Rectangular Tube
- The following model is solved using CalculiX solver.
Tutorial with Complete Steps,
Objective
Analyse the buckling behaviour of a hollow box under compression, considering a small internal pressure.
| Parameter | Value |
| W : Width ( X , Y) | 100 mm |
| H : Height ( Z ) | 150 mm |
| Pressure : Elastic Load Limit | 40 KN |
1. Define Material
Material 1 : Steel
| Parameter | Value |
| Young’s Modulus | 210000 MPa |
| Poisson’s Ratio | 0.3 |
| Density | 7.8E-09 tonne/mm³ |
2. Define Shell Property
| Parameter | Value |
| Thickness | 1 mm |
| Material | Steel |
3. Meshing
Element size 8.33 mm x 10 mm.
Shell elements are created using 2D Mapped Mesh feature.
4. Boundary Conditions
- Lower Nodes : All DOF (1 – 6) Constrained
- Upper Nodes : All DOF (1 – 6) Constrained
- Internal Pressure 1 MPa applied to inner surfaces (Yellow)
5. Static Analysis with Calculix Solver
Total Displacement
6. Post Processing
Export deformed data from result : Export deformed data (scaled) to INP Format.
7. Import Deformed scaled INP
Deformed scaled INP with OVERWRITE.
8. Modify STEEL Material Property
Add Plastic Property
| Stress (MPa) | Strain Value |
| 100 | 0 |
| 200 | 0.3 |
| 300 | 1 |
9. Boundary Conditions
- Lower Nodes : All DOF (1 – 6) Constrained (Green)
- Upper Nodes : All DOF (1 – 6) Constrained (Green)
- Specified Displacement: -40 in Z direction (Pink)
10. Static Non-Linear Analysis Settings (Calculix)
Analysis Results
Deformed result
vonMises Stress last Step results
vonMises stress result analysis
Force Displacement Plots
Note that 40 kN is the elastic limit in the linear analysis.
Full History
Detail of transition to collapse