Downloaded from https://www.everyspec.com MIL-STO-810C 4.1 Test item operation. Unless otherwise specified, the test item shal1 be operated during application of vibration (resonance search, resonance dwell, cycling, and random vibration) so that functional effects caused by these tests may be evaluated. Procedure IA, IIA and IIB provide for a functional vibration test and an endurance vibration test. The test item shall meet performance requirements as specified in the detail equipment specification and General Requirements, 3.2 while the functional vibration test levels are being applied.
When a test item performance t~t is required during vibration and the time required for the performance test is greater than the duration of the vibration test, the performance test may be abbre- viated accordingly. The test item shall be operated and inspected and the results shall be obtairiedin accordance with General Requirements, 3.2 4.2 Mounting techniques. The test item shall be attached by its normal mounting means, either directly to the vibTation exciter or transition table, or by means of a rigid fixture capable of transmitting the vibra- tion conditions specified herein.
Precautions shall be taken in the establishment of mechanical interfaces to minimize the introduction of extraneous responses in the test ‘setup. The test load shall be distributed as uniformly as possible on the vibration exciter table in order to minimize effects of unbalanced loads. The input control sensing device(s) shall be rigidly attached to the vibration table, or fixture if used, as near as possible to the attachment point(s) of the test item. Additional vibration sensors shall b,e located in or on the test item to determine resonant fre- quencies and amplification factors.
Locations to be selected should include main structure, printed circuit boards, large components, and modules, where practicable. The sensor sizes and weights shall be limited so that their effect.on the dynamic responses being measured is minimal For sinusoidal vibration, when necessary for obtaining uniform results, a tracking filter should be used in the vibration exciter control feedback loop prior to the servo input. 4.3 Combined temperature-vibrationtest. Tests shall be performed under room ambient conditions unless a high or low temperature vibration test is specified, in which case the temperature extremes and time duration also shall be as specified in the equipment specification.
4.5 Common test techniques 4.5.1 Sinusoidal vibration tests. The vibration shall be applied along each of three mutually perpendicular axes of the test item. The vibra- tory acceleration levels or double amplitudes of the specified test curve shall be maintained at the test item mounting points. When necessary for obtaining uniform results, a tracking filter should be used in the exciter control feedback loop prior to the servo input. When specified, for METHOD 514.2 514.2-4