Fine ceramics (advanced ceramics, advanced technical ceramics) — Test method for flexural strength of monolithic ceramic thin plates at room temperature by three-point or four-point bending

This document describes a test method for the flexural strength of monolithic ceramic thin plates at room temperature by three-point bending or four-point bending. This document is intended for use with monolithic ceramics and whisker- or particulate-reinforced ceramics which are regarded as macroscopically homogeneous. It does not include continuous-fibre-reinforced ceramics composites. This document is applicable to ceramic thin plates with a thickness from 0,2 mm to 1,0 mm. This document is for material development, material comparison, quality assurance, characterization and reliability data generation.

Céramiques techniques — Méthode d'essai de la résistance en flexion des plaques minces en céramique monolithique à température ambiante en flexion trois ou quatre points

General Information

Status
Published
Publication Date
03-Feb-2020
Technical Committee
Drafting Committee
Current Stage
6060 - International Standard published
Start Date
04-Feb-2020
Completion Date
04-Feb-2020
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ISO 23242:2020 - Fine ceramics (advanced ceramics, advanced technical ceramics) -- Test method for flexural strength of monolithic ceramic thin plates at room temperature by three-point or four-point bending
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INTERNATIONAL ISO
STANDARD 23242
First edition
2020-02
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Test method for flexural strength
of monolithic ceramic thin plates at
room temperature by three-point or
four-point bending
Céramiques techniques — Méthode d'essai de la résistance en flexion
des plaques minces en céramique monolithique à température
ambiante en flexion trois ou quatre points
Reference number
ISO 23242:2020(E)
ISO 2020
---------------------- Page: 1 ----------------------
ISO 23242:2020(E)
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© ISO 2020

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ii © ISO 2020 – All rights reserved
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ISO 23242:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 3

5 Apparatus ..................................................................................................................................................................................................................... 3

5.1 Bend testing machine ........................................................................................................................................................................ 3

5.2 Bend test fixture..................................................................................................................................................................................... 3

5.2.1 General...................................................................................................................................................................................... 3

5.2.2 Bearings ................................................................................................................................................................................... 4

5.2.3 Positioning of bearings ............................................................................................................................................... 4

5.2.4 Fixture material ................................................................................................................................................................ 5

5.3 Calibrated micrometer ..................................................................................................................................................................... 5

5.4 Metallurgical microscope ............................................................................................................................................................... 5

6 Test piece dimension and preparation.......................................................................................................................................... 5

6.1 Shape and dimensions of test piece ...................................................................................................................................... 5

6.1.1 Machined specimens .................................................................................................................................................... 5

6.1.2 As-fired specimens ......................................................................................................................................................... 6

6.2 Test piece preparation ...................................................................................................................................................................... 6

6.2.1 General...................................................................................................................................................................................... 6

6.2.2 As-fired ..................................................................................................................................................................................... 7

6.2.3 Customary machining procedure ...................................................................................................................... 7

6.2.4 Component-matched procedure ........................................................................................................................ 7

6.2.5 Handling of specimens ........................................................................................................................................... ..... 7

6.2.6 Number of test pieces .................................................................................................................................................. 7

7 Test procedure ........................................................................................................................................................................................................ 7

7.1 Initial dimensions measurement for specimen type identification .......................................................... 7

7.2 Specimen marking ............................................................................................................................................................................... 7

7.3 Bend test fixture..................................................................................................................................................................................... 8

7.4 Fixture cleaning ...................................................................................................................................................................................... 8

7.5 Setting test piece in bend fixture ............................................................................................................................................. 8

7.6 Pre-loading ................................................................................................................................................................................................. 8

7.7 Protection from fracture fragments ...................................................................................................................................... 8

7.8 Crosshead speed .................................................................................................................................................................................... 8

7.9 Application of test force .................................................................................................................................................................. 9

7.10 Retrieval of broken fragments for successive measurements ........................................................................ 9

7.11 Measurement of test piece thickness and width ....................................................................................................... 9

7.12 Fractography ............................................................................................................................................................................................. 9

8 Calculation ...............................................................................................................................................................................................................10

8.1 Three-point flexural strength ..................................................................................................................................................10

8.2 Four-point flexural strength .....................................................................................................................................................11

8.3 Mean and standard deviation ..................................................................................................................................................11

9 Test report ................................................................................................................................................................................................................11

10 Weibull size scaling .........................................................................................................................................................................................12

Annex A (informative) Chamfer correction factors ............................................................................................................................13

Bibliography .............................................................................................................................................................................................................................15

© ISO 2020 – All rights reserved iii
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ISO 23242:2020(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

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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

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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 2020 – All rights reserved
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INTERNATIONAL STANDARD ISO 23242:2020(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Test method for flexural strength of
monolithic ceramic thin plates at room temperature by
three-point or four-point bending
1 Scope

This document describes a test method for the flexural strength of monolithic ceramic thin plates at

room temperature by three-point bending or four-point bending.

This document is intended for use with monolithic ceramics and whisker- or particulate-reinforced

ceramics which are regarded as macroscopically homogeneous. It does not include continuous-fibre-

reinforced ceramics composites. This document is applicable to ceramic thin plates with a thickness

from 0,2 mm to 1,0 mm.

This document is for material development, material comparison, quality assurance, characterization

and reliability data generation.
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 1101, Geometrical product specifications (GPS) — Geometrical tolerancing — Tolerances of form,

orientation, location and run-out

ISO 3611, Geometrical product specifications (GPS) — Dimensional measuring equipment: Micrometers for

external measurements — Design and metrological characteristics

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 14704:2016, Fine ceramics (advanced ceramics, advanced technical ceramics) — Test method for

flexural strength of monolithic ceramics at room temperature
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
flexural strength

maximum nominal stress at fracture of a specified elastic plate loaded in bending

© ISO 2020 – All rights reserved 1
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ISO 23242:2020(E)
3.2
three-point flexure

configuration of flexural strength testing where a specimen is loaded at a location midway between

two support bearings
Note 1 to entry: See Figure 1 a) and Table 1.

Note 2 to entry: The bearings may be cylindrical rollers or cylindrical bearings.

3.3
four-point flexure

configuration of flexural strength testing where a specimen is loaded equally by two bearings located

symmetrically between two support bearings
Note 1 to entry: See Figure 1 b) and Table 1.
a) Three-point flexure
b) Four-point flexure
Key
1 loading bearing(s)
2 support bearings
3 specimen
Figure 1 — Flexural test configurations
2 © ISO 2020 – All rights reserved
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ISO 23242:2020(E)
Table 1 — Specimen type and dimension of bend test fixtures

Specimen Specimen Bending Lower Length of fixture moment arm Diameter of bearings

type thickness mode span
a mm
d L
mm mm
I 0,5 ≤ d ≤ 1,0 3-point 30 ± 0,1 ― 4,5 to 5,0
I 0,5 ≤ d ≤ 1,0 4-point 30 ± 0,1 10 ± 0,1 4,5 to 5,0
II 0,2 ≤ d < 0,5 3-point 15 ± 0,1 ― 4,5 to 5,0
II 0,2 ≤ d < 0,5 4-point 15 ± 0,1 5 ± 0,1 2,5 to 3,0
3.4
fully articulating fixture

test fixture designed to apply uniform and even loading to test specimens that can have uneven, non-

parallel or twisted surfaces
3.5
semi-articulating fixture

test fixture designed to apply uniform and even loading to specimens that have flat and parallel surfaces

4 Principle

A plate specimen with a rectangular cross-section is loaded in flexure until fracture. The load at

fracture, the test fixture and specimen dimensions are used to compute the flexural strength of the

specimen, which is a measure of the uniaxial tensile strength of a ceramic. The material is assumed to

be isotropic and linearly elastic.
5 Apparatus
5.1 Bend testing machine

A suitable testing machine capable of applying a uniform crosshead speed shall be used. The testing

machine shall be in accordance with ISO 7500-1, with an accuracy of 1 % of the indicated force at

fracture. The test load of ceramic thin samples ranges roughly between 20 N and 200 N. A load cell shall

be selected so that the fracture load of thin plates is not close to the limits of load capacity interval, i.e.

the lower limit for high-load cell capacity and the upper limit for low-load cell capacity.

5.2 Bend test fixture
5.2.1 General

Three- or four-point flexure configurations shall be used, as illustrated in Figure 1 and Table 1. The

fixture shall have bearings that are free to roll, as described in 5.2.2, in order to eliminate frictional

constraints when the specimen surfaces expand or contract during loading. In addition, the fixture shall

be designed so that parts “articulate” or tilt to ensure uniform loading to the specimen. The articulation

shall be designed so that parts of the fixture can rotate, as specified in ISO 14704:2016, Figure B.1, to

ensure even loading on the left and right bearings. An articulation is also needed to ensure that all the

bearings contact the specimen surfaces evenly and apply a uniform load. Semi-articulated fixtures have

some articulating or tilting capabilities and may be used with specimens that have flat and parallel

surfaces, such as those of machined specimens. A semi-articulating fixture shall have pairs of upper

and lower bearings that articulate to match the specimen surfaces, as specified in ISO 14704:2016,

Figures B.2 and B.3. Fully articulated fixtures have more moving parts and shall be used for specimens

that do not have flat and parallel surfaces. They allow independent articulation of the bearings. Fully

articulated fixtures are often necessary for as-fired, heat-treated or oxidized specimens, since uneven

loading can cause twisting and severe errors. A fully articulating fixture may also be used with

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ISO 23242:2020(E)

machined specimens. For further detail on both semi-articulating and fully articulating fixtures, refer

to ISO 14704.
5.2.2 Bearings

Specimens shall be loaded and supported by bearings. The bearings may be cylindrical rollers or

cylindrical pins. The bearings shall be made of a steel which has a hardness of no less than HRC 40 for

specimen strengths up to 1 400 MPa, or no less than HRC 46 for specimen strengths up to 2 000 MPa.

Alternatively, the bearing may be made of a ceramic or a hard metal wi
...

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