ISO 17167:2018

Fine ceramics (advanced ceramics, advanced technical ceramics) — Mechanical properties of monolithic ceramics at room temperature — Determination of flexural strength by the ring-on-ring test

This document specifies a method for the determination of the nominal equibiaxial flexural strength by the ring-on-ring test of advanced monolithic technical ceramic materials at room temperature. This document is applicable to materials with a grain size less than 100 µm.

Céramiques techniques — Propriétés mécaniques des céramiques monolithiques à température ambiante — Détermination de la résistance à la flexion à l'aide de doubles anneaux

General Information

• Status: Published
• Publication Date: 07-Nov-2018
• ICS: 81.060.30 - Advanced ceramics
• Technical Committee: ISO/TC 206 - Fine ceramics
• Drafting Committee: ISO/TC 206 - Fine ceramics
• Current Stage: 9093 - International Standard confirmed
• Start Date: 06-Mar-2024
• Completion Date: 14-Feb-2026

Overview

ISO 17167:2018 specifies a standardized method to determine the nominal equibiaxial flexural strength of advanced monolithic technical ceramics at room temperature using the ring-on-ring test. It applies to fine ceramics (advanced/technical ceramics) with a grain size less than 100 µm. The test uses a round, discoidal specimen loaded between two concentric rings; strength is calculated from the fracture load, geometry and material Poisson ratio under the assumption of linear elastic equibiaxial bending.

Key topics and requirements

• Scope: Equibiaxial flexural strength (ring-on-ring) of monolithic ceramics at room temperature; grain size < 100 µm.
• Test principle: Axial load applied through a small loading ring to a disk supported on a larger concentric support ring; fracture load is used to compute nominal flexural stress.
• Test pieces: Round disks with controlled thickness and diameter; surface finish options include as-fired, ground/polished, or agreed procedure. Surface preparation strongly influences results.
• Test jig and dimensions:
  • Loading ring contact diameter: 12 ± 0.1 mm
  • Support ring contact diameter: 30 ± 0.1 mm
  • Ring contact radius of curvature: 2 ± 0.2 mm
  • Rings hardened (≥ 500 HV or ≥ 40 HRC) to minimize damage
  • Centre alignment tolerance: ≤ 0.2 mm
  • Ring flatness/waviness: ≤ 0.02 mm
  • Rubber film under support ring: thickness 0.6 ± 0.1 mm, Shore A hardness 60 ± 5
• Apparatus & measurement:
  • Test machine: shock-free loading, record maximum force; accuracy per ISO 7500‑1 (grade 1).
  • Dimensional measurement: resolution ≤ 0.1% of dimension (e.g., thickness resolution ≤ 0.002 mm, diameter ≤ 0.04 mm).
  • Environmental monitoring: temperature resolution ≥ 1 °C, humidity resolution ≥ 5% RH.
• Data interpretation: Results reported as mean ± standard deviation; further statistical analysis (for design data) recommended (see ISO 20501). Fractography is advised to identify fracture origins.
• Warnings: Exercise caution when extrapolating ring-on-ring strength to other stress states, geometries, rates, or environments.

Applications

• Material development and characterization of advanced ceramics (e.g., alumina, zirconia-based ceramics).
• Quality control and batch verification in ceramic manufacturing.
• Generating design data for engineering components that rely on biaxial strength information (thin disks, implant ceramics).
• Fractography and failure analysis to locate strength-limiting defects (surface, edge, or internal).

Who should use ISO 17167:2018

• Materials scientists and ceramic engineers performing mechanical testing of fine ceramics.
• Quality and laboratory managers in production and R&D environments.
• Test laboratories seeking ISO-compliant procedures for equibiaxial flexural testing.
• Designers and reliability engineers requiring standardized biaxial strength data.

Related standards

• ISO 7500-1 (calibration/verification of force-measuring systems)
• ISO/IEC 17025 (laboratory competence)
• ISO 6474-1 and ASTM C1499 (related ceramic flexural test methods)
• ISO 20501 (statistical evaluation of strength data)

Keywords: ISO 17167:2018, ring-on-ring test, equibiaxial flexural strength, fine ceramics, monolithic ceramics, advanced ceramics, mechanical properties, flexural strength test.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 17167
First edition
2018-11
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Mechanical properties of monolithic
ceramics at room temperature —
Determination of flexural strength by
the ring-on-ring test
Céramiques techniques — Propriétés mécaniques des céramiques
monolithiques à température ambiante — Détermination de la
résistance à la flexion à l'aide de doubles anneaux
Reference number
©
ISO 2018
© ISO 2018
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: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Significance and use . 2
6 Apparatus . 2
6.1 Test machine . 2
6.2 Test jig . 3
6.3 Calliper or alternative calibrated device for the measurement of the test piece thickness . 4
6.4 Device for measuring the temperature and humidity . 4
7 Test pieces . 4
7.1 General . 4
7.2 Dimensions and tolerances . 5
7.3 Surface finish . 6
7.3.1 General. 6
7.3.2 Surface finishing I: as-fired . 7
7.3.3 Surface finishing II: grinding/lapping/polishing . 7
7.3.4 Surface finish III: finishing by agreed procedure . 7
7.3.5 Check of dimensions . 7
7.3.6 General requirements . 8
7.3.7 Number of test pieces . 8
7.4 Precautions . 8
8 Procedure. 8
9 Calculations. 9
10 Test report .10
Annex A (informative) Typical fracture patterns of ceramic test pieces after a ring-on-ring test .11
Bibliography .13
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 206, Fine ceramics.
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.
iv © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 17167:2018(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Mechanical properties of monolithic ceramics
at room temperature — Determination of flexural strength
by the ring-on-ring test
1 Scope
This document specifies a method for the determination of the nominal equibiaxial flexural strength by
the ring-on-ring test of advanced monolithic technical ceramic materials at room temperature.
This document is applicable to materials with a grain size less than 100 µm.
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 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part 1:
Tension/compression testing machines — Calibration and verification of the force-measuring system
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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/
3.1
equibiaxial flexural strength
σ
rr
maximum nominal stress at the test piece surface supported by the material at the instant of failure
when loaded in linear elastic equibiaxial bending by the ring-on-ring test
Note 1 to entry: The ring-on-ring test for the determination of flexural strength is often referred to as biaxial
bending test or equibiaxial bending test (see Reference [1]). These names should not be used without the
reference to the ring-on-ring test conditions as there are some other test arrangements for which the term is
used or could also be used, such as the ball-on-three-balls test, the punch-on-three-balls test, the ball-on-ring
test and the punch-on-ring test.
4 Principle
A round discoidal test piece with a constant thickness is positioned between two concentric rings of
different diameters and loaded by an axial force.
The nominal equibiaxial flexural strength is calculated from the axial force which acts during the
moment of fracture, the geometry of the test piece and the test arrangement, as well as the Poisson
ratio of the test piece material.
5 Significance and use
This test is intended to be used for material development and characterization, quality control and
design data acquisition purposes. The strength level determined by the test is calculated on the
basis of linear elastic bending behaviour of a round, disk-like thin plate on the assumption that the
material being tested is elastically homogeneous and isotropic and shows a linear (Hooke) stress-strain
behaviour.
The result obtained from a strength test is determined by a large number of factors associated with
the microstructure of the material, the surface finishing procedure applied in preparation of the test
pieces, the size and shape of the test piece, the mechanical function of the testing apparatus, the rate
of load application and the relative humidity (RH) of the ambient atmosphere. As a consequence of the
brittle nature of ceramics, there is usually a considerable range of results obtained from a number of
nominally identical test pieces. These factors combined mean that caution in the interpretation of test
results is required. For many purposes, and as described in this document, the results of strength tests
can be described in terms of a mean value and a standard deviation. Further statistical evaluation of
results is required for design data acquisition and can be desirable for other purposes (see ISO 20501).
This method places closely defined restrictions on the size and shape of the test piece and on the
function of the test apparatus in order to minimize the errors that can arise as a consequence of the test
procedure.
NOTE The basis for the choice of dimensions and tolerances of test pieces and of the requirements of the test
jig can be found in ISO 6474-1, ASTM C1499 and Reference [1].
All other test factors are required to be stated in the test report (see Clause 10) in order to allow inter-
comparison of material behaviours. It is not possible rigorously to standardize particular surface
finishes since these are not absolutely controllable in mechanical terms. The inclusion of a standard
grinding procedure (see 7.3) as one of the surface finish options in this method is intended to provide a
means of obtaining a minimum amount of residual grinding damage to the test material.
WARNING — The extrapolation of equibiaxial flexural strength data to other geometries of
stressing, to single-axial stressing, to other rates of stressing or to other environments should
be viewed with caution.
The information about the origin of fracture in an equibiaxial flexural strength test can be a valuable
guide to the nature and position of strength-limiting defects. Fractography of test pieces is highly
recommended (see e.g. ASTM C1499, Reference [1], Reference [2]) and Annex A. In particular, the test
can identify fracture origins as being edge defects (caused by edge preparation), surface defects (caused
by surface preparation) or internal defects (caused by manufacturing inhomogeneities such as pores,
large grains or impurity concentrations). Not all advanced monolithic technical ceramics are amenable
to clear fractography.
6 Apparatus
6.1 Test machine
The test machine shall be capable of applying a force over a ball or a suitable articulation device in
that way that the loading ring acts perpendicular to the surface of the test piece so that the two rings
(loading ring and support ring) have uniform contact to the face surfaces of the test piece.
The machine shall be capable of applying the force shock-free and with controlled force or displacement.
The test machine shall be equipped for recording the maximum force applied to the test piece. The
accuracy of the test machine shall be in accordance with ISO 7500-1, grade 1.
2 © ISO 2018 – All rights reserved

6.2 Test jig
The test jig for the ring-on-ring test shall be as specified below in order to minimize misalignments and
frictional forces applied to the test piece.
NOTE 1 The precise construction of the test jig is not fixed in this document but the function is.
A schematic test setup for the examination of the nominal equibiaxial flexural strength by the double-
ring flexural test is shown in Figure 1.
Key
1 loading ring d contact diameter of the loading ring
2 thin adhesive film on the test piece d contact diameter of the support ring
3 test piece D diameter of the test piece
4 rubber film under the test piece F force applied
5 support ring r contact radius
Figure 1 — Example of a test setup for the determination of flexural strength by the ring-on-
ring test
The test jig shall consist of two concentric rings of different diameters, namely the support ring (large),
and the loading ring (small), see Figure 1.
The following standard dimensions shall be observed:
— contact diameter of the loading ring, d : (12 ± 0,1) mm;
— contact diameter of the support ring, d : (30 ± 0,1) mm;
— radius of curvature of the rings in the region of contact with the test piece surface, r: (2 ± 0,2) mm.
NOTE 2 This test setup has been used for decades to characterize the stress of advanced technical alumina
ceramics for orthopaedic implants (see ISO 6474-1).
A suitable centring device or procedure for the test jig shall be used ensuring a centred positioning of
the loading ring, the test piece and the support ring to one another within 0,2 mm.
Either the support ring or the loading ring shall be fixed to the punch of the test machine used so that
an adjustment of the rings to the test piece is also possible if the test piece is not perfectly coplanar flat.
The two rings shall be made from hardened steel with a Vickers hardness greater than 500 HV or
greater than 40 HRC (Rockwell C-scale), or another material with at least the hardness of the material
tested (e.g. hard metal, ceramic) to minimize damage to the rings which can occur during the fracture.
To compensate small deviations of the surface flatness of the discoidal test piece, a thin rubber film
with a thickness of (0,6 ± 0,1) mm and a shore A hardness of (60 ± 5) shall be positioned between the
support ring and the test piece.
The flatness (and/or waviness) of the loading and the supporting rings shall be equal or smaller than
0,02 mm.
6.3 Calliper or alternative calibrated device for the measurement of the test piece
thickness
For the determination of the test piece dimensions, a calibrated calliper or an alternative calibrated
device with a resolution ≤ 0,1 % of the dimension to be measured shall be used.
It means that the resolution of the measurement device for the test piece thickness shall be ≤ 0,002 mm
and for the test piece diameter ≤ 0,04 mm.
6.4 Device for measuring the temperature and humidity
A device for measuring the temperature with a resolution of at least 1 °C and a humidity measuring
device with a resolution of at least 5 % RH shall be used.
7 Test pieces
7.1 General
The test pieces shall be prepared by processes in accordance with the technologies used during the
production of the products. They may either be specially processed to, or close to, the final required
dimensions specified in 7.2, or may be machined from larger blocks or components.
NOTE 1 The strength of many types of advanced monolithic technical ceramics is strongly
...

INTERNATIONAL ISO
STANDARD 17167
First edition
2018-11
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Mechanical properties of monolithic
ceramics at room temperature —
Determination of flexural strength by
the ring-on-ring test
Céramiques techniques — Propriétés mécaniques des céramiques
monolithiques à température ambiante — Détermination de la
résistance à la flexion à l'aide de doubles anneaux
Reference number
©
ISO 2018
© ISO 2018
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: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Significance and use . 2
6 Apparatus . 2
6.1 Test machine . 2
6.2 Test jig . 3
6.3 Calliper or alternative calibrated device for the measurement of the test piece thickness . 4
6.4 Device for measuring the temperature and humidity . 4
7 Test pieces . 4
7.1 General . 4
7.2 Dimensions and tolerances . 5
7.3 Surface finish . 6
7.3.1 General. 6
7.3.2 Surface finishing I: as-fired . 7
7.3.3 Surface finishing II: grinding/lapping/polishing . 7
7.3.4 Surface finish III: finishing by agreed procedure . 7
7.3.5 Check of dimensions . 7
7.3.6 General requirements . 8
7.3.7 Number of test pieces . 8
7.4 Precautions . 8
8 Procedure. 8
9 Calculations. 9
10 Test report .10
Annex A (informative) Typical fracture patterns of ceramic test pieces after a ring-on-ring test .11
Bibliography .13
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 206, Fine ceramics.
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.
iv © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 17167:2018(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Mechanical properties of monolithic ceramics
at room temperature — Determination of flexural strength
by the ring-on-ring test
1 Scope
This document specifies a method for the determination of the nominal equibiaxial flexural strength by
the ring-on-ring test of advanced monolithic technical ceramic materials at room temperature.
This document is applicable to materials with a grain size less than 100 µm.
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 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part 1:
Tension/compression testing machines — Calibration and verification of the force-measuring system
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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/
3.1
equibiaxial flexural strength
σ
rr
maximum nominal stress at the test piece surface supported by the material at the instant of failure
when loaded in linear elastic equibiaxial bending by the ring-on-ring test
Note 1 to entry: The ring-on-ring test for the determination of flexural strength is often referred to as biaxial
bending test or equibiaxial bending test (see Reference [1]). These names should not be used without the
reference to the ring-on-ring test conditions as there are some other test arrangements for which the term is
used or could also be used, such as the ball-on-three-balls test, the punch-on-three-balls test, the ball-on-ring
test and the punch-on-ring test.
4 Principle
A round discoidal test piece with a constant thickness is positioned between two concentric rings of
different diameters and loaded by an axial force.
The nominal equibiaxial flexural strength is calculated from the axial force which acts during the
moment of fracture, the geometry of the test piece and the test arrangement, as well as the Poisson
ratio of the test piece material.
5 Significance and use
This test is intended to be used for material development and characterization, quality control and
design data acquisition purposes. The strength level determined by the test is calculated on the
basis of linear elastic bending behaviour of a round, disk-like thin plate on the assumption that the
material being tested is elastically homogeneous and isotropic and shows a linear (Hooke) stress-strain
behaviour.
The result obtained from a strength test is determined by a large number of factors associated with
the microstructure of the material, the surface finishing procedure applied in preparation of the test
pieces, the size and shape of the test piece, the mechanical function of the testing apparatus, the rate
of load application and the relative humidity (RH) of the ambient atmosphere. As a consequence of the
brittle nature of ceramics, there is usually a considerable range of results obtained from a number of
nominally identical test pieces. These factors combined mean that caution in the interpretation of test
results is required. For many purposes, and as described in this document, the results of strength tests
can be described in terms of a mean value and a standard deviation. Further statistical evaluation of
results is required for design data acquisition and can be desirable for other purposes (see ISO 20501).
This method places closely defined restrictions on the size and shape of the test piece and on the
function of the test apparatus in order to minimize the errors that can arise as a consequence of the test
procedure.
NOTE The basis for the choice of dimensions and tolerances of test pieces and of the requirements of the test
jig can be found in ISO 6474-1, ASTM C1499 and Reference [1].
All other test factors are required to be stated in the test report (see Clause 10) in order to allow inter-
comparison of material behaviours. It is not possible rigorously to standardize particular surface
finishes since these are not absolutely controllable in mechanical terms. The inclusion of a standard
grinding procedure (see 7.3) as one of the surface finish options in this method is intended to provide a
means of obtaining a minimum amount of residual grinding damage to the test material.
WARNING — The extrapolation of equibiaxial flexural strength data to other geometries of
stressing, to single-axial stressing, to other rates of stressing or to other environments should
be viewed with caution.
The information about the origin of fracture in an equibiaxial flexural strength test can be a valuable
guide to the nature and position of strength-limiting defects. Fractography of test pieces is highly
recommended (see e.g. ASTM C1499, Reference [1], Reference [2]) and Annex A. In particular, the test
can identify fracture origins as being edge defects (caused by edge preparation), surface defects (caused
by surface preparation) or internal defects (caused by manufacturing inhomogeneities such as pores,
large grains or impurity concentrations). Not all advanced monolithic technical ceramics are amenable
to clear fractography.
6 Apparatus
6.1 Test machine
The test machine shall be capable of applying a force over a ball or a suitable articulation device in
that way that the loading ring acts perpendicular to the surface of the test piece so that the two rings
(loading ring and support ring) have uniform contact to the face surfaces of the test piece.
The machine shall be capable of applying the force shock-free and with controlled force or displacement.
The test machine shall be equipped for recording the maximum force applied to the test piece. The
accuracy of the test machine shall be in accordance with ISO 7500-1, grade 1.
2 © ISO 2018 – All rights reserved

6.2 Test jig
The test jig for the ring-on-ring test shall be as specified below in order to minimize misalignments and
frictional forces applied to the test piece.
NOTE 1 The precise construction of the test jig is not fixed in this document but the function is.
A schematic test setup for the examination of the nominal equibiaxial flexural strength by the double-
ring flexural test is shown in Figure 1.
Key
1 loading ring d contact diameter of the loading ring
2 thin adhesive film on the test piece d contact diameter of the support ring
3 test piece D diameter of the test piece
4 rubber film under the test piece F force applied
5 support ring r contact radius
Figure 1 — Example of a test setup for the determination of flexural strength by the ring-on-
ring test
The test jig shall consist of two concentric rings of different diameters, namely the support ring (large),
and the loading ring (small), see Figure 1.
The following standard dimensions shall be observed:
— contact diameter of the loading ring, d : (12 ± 0,1) mm;
— contact diameter of the support ring, d : (30 ± 0,1) mm;
— radius of curvature of the rings in the region of contact with the test piece surface, r: (2 ± 0,2) mm.
NOTE 2 This test setup has been used for decades to characterize the stress of advanced technical alumina
ceramics for orthopaedic implants (see ISO 6474-1).
A suitable centring device or procedure for the test jig shall be used ensuring a centred positioning of
the loading ring, the test piece and the support ring to one another within 0,2 mm.
Either the support ring or the loading ring shall be fixed to the punch of the test machine used so that
an adjustment of the rings to the test piece is also possible if the test piece is not perfectly coplanar flat.
The two rings shall be made from hardened steel with a Vickers hardness greater than 500 HV or
greater than 40 HRC (Rockwell C-scale), or another material with at least the hardness of the material
tested (e.g. hard metal, ceramic) to minimize damage to the rings which can occur during the fracture.
To compensate small deviations of the surface flatness of the discoidal test piece, a thin rubber film
with a thickness of (0,6 ± 0,1) mm and a shore A hardness of (60 ± 5) shall be positioned between the
support ring and the test piece.
The flatness (and/or waviness) of the loading and the supporting rings shall be equal or smaller than
0,02 mm.
6.3 Calliper or alternative calibrated device for the measurement of the test piece
thickness
For the determination of the test piece dimensions, a calibrated calliper or an alternative calibrated
device with a resolution ≤ 0,1 % of the dimension to be measured shall be used.
It means that the resolution of the measurement device for the test piece thickness shall be ≤ 0,002 mm
and for the test piece diameter ≤ 0,04 mm.
6.4 Device for measuring the temperature and humidity
A device for measuring the temperature with a resolution of at least 1 °C and a humidity measuring
device with a resolution of at least 5 % RH shall be used.
7 Test pieces
7.1 General
The test pieces shall be prepared by processes in accordance with the technologies used during the
production of the products. They may either be specially processed to, or close to, the final required
dimensions specified in 7.2, or may be machined from larger blocks or components.
NOTE 1 The strength of many types of advanced monolithic technical ceramics is strongly
...