Finite Element Analysis

Complexity

Ships are becoming more complex due to e.g. structural discontinuity, complex loading conditions. Extensive structural analysis are more often required by classification societies and ship owners to prove the structural integrity and/or optimize the design. Moreover, these structural analyses are pushed forward in the design cycle. This requires shorter modelling and analyzing times. To make this possible “in house” developed software is used to make connections between our Finite Element software: ANSYS APDL and other software packages like Rhinoceros (geometry modelling) and NAPA (stability and loading). The model connection with Rhinoceros makes it possible to exchange the geometry, attributes like plate thickness, material quality and identification. Complex loading conditions (including floating condition) can be imported from NAPA to create a balanced loading condition.

Calculations

Other, more specific calculations can also be performed like: - Modal analysis - Non-linear material behavior - Fatigue analysis - Local stability analysis: To calculate the stability of an unstiffened plate panel with unusual shapes and/or loading patterns an “in house” developed method is used. This method isolates the unstiffened panel and load pattern obtained from a global FE model. After applying an imperfection, a nonlinear analysis determines the load bearing capacity of the panel. For every analysis performed by DEKC Maritime, a complete report will be delivered containing a description of the FE model, an overview of the boundary conditions (loading conditions), discussion of the results and recommendations for optimizing.

Analysis

From the global analysis results valuable data can be extracted. Stress envelopes can be produced from the applied loading conditions to obtain a complete overview of the maximum occurring stresses (including compressive stresses for a buckling analysis) and corresponding loading condition. Further absolute deflections can be recalculated to relative deflections to estimate (for example) the necessary glue thicknesses for window frames. A global FE model can further be used as a base for sub model analysis. In such an analysis, an area of interest can be further detailed and provided with a finer mesh. The edges of the sub model will be loaded with prescribed translations and rotations obtained from the global analysis. This way more realistic results can be obtained.