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Simulation of Collisions between RORO Vessels with Improved Double-Hull Designs - Influence of Modelling Parameters in Explicit Finite Element Analysis

Michael Odefey
Göteborg : Chalmers tekniska högskola, 2011. 84 s. Report. X - Department of Shipping and Marine Technology, Chalmers University of Technology, Göteborg, Sweden, 2011.
[Examensarbete på avancerad nivå]

In this thesis the behaviour of the x-core double-hull design was investigated in various collision situations between two RORO vessels and compared to a conventional double-hull design using explicit finite element analysis. The purpose was, besides the examination of the x-core structure’s increased crashworthiness, to investigate how different parameters influence the collision simulations. From this, recommendations were deduced on how to model future simulations most effectively. To achieve this, geometry models of both doublehulls and a striking bow section were created from CAD-data and drawings. The material model of a regular-strength shipbuilding steel was extended with the GL-approach describing a constant effective plastic failure strain, the PES-criterion describing a failure strain being dependent on sheet thicknesses of the shell model and mean edge lengths of the elements, and the RTCL-criterion accounting for triaxiality and introducing a damage variable. The RTCLcriterion was calibrated with simulated tensile tests. Collision simulations were carried out at two different draughts, hitting on a web frame and between two web frames, respectively. The collision angle was varied from the perpendicular angle to the struck hull to a 15 degrees inclination, and the influence of dynamic friction was examined. The conventional hull’s level of detail was reduced and the x-core’s mesh was coarsened and the resulting savings in time and errors in absorbed energy were examined. It was found that the x-core structure shows the potential to provide a higher crashworthiness than the conventionally used hull. The PES-criterion responded well to changing sheet thicknesses, while the GL-approach and the RTCL-criterion were totally and virtually independent of them, respectively. Collisions from the inclined direction yielded higher energies than from the perpendicular one, which showed Minorsky’s method to be inaccurate for this kind of collision. A comparison between results obtained from simulations regarding and disregarding friction showed only minor differences in the behaviour of folding structures and none in the absorbed energies. Simplification of the conventional double-hull and coarsening of the mesh of the x-core double-hull showed that the PES-criterion yielded the best compromise between reduction of calculation time and introduced error in this investigation.

Nyckelord: crashworthiness; explicit finite element analysis; failure criterion; friction; x-core.

Publikationen registrerades 2011-08-25. Den ändrades senast 2013-04-04

CPL ID: 144895

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