I I MIL-STD-81OD Downloaded from https://www.everyspec.com 19 July 1983 This relationship is a simplified expression of linear fatigue damage accumulation for typical materials used in-electronic equipment. More sophisticated analysis techniques can be used.when warranted. The recommended value of M is 4.0. (Note: if this equation is used for,sine calculation, W represents peak g and M 6.) I-4:10 Yibration isolation devicw. Vibration isolators (shock mounts), isolated equipment shelves, and other devices designed to protect equipment from platform or shipping environments use low-frequency resonance to attenuate high-frequency vibration inputs.
Effective performance of.these devices depends on adequate frequency separation between isolation resonant frequencies, and equipment resonant frequencies, and.sway space (clearance around isolated ,= elements) to avoid impacts of the isolated elements with surrounding equipment and structure. In addition, all military equipment should have a minimum level of ruggedness even if it will be protected by isolation in its application environment. To assure that these requirements are met, sway amplitude and isolation characteristics (transmissibility veraua frequency) should be measured during all vibration tests. This is also true when sub-elements are isolated within equipment items.
Further, all isolated equipment should pass the Minimum Integrity Test requirements (I-3.2.12). These parameters should be measured at each test level. This is necessary because isolation devices are nonlinear. ‘ a I-4.11 lest set~. Unless otherwise specified in the individual test description (section I-3), the test item shall be attached to the vibration exciter by means of a rigid fixture capable of transmitting the vibration conditions specified. The fixture should input vibration to racks, panels, and/or vibration isolators to simulate as accurately as possible the vibration transmitted to the test item in service.
However, all equipment items o protected from vibration by these means should also pass the minimum test requirements of I-3.2.12 with the test item hard-mounted to the fixture. 1-4.12 During all platform-induced vibration simulations, the test item should be functioning and its performance should be Performance to full specification requirements should be required during all functional tests. Measurement of performance level attairiedshould be required when.endurance levels are higher ! levels (I-4,8). ~ measuredr” than functional I-4.13 Summarv of test information reaulred. The following required in the teat plan ta adequately conduct the tests of information is section II: a.
Test procedure b. Test item canfiguration c. Operational requirements d. Test levels and durations . e. Test set-up description f. Accelerometer lacatian and calibration METHOD 514.3 19 July 1983 514.3-64