ISO TR 1281-1:2021 pdf download.Rolling bearings — Explanatory notes on ISO 281 — Part 1: Basic dynamic load rating and basic rating life.
This document specifies supplementary background information regarding the derivation of mathematical expressions and factors given in ISO 281:2007.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 281:2007, Rolling bearings — Dynamic load ratings and rating life
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 281:2007 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Symbols
A constant of proportionality
A 1 constant of proportionality determined experimentally
B 1 constant of proportionality determined experimentally
C 1 basic dynamic radial load rating of a rotating ring
C 2 basic dynamic radial load rating of a stationary ring
C a basic dynamic axial load rating for thrust ball or roller bearing
C a1 basic dynamic axial load rating of the rotating ring of an entire thrust ball or roller bearing
C a2 basic dynamic axial load rating of the stationary ring of an entire thrust ball or roller bearing
C ak basic dynamic axial load rating as a row k of an entire thrust ball or roller bearing
C a1k basic dynamic axial load rating as a row k of the rotating ring of thrust ball or roller bearing
C a2k basic dynamic axial load rating as a row k of the stationary ring of thrust ball or roller bearing
X a radial load factor for thrust bearing
Y axial load factor for radial bearing
Y a axial load factor for thrust bearing
Z number of balls or rollers per row
Z k number of balls or rollers per row k
a semimajor axis of the projected contact ellipse
a 1 life adjustment factor for reliability
b semiminor axis of the projected contact ellipse
c exponent determined experimentally
c c compression constant
e measure of life scatter, i.e. Weibull slope determined experimentally
e limiting value of F a /F r for the applicability of different values of factors X and Y in the new edition
f c factor which depends on the geometry of the bearing components, the accuracy to which the various components are made, and the material
h exponent determined experimentally
i number of rows of balls or rollers
l circumference of the raceway
r cross-sectional raceway groove radius
r e cross-sectional raceway groove radius of outer ring or housing washer
r i cross-sectional raceway groove radius of inner ring or shaft washer
t auxiliary parameter
z o depth of the maximum orthogonal subsurface shear stress
α nominal contact angle
α′ actual contact angle
γ D w cos α/D pw for ball bearings with α ≠ 90°
D w /D pw for ball bearings with α = 90°
D we cos α/D pw for roller bearings with α ≠ 90°
D we /D pw for roller bearings with α = 90°
ε parameter indicating the width of the loaded zone in the bearing
η reduction factor
λ reduction factor
µ factor introduced by Hertz
ν factor introduced by Hertz, or adjustment factor for exponent variation
σ max maximum contact stress
Σρ curvature sum
τ o maximum orthogonal subsurface shear stress
φ o one half of the loaded arc
5 General
The derivation of the basic dynamic load ratings is described in Formulae (1) to (46). The dynamic equivalent load and the radial and axial load factors are covered in Formulae (47) to (82), while basic rating life is described in Formulae (83) to (89).ISO TR 1281-1 pdf download.ISO TR 1281-1 pdf download
