Helps us to understand whether a product will work to everyone’s expectations.

Types of FEA

If the cost of prototyping a part through manufacture is prohibitive, or you are on a tight timescale but looking at a lengthy test period, FEA will deliver time savings and the reduction of test cycles and therefore cost. This can be done through simulated analysis of product failure. FEA enables us to help you to develop and improve designs prior to cutting a tool. It can also be used to retrospectively analyse potential causes of a product failure.

Types of FEA

  • 2D modelling can be used for anything from a simple preliminary check, through to asymmetric analysis, gasket section compression (planar,  effects of shaft displacement in seals, bump stop displacements, etc.). Element mesh can be more refined in some applications depending on the level of material displacement or stress refinement​.
  • 3D modelling allows for direct import of product CAD files for more complex geometries including, but not limited to, assembly, large deformation, large strain, complex multi body movements and proximity mitigation of deformation under load.

Linear vs. non-linear FEA

  • Linear: this type of analysis method is commonly included in 3D CAD packages. It is generally used for materials such as steel, which has a linear response to stress/strain = E (Young’s modulus) and requires a far less complex analysis. This type of analysis is not sufficient for polymers because they do not exhibit a linear material relationship of stress/strain.
  • Non-linear: polymers are inherently nonlinear and require a complex curve fit based on a hyper elastic polymer model is required, which is not typically available in CAD programmes. This methodology allows us to cover both static and dynamic scenarios, geometric non-linear scenarios for large deflections or strain, material non-linear scenarios such as creep, plasticity, viscoelasticity, hyperelasticity etc.
Rubber product analysis

How does FEA work?

Using a linear material model on polymer data will typically over predict the response of the material.

Therefore, highly specialised material models are needed to allow for a nonlinear stress-strain relationship and temperature-dependent material properties, with specialist material testing required to feed the analysis models with fully representative data. One typical material model is the Ogden strain energy function:

The Ogden deviatoric strain energy function is given by the following series expansion:

Ogden Strain Energy Function

The Ogden model will allow for the non-linear material response, leading to accurate analysis results. Our investigations of rubber and polymer failures will help to reduce and identify potential failures.

This means that in order to work with a true representation of the material real-world response to stress-strain, particularly when temperature is applied, we need to test the polymer material under conditions that closely replicate the application conditions, and fully characterise its specific responses, before using those outputs within the modelling software.

Use of nodes within Non-linear Rubber FEA

The analysis software uses a system of nodes.

Nodes carry extrapolations of stress/strain and other engineering outputs; it is not simply a case of uploading a model and applying the material and loading conditions, which is where the skill and knowledge of the FE analyst is required.

Finite Element Analysis (FEA)

Points of interest may consist of:

  • Fracture point of previously tested material
  • Corners
  • Complex detail
  • High stress areas.

A wide range of functions are available such as:

  • Thermal heat transfer
  • Strain / stress types including Von Mises, Cauchy, Comp and directional dependent
  • Force, displacement, velocity, acceleration.

Multiple loading conditions which may be applied to a system to allow accurate replication of intended application such as:

  • Point, pressure, thermal, gravity, and centrifugal static loads
  • Thermal loads from heat transfer analysis
  • Reaction deformation
Finite Element Analysis (FEA)

Interpretation of results: investigation of rubber and polymer product failures

Results interpretation in polymer FEA is where the skill of the analyst and knowledge of polymers really comes into play; it is not simply a case of reviewing the analysis results against the tested material properties, because whilst the results will provide the calculated stress, deformation etc., it cannot account for the specific requirements of polymer design and manufacture. For example, whilst the predicted stress result may be within the material’s ultimate tensile strength (UTS), it might be that repetitive loading to a near UTS value will damage the polymer’s material structure, leading to degradation of the material and ultimate failure of the part.

Dynamic simulation of the anticipated results then gives a real insight into the likely articulation of a product. Using our FEA software, we are able to advise whether a proposed design will function to your specifications prior to manufacture of a mould tool; this has potential for significant cost saving on new development projects. We can also use the FEA software in the case of previous product failures to help determine what design modifications are necessary to ensure the product will function as required on future variants.

Our expertise in action

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A race against time for design and production

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Unusual solutions to solve a unique problem

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Problem solving and production for fluid engineering

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