Modeling and Simulation of Ice Body/Ship Structure Collision with Inelastic Structural Deformation Including Rupture and Tearing
NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD WEST BETHESDA United States
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This report documents numerical simulations of rigid and nonrigid ice body impact on notional naval surface ship structure. The impacting body first indents the hull structure a prescribed amount and then slides along the hull in scoring fashion across several hull frames. Initial analyses assume a rigid indenter, and subsequent analyses utilize indenter material models used in prior analyses to represent localized ice crushing. The ice material models do not capture spalling, flaking, or ice rubble confinement. These simulations allow permanent set deformation in the hull structure, as well as structural rupture and tearing according to dependence of failure strain on stress triaxiality under plane-stress assumptions. The simulations benefit from mesh-dependence-mitigating practices developed by other U.S. Navy analysts. These studies demonstrate both simulation capability and engineering insights. Although structural permanent set and tearing damage is greatest when the indenting-and-scoring body is rigid and damage decreases as ice rigidity decreases, the peak load does not parallel this trend. Since structural capacity falls from the undamaged structure level once tearing begins, and since tearing failure commences early in the rigid-indenter event, the peak load developed by a less-than-rigid indenter is greater than that induced by a rigid indenter. Another notable finding is that a more-compliant indenter develops high load at a stiff bulkhead location before tearing occurs. This result indicates that structural hard spots are likely tearing initiation locations and illustrate interaction between local structure compliance and assumed ice strength in rupture and tearing prediction.
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