Problem
Verify structural integrity of a rear double wishbone suspension assembly under representative cornering and braking loads using static finite element analysis. The goal was to validate stress and displacement results against analytical hand calculations and assess factor of safety across the assembly.
Approach
Three part study combining hand calculations, finite element analysis, and mesh refinement.
- Phase 1 (Analytical): Free body diagram of the 6-body assembly (lower arm, upper arm, knuckle, shock clamp, plunger, tube). Pin reaction forces solved analytically before any FEA to establish expected results.
- Phase 2 (Full assembly FEA): Applied loads of 35 lbf horizontal and 65 lbf vertical at the knuckle. Modeled the shock absorber as both a fixed constraint and a spring element (k = 800 lbf/in) to compare displacement response.
- Phase 3 (Mesh convergence): Refined mesh on the lower arm to 134,000 nodes to confirm stress convergence and determine local factor of safety under higher-fidelity conditions.
Materials: AISI 4340 normalized steel for control arms (yield strength 145 ksi), cast carbon steel for knuckle and shock components.
Pin reactions (analytical): A = 118.3 lbf, B = 131.5 lbf, C = 66.5 lbf, D = 49.0 lbf, E = 131.5 lbf, G = 49.0 lbf.
Results
| Study | Peak von Mises | Max y-displacement |
|---|---|---|
| Fixed shock (full assembly) | 22.9 ksi | 0.00546 in |
| Spring shock (k = 800 lbf/in) | 22.9 ksi | 0.586 in |
| Lower arm, refined mesh (134k nodes) | 66.5 ksi | 0.421 in |
Assembly factor of safety: approximately 6.3 (22.9 ksi vs. 145 ksi yield strength). Lower arm local minimum factor of safety: 1.55 under refined mesh conditions. Peak sigma x in fixed and spring studies: 18.9 ksi (compression).
My Role
Solo project. All hand calculations, SolidWorks 3D assembly, simulation setup, mesh convergence study, and written technical report were completed independently.