DD(X) UNDEX
DD(X) Machinery and Electronics Shock Mitigation Rafting:  Device Algorithm Development

Joel Myers, Northrop Grumman Ship Systems
Mr. Jeff O'Brien, Anteon
Brendan Woolrich, Anteon
Vince Godino, Anteon
Russ Miller, Anteon

Abstract: The DD(X) approach for reducing the shock environment for machinery and electronics equipment is to employ shock mitigated rafting systems.  The reduced shock environment allows for the use of commercial-off-the-shelf (COTS) or modified COTS (MOTS) equipment instead of heavier and more expensive shock hardened equipment.  The testing and analysis methods developed to obtain validated algorithms for the modeling and simulation (M&S) of rafting shock mitigating devices (e.g. isolators and dampers) are presented.  Results are compared for the new algorithm approach versus typical algorithm approaches to demonstrate the benefits of the new approach. 

Static and dynamic large-amplitude tests of isolators provide the nonlinear and hysteretic force-deflection data from which isolation device algorithms are developed.  The static tests are conducted in three independent directions and provide a lower bound on the stiffness of the mount as a function of displacement.  Dynamic tests are most economically performed using drop tests, which can be conducted using various masses and drop heights to characterize the dynamic response of the mounts at different velocities.  The dynamic tests provide valuable hysteresis loop information (used to derive the damping terms of the isolation algorithm) as the isolator cycles through loading and unloading during the tension and compression cycles.  Photos of the newly fabricated mount test devices are presented.  Comparisons between the isolation device test data and the newly developed isolator algorithms are presented.  A list of the isolators that have been characterized during the DD(X)!
program are provided.

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