ISO 6281:2020

INTERNATIONAL ISO
STANDARD 6281
Second edition
2020-02
Plain bearings — Testing under
conditions of hydrodynamic and
mixed lubrication in test rigs
Paliers lisses — Essai des paliers lisses dans les conditions de
lubrification hydrodynamique et mixte dans des machines d'essai
pour paliers
Reference number
©
ISO 2020
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definition . 1
4 Symbols . 1
5 Test objectives for bearing properties . 2
6 Test rigs . 3
6.1 General recommendations. 3
6.2 Generic types of test rig . 4
7 Test procedures . 6
7.1 General . 6
7.2 Running-in ability . 6
7.3 Wear resistance . 7
7.4 Compatibility between bearing and journal material (resistance to adhesion) . 7
7.5 Embeddability (foreign particles absorption) . 7
7.6 Resistance to journal scoring and abrasion . 7
7.7 Conformability . 7
7.8 Deformability (compressive strength) . 7
7.9 Resistance to erosion (cavitation erosion, fluid erosion, particle erosion) . 7
7.10 Static load carrying capacity . 8
7.11 Dynamic load carrying capacity (fatigue strength) . 8
7.12 Friction characteristics . 8
7.13 Lubricant flow rate characteristics. 8
7.14 Temperature increase characteristics . 8
8 Testing and test report . 8
8.1 General . 8
8.2 Test rig . 9
8.3 Measuring equipment . 9
8.3.1 General. 9
8.3.2 Measuring equipment for independent variables (which can also be time-
dependent) . . 9
8.3.3 Measuring equipment for dependent variables (which can also be time-
dependent) . . 9
8.4 Test bearing and journal .10
8.4.1 General.10
8.4.2 Test bearing .10
8.4.3 Journal . .11
8.5 Lubricant and lubricant supply method .11
8.5.1 Lubricant .11
8.5.2 Lubricant supply method .12
8.6 Operating conditions (test conditions) .12
8.6.1 General.12
8.6.2 Bearing load .12
8.6.3 Sliding velocity.12
8.6.4 Lubricant supply condition .12
8.6.5 Ambient conditions .13
8.7 Test results.13
8.7.1 General.13
8.7.2 Hydrodynamic parameters (including estimated results) .13
8.7.3 Assessment of bearing performance .14
8.8 Discussion of test results and remarks .14
Bibliography .15
iv © ISO 2020 – All rights reserved

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 of 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
www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 123, Plain bearings, Subcommittee SC 2,
Materials and lubricants, their properties, characteristics, test methods and testing conditions.
This second edition cancels and replaces the first edition (ISO 6281:2007), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— editorial changes;
— reference to ISO 9045 has been replaced by ISO 4378 (all parts);
— Clause 1 has been edited to be in line with ISO drafting rules;
— the unit of the dynamic viscosity in Clause 4 has been modified.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
INTERNATIONAL STANDARD ISO 6281:2020(E)
Plain bearings — Testing under conditions of
hydrodynamic and mixed lubrication in test rigs
1 Scope
This document defines requirements for the testing of lubricated plain journal bearings in test rigs,
running under conditions of hydrodynamic or mixed lubrication, during bearing and/or material
development. It deals with both static and dynamic loading in solid and multi-layer journal bearings. It
is not applicable to the testing of dynamic characteristics of lubricant film in journal bearings applied in
calculation of vibration and stability of turbo-rotors.
NOTE It is intended that further details of test procedures be established when carrying out testing
based on this document.
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 4378 (all parts), Plain bearings — Terms, definitions, classification and symbols
3 Terms and definition
...

INTERNATIONAL ISO
STANDARD 6281
Second edition
2020-02
Plain bearings — Testing under
conditions of hydrodynamic and
mixed lubrication in test rigs
Paliers lisses — Essai des paliers lisses dans les conditions de
lubrification hydrodynamique et mixte dans des machines d'essai
pour paliers
Reference number
©
ISO 2020
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definition . 1
4 Symbols . 1
5 Test objectives for bearing properties . 2
6 Test rigs . 3
6.1 General recommendations. 3
6.2 Generic types of test rig . 4
7 Test procedures . 6
7.1 General . 6
7.2 Running-in ability . 6
7.3 Wear resistance . 7
7.4 Compatibility between bearing and journal material (resistance to adhesion) . 7
7.5 Embeddability (foreign particles absorption) . 7
7.6 Resistance to journal scoring and abrasion . 7
7.7 Conformability . 7
7.8 Deformability (compressive strength) . 7
7.9 Resistance to erosion (cavitation erosion, fluid erosion, particle erosion) . 7
7.10 Static load carrying capacity . 8
7.11 Dynamic load carrying capacity (fatigue strength) . 8
7.12 Friction characteristics . 8
7.13 Lubricant flow rate characteristics. 8
7.14 Temperature increase characteristics . 8
8 Testing and test report . 8
8.1 General . 8
8.2 Test rig . 9
8.3 Measuring equipment . 9
8.3.1 General. 9
8.3.2 Measuring equipment for independent variables (which can also be time-
dependent) . . 9
8.3.3 Measuring equipment for dependent variables (which can also be time-
dependent) . . 9
8.4 Test bearing and journal .10
8.4.1 General.10
8.4.2 Test bearing .10
8.4.3 Journal . .11
8.5 Lubricant and lubricant supply method .11
8.5.1 Lubricant .11
8.5.2 Lubricant supply method .12
8.6 Operating conditions (test conditions) .12
8.6.1 General.12
8.6.2 Bearing load .12
8.6.3 Sliding velocity.12
8.6.4 Lubricant supply condition .12
8.6.5 Ambient conditions .13
8.7 Test results.13
8.7.1 General.13
8.7.2 Hydrodynamic parameters (including estimated results) .13
8.7.3 Assessment of bearing performance .14
8.8 Discussion of test results and remarks .14
Bibliography .15
iv © ISO 2020 – All rights reserved

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 of 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
www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 123, Plain bearings, Subcommittee SC 2,
Materials and lubricants, their properties, characteristics, test methods and testing conditions.
This second edition cancels and replaces the first edition (ISO 6281:2007), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— editorial changes;
— reference to ISO 9045 has been replaced by ISO 4378 (all parts);
— Clause 1 has been edited to be in line with ISO drafting rules;
— the unit of the dynamic viscosity in Clause 4 has been modified.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
INTERNATIONAL STANDARD ISO 6281:2020(E)
Plain bearings — Testing under conditions of
hydrodynamic and mixed lubrication in test rigs
1 Scope
This document defines requirements for the testing of lubricated plain journal bearings in test rigs,
running under conditions of hydrodynamic or mixed lubrication, during bearing and/or material
development. It deals with both static and dynamic loading in solid and multi-layer journal bearings. It
is not applicable to the testing of dynamic characteristics of lubricant film in journal bearings applied in
calculation of vibration and stability of turbo-rotors.
NOTE It is intended that further details of test procedures be established when carrying out testing
based on this document.
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 4378 (all parts), Plain bearings — Terms, definitions, classification and symbols
3 Terms and definition
...