Computer-aided engineering

Computer-aided Engineering (CAE) is an overarching description for different digital tools used for simulating performance or improving a design. As part of normal engineering practices, an engineer designing parts needs to assess it against several criteria, which might be simplified into either “performance” or “cost”.

In the performance class, the assessment is typically around strength.

  • Will this part withstand normal operational forces (eg potholes in the road)?
  • Will this part survive for the life of the motorcycle (durability and fatigue)?

In the cost class, the assessment is focused on:

  • How much does the part weigh or contribute to the weight of the design?
  • How much raw material does this part consume?
  • How much does it cost to manufacture?

CAE tools help answer these questions but in reality, they are the domain of industry due to the cost of software and the time and knowledge needed to use them effectively. Whilst some high-end custom bike builders are dabbling in CAE, for your average garage bike builder, they are out of reach.

Different digital tools are available for different purposes, but some more common areas of analysis that might be found in vehicle engineering would be:

  1. Static and dynamic stress estimation (Finite Element Analysis, or “FEA”)
  2. Computational Fluid Dynamics, or “CFD”
  3. Motion simulation
  4. Topological optimization

Finite Element Analysis is a mathematical method for calculating predicted strain. Strain is the movement of the material when forces are applied to it. Depending on the specific material chosen by the design engineer, the strain will result in a certain level of stress within the part. Materials are categorised by the level of stress they can withstand, so a high strain (and therefore a high stress) might indicated a stronger material is required, or the shape of the part should be changed.

Computational Fluid Dynamics (CFD) is another mathematical method used for quantifying fluid flow questions. Prior to the advent of powerful computers, designers used wind tunnels to investigate air flow around aircraft and vehicles. Now, airflow can be simulated digitally, and changes made to the digital design prior to further retesting.

For parts that normally move in relation to each other, motion simulation provides visualization of the path the parts take. A simple example might be the motion of the swinging arm and rear wheel on your motorcycle.

Topological optimization is a recent addition to the designer’s toolkit. Finite Element Analysis indicates specific locations in the design that are predicted to have high stress, and other locations that have lower stress. If a region of the part exhibits very low stress, it contributes nothing to the strength of the design, and simply adds weight.

Armed with this knowledge, the designer can reduce the size of the part in the low stress area to reduce its weight. They can retest the design with FEA to confirm the part strength is still predicted to be adequate. Topological optimisation hands this iteration process over to the processing power of modern computers. With given loads and specific constraints, the application then assesses the strength of the design, then amends the shape and reassesses it again, all automatically.

The resulting shape can appear quite organic, and the obvious question might be “well, how do I make it?”. Very organic shapes might only be feasible with high-end metal 3D-printing, which in itself might be outside the budget for your build.

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