Downloaded from https://www.everyspec.com MIL-STD-81OD 19 July 1983 Thin silicone rubber and rip-stop nylon sheetings have been found to ge suitable shroud materials. To provide the rapid temperature changes ,required, one method uses insulated tanks or hot and cold fluids which are pumped through heat exchangers as required to temperature-conditionthe blower-driven air., By increasing the blower speed or by.narrowing the circumferential gap between the surface of the test item and the shroud (uaUally between 2 and 4 cm), ~. the boundary air velocity can be raised to provide the needed rapid.heat, transfer to or,from the store to simulate the captive flight conditions.
The arrangement is diagramed in figure 523.0-7. 11-1.5 Electrical s ress eq.u@M&. t Basic electrical atresses always present in electrical or electronic circuits are.produced by power on/off transients and resulting localized thermal shocks, and also by hot spots accompanyingthe full power condition. A switching system is normally used to form typical patterns of store operation during tbe composite mission test cycle. The use of equipment to modify the power source to the etore(s), to simulate likely ,. variations (voltage, frequency, transients, ripple, noise, etc.) met during mission operations, is optional. 11-1.6 lnsjirumentati.smand control 11-1.6.1 Functional monitor~ of the store.
The operating stores should be adequately monitored to indicate failures when they ,occur. Some form of. manual or automatic test performed at intervals (at least once for each composite mission cycle) can be used. Failure criteria, based on equipment specifications and functional requirements, must be clearly defined. Functional monitoring must be accomplished without adversely affecting.~he, environmental emulation. Functions which can only be measured outside the’ environmental chamber should be checked at intervals which are short compared to.the equipmentts mean-time-to-failure. II-1.6.2 ,Yibration~ ,. ,..’ 11-1.6.2.1 Acouatlc stl-.
The acoustic eignal source is normally a pre-recorded tape or the shaped output of a noise.generator. Filters are used as required to control spectral distribution. Intensity level ie monitored by calibrated microphones. Microphone placement should conform with II-2.,steP 6, method 515.3 unless other placement can be juetified by measurement and analysis. 11-1.6.2.2 Mechanical stimulua. The shaker input signal is normally“a pre- recorded tape or the shaped output of a noise generator. Filters are used as required to control spectral distribution.
Intensity level iS monitored.by ~ calibrated accelerometers mounted on or in the store(s) which measure the vibration.response (ace 11-1.6.2.3, next). The shaker frequency range is limited (typically Hz) so that feedback cOntrOl is unnecessary. 1 . ,., 0 METHOD 523.0 19 July 1983 523.0-14