Chassis Lightweighting with Topology Optimisation

The problem

Every kilogram removed from an EV structure saves energy or allows a smaller battery. Topology optimisation suggests where material is needed, but its organic output cannot be built directly and is easily misread. Students need a disciplined process from design space to a validated, manufacturable part.

Objectives

• Define the design space, preserved regions and load cases for a chassis component.
• Run Topology Studies with stiffness-to-weight and mass-constrained goals.
• Apply manufacturing controls such as symmetry, demould direction and minimum thickness.
• Reinterpret the result into a parametric, manufacturable part.
• Verify the new design with static and mesh convergence studies and compare with the baseline.

What you need

Key concepts

Topology optimisation

A method that removes material from a design space while meeting a goal, such as maximum stiffness for a given mass. The result is a density field, not a finished part.

Preserved region

Geometry that must stay, such as bolt bosses and mounting faces. It is excluded from material removal.

Manufacturing controls

Constraints such as demould direction, symmetry and thickness that steer the result towards a part that can be cast, forged or machined.

Reinterpretation

Rebuilding the optimised shape as clean, parametric features. The rebuilt part must be re-analysed because it differs from the raw result.

Step-by-step guide

1. 1

   Pick the component and baseline

   Choose a chassis component with clear loads, such as a suspension mount bracket or a motor-to-frame cross member from an example EV. Model the baseline part, assign an example material such as 6061-T6 aluminium or a cast alloy, and record its mass. Define three load cases from example vehicle loads, such as vertical bump, braking and cornering, with forces at the mounting points.

   Checkpoint: A baseline part with mass and a table of load cases with forces and directions.

2. 2

   Analyse the baseline

   Run Static studies for each load case with realistic fixtures at bolt faces, using Bolt connectors or fixed faces with a note on the assumption. Run a mesh convergence on the peak stress location by refining a mesh control until peak stress changes by less than about 5 per cent. Record peak von Mises stress, maximum displacement and factor of safety. These are the targets the lighter design must still meet.

   Checkpoint: Baseline stress, displacement and factor of safety for each case, with a convergence plot.

3. 3

   Build the design space

   Create a configuration with a solid block filling all space the part may occupy, checked against neighbouring parts in the assembly with Interference Detection. Keep bolt holes and mounting faces. Make the design space generous, because topology can only remove material. Note the packaging limits in the report so the final shape stays within them. Split the design space body from the preserved regions with Split or separate bodies so the Topology Study can treat them differently.

   Checkpoint: A design-space body that fills the allowed envelope and passes Interference Detection with neighbours.

4. 4

   Set up the Topology Study

   Create a Topology Study, apply fixtures and the three load cases, and set the goal to Best Stiffness to Weight ratio first. Add preserved regions around bolt bosses with a margin. Add a mass constraint, for example keep 30 per cent of the design space mass. Use a fine enough mesh that thin members are represented, since a coarse mesh gives blocky, misleading results.

   Checkpoint: The study runs and the density plot shows a clear load path between the load and fixture points.

5. 5

   Add manufacturing controls

   Rerun with manufacturing controls appropriate to the process: a demould direction for casting, a symmetry plane if the part is symmetric and a minimum thickness so no member is thinner than can be made. Compare results with a displacement constraint goal (Minimize Mass with a limit on displacement) so you know how the result depends on the goal you choose.

   Checkpoint: At least three topology results with different goals or controls, compared side by side.

6. 6

   Export and interpret the result

   Use the mass-density slider to view the result at a sensible threshold and export the smoothed mesh as a reference body. Insert it into a new part configuration. Identify the main load paths, such as ribs and webs, and decide how to make them with the chosen process. Do not use the mesh directly as a production part. Compare the shape at two or three density thresholds, because a member that vanishes at a slightly higher threshold is probably not essential.

   Checkpoint: A sketch or note that names each main load path in the topology result and how it will be built.

7. 7

   Rebuild as a parametric part

   Model the new part with sketches, extrudes, ribs and fillets that follow the topology load paths, using the mesh only as a visual guide. Add draft and fillets suitable for casting, or flat faces and simple pockets for machining. Drive rib thickness and pocket depth with dimensions you can change later. Check mass against the baseline. Name the key rib and wall dimensions clearly, because they will be the variables in later verification iterations.

   Checkpoint: A fully parametric part whose mass is lower than the baseline and which rebuilds without errors.

8. 8

   Verify the new design

   Run the same Static studies on the rebuilt part with the same fixtures, loads and mesh convergence routine as the baseline. Compare peak stress, displacement and factor of safety for every load case. If a target is missed, thicken the relevant rib and rerun rather than going back to topology. Check whether stress concentrations have moved to new fillets. Keep the baseline and the final design in configurations of the same file so the comparison is easy to reproduce.

   Checkpoint: The redesigned part meets every baseline target with a recorded mass saving.

9. 9

   Check manufacture and cost

   Check draft with the Draft Analysis tool for a cast part, or check that pockets can be reached by a standard cutter for a machined part. Use DFMXpress for basic manufacturability rules. If you have SOLIDWORKS Costing, compare estimated cost of the baseline and final parts using the same template, and note that costing templates need realistic shop rates to be meaningful.

   Checkpoint: A manufacturability checklist passed and, if available, a cost comparison.

10. 10

    Report the lightweighting

    Present baseline, design space, topology results under different goals, reinterpretation and verification in one table: mass, peak stress, displacement and factor of safety per load case. Discuss how much of the topology mass saving survived reinterpretation and why. State that a physical test or strain-gauge measurement would be needed to confirm the results. Include images of the design space, topology plots, the exported mesh overlay and the final part so the reader can follow each decision. Add the mesh convergence plots for both designs.

    Checkpoint: A report showing the full chain from baseline to verified design with a clear mass saving.

Testing & validation

• Mesh convergence on both baseline and final designs.
• Same fixtures and load cases used for baseline and final.
• Final design meets every baseline stress and displacement target.
• Draft or machinability checked for the chosen process.

Expected results

A lightweighted, manufacturable EV chassis component with verified stress and stiffness, a quantified mass saving and a documented route from design space through topology results to the final part.

Take it further

• Add a frequency constraint and compare results.
• Print the final part in a scaled polymer and load-test it to compare with Simulation.
• Compare casting and machining controls for the same component.

Viva and review questions

Learn it at DIYguru

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