Alloy Wheel Rim Analysis for Radial and Cornering Loads

The problem

EVs are heavier than similar petrol two-wheelers, and hub motors change how the wheel is loaded and supported. Wheels must pass radial and cornering fatigue tests defined in standards, and a good static analysis is the first step. Poorly applied loads, such as a point force on the rim, give misleading stress peaks.

Objectives

• Model an alloy wheel with spokes and a rim profile suitable for analysis.
• Apply realistic radial and cornering loads with bearing-type distributions.
• Use symmetry or cyclic symmetry where valid to reduce model size.
• Report stress, deflection and factor of safety and compare spoke designs.

What you need

Key concepts

Radial load

The vertical load from the tyre to the rim, spread over an arc near the contact patch rather than at a point.

Bearing Load

A SOLIDWORKS Simulation load that spreads a force over a cylindrical face with a sinusoidal or parabolic distribution, similar to how a tyre bears on a rim.

Cornering moment

Lateral tyre force at the ground creates a bending moment on the wheel about the hub. Cornering fatigue tests reproduce this with a rotating moment.

Cyclic symmetry

When geometry and loading repeat around an axis, one sector can be analysed with cyclic boundary conditions. A single radial load is not cyclic, so the full wheel is needed for it.

Step-by-step guide

1. 1

   Define the wheel and loads

   Choose an example 12-inch scooter alloy wheel for a hub-motor or chain-drive EV. Calculate the maximum static wheel load from an example vehicle mass and weight distribution, and multiply by a stated dynamic factor for the radial case. Define a cornering case with a stated lateral force at the contact patch. Note that wheels must meet current Indian wheel standards for your vehicle class, which you should check.

   Checkpoint: A load table for radial and cornering cases, with assumptions and the standard to be checked listed.

2. 2

   Model the wheel

   Revolve the rim profile including flanges, bead seats and a drop centre. Model one spoke with a lofted section and use Circular Pattern for the rest. Add the hub bore and bolt holes or a motor flange. Fillet the spoke-to-rim and spoke-to-hub joints with realistic radii, since sharp corners create singularities. Assign an aluminium casting alloy from the material library and check its properties.

   Checkpoint: A clean solid wheel with realistic fillets, and mass properties giving a plausible wheel mass.

3. 3

   Hand-check the spoke

   Estimate the force in the spoke nearest the contact patch under the radial load by assuming it carries a stated share of the load, and calculate its bending stress as a short cantilever from the hub. Estimate rim bending between spokes as a curved beam. These rough checks are only for order of magnitude, since a wheel shares load between spokes.

   Checkpoint: Hand estimates of spoke and rim stress written down with assumptions, to compare with the model.

4. 4

   Set up the radial case

   Create a static study on the full wheel. Fix the hub bore or bolt faces, depending on the mounting. Use split lines to create a bead-seat face over an arc of about 40 to 60 degrees at the bottom and apply a Bearing Load there with a sinusoidal distribution in the downward direction. Add tyre pressure as a pressure load on the rim well if you want, stating the value.

   Checkpoint: The study solves, reaction forces equal the applied load and the deformed shape shows the rim flattening near the contact.

5. 5

   Set up the cornering case

   Apply the lateral force as a remote load at the contact patch location, connected to the bead-seat faces on the loaded side. This creates the correct cornering moment about the hub. Fix the hub as before. Also create a version where the load is rotated to sit between two spokes and one where it sits on a spoke, since results differ with position.

   Checkpoint: Cornering results for load on a spoke and between spokes, with reaction moments matching the applied moment.

6. 6

   Try cyclic symmetry for uniform loads

   For a uniform tyre pressure load or centrifugal load from rotation, cut one spoke sector with a split or extruded cut and apply the Cyclic Symmetry fixture on the cut faces, with the axis through the hub. Compare its stress with the full-wheel model under the same uniform load. Explain why the radial and cornering cases cannot use it. Use the same mesh size in both models near the spoke roots to make the comparison fair.

   Checkpoint: The sector model agrees with the full model under uniform load within a few per cent and uses far fewer elements.

7. 7

   Converge the mesh

   Add mesh controls at the spoke roots, rim flange and bolt holes. Run the radial case at three mesh densities and plot peak stress at the spoke root against element size. Identify any singularity at sharp edges or fixtures. Use curvature-based mesh and check mesh quality plots. Keep the probe at a fixed location just away from the fillet tangent edge so each mesh is compared at the same point. Record the element count and solve time for each run.

   Checkpoint: Peak stress at the spoke root changes by less than about 5 per cent between the last two meshes.

8. 8

   Compare designs

   Create configurations with five, six and ten spokes, or thicker spoke sections, keeping mass similar. Run the radial and cornering cases for each and record mass, peak stress, minimum factor of safety and rim deflection. Use a Design Study if you want to sweep spoke thickness automatically. Pick a design that meets the target factor of safety with the lowest mass.

   Checkpoint: A comparison table and a chosen design that meets the target in both cases.

9. 9

   Report

   Write a report with load derivation, model, fixtures and load distributions, hand estimates, convergence, results for each case and position, the design comparison and the chosen design. State the limits: static loads only, no casting porosity, no tyre model. Note that the real standard tests are fatigue tests, so a fatigue study and physical test are needed. Include contour plots with the same colour scale for each design so they can be compared at a glance.

   Checkpoint: A report with traceable inputs, convergence evidence and clear limits.

Testing & validation

• Reaction forces and moments balance applied loads.
• Hand estimates and model results agree in order of magnitude.
• Cyclic symmetry model agrees with full model under uniform load.
• Mesh convergence at spoke roots.

Expected results

A wheel rim analysis with realistic load distributions for radial and cornering cases, a verified cyclic-symmetry shortcut for uniform loads, a spoke design comparison and stated limits.

Take it further

• Run a fatigue study for the cornering case with a rotating load.
• Model the hub motor flange and motor torque.
• Run a drop test study for kerb impact.

Viva and review questions

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