Downloaded from https://www.everyspec.com MIL-STD-810D 19 July 1983 ~ Jest inteI’rUDt~. If an unscheduled interruption occurs while the test item at a speeified test level, the test should resume at the “testlevel. The test duration time should be the sum of the times at the test level prior to and following the interruption. I-4.2 Dver-acceleratio~. If the teat item is subjected to acceleration loads in excess of the level specified for the test, the test must be stopped and the test item inspected and functional-tested. Based on the inspection and functional test, an engineeringdecision should be made as to whether testing should be resumed with the same teat item or a new test item.
I-4.3 S1.lavaDace measurementa. If a piece of equipment is mounted on isolators, the’test should be run with the equipment mounted on the isolatcms and the sway space should be measured to indicate potential interference with adjacent equipment. I-4.U Acceleration sirnilati~.” Carefu,lassessment of the function and characteristics’of’the test item”has to be made in selecting the apparatus on which the acceleration testa are to be performed due to the differences‘in the manner in which acceleration loads are produced. There are two types of aPParatus that are commonly used: the centrifuge and a track/rocket-powered sled combination. 0 1-4.4.1 Cen trifu~.
The centrifuge generates acceleration loads by rotation about a fixed axis. The direction of acceleration is always radially toward the center of rotation of the centrifuge, whereas the direction of the load induced by acceleration is ‘alwaysradially away from tbe ax’is“ofrotation. When mounted directly on the test arm, the test item expe~iences both rotational and translational motion. The direction of the acceleration and the load induced is constant with respect to the test item for a given rotational speed, but the test item rotates 36o ,degreesfor each revolution of the arm.
Certain centrifuges have counter-rotating fixtures mounted on the te.Vtarm to correct for rotation of the test item. With this arrangement, the teat item maintaina a fixed direction with respect to space, but the direction Df the acceleration and the induced load rotates 36o degreea around the. specimen for each revolution of the arm. Another characteristic is that the acceleration and induced load are in direct proportion to the distance from the center of rotation.
This necessitates the selection of a centrifuge of adequate size so that the portions of the test item nearest to and furthest from the center of rotation are subjected to not less than 90 percent or more than 110 percent, respectively~ of the specified teat level. 1-4.4.2 . The track/rocket-powered sled arrangement generates linear acceleration in the direction of the sled acceleration. The test item mounted on the sled is uniformly subjected to the same acceleration level as the sled experiences. The acceleration test level and the time duration at the test level is dependent upm the length Df the track, the power of the rocket, and the rocket charge.
The sled track generally will produce a significant vibration environment due to track roughness. Typically this vibration is significantly more severe that the normal service use environment. . METHOD 513.3 19 July 1983 513.3-9