To cover every part of the suspension that needs structural analysis more involved than straight axial or torsional force, and to optimise those parts with FEA and sound theory.
Structures is the parent grouping for ARB, Arms, Rods, Bellcranks, Wheel Hubs and Dampers. It carries no costed parts of its own. Its function is the shared method every child subsystem follows, and the shared hardware standard they all use. That hardware standard is fixed across all suspension points: NAS-620x National Aerospace Standard bolts, MS21042-x Military Standard jet nuts, FK alloy steel rod ends, FK WSSX4TV stainless spherical bearings at the uppers and Aurora HAB-5TG at the lowers, with spacers in every spherical bearing in a tab so loads transfer properly.
The four-step method is written down and followed: 1. Goal setting. Establish the intended outcome before thinking about how to achieve it: saving money, reducing weight, improving performance, handling an increased load case, or reducing manufacturing time and skill. Then set concrete milestones for what a successful design looks like, and get them approved by whoever is overseeing the design, before the work starts. 2. Free-body diagram. Before any analysis, draw a detailed FBD and think carefully about worst-case scenarios and load paths. 3. Analysis. Hand calculate first where possible, including stress concentration factors, to validate the FEA. Then build the FEA model to find areas of interest and confirm viability against factor of safety (>=1.3), deflection goals and fatigue life. Then iterate and remove material from non-load-bearing areas, with the caveat that a topology study will not consider load cases it was not given. 4. Vehicle dynamics impact. State what the part's deflection and weight do to full-car performance. The example given is that an upright deflecting 0.01 degrees in toe results in a quantifiable change in lateral load capability at the tire. The method is the same for every structural part in this subteam, and it is followed in order rather than picked from: 1. Set the goal and the concrete milestones for a successful design, and get them approved, before any analysis starts. 2. Draw a detailed free-body diagram and think through worst-case scenarios and load paths. 3. Hand calculate where possible, including stress concentration factors, then build the FEA model, then iterate and remove material from non-load-bearing areas. 4. State what the resulting deflection and weight do to full-car performance. Hardware is standardised across all suspension points so the fastener analysis is done once rather than per part: NAS-620x bolts, MS21042-x jet nuts, FK alloy steel rod ends, FK WSSX4TV spherical bearings at the uppers and Aurora HAB-5TG at the lowers, with a spacer in every spherical bearing in a tab.
- Design every structural component to the risk-graded factor of safety scale rather than to a single number. - Validate FEA against hand calculation and, where possible, against physical test. - Standardise hardware across all suspension points so fastener analysis is done once. - Improve confidence in the analysis enough to keep optimising weight. Previous simulations were single-body with boundary conditions that may not represent component interaction, showing singularities near constraints and modelling no bolt preload.
- Single-body analysis limitations. CR26I built a full-corner model (spindle to upper arm, lower arm and tie rod, with preload at bolted connections and wheel bearings given a uniform modulus based on radial stiffness at load, roughly 165 GPa). The hand calculation for the spindles matched the full-corner result most closely; joint preload altered stress distribution; resultant stresses in the full-corner model were lower than in single-body runs. - Frame manufacturing variability feeding into structural models. Several suspension points measurably deviated from nominal on CR26I, so the process now includes collecting FARO data on the frame tabs and adjusting the structural models and load paths to match.
SolidWorks static FEA and ANSYS for full-corner models. Altair HyperWorks MotionView for suspension load paths. Hand calculation as the primary validation of FEA. FARO arm for as-built geometry. MTS Criterion 43 and MTS Exceed load frames for physical validation.