ISO 20056-1:2017

Rolling bearings — Load ratings for hybrid bearings with rolling elements made of ceramic — Part 1: Dynamic load ratings

ISO 20056-1:2017 specifies methods of calculating the dynamic load ratings for hybrid bearings with bearing rings made of contemporary, commonly used, high quality hardened bearing steel, in accordance with good manufacturing practice and rolling elements made from silicon nitride in contemporary, commonly used, high material and manufacturing quality and surface finish. For balls, ISO 26602[6] together with ISO 3290‑2[2] are applicable. For rollers, ISO 12297‑2[3] is applicable and ISO 26602[6] is applicable in an analogous way.

Roulements — Charges de base pour roulements hybrides avec éléments roulants en céramique — Partie 1: Charges dynamiques de base

General Information

• Status: Published
• Publication Date: 10-Dec-2017
• ICS: 21.100.20 - Rolling bearings
• Technical Committee: ISO/TC 4/SC 8 - Load ratings and life
• Drafting Committee: ISO/TC 4/SC 8 - Load ratings and life
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 09-Mar-2023

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 20056-1
First edition
2017-12
Rolling bearings — Load ratings for
hybrid bearings with rolling elements
made of ceramic —
Part 1:
Dynamic load ratings
Roulements — Charges de base pour roulements hybrides avec
éléments roulants en céramique —
Partie 1: Charges dynamiques de base
Reference number
ISO 20056-1:2017(E)
©
ISO 2017

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ISO 20056-1:2017(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
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ii © ISO 2017 – All rights reserved

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ISO 20056-1:2017(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 1
5 Dynamic load rating . 3
5.1 Ball bearings . . 3
5.1.1 Basic dynamic radial load rating . 3
5.1.2 Basic dynamic axial load rating . 3
5.1.3 Rating and reduction factors for hybrid ball bearings . 4
5.2 Roller bearings . 5
5.2.1 Basic dynamic radial load rating . 5
5.2.2 Basic dynamic axial load rating . 5
5.2.3 Rating and reduction factors for hybrid roller bearings. 6
Annex A (informative) Calculation of the fatigue load limit C . 7
u
Annex B (informative) Tabulated guide values for the factor f . 8
c
Bibliography .14
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ISO 20056-1:2017(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see the following
URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 4, Rolling bearings, Subcommittee SC 8,
Load ratings and life.
A list of all parts in the ISO 20056 series can be found on the ISO website.
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ISO 20056-1:2017(E)

Introduction
Hybrid bearings are rolling bearings with raceways consisting of commonly used steel rolling bearings
and rolling elements made from silicon nitride (for definitions, see ISO 5593). Due to the higher modulus
of elasticity of the ceramic rolling elements, hybrid bearings have a noticeably smaller contact ellipse at
the same load than rolling bearings with rolling elements made of rolling bearing steel. This will lead
theoretically to a reduction of the dynamic load-carrying capacity.
In practice, hybrid bearings are used in numerous industrial applications, where these bearings show
at least the same service life as conventional rolling bearings with steel rolling elements. Thus for the
typical range of application of hybrid bearings, the theoretical reduction of the dynamic load rating
is not observed in actual applications. The smaller contact ellipse and the material combination of
ceramic-steel will lead to noticeably lower surface shear stress in the rolling contact, which again will
lead to a higher load-carrying ability. This is reflected by defining a higher b factor compared to steel
m
bearings, which compensates for the higher contact stress under the same load.
Therefore, the formulae specified in this document give the same dynamic load ratings as defined per
ISO 281 for rolling bearings with identical internal geometry and rolling elements made of steel.
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INTERNATIONAL STANDARD ISO 20056-1:2017(E)
Rolling bearings — Load ratings for hybrid bearings with
rolling elements made of ceramic —
Part 1:
Dynamic load ratings
1 Scope
This document specifies methods of calculating the dynamic load ratings for hybrid bearings with
bearing rings made of contemporary, commonly used, high quality hardened bearing steel, in accordance
with good manufacturing practice and rolling elements made from silicon nitride in contemporary,
[6]
commonly used, high material and manufacturing quality and surface finish. For balls, ISO 26602
[2] [3] [6]
together with ISO 3290-2 are applicable. For rollers, ISO 12297-2 is applicable and ISO 26602 is
applicable in an analogous way.
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, Rolling bearings — Dynamic load ratings and rating life
ISO 5593, Rolling bearings — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5593 and ISO 281 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
For the purpose of this document, the following symbols apply.
b rating factor for contemporary, commonly used, high quality hardened bearing steel in accord-
m
ance with good manufacturing practice, the value of which varies with bearing type and design
C basic dynamic axial load rating, in N
a
C basic dynamic radial load rating, in N
r
C fatigue load limit, in N (see Annex A)
u
D pitch diameter of ball or roller set, in mm
pw
D nominal ball diameter, in mm
w
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ISO 20056-1:2017(E)

D roller diameter applicable in the calculation of load ratings, in mm
we
E modulus of elasticity of ceramic rolling elements, in MPa (E = 300 000 MPa)
Ce Ce
E modulus of elasticity of rolling bearing steel, in MPa (E = 207 000 MPa, according to ISO 281)
St St
E(χ) complete elliptic integral of the second kind
f factor which depends on the geometry of the bearing components, the accuracy to which the
c
various components are made, and the material
i number of rows of rolling elements
L effective roller length applicable in the calculation of load ratings, in mm
we
Q fatigue load limit of a single contact, in N
u
r cross-sectional raceway groove radius of outer ring or housing washer, in mm
e
r cross-sectional raceway groove radius of inner ring or shaft washer, in mm
i
Z number of rolling elements in a single-row bearing; number of rolling elements per row of a
multi-row bearing with the same number of rolling elements per row
α nominal contact angle, in degrees
γ auxiliary parameter,γ = D × cos α / D for ball bearings with α ≠ 90°
w pw
 γ = D  / D for ball bearings with α = 90°
w pw
 γ = D × cos α / D for roller bearings with α ≠ 90°
we pw
 γ = D  / D for roller bearings with α = 90°
we pw
η reduction factor for thrust bearings
λ reduction factor
v adjustment factor for exponent variation
v Poisson's ratio of ceramic rolling elements (v = 0,26)
Ce Ce
v Poisson's ratio of rolling bearing steel (v = 0,30, according to ISO 281)
St St
-1
∑ρ curvature sum, in mm
σ Hertzian contact stress at which the fatigue limit of the raceway is reached, in MPa
Hu
χ ratio of semi-major to semi-minor axis of the contact ellipse
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ISO 20056-1:2017(E)

5 Dynamic load rating
5.1 Ball bearings
5.1.1 Basic dynamic radial load rating
The basic dynamic radial load rating of a hybrid ball bearing is given by Formulae (1), (2) and (3):
0,7 2/3 1,8
C = b × f × (i × cos α) × Z × D for D ≤ 25,4 mm (1)
r m c w w
and
0,7 2/3 1,4
C = 3,647 × b × f × (i × cos α) × Z × D for D > 25,4 mm (2)
r m c w w
with
-3
10
 10
04, 1 13, 9 04, 11
  17, 2  3 
2 × r r 2 × rD-
  1 - γ  
() 1 - γ
   
03,
i i ew
 
f =×29,038 580 λγ× ×× ×+11,04 ××
     
c  
 
 
113/
 
2 × rD- 1 + γ r 2 × rD-
 
   
 
iw 1 + γ e iw
()
 
 
 
(3)
Tabulated guide values for the factor f are given in Annex B. The values of f given in Table B.1 apply
c c
to bearings with a cross-sectional raceway groove radius not larger than 0,52 D in radial and angular
w
contact ball bearing inner rings and not larger than 0,53 D in radial and angular contact ball bearing
w
outer rings and self-aligning ball bearing inner rings.
The load-carrying ability of a bearing is not necessarily increased by the use of a smaller groove radius,
but it is reduced by the use of a groove radius larger than those indicated in the previous paragraph.
5.1.2 Basic dynamic axial load rating
5.1.2.1 Thrust ball bearings with contact angle α < 90°
The basic dynamic axial load rating of a hybrid thrust ball bearing with contact angle α < 90° is given by
Formulae (4), (5) and (6):
0,7 2/3 1,8
C = b × f × (cos α) × tan α × Z × D for D ≤ 25,4 mm (4)
a m c w w
and
0,7 2/3 1,4
C = 3,647 × b × f × (cos α) × tan α × Z × D for D > 25,4 mm (5)
a m c w w
with
-3
10
 10
04, 1 13, 9 04, 1
  17, 2  3 
2 × rD-
 2 × r  1 - γ  r 
() 1 - γ
   
03,
i i ew
 
f =×70,825 8060 λη×× ××γ ×+1 ××
     
 
c
   
13/  
2 × rD- 1 + γ r 2 × rD-
 
     
iw 1 + γγ e iw
()
 
 
 
(6)
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ISO 20056-1:2017(E)

where
Z is the number of balls carrying load in one direction.
Tabulated guide values for the fac
...