Finite element analysis

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Part of a series on vessels'

Structure

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Concepts

Finite Element Analysis

Finite element analysis (FEA) is a numerical process for evaluating stress and deflection in structures based on first-principals calculations. Today, this is handled by specialized computer software.

Contents

The FEA Process

  1. A model is built, including all structural components of interest.
  2. The model is then reduced to finite elements & nodes, forming a mesh. The density of the mesh does not have to be uniform, areas of interest or concern can have a finer mesh for more accurate results.
  3. Loads are applied, and the resulting displacement of nodes is calculated. The change in element lengths provides an indication of the stress distribution.

Uses of FEA

FEA may be used to increase structural efficiency, to guide or ensure the suitability of novel or heavily loaded constructions, or to locate potential stress concentrations in a vessel. For example, a stiffener which is highly loaded on one end and unloaded at the other may be replaced with a tapered bracket, reducing overall weight; or a lifting device may be evaluated to ensure adequate strength and rigidity of it's foundation.

Advantages of FEA

  • May speed up structural approval by classification societies.
  • Specialized vessel types do not have the benefit of accumulated knowledge, FEA processes can speed both development and design reviews/approvals.
  • Models may be reused, i.e., vibration analysis, additional FEA studies, etc.
  • Additional classification annotations may be available for extended fatigue life, etc. where whole vessel structures are considered.

Caveats

  • Loads must be carefully applied and accurate, poor inputs may not necessarily be obvious.
  • The mesh used must be accurate & dense enough to be representative.
  • Creation of meshes of large arrangements can be lengthy
  • Computationally intensive
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