# Finite Elements

- If L/t > 20 and R/t > 20: Thin shell assumptions are valid (Kirchhoff or Mindlin shell models)
- If 10 < L/t < 20 and 10 < R/t < 20: Moderately thick shell (Mindlin model)
- If 4 < L/t < 10 and 4 < R/t < 1: Thick shell
- If L/t < 4 or R/t < 4: Solids

- Shell theory: 2D mesh of the mid-surface
- Thick shell: 3D mesh with constant normal stress assumption
- Solids: 3D mesh without constant normal stress assumption

- The number of integration points
- The stress updating method
- Large or small strain assumption
- Plasticity options for necking and material law integration
- Type of element and hourglass formulation