File:UPDATED APPROACH TO SHOCK FAILURE ASSESSMENT OF SHIPBOARD EQUIPMENT (IA updatedapproacht1094564136).pdf

Naval vessels are subjected to underwater explosions that impart a mechanical shock onto the ship structure, its subsystems, equipment and crew. This violent shock loading, although not in direct contact with the ship hull, seeks to cause significant damage and even failure of critical components, potentially rendering vital systems inoperable. To ensure deployment of robust systems, shock hardening of surface ships is established in part through shock qualification of mission-essential shipboard equipment. Current shock qualification methods predominantly rely on demonstration of satisfactory performance under prescribed physical testing schedules using standardized shock test machines. A pass/fail rating is assigned based on post-test operational evaluation and visual inspection of structural elements, not from measured response values. An updated shock failure assessment approach is found through numerical experimentation of standard shock platform models, full ship simulations and reduced order equipment models approximating various shock testing scenarios. Introduction of a simple functional failure representation provides a definite means by which to assess the response severity and time at failure. Threshold values for the peak velocity response and change in displacement are thusly established and proposed as deterministic shock failure criteria in order to reduce uncertainty in the shock qualification of shipboard equipment.

Subjects: fluid structure interaction; underwater explosions; ship shock; ship survivability; mechanical shock; equipment fragility; pseudo velocity; failure criteria; peak velocity; change in displacement; shock severity; functional failure; damage boundary