Title: Design, Testing Results and Comparative Performance of a Negative Stiffness-Based Deck Suspension System for Mitigation of Shock and Vibration in a High-Speed Craft
Authors: Christopher Henry, Sloan Smith, Chris Swanhart, Robert Walling, Jeff Bowles, Nersesse Nersessian, Paul Dillingham, Geoffrey McKnight, Mark Rice
Abstract: Under Phase 2 of the Defense Advanced Research Projects Agency (DARPA)’s Structural Logic program, HRL along with its combined university and commercial team have applied negative-stiffness technology to the extreme-shock and -vibration environment to help prevent injuries in high-speed planing craft. Based on experimentally validated heave-and-pitch simulations, we designed an integrated boat structure with targeted nonlinear stiffness and damping properties to significantly reduce shock and vibration loads to passengers based on anticipated loads and accelerations. Our team implemented a novel scantling based on a 23’ Specmar Inc. Orca kit boat with an open hull and deck that are laterally constrained in sway and surge by a hinge at the bow and laterally-mounted vertical rollers at the aft bulkhead. The deck is supported with a bilateral arrangement of a two-stage simulation-optimized, negative stiffness-based suspension. This arrangement is dynamically stable at the craft’s upper speed limit (30- to 35-knots) and proves robust to a range of open water sea conditions. Using this technology concept demonstrator craft, we show time-domain acceleration reductions and improvements in program metrics (reductions in daily equivalent static compression dose value for an 8 hour endurance (SED8), lumbar acceleration and frequency-weighted root-mean-square (RMS) acceleration) relative to an identical boat ballasted to the same mass, longitudinal center of gravity and radius of gyration. Our results show these completely passive negative-stiffness devices—which decouple static load-handling capability from dynamic performance—provide heave-selective acceleration isolation benefits to a moving cockpit and deck area, including 25- to 35-percent reduction in SED8, 50-percent reduction in lumbar accelerations at near design speeds without increases in sea-sickness probability. To further improve the dynamic performance, we recommend continued development of a lower-mass variant that minimizes payload impact, maintains responsiveness, and continues to meet dynamic stability criteria. Simulations, suspension design selection and validation of this craft are highlighted in a companion paper.
The views, opinions and/or findings expressed are those of the authors and should not be interpreted as representing the official views or policies of the Department of Defense or the U.S. Government.