I Downloaded from https://www.everyspec.com 19 JUIY 1983 I This peak bandwidth should be readily achieved by even the least sophisticated digital random vibration control system. The bands between the vibration peaks MIL-STD-81OD are filled with broadband random vibration at a level representative of the platform being simulated. When variable RPM cases (see I-3.2.4) are being I simulated, wider bandwidths will be required. ~ 1-4.6 irvzdeveloDment tes~. Engineering development testing is used to uncover design and construction deficiencies as quickly aa p’osaibleand to evaluate subsequent corrective actions.
It should begin as early as practical in the development phase and continue as tbe design matures. The ultimate purpose is to asaure that developed equipment is compatible with the platform environment and that qualification testing does not reveal that more development work needs to be done. be The tests have a variety of objectives. Therefore, considerable freedom can taken in selecting test vibration levels, excitation, frequency ranges and duratione. Typical programs may include resonant search accomplished by exposing the item to low-level sweep sine input over the frequency range of concern, Sine dwells are then used to obtain mode shapes.
Fast Fourier transform analyses of random inputs can also be used to accomplish this. Mode shape and frequency determinations are necessary for verifying structural dynamic models and for discovering platform/equipment compatibilityy problems. Once mode shapes as well as module frequencies have been identified, the test item may be’exposed to dwell, swept-sinusoidal or random excitation testing. The vibration intensity of this testing is selected to accomplish specific test objectives.
The level may be lower than the field environment to avoid excessive damage.to a prototype, higher to verifY the test items1 structural integrity, or raised’in steps to evaluate performance variations and obtain failure data. I-4.7 IJDvironmental~. Worthiness testing is performed to verify that prototype or test versions of equipment are adequate fOr use in a system or subsystem test. Levels and durations should be selected to provide confidence that the equipment will perform well enough to support the test program with an acceptable level of maintenance. In cases where safety is a factor, the teat must be adequate to assure safe operation or possible fail- safe operation.
Levels are usually typical operating levels unless safety is involved; then maximum operating levels are necessary. Durations are either long enough to check equipment function or an arbitrary short time (5-10 minutes), whichever is greater. I-4.8 ~. ica lm. t. Qualification tests are used to verify that production equipment is capable of operating to specified performance criteria throughout the range of environments of its service application and to provide reasonable assurance that life requirements will be met (see 1-4.3). This normally reauires funtional tests to accomplish the first goal and endurance tests fOr I the second, I I METHOD 514.3 19 JUIY 1983 514.3-62