Press/Shrink Fit Interference Calculator mechanism

Model scope

The pressure and hoop-stress expressions can be used only as a hub-dominant or rigid-shaft approximation under explicitly defined diameter and interference conventions. They do not fulfill the stated claim of calculating press-fit assembly behavior for deformable shaft/hub parts, and the torque output is entirely unspecified.

• The pressure formula accounts only for hub deformation and omits shaft deformation; it is not the standard full press-fit formula for a deformable shaft and hub. For a same-material shaft and hub, the shaft compliance term must be included.
• The formula does not define whether δ is diametral or radial interference. The shown denominator is consistent with diametral interference when d is the contact diameter and the shaft is treated as rigid; radial interference would introduce a factor-of-two difference.
• The notation ro suggests an outer radius, while the inputs are specified as diameters. The squared ratio is dimensionless either way only if ro and d use the same geometric convention, but the linear d in the pressure denominator must specifically be the contact diameter under the supplied formula.
• The claimed transmittable torque output has no formula. It requires at least a friction coefficient, contact area or effective contact length, and a defined torque model; it cannot be calculated from the listed inputs.

Units and conventions

• Test calculations interpret d and ro as contact and outer diameters, respectively, despite the variable name ro.
• δ is interpreted as diametral interference, using the supplied pressure equation.
• E and p use consistent pressure units; δ and d use the same length units.
• ν is dimensionless.
• Hoop stress is interpreted as the hub bore-surface Lamé hoop stress, with d and ro expressed using the same diameter or radius convention.
• The supplied formulas are evaluated as written, even though they are incomplete for a deformable shaft.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "d": 50,
    "ro": 100,
    "delta": 0.1,
    "E": 210000,
    "nu": 0.3,
    "units": "d, ro, delta in mm; E in MPa"
  },
  "expected_outputs": {
    "contact_pressure_p": 213.559322,
    "hoop_stress_hub": 355.932203,
    "transmittable_torque": null
  },
  "working": "ro²=100²=10000; d²=50²=2500; ratio=(ro²+d²)/(ro²-d²)=(10000+2500)/(10000-2500)=12500/7500=5/3=1.6666667. Denominator=d(ratio+ν)=50(1.6666667+0.3)=50(1.9666667)=98.3333333. Numerator=Eδ=210000×0.1=21000 MPa·mm. p=21000/98.3333333=213.559322 MPa. Hoop stress=p×ratio=213.559322×1.6666667=355.932203 MPa. Torque is undefined because no torque formula or friction data are supplied."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

The specification leaves torque underdetermined because friction coefficient and contact length are absent, and it does not define whether interference is diametral or radial. The formula also becomes undefined at ro=d and produces nonphysical continuation results for ro<d unless the instrument rejects those inputs.

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche5/tranche5-results.json
• BOUNDARY_HAZARD_CATALOG.json