A dynamic pressure distribution model for ice pressure load patches used in numerical simulations

Lande Andrade, Sthéfano (2023) A dynamic pressure distribution model for ice pressure load patches used in numerical simulations. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The work presents a model for ice load pressure patch representation in numerical structural simulation that captures the non-uniform pressure distribution as a function of the ice-structure interface shape. For this purpose, the first step of the work was the analysis of pressure data from ice impact experiments. This work presents the ice pressure distribution recorded and analysed in high temporal- and spatial-resolutions. The results show regions of high- and low-pressure zones (i.e., HPZ and LPZ) at the ice-indenter interface, which agree with previous works. Furthermore, based on the visual analysis of the pressure maps and ice specimen test faces, it was possible to hypothesise that the pattern assumed by the HPZ could be explained by the shape of the contact area. Based on this observation a geometric model for HPZ and LPZ representation over any contact area was developed and it is presented in this work for the first time. The methodology uses the topological skeleton and distance field information of the ice contact area’s shape to define the HPZ and LPZ associated to a contact area from the high-strain-rate interaction between an ice feature and a flat structure. The results from this methodology compare favourably with experimental observations of the HPZ distribution patterns. Finally, this led to the development of a new energy-coupled ice load model called NILAS (Non-uniform Ice Load Application System). The NILAS is capable of accounting for structural deformation energy during the simulation, while also generating non-uniform ice load pressure patches. The NILAS is designed for use in numerical structural simulations for the assessment of damage to non-polar class structures and overloaded polar class structures. While simpler methods that use uniform pressure patches with correction factors (e.g., IACS UR I) can approximate the effects of load concentration caused by HPZ, the NILAS model can directly include these regions of pressure concentration into the load patch. Therefore, the new model can account for the path-dependent plasticity associated with localized deformation response to the HPZ, which is of particular importance for non-ice class ships and overloaded ice-class ships.

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