Downloaded from https://www.everyspec.com MIL-STD-81OD .19 July”1983 1-4.1 *S. .. In the event‘of the ooourrence of an unprogrammed test interruption, the test shall.be initiated from the point of interruption using the same “specifictest item. . . .3-Q .2 QY@Qak.’”’ .Any interruption in the test that results in a more extreme exposure of the.test item th”anrequired by the equipment specification should be followed by a complete physical inspection of the test item and an operational check prior.to continuation of test. An engineering 3udgment ehall be made whether to continue testing with the overtested item, to obtain a new item, or to consider the test completed. ..
,, .;I-4.3 All incidents where the test items do not meet the ~.,equipment opetiating requirements shall be analyzed to determine the cause and r . impact of such occurrences’.“.Corrective actions shall be DrODOSed or implemented to meet performance requirements. ,,. : 1-4.4 S9ectrum ~n te~ 1-4.4.1 .- Gunfire vibration testing is done using pulses repeated at the gunfire rate. The generated spectra should have discrete acceleration magnitude whose frequencies (f) correspond to the expression f = fl; where fl is the basic gunfire rate and =1,2, 3,. ..K. The last integer (K) ia that value for for whioh fl.is nearest to the maximum,test frequency of 2000 Hz.
The pulse test spectrum shall be defined by an envelope that outlines the amplitude determined from the prediction method given in paragraph 1-3.2.1.2 or measured data. I-4-U.2 ~. Gunfire vibration testing can be done using a properly shaped broadband random vibration spectrum. It is characterized by broadband random vioration.. with four vibration peaks that occur at the first three harmonics and the furidamentalfrequency of the firing rate for the onboard guns., ,. It has been experienced that the,dynamic range required t? produce and control this broadband random vibration is beyond the ability of mo:t available vibration controllers.
A way of working around this problem is to enter into the vibration controller the desired broadband random spectrum with its strong vibration peaks. At those frequencies which have the Sntense vibration peaks, sine waves can be electronically added to the input to the vibration shaker amplifier. The amplitude of these sine waves should be such that.the vibration levels produced at those frequencies ia slightly less than the desired spectrum level. The vibration controller can make the final adjustment to achieve the needed test level. This method allows the gunfire test to be done in a closed loop with commonly available laboratory test equipment. FftTHOD519’.3 19 July 1983 519.3-15