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FEA · Finite element analysis

Non-linear analysis (FEA)

For standard industrial products, non-linear analysis is primarily used when analyzing assemblies with mating surfaces that come into contact, slide, or experience friction as loads are applied, as well as plastic snap-fits. Because the contact area changes dynamically, linear static solvers yield inaccurate results. Non-linear analysis accurately calculates true stresses and assembly forces, ensuring that no point within the assembly exceeds its yield strength during operation or assembly

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What it is

Three sources of non-linearity.

  • Contact. Parts that touch, separate or slide against each other: snap-fits, clamps, bolted and press-fit joints, seals.
  • Large deformations. Thin walls, flexible arms and springs whose stiffness changes as they deform, and buckling.
  • Material. Plastic deformation of metals and thermoplastics, and hyperelastic materials such as rubber.

Non-linear models need more input data and more checking than linear ones: material curves, friction, the load sequence. We say which of these the answer depends on, and how well they are known.

Typical questions

  • Is a snap-fit likely to see excessive deformation or stress?
  • What forces or deformations occur during assembly?
  • How is the load shared between parts in contact?
  • Will the part deform permanently under an overload?
  • Does a seal keep enough contact pressure?
  • At what load does a thin-walled part buckle?
Worked example

How FEA fits into a wider engineering investigation.

Plastic part design

Developing a reliable plastic snap-fit

A manufacturer needs a snap-fit for a new product. Several requirements interact.

A complete assessment considers
  • Assembly force
  • Retention force
  • Elastic deformation
  • Permanent deformation
  • Fatigue or repeated assembly
  • Material selection
  • Manufacturing feasibility
  • Tolerances
  • Temperature effects
What FEA adds

It compares alternative geometries and estimates deformation, stress and forces under defined assumptions.

What decides

Design iterations are settled before tooling, then confirmed by physical testing, often on printed prototypes.

Design for Manufacturing (DfM) Product Development Material and Manufacturing Process Selection
Open-source FEA

Professional analysis, without enterprise licence costs.

Commercial FEA packages often cost thousands of euros a year per seat, and that cost ends up in the price of every study. We work with a mature open-source toolchain instead, so an SME pays for engineering time, not for software licences.

The solver, CalculiX, is a long-established finite element code that reads the widely used Abaqus-style input format.

Honest about the limits

Where a question genuinely needs a feature that only a commercial package offers, we say so before the work starts.

The workflow

  1. Geometry: FreeCAD

    The CAD model is prepared for analysis and simplified where details don't affect the answer.

  2. Set-up and mesh: PrePoMax with Netgen

    Materials, loads, supports and contacts are defined, each assumption is recorded, and the mesh is refined where stresses concentrate.

  3. Solution: PrePoMax with CalculiX

    The model is solved and checked: convergence, mesh sensitivity and plausibility against hand calculations.

  4. Post-processing: PrePoMax and ParaView

    Stresses, displacements and reactions are extracted and presented as clear images and figures for the decision.

Product names are trademarks of their respective owners.

Related projects

A real project.

Product engineering

A 3-axis gimbal for serial production

Parts designed for injection moulding, checked with FEA before tooling is committed.
See the project

All projects: FEA

Related services

Every service is also available on its own. We only suggest a combination when the project actually needs it.

Product Development

From the technical idea to a product ready for production.

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Design for Manufacturing (DfM)

A product is not well designed just because it works. It has to be made reliably and at a sensible cost.

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Failure Investigation

When a part breaks or deforms, the right question is not only "how high is the stress?" but "why did it happen?".

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Injection Moulding Troubleshooting

We examine the part, the mould, the material and the process to find the real cause.

View service

Do you have an engineering question? Let's discuss it.

Tell us what you are developing, changing or trying to fix. We first look at the engineering question, then say plainly what is worth doing: a calculation, a design review, a test, a simulation, or a combination.

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