Finite element analysis (FEA) data identifies a likely failure cause by showing where stresses, deformation, or instability exceed the structure's acceptable limits. Interpret the results alongside material properties, loading, constraints, and mesh quality rather than treating the colour plot alone as proof.
Interpreting the Results
First, confirm that the simulation represents the real structure. Check the applied loads, boundary conditions, material properties, geometry, contacts, and joint assumptions. An unrealistic fixed support can create an artificial stress concentration, while an omitted load can hide the real failure mode.
Next, locate the region where failure began and compare it with the FEA outputs:
| FEA result | What it may indicate |
|---|---|
| High von Mises stress | Likely yielding in a ductile material if exceeds the yield strength |
| High principal tensile stress | Cracking risk in brittle materials, especially near holes, corners, or notches |
| Excessive displacement | Loss of stiffness or unacceptable deflection, even if the material has not yielded |
| Low factor of safety | Failure is predicted where approaches or falls below |
| Buckling mode or low buckling load factor | Instability of a slender member under compression |
| Repeated cyclic stress | Possible fatigue failure below the material's static yield strength |
A local stress peak must be treated carefully. It may represent a genuine stress concentration, but it can also be a stress singularity caused by an idealized sharp corner, point load, or perfectly fixed constraint.
Check mesh convergence by refining the mesh near the suspected failure area. If the overall stress and displacement pattern stabilizes, confidence in the result increases. Finally, compare the predicted failure location and mode with physical evidence such as cracking, permanent deformation, or buckling.
IB Exam Technique
For B3.2 HL, link FEA evidence to a specific structural failure mode and justify your conclusion using material limits, loading, and constraints. Avoid the common misconception that the red region automatically proves failure; colour scales are relative, and results require numerical comparison and validation.