(1) Separation of components.
(2) Chemical reagent protection failure.

3. Electrical factors

(1) Changes in electrical and electronic components.
(2) Rapid condensation or frost caused by electronic or mechanical failure.
(3) Excessive static electricity.

1. Temperature control accuracy: for the need to accurately control the temperature of the test project, you need to choose a high control accuracy of the hot and cold temperature shock tester.
2. Operation and control system: test samples in different environments, such as quality indicators need to operate the control system is simple and convenient, and can flexibly design different experimental programmes.
3. Test chamber size: need to choose the appropriate size of the test chamber according to the actual needs to ensure that the sample can be placed and tested at different temperatures.
4. Refrigeration and heating mode: At present, there are two main cooling and heating modes in the thermal shock test chamber, i.e. mechanical and liquid nitrogen. Mechanical type is suitable for small test chamber, liquid nitrogen type is suitable for large test chamber or need to reach the target temperature in a very short period of time test project.
5. Safety performance: the need to choose the hot and cold temperature impact tester in line with safety standards, and take into account the safety measures in the test chamber, such as fire, explosion, etc..

1. The equipment itself: for example, the heating element or temperature sensor is damaged or malfunction.
2. Environmental factors: for example, the ambient temperature or humidity conditions around the test chamber may affect the temperature control inside the test chamber.
3. Perational problems: for example, the test box is not used in the correct way, or the operator does not understand how to properly set and control the temperature and other parameters.

1. Check the equipment itself to ensure that the heating element and temperature sensors are operating normally. If there is a problem with the equipment, it needs to be repaired or replaced in time.
2. Adjust the environmental conditions around the test chamber, such as adjusting the room temperature or humidity and other parameters to ensure that the temperature control inside the test chamber is more stable.
3. Ensure that the operator has sufficient skills and knowledge about how to properly set and control the temperature and other parameters of the test chamber. If required, training and guidance can be provided.

1. Sometimes it may also be a cold thermal shock test box wall of the heat conduction is not smooth, resulting in high-temperature box leakage of heat or cold leakage of low-temperature box heat loss, in order to compensate for the loss of the inevitable air supply temperature difference, high-temperature box air supply temperature is higher than the box temperature, while the low-temperature box air supply temperature is lower than the temperature of the box, the temperature difference between this air supply also makes the test box box to produce the temperature is not uniform may be.
2. Cold thermal shock test box box temperature is not uniform due to the box wall six-sided heat transfer coefficient is not equal or because there are threading holes and other local heat transfer, but also so it will make the box wall radiation convection heat transfer is not uniform, affecting the temperature uniformity of the test box.
3. If the cold thermal shock test box chamber put enough to affect the overall internal heat convection test samples, it will affect the internal temperature uniformity to a certain extent, such as LED lighting products, the products themselves have a luminous heat, become a thermal load, then for the temperature uniformity of the existence of a great impact.
4. The structure of the thermal shock test chamber test box, which to a large extent affects the temperature uniformity between the work, due to the structure is difficult to completely symmetrical, thus causing a great impact on the temperature uniformity.

• First, the heat load: If the test chamber placed in the test chamber enough to affect the overall internal heat convection test samples, will inevitably affect the internal temperature uniformity to a certain extent, such as the placement of LED lighting products, the product itself exists in the luminous heat, become a heat load, then for the temperature uniformity of the existence of a great impact.
• Second, heat transfer: As the studio wall of the box before and after the left, right, up and down six sides of the heat transfer coefficient is different, some have threading holes, detection holes, test holes, etc. lead to local heat dissipation, heat transfer, so that the box temperature is not uniform, so that the box wall amplitude convection heat transfer is also not uniform, affecting the temperature uniformity.
• Third, heat radiation: design problems lead to the test box in the internal structure, space design is difficult to achieve uniform symmetrical structure, and asymmetric structure will inevitably lead to internal temperature uniformity bias, this level is mainly reflected in the sheet metal design and sheet metal processing, such as: the design of the air duct, the placement of the heat pipe location, the size of the fan power and so on.
• Fourth, sealing: box and door sealing is not tight, such as: sealing non-custom seams, the door leakage, etc., thus affecting the temperature uniformity of the workspace.
• Fifth, the test sample selection and placement of reasonableness: if the test object is too large, or the test object is placed in the high and low temperature test chamber working room location or way is not appropriate, so that the air inside the convection is blocked, but also produces a large temperature uniformity of the deviation. Such as placing the test product next to the air duct, seriously affecting the wind circulation, of course, the temperature uniformity will be greatly affected. Sixth, due to the different structure of the inner wall, so it will lead to the temperature of the inner wall of the test chamber will not be uniform, which in turn affects the heat convection inside the chamber caused by the internal temperature uniformity deviation.