{
 "generatedBy": "demos/ring_box/pack.js from demos/ring_box/out/fea_slit (CalculiX 2.21, 37k C3D10)",
 "study": {
  "foam": "PU flexible foam 35 kg/m3, E 60 kPa, nu 0.25",
  "stiffnessNperMM": 0.637,
  "bandWidthMM": 3.2,
  "slitMM": 0.4,
  "imprintMM": 1.4,
  "squeezePerSideN": 0.892,
  "muVelvetOnGold": 0.5,
  "ringG": 17.525,
  "pullOutN": 0.892,
  "holdG": 5.2
 },
 "rows": [
  [
   "Foam",
   "PU 35 kg/m³ · 60 kPa"
  ],
  [
   "Band imprint",
   "1.40 mm per side"
  ],
  [
   "Pillow stiffness",
   "0.64 N/mm"
  ],
  [
   "Squeeze on band",
   "1.78 N"
  ],
  [
   "Pull-out, μ 0.5",
   "0.89 N"
  ],
  [
   "Holds the ring at",
   "≈ 5 g",
   "ok"
  ],
  [
   "Memory foam / EVA",
   "1.3 g / 86.4 g"
  ]
 ],
 "note": "Linear FEA of one pillow, fixed against the wall and sliding on the floor, with the band imprint as the loaded face; force scales with the imprint depth. Soft PU plateaus past roughly 5-10 % local strain, so read these as upper bounds: a 35-45 kg/m³ grade keeps a firm hold with a fingertip push in and out. EVA would grip about 16 times harder, too stiff to seat by hand; memory foam lets the ring fall out with a shake."
}