Finite Element Analysis software package ANSYS Mechanical was used to simulate possible loading scenarios the steering wheel may encounter under operating conditions so that its structural performance could be analysed.
All design iterations were simulated, focusing primarily on principle stresses and shear stress. A stress safety factor of >2.0 was the pass/fail criteria.
The stress safety factor was used as it is independent of material properties allowing the different materials used within the assembly to be analysed together.
| Model Loading and Support Faces - Red = Loading, Purple = Support | Models Imported from SolidWorks |
Three loading conditions were analysed in line with common forces a driver may put through the steering wheel during operation. The force magnitudes were based upon recommendations from Formula Student design judges and experimental data.
Fixed supports were placed on the faces where driver’s hands would grip the steering wheel and at the face where the shift mechanism boss attaches to the steering column.
| Sample Mesh Density |
| Mesh Convergence Study Plot |
The accuracy of results is heavily dependent on the mesh used. An initial simulation with an automatically generated mesh was run to highlight the main areas of high stress concentrations so that a finer mesh could be focused on such areas.
A tetrahedral mesh was used across the whole body, concentrated around the interface between the back of the steering wheel and the boss using the sphere of influence tool. Larger element sizes were left in less critical areas to reduce total elements and subsequent computing times.
A mesh convergence study was undertaken by incrementally reducing the minimum element size within the sphere of influence until outputs of maximum principle stress became consistent to within ± 3% over a reasonable range of mesh nodes.
| 1st Iteration Stress Safety Factor Contour Plot |
| 1st Iteration Shear Stress Contour Plot |
Above two plots highlight the areas of weakness in early designs with areas of red and yellow. A stress safety factor of 0.86 was obtained and shear stresses exceeded the yield strength of the vacuum formed ABS steering wheel back.
A study was undertaken to investigate whether the inclusion of an aluminium backing plate between the steering wheel and the boss would improve structural performance.
| Backing Plate Configuration Iterations |
| 2nd Iteration with Double Backing Plate Stress Safety Factor Contour Plot |
| 2nd Iteration with Double Backing Plate Shear Stress Contour Plot |
The inclusion of an aluminium backing plate increased the second moment of area at the weakest area of the steering wheel and successfully improved its resistance to bending and shear.
| Final Design Stress Safety Factor Contour Plot - Front |
| Final Design Stress Safety Factor Contour Plot - Back |
