DESIGN AND EVALUATION OF ISOLATION OF LIGHTWEIGHT SHIPBOARD ELECTRONICS

摘要

Shipboard components, such as mission critical electronic enclosures, must be protected against high shock loads due to near miss underwater explosions. Such components must meet MIL-DTL-901D/E requirements. Shock mitigation mounts are designed and evaluated for an unusually lightweight (17-pound) electronic enclosure which must qualify for heavyweight barge test. The reason for meeting the heavyweight (versus lightweight) shock test requirements is due to the isolator displacement exceeding 1.5 inches in any direction under shock loading. The shock mitigation units must perform when mounted on 8, 14, or 25 Hz decks. In the first approximation, the electronic rack is modeled as a rigid body with 6 degrees of freedom. Each mount is modeled using 6-degree of freedom system with its own weight, spring and damping. Non-linear spring rates and damping rates are extracted from experiment data. The near miss explosions provide a harsh dynamics environment. In the case of 8, 14, and 25 Hz decks, the maximum shock inputs are 40 and 10 Gs, 60 and 10 Gs, 80 and 30 Gs in vertical and side-to-side directions, respectively. The shock mitigation is evaluated, and the results showed a huge success. In the case of 8 Hz deck, the maximum shock output is 14 Gs (65% reduction) and 12 Gs in vertical and side-to-side directions, respectively. In the case of 14 Hz deck, the maximum shock output is 19 Gs (68% reduction) and 10 Gs in vertical and side-to-side directions, respectively. In the case of 25 Hz deck, the maximum shock output is 14 Gs (83% reduction) and 18 Gs (40% reduction) in vertical and side-to-side directions, respectively. In general, accelerations are expected to stay below 20G for all conditions. As for displacement, the unit is predicted to stay within the 5 inch (combined) vertical shock envelope for all three deck conditions.