Ice-induced fatigue damage analysis of ship in broken ice fields based on the DEM-FEM method
Polar transport vessels are subjected to repeated collisions with sea ice while navigating through broken ice fields,resulting in cyclic structural damage accumulation and exacerbated fatigue issues.A coupled discrete element-finite element(DEM-FEM)approach is proposed to evaluate ice-induced fatigue damage for ships operating in broken ice seas.A mixed sea ice model and numerical crushed ice channel representing actual ice conditions are first generated.Ice loads act-ing on the ship hull during interactions with sea ice are computed using the discrete element method(DEM).These ice load time histories are applied as dynamic loading in finite element method(FEM)analyses of the ship hull structure.FEM ana-lyses produce hotspot stress time histories for various fatigue loading scenarios.The stress levels of the stress time histories were counted using the improved four-peak-valley rain-flow counting method,and the total fatigue damage of the hotspot was calculated by the S-N curve method based on the linear cumulative damage criterion.Finally,the results from the pro-posed method are compared with those from the LR's specification approach to verify its applicability.This method can provide a reference for the assessment of ice-induced fatigue damage of ships navigating in the broken ice fields.
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