Simulation Case study

Suspension upright: one design, every load case

A part optimized for a single load case looks efficient, then turns out weak when the load changes direction. Here is the same solver, the same mass, two answers.

Material layout optimized for the bump case only — **Baseline:** optimized for the 3g bump case only.

Material layout optimized for the worst of bump, braking and cornering — **All cases:** minimizes the worst of bump, braking and cornering (p-norm min-max compliance).

2D plane-stress simulation of a synthetic part. Not a physical test. 3D solves are in development. Density maps are the solver's own output fields, rendered without retouching.

Problem

A suspension upright sees a 3g bump, hard braking and cornering. A part optimized only for the bump looks efficient but is weak in the other cases.

Setup

260 × 260 mm design space, 40 mm thick, 4140 steel
hub bore and upper/lower arm mounts as hard points
35% material fraction, 120 × 120 plane-stress elements
three load cases: bump 3g, braking, cornering
SIMP with optimality-criteria updates, density filter, p-norm min-max over the load cases
about one minute per solve

Result, same mass (8.69 kg)

Simulationvs the bump-only baseline

about 41%stiffer in the worst load case (29% lower worst-case compliance), same 8.69 kg mass

14%lower peak von Mises stress (58.9 to 50.9 MPa)

4.2x → 4.9xmargin to the material's endurance limit

8.69 kg is 59% lighter than a solid block of the same envelope (21.2 kg).

Per load case (simulation)
Load case	Peak von Mises, baseline (MPa)	Peak von Mises, all cases (MPa)	Compliance, baseline	Compliance, all cases
bump 3g	32.6	50.9	530	779
braking	27.4	29.2	244	274
cornering	58.9	31.5	1454	1032

The baseline wins on the bump case it was built for and loses badly on cornering. The all-cases part gives up a little bump stiffness to cut the worst case. Lower compliance is stiffer.

The spec that drove it

This is the contract format: you own it, the solver works only inside it. Coordinates are fractions of the envelope. The load values are synthetic.

{
  "name": "Demo upright, front-left (synthetic)",
  "note": "Design-domain spec: the CLIENT supplies this. Engine optimizes inside it. Coords are fractions (0..1) of the bounding envelope; a real frame maps hard-point mm -> fractions.",
  "units": "mm_N_MPa",
  "domain": { "width": 260, "height": 260, "thickness": 40, "nelx": 120, "nely": 120 },
  "material": { "name": "4140 steel", "E": 205000, "nu": 0.29, "rho_kg_mm3": 7.85e-6, "sigma_endurance": 250 },
  "optimization": { "volfrac": 0.35, "penal": 3.0, "rmin": 3.5, "maxiter": 60, "p_norm": 8.0 },
  "hard_points": [
    { "id": "hub",  "type": "bore", "cx": 0.60, "cy": 0.50, "r_inner": 0.17, "r_outer": 0.235, "role": "load_surface" },
    { "id": "uca",  "type": "pad",  "box": [0.10, 0.30, 0.84, 0.98], "role": "anchor" },
    { "id": "lca",  "type": "pad",  "box": [0.10, 0.30, 0.02, 0.16], "role": "anchor" }
  ],
  "keep_out": [],
  "load_cases": [
    { "label": "bump 3g",   "at": "hub", "Fx": 0,      "Fy": 45000, "M": 0      },
    { "label": "braking",   "at": "hub", "Fx": -25000, "Fy": 20000, "M": 0      },
    { "label": "cornering", "at": "hub", "Fx": 0,      "Fy": 15000, "M": 7.0e6  }
  ]
}

Send us a spec.

Envelope, mounting points, keep-outs, material and the loads it has to survive. A sketch and a few numbers are enough to start. We reply with what we can solve, what we need, and a first scope.

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