ANALYSIS OF A SHIP HULL

This project was done as part of my third-year module called Finite Element Analysis in Solid Mechanics. The main focus of this project involved modelling a section of a ship hull and then analysing the static stresses along with the buckling load and modal response. The ship hull section is composed of three beam entities shown below. Two models of the ship hull were constructed to assess the effectiveness of different analysis methods. Firstly a shell model was constructed using Ansys SpaceClaim. Then a solid model was constructed in Solidworks and imported into Ansys DesignModeler.

Once the models had been created the appropriate boundary conditions and loading forces were added. While both the solid and shell model had fixed corners the other boundary conditions varied slightly. In the solid model, the outer face of the stiffener plates had the Z displacement fixed. Then a fixed X displacement was added to the lateral surfaces. On the other hand, the shell model had the fixed displacements applied to the edges shown in the figures below.

Mesh Elements Used

Shell model: Analyses were run using triangular and quadrilateral elements.

Solid model: The analyses were run using second-order tetrahedral and hexahedral elements. Second-order elements were used as they prevent issues such as shear locking. With regards to the hexahedral meshing, it's important to note that Ansys offers two meshing methods called "Hex dominant" and "Multizone" meshing. Of these "Multizone" meshing was chosen due to the model's high surface area to volume ratio which would require smaller elements for the meshing to complete, thus requiring more computational time.

Static analysis

Initially, a static study was conducted to examine the stresses and deformations experienced by the ship hull as a result of the water pressure. Therefore a static load of 10,000 Pa was applied to the bottom face of the hull.

Modal analysis

As the ship hull would also experience dynamic loads due to the waves and the vibrations from the engine it was decided to also conduct a modal analysis.

Buckling analysis

As the ship hull may deform due to the dynamic loading from the waves and water pressure, areas of tension and compression would be present. Therefore a buckling analysis was conducted to examine the effect of the compressive loads

Final results

To ensure the accuracy of each study a mesh convergence was conducted analysing the effect of different element sizes on the results. The data from the mesh results is summarized below. Finally, after conducting all three analyses the numerical results were collected and compared against the theoretical values, allowing for proper validation. These results are summarized in the tables below.

For more information or any queries regarding this project please email me at vadakumcherydylan@gmail.com