The big idea: Finite element analysis breaks a part into thousands of small elements and calculates how each one deforms under a load, then colours the result.
What the statement asks: The statement asks you to interpret the output — to read the picture and say what a designer should do about it.
A loaded bracket, its stress concentration at the fillet, and the three things a designer does about it.
Interactive diagram
Explore the labelled diagram, charts and maps for this topic in full study mode.
Three inputs before any colour appears: A material, so the software knows the stiffness and strength. The loads — how much force, where, and in what direction. The constraints — which faces are held still.
Change any one and the picture changes, which is why a result is always quoted with its set-up.
Free preview
This is the free notes preview
You're reading the free notes. Aimnova Pro unlocks the full study experience — and you can try it with your first topic free to keep:
- FlashcardsLock in vocabulary and key terms with spaced repetition.
- Practice questionsAnswer exam-style questions and get instant AI marking.
- Mock exams & past-paper vaultSit full mocks and see exactly how examiners award marks.
- Personalised study planA daily plan built around your exam date and weak areas.
What to say about an FEA image
Where is the peak?
Red marks the highest stress. It almost always appears where the section changes suddenly — a sharp internal corner, a fillet, a hole, a bolt seat.
How does the peak compare with the material?
Red does not mean failure. Read the scale: if the peak is below the yield strength it is within limits, and if it is above it, the part will deform permanently.
Where is it blue?
Blue is material doing almost nothing. Those regions are where a redesign can remove weight and cost for no loss of strength.
What is the design change?
Increase a radius so the section changes gradually, add material where the stress is, remove it where it is blue, or change the load path altogether.
| What you see | What it means | What to do |
|---|---|---|
| A red band at a sharp internal corner | A stress concentration — stress rises where the shape changes suddenly | Add a generous radius so the change is gradual |
| Red around a bolt hole | The load is being carried through too small an area | Enlarge the washer face, or spread the load over more fixings |
| A large blue region far from the load | Material that is carrying almost nothing | Remove it — a rib or a web will do the same job for less mass |
| Deformation far larger than expected | A stiffness problem rather than a strength problem | Change the section shape, not the material — depth matters more than mass |
See how examiners mark answers
Answer exam-style questions with model answers. Learn exactly what earns marks and what doesn't.
An FEA result is a simulation of the case you described. It is precise about that case, and it says nothing about the cases you did not describe — which is where real products fail.
What it simulated
- One load, in one direction, applied steadily
- A perfect material, with no voids or weld lines
- A perfect fixing that never moves
- A single moment in time
What it did not
- Being dropped, or loaded off-centre by a real user
- A printed part, which is weak across its layers
- A bolt that loosens over a year
- Fatigue from a million small cycles
Use it to decide where to look: FEA tells you which region deserves attention and roughly how much. It does not replace a physical test.
The honest sentence to write: the analysis identified the fillet as the critical region, so the redesigned bracket was then loaded physically to confirm it.
Why designers use FEA
Test before anything is made
Forces, stresses and heat are simulated on the CAD model, so weak points are found without building a prototype.
Cheaper and faster
Fewer physical prototypes and destructive tests: changes cost minutes in software, not weeks in the workshop.
Change and re-test
Add a radius or thicken a wall, run it again and compare: the design is optimised in quick loops.
Lighter parts
Blue regions carry little stress, so material can be removed there, saving weight and cost (wings, drone arms, chair frames).
Process too, not just product
Flow and thermal analysis of a mould shows how plastic fills and cools, so wall thickness and gates are changed before the tool is cut.
FEA beside the other ways of testing a design
Solid model
The complete part with volume and mass: the data FEA needs, and the file a prototype is 3D printed from.
Animation
Simulates the product moving, such as a mechanism opening and closing, to check it works and does not collide.
FEA
Simulates loads on joints and linkages, including repeated use and harsh conditions, to find where it will fail.
Physical model
Something users can hold: size, proportion, texture and feel give realistic feedback that a simulation cannot.
How this is tested — interpreting an FEA output and turning it into a design change. It comes up two ways:
Paper 1 — multiple choice
- Identify where a stress concentration will occur.
- Read a stated FEA result against a material's yield strength.
Paper 2 — analysing a product
- Interpret a supplied FEA image of a component.
- Explain what an FEA result does and does not establish.
The trap: Saying "the red area will break". Red marks the highest stress in this simulation; whether it fails depends on how that peak compares with the strength of the material.
An FEA of an aluminium drill-mount bracket, loaded with 500 N at its free end, shows a red band at the fillet where the arm meets the fixed plate, and a large blue region at the free end. Analyse this result.
Model answer plan
See the answer broken into clear points, with guidance on how each point earns marks.