Bearing Analysis — validation & limitations

What it calculates

• ISO 281 L10 basic and modified rating life (Lnmh) with the aISO life modification factor
• Dynamic equivalent load P per ISO 281 X/Y factors (interpolated DGBB table, angular-contact, tapered and spherical roller)
• Viscosity ratio κ and reference kinematic viscosity ν₁ per the ISO 281:2007 reference-viscosity relation
• Static safety factor s0 and equivalent static load P0 per ISO 76
• Built-in catalogue of typical conservative ratings — computed from each size's boundary dimensions — for deep-groove ball, angular-contact, cylindrical, tapered and spherical roller bearings (6000–32000 series)
• Opposed-pair induced axial load — give the opposing bearing's radial load and the tapered / angular contact pair's own thrust is carried into P and P0
• Sensitivity / tornado chart — ±20% variation on radial load, axial load, speed and dynamic capacity

Standards this tool applies

• ISO 281 — ISO 281:2007 L10h, Lnmh, aISO, κ and s0 (ISO 76) with a built-in catalog, sensitivity chart and PDF report. Ball-bearing aISO follows the standard; roller aISO is as recalled, not verified, and conservative-min with a previous estimate.
• ISO/TS 16281 — Internal load distribution by the method of ISO/TS 16281 — per-element load, loaded contact angle, load-zone extent, and radial, axial and tilting stiffness for ball bearings. It does NOT compute the modified reference rating life L_nmref of ISO/TS 16281, and is not an ISO/TS 16281 compliance calculation; the L10 and Lnmh figures on that page remain ISO 281. Roller bearings, centrifugal rolling-element load and ring flexibility are outside the implementation.

Related standards — reference only, not implemented

• DIN 732reference only — Bearing rating life and static safety to ISO 281 / ISO 76 — the load side of the same bearing selection.

Validation evidence — independent reference cases (1)

Each case runs the tool's engine on a worked example whose values come from a published source or a hand derivation from the cited equations, and an automated regression test asserts the engine against those values within the stated tolerance. "Conservative" means the engine is known to sit on the safe side of the reference and the test asserts that side. Sources are cited; their text is not reproduced.

• Modified rating life Lnmh = a1·a_ISO·L10h, kappa to verdict

  Agrees

  Source: ISO 281:2007 eq. (1), Table 12 (a1), Table 13 (cleanliness), §9.3.3.2 (a_ISO radial ball); bearing-maker catalogue rated viscosity

  Inputs: 6208 deep groove, d 40 / D 80 mm, C 32.5 kN, C0 19.0 kN, Fr 5 kN, VG 32 at 40 C, clean; A 3000 rpm R90, B 500 rpm R95

  Quantity	Reference value	Tolerance
  kappa (case A)	3.0170	1e-6 relative
  a_ISO (case A)	6.1541	1e-5 relative
  Lnmh (case A)	9 389.2 h (FAIL)	1e-5 relative
  Lnmh (case B)	13 572.2 h (CHECK)	1e-5 relative

  Conservative simplification: The engine's 'clean' class takes the lower end of the ISO 281 high-cleanliness range (eta_c 0.6).

  tests/golden/REF-bearings-modified-life.golden.test.ts

Limitations

Conservative simplifications

• Modified rating life Lnmh = a1·a_ISO·L10h, kappa to verdict — The engine's 'clean' class takes the lower end of the ISO 281 high-cleanliness range (eta_c 0.6).

Not checked by this tool

• Grease service life / relubrication interval — Only rolling-contact fatigue life is computed; check the grease life with the grease or bearing maker's method
• Variable load and speed duty cycle — One constant load point is rated; combine a duty spectrum into an equivalent load (ISO 281) by hand or with the maker
• Oscillating (non-rotating) motion — ISO 281 assumes full rotation; use the maker's oscillation method (or /slewing for slow-turning rings)
• Shaft and housing fits, seat form and abutment shoulders — Mounting fits are not modelled; take the tolerance classes and shoulder heights from the bearing maker
• Electrical current passage (inverter-fed motors, generators) — Not assessed; use insulated or hybrid bearings per the maker's guidance
• Standstill vibration (false brinelling) and transport damage — Not assessed; follow the maker's guidance for bearings that vibrate while stationary
• Seal, cage and lubricant temperature and speed limits — Check the seal, cage and grease ratings in the bearing maker's data