Downloaded from https://www.everyspec.com condensation and temperature response patterns. Test planners and environmental specialists will consult with each other on how the climatic design values apply to testing. (See para, 1-6c(3).) (2) Accelerated and aggravated tests. Accelerated tests approximate conditions, which may occur in nature, but with a greater frequency or duration than would be expected naturally. Aggravated tests involve subject materiel to more extreme conditions than are found in nature. The results of accelerated and aggravated tests are evaluated in terms of what they imply for future service performance.
Specifically, they give rapid feedback on problems requiring corrective action as well as statistical data on the margin of safety provided by the design. Comparing results of these tests with results of field climatic tests of service performance will give a better interpretation of results. It also increases confidence in the use of such techniques in subsequent similar situations. In chamber tests, developers are cautioned that subjecting materiel to more extreme conditions than are found in nature may introduce problems that will not occur when testing is conducted in the natural environment.
(An example is the liquification of TNT, which does not occur at temperatures below 150 ° or 66 ° C.) This is overtesting. On the other hand, the successful conclusion of chamber tests does not guarantee than an item of equipment will operate satisfactorily in the natural environment, because nature involves complex, synergistic effects that cannot presently be induced in chambers (para 2-9). Such factors must be considered by the developer when evaluating results obtained in chambers. Test planners and environmental specialists will consult with each other to determine the extreme combinations of conditions that occur in nature. (See para 1-6c(3).) b. Natural climatic test.
Although climatic conditions during a field day test are not likely to be as extreme as the values specified in chapter 2, there are distinct advantages to conducting tests in a real world environment where the combined effects of several climatic factors can cause difficulties not revealed by chamber testing. (See para 2-8 and 2- 9.) On the other hand, when tests are conducted under less than the specified extreme conditions, the adequacy of the natural tests must be reviewed particularly when test results are marginal. Consideration should then be given to results obtained under simulated extreme conditions.
Data describing climatic conditions prevailing during field tests at the test site will be recorded to provide a basis for future evaluation. Chapter 2 CLIMATIC CRITERIA Section I GENERAL 2–1. Climatic design types. a. Hot. The world’s highest air temperatures occur in the areas identified with the hot climatic design type in figure 2-1. These are primarily low latitude deserts, which, in addition to very high air temperatures, concurrently experience very low relative humidities (except in the hot-humid areas) and intense solar radiation. Two daily cycles, described in paragraphs 2-4a and b, make up the hot design type— (1) Hot-dry. (2) Hot-humid. b. Basic.
The humid tropics and the midlatitudes (basic design type) are characterized by temperatures more moderate than the extremes of the other design types. Areas where the basic type applies are more widespread than the hot and cold design types combined. They also include most of the densely populated, highly industrialized sectors of the world. All general purpose Army materiel is expected to perform satisfactorily under all conditions formally identified as extremes in the basic design type, according to paragraph 1-5a.
Since microbial deterioration is a function of temperature and humidity and is an inseparable condition of hothumid tropics and the midlatitudes, it must be considered in the design of all standard general-purpose materiel. Four daily cycles, described in paragraphs 2-5a-c, are recognized for the basic design types— (1) Constant high humidity. (2) Variable high humidity. (3) Basic hot. (4) Basic cold. c. Cold. The cold climatic design type areas in figure 2-1, which are confined to the Northern Hemisphere, have temperatures much lower than the basic cold areas but not as low as the severe cold areas. The cold cycle is described in paragraph 2-6. d. Severe cold.
The severe cold climatic design type areas in figure 2-1 have the lowest temperatures on the surface of the earth, except Antarctica, which is not considered in this regulation. These low temperatures are found in the northern continental interiors and the Arctic. The severe cold condition is described in paragraph 2-7. 6 AR 70–38 • 15 September 1979