MIL-STD-810G High Temperature Test--Climatic Chamber

The MIL-STD-810G test method was developed specifically for dod applications, but can also be customized for commercial applications and includes a variety of environmental tests, including: Low Pressure (Altitude) ,High Temperature,Low Temperature,Temperature Shock,Salt Fog ,Sand and Dust,Vibration,shock, this article is mainly about High temperature test 501.5 in MIL-STD-810G test method

Purpose

The MIL-STD 810G high temperature test helps to assess the impact of high temperature conditions on performance, integrity and material safety. This method is best suited for materials that may be used at temperatures higher than standard ambient temperatures. According to the MIL-810H high temperature regulation, all tests shall be performed in a high temperature test chamber.

Application

Use this method to evaluate materials that may be deployed in areas where the temperature (ambient or induced temperature) is higher than the standard ambient temperature.

Restriction

1. Evaluate the time-dependent performance degradation (aging) effects that occur during sustained long-term exposure to high temperatures (in storage or operating mode), where synergistic effects may be involved. For such a high temperature aging effect, it is tested in a natural environment.
2. Evaluate materials in high temperature environments where solar radiation creates a significant thermal gradient in the material. To simulate a direct solar impact, use Method 505.5, step 1.
3.Evaluating actinic (photochemical) effects (use Method 505.5, Procedure II).
4.Evaluating the effects of aerodynamic heating.
5. While high-temperature testing of munitions may be considered, safety or hazard tests should be performed in accordance with MIL-STD-2105C(para. 6.1, ref. 6.1D)

Climatic conditions.

Determine the appropriate climatic conditions for the geographical area in which materials are handled and stored. There are usually two types of high temperatures: dry heat and alkaline heat. Data for these areas are shown in Tables 501.5-1, -2 and -3. Determine high temperature levels related to:
1.Climatic area of concern.
2. Solar radiation exposure: Is it directly exposed to materials, containers, shields, etc.?
3. Heat transfer path analysis from ambient air and solar radiation to materials.

Table 501.5-I. Summary of high temperature diurnal cycle ranges
Design Type	Location	Ambient Air ℃	Induced ℃
Basic Hot(A2)	Many parts of the world, extending outward from the hot dry category of the southwestern United States, northwestern Mexico, central and western Australia, Saharan Africa, South America, southern Spain, and southwest and south central Asia.	30-43 (86-110	30-63 (86-145)
Hot Dry(Al)	Southwest and south central Asia, southwestern United States, Saharan Africa, central and western Australia, and northwestern Mexico	32-49 (90-120)	33-71 (91-160)

The diurnal cycles for temperature and humidity are given in tables 501.5-II and -III.
Induced conditions are air temperature levels to which materiel may be exposed during extreme storage or transitsituations, or non-operational but in the operational configuration without containerization.


1.These cycles were obtained from AR 70-38, 1 August 1979 (see paragraph 6.1, reference c), and essentially conform to those in MIL-HDBK-310 and NATO STANAG 4370, AECTP 200 (paragraph 6.1, references a andb). These values represent typical conditions throughout a typical day in this climatic category. "Induced Conditions" are air temperature levels to which materiel may be exposed during storage or transit situations that are aggravated by solar loading, or during non-operating situations but in an operational configuration and not containerized.
2.Humidity control during high temperature testing is generally not necessary. Use these values only in special cases where, for instance, it is known that high levels of temperature and humidity occur simultaneously.
3.Data were originally recorded in °F and converted to °C. Hence, table data conversion may not be consistent.

Exposure duration.

Determine the exposure time the material will experience under each of the identified exposure conditions. The exposure can be constant or cyclic, in which case it is also necessary to determine the number of times the exposure occurs.
 

Constant temperature exposure

For thermostatic exposure (used only for items near heating equipment or when the operation of the item needs to be verified at a specified constant temperature), soak the test item until its temperature is stable and maintain the test temperature for at least two hours after the test item is stable.
 

Cyclic temperature exposure

For cyclic exposure, the test duration is determined based on an estimate of the number of cycles required to meet the design requirements and the guidelines below. The duration of heat exposure may be as important as the temperature itself. Because procedures I and II may expose the test item to cycle temperatures, the number of cycles is critical. (The cycle is 24 hours unless otherwise stated.)
 

1. Procedure I- Storage.

The number of cycles of storage tests is set to at least seven times to be consistent with the 1% frequency of extreme temperature hours in the worst months of the year on average in the worst locations. (The maximum temperature per cycle is about an hour.) When considering extended storage time, critical materials or materials that are very sensitive to high temperatures, increase the number of cycles to ensure that design requirements are met.
 

2. Procedure II- Operation.

The minimum number of cycles of the operational exposure test is three. This number is usually sufficient for the test item to reach its maximum response temperature. When a repeated temperature response is difficult to obtain, a maximum of 7 cycles is recommended.

Multiple versions of the high temperature test procedure have been available for MIL-STD-810 high temperature test. Below is a list of each version and the corresponding method number
MIL-STD-810A Test Method 501.1 High Temperature Testing
MIL-STD-810B Test Method 501 High Temperature Testing
MIL-STD-810C Test Method 501.1 High Temperature Testing
MIL-STD-810D Test Method 501.2 High Temperature Testing
MIL-STD-810E Test Method 501.3 High Temperature Testing
MIL-STD-810F Test Method 501.4 High Temperature Testing
MIL-STD-810G Test Method 501.5 High Temperature Testing
MIL-STD-810H Test Method 501.7 High Temperature Testing
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