Element Types
The most common finite element types and when to use each.
The choice of element type affects both accuracy and computation time. Dr.Q uses second-order tetrahedra (Tet10) by default, which is suitable for most structural analyses.
Solid elements
Solid elements model three-dimensional bodies. They have nodes at corners and optionally at midpoints of edges.
| Element | Nodes | Notes |
|---|---|---|
| Tet4 (linear tetrahedron) | 4 | Fast but stiff, too inaccurate for most structural analyses |
| Tet10 (quadratic tetrahedron) | 10 | Dr.Q default, good accuracy, works well with automatic meshing |
| Hex8 (linear hexahedron) | 8 | More accurate than Tet4, but requires structured meshing |
| Hex20 (quadratic hexahedron) | 20 | Best accuracy for solid elements, hard to generate automatically |
Why quadratic elements?
Linear elements (Tet4, Hex8) have straight edges. Quadratic elements (Tet10, Hex20) have midpoint nodes on each edge, so they can represent curved geometry accurately and capture bending-dominated deformation without artificial stiffness.
For most structural problems with automatic meshing, Tet10 is the right choice. It combines accuracy with the ability to mesh any geometry automatically.
Shell and beam elements
For thin-walled structures (sheet metal, pipes) or slender members (beams, frames), solid elements are inefficient, you'd need many elements through the thickness to get accurate results. Shell and beam elements are purpose-built for these cases.
Dr.Q's automatic mesher produces solid elements, and shell and beam element formulations also exist in the solver. For thin-walled structures a sufficiently refined solid mesh gives accurate results, though a shell model would be more efficient.
First-order vs second-order
As a general rule: always use second-order elements (Tet10) rather than first-order (Tet4). The accuracy improvement is significant and the increased computation cost is worth it.