Building an efficient model in FEA requires a thorough understanding of the types of elements available. Several element types are commonly used in FEA, depending on the nature of the problem and the desired level of accuracy. Here are some of the commonly used element types in FEA:
1. Truss Elements: These are one-dimensional elements used to model structures subjected to axial forces. They have 2 nodes and can only deform in the axial direction.
2. Beam Elements: Similar to truss elements, beam elements are one-dimensional and used to analyze structures subjected to bending and torsion. They have 2 nodes with three translations and three rotations per node and can deform in both axial and transverse directions.
3. Shell Elements: Shell elements are two-dimensional and used to model thin-walled structures like plates and shells. They can have 3 to 8 nodes, be oriented in any direction of 3D space and transmit all translational and rotational degrees of freedom except the rotation around the normal of the element. They have both in-plane and out-of-plane degrees of freedom and can represent bending, membrane, and shear behavior.
4. Solid Elements: Solid elements are three-dimensional and used to analyze solid structures. They represent the material as a continuum and can accurately capture complex deformations and stress distributions within the volume. They contain 8 to 20 nodes and transmit 3 translational degrees of freedom per node.
5. Plane Stress/Strain Elements: These are two-dimensional elements used to analyze problems that are confined to a plane, such as thin structures or components subjected to predominantly in-plane loads. They contain 3 or 4 nodes and only 2 translational degrees of freedom per node in their plane.
6. Axisymmetric Elements: These elements are used when analyzing structures with rotational symmetry, such as cylinders or spheres. They reduce the problem to a two-dimensional axisymmetric representation.
7. Plate Elements: Plate elements are used for analyzing thin plates or membranes subjected to bending or membrane forces. They have 3 degrees of freedom per node, 1 out of plane translation and 2 rotations.
8. Shell-Element Types: Different types of shell elements, such as triangular or quadrilateral elements, are available in FEA software packages. These elements offer various levels of accuracy and computational efficiency.
9. Specialized Elements: Depending on the software and specific analysis requirements, there may be specialized elements available, such as cable elements, joint elements, or fluid elements for fluid-structure interaction problems.
The critical issue when selecting elements for your FEA is knowing how the structure will behave before you begin the modelling work. You must understand the load path in your structure to be able to select the right elements.