ISO 20808:2004
(Main)Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of friction and wear characteristics of monolithic ceramics by ball-on-disc method
Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of friction and wear characteristics of monolithic ceramics by ball-on-disc method
ISO 20808:2004 specifies a procedure for and provides guidance on the determination of the coefficient of friction and the specific wear rate for monolithic ceramics. In this method, the materials are tested in pairs, in a ball-on-disc configuration, under dry, non-abrasive conditions.
Céramiques techniques — Détermination des caractéristiques de frottement et d'usure des céramiques monolithiques par la méthode "bille sur disque"
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 20808
First edition
2004-02-01
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Determination of friction and wear
characteristics of monolithic ceramics by
ball-on-disc method
Céramiques techniques — Détermination des caractéristiques de
frottement et d'usure des céramiques monolithiques par la méthode
«bille sur disque»
Reference number
ISO 20808:2004(E)
©
ISO 2004
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ISO 20808:2004(E)
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ii © ISO 2004 – All rights reserved
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ISO 20808:2004(E)
Contents Page
Foreword. iv
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 1
4 Significance and use . 2
5 Test materials and specimen preparation. 2
5.1 Materials. 2
5.2 Ball specimen. 2
5.3 Disc specimen. 3
6 Apparatus. 3
7 Testing procedure. 4
7.1 Determination of specimen density . 4
7.2 Treatment of specimen before test . 4
7.3 Measurement of mass before test. 4
7.4 Preparation of wear test . 4
7.5 Testing conditions. 4
7.6 Measurement of friction force . 5
7.7 Measurement of mass after test . 5
7.8 Measurement of wear scar on ball specimen. 5
7.9 Measurement of wear track on disc specimen .5
7.10 Number of test repeats. 5
8 Calculation of test results . 6
8.1 Specific wear rate of ball specimen . 6
8.2 Specific wear rate of disc specimen . 7
8.3 Coefficient of friction . 8
8.4 Rounding off of numerical values . 8
9 Test report. 8
Bibliography . 9
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ISO 20808:2004(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 20808 was prepared by Technical Committee ISO/TC 206, Fine ceramics.
iv © ISO 2004 – All rights reserved
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INTERNATIONAL STANDARD ISO 20808:2004(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Determination of friction and wear characteristics
of monolithic ceramics by ball-on-disc method
1 Scope
This International Standard specifies a procedure for and provides guidance on the determination of the
coefficient of friction and the specific wear rate for monolithic ceramics. In this method, the materials are
tested in pairs, in a ball-on-disc configuration, under dry, non-abrasive conditions.
2 Normative references
The following referenced documents are indispensable for the application 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 31-0, Quantities and units — Part 0: General principles
ISO 1101, Geometrical Product Specifications (GPS) — Geometrical tolerancing — Tolerances of form,
orientation, location and run-out
ISO 3274, Geometrical Product Specifications (GPS) — Surface texture: Profile method — Nominal
characteristics of contact (stylus) instruments
ISO 3599, Vernier callipers reading to 0,1 and 0,05 mm
ISO 3611, Micrometer callipers for external measurement
ISO 4287, Geometrical Product Specifications (GPS) — Surface texture: Profile method — Terms, definitions
and surface texture parameters
ISO 18754, Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of density
and apparent porosity
3 Terms and definitions
For the purposes of this document the following terms and definitions apply.
3.1
wear
progressive mass removal from the surface of solid material due to relative motion with a contacting
substance or substances
3.2
wear test
method of evaluating the friction and wear performance of materials in sliding contact
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ISO 20808:2004(E)
3.3
ball-on-disc method
one of the wear test methods in which the sliding contact is brought about by pushing a ball specimen on to a
rotating disc specimen under a constant load
3.4
friction force
resisting force tangential to the interface between two bodies, when one body moves or tends to move relative
to the other under the action of a normal force pressing these bodies together
3.5
coefficient of friction
µ
dimensionless ratio of the friction force, F , to the applied normal force, F
f p
µ = F /F
f p
3.6
specific wear rate
W
s
rate of material removal by wear, expressed by means of the wear volume, V, per unit applied normal force,
F and unit sliding distance, L where W = V/( F × L)
p p
s
4 Significance and use
This International Standard gives guidance on conducting a sliding friction and wear test in a ball-on-disc
configuration. It shall be used to determine the wear resistance and friction generated in uniaxial sliding
contacts between ceramics.
It should be noted that there are many parameters in sliding contact that affect the magnitude of friction and
wear. The aim of performing any wear test is to simulate, as closely as possible, the conditions that occur in
the real application. As the deviation between the test conditions and the application conditions becomes
larger, the test results become less relevant. To add credence to the test results, the appearance of the worn
surfaces from the test samples shall be compared with the appearance of the worn surface from the actual
worn component in order to ensure that similar wear mechanisms have taken place in each case.
The recommended test conditions suggested in this International Standard shall be used when the application
conditions are not well defined but general comparison among materials is required.
5 Test materials and specimen preparation
5.1 Materials
This test method can be applied to a variety of materials. The only requirement is that ball and disc specimens
having the dimensions specified below can be prepared, and that they shall withstand the stresses imposed
during the testing without failure or excessive flexure. In principle, the ball and disc specimen should be from
the same material, but ball and disc specimens from different materials can also be tested by this method. Any
pertinent details of the materials such as their dimensions, surface finish, material type, composition,
microstructure and processing treatments shall be supplied.
5.2 Ball specimen
The ball specimen shall be a true sphere of more than 5 mm diameter, or a straight rod whose end part is
machined to a spherical cap. The recommended diameter of the sphere is 10 mm. The surface roughness of
the specimen shall be not more than 0,1 µm Ra as specified in ISO 4287.
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ISO 20808:2004(E)
5.3 Disc specimen
The disc specimen shall be more than 3 mm in thickness and be large enough to enable the testing surface to
contain a sliding circle of more than 30 mm diameter. The surfaces of the disc shall be flat and parallel to
within 0,02 mm as specified in ISO 1101. The roughness of the test surface shall be not more than 0,1 µm Ra
as specified in ISO 4287.
6 Apparatus
6.1 Ball-on-disc method testing apparatus.
The testing apparatus shall consist of:
the disc holder, for securing a disc specimen;
the drive system for rotating the disc;
the ball holder for gripping a ball specimen;
the loading mechanism for pushing the ball specimen on to the disc specimen;
t
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