ISO 27727:2008

Rubber, vulcanized — Measurement of fatigue crack growth rate

ISO 27727:2008 specifies a method for the determination of the fatigue crack growth rate of vulcanized rubber under repeated loading over an extended period of time. The crack starts from the tip of a cut made in the test piece before the test, and grows progressively until it finally becomes large enough for complete fracture to occur. Using a pure-shear test piece, measurements are made to monitor the crack growth under the cyclic loading in order to obtain the crack growth rate, i.e. the increase in crack length per cycle. Tests are carried out at various tearing energies by varying the strain energy density in the test piece. This is done by changing the strain amplitude.

Caoutchouc vulcanisé — Mesurage du taux de croissance des craquelures de fatigue

General Information

• Status: Published
• Publication Date: 17-Aug-2008
• ICS: 83.060 - Rubber
• Technical Committee: ISO/TC 45/SC 2 - Testing and analysis
• Drafting Committee: ISO/TC 45/SC 2/WG 3 - Degradation tests
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 24-Jun-2021

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 27727
First edition
2008-09-01
Rubber, vulcanized — Measurement of
fatigue crack growth rate
Caoutchouc vulcanisé — Mesurage du taux de croissance des
craquelures de fatigue
Reference number
ISO 27727:2008(E)
ISO 2008
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ISO 27727:2008(E)
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© ISO 2008

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ii © ISO 2008 – All rights reserved
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ISO 27727:2008(E)
Contents Page

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

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

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

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

4 Principle................................................................................................................................................. 2

5 Apparatus.............................................................................................................................................. 2

5.1 Fatigue crack growth rate test machine............................................................................................. 2

5.2 Image-processing device..................................................................................................................... 2

5.3 Temperature-controlled chamber ....................................................................................................... 2

5.4 Thickness- and width-measurement instruments............................................................................. 2

6 Test pieces............................................................................................................................................ 3

6.1 Dimensions............................................................................................................................................ 3

6.2 Number of test pieces .......................................................................................................................... 3

6.3 Time interval between moulding and testing..................................................................................... 4

6.4 Conditioning.......................................................................................................................................... 4

6.5 Preparation of test pieces for testing ................................................................................................. 4

7 Test conditions ..................................................................................................................................... 5

7.1 Temperature.......................................................................................................................................... 5

7.2 Cycle frequency.................................................................................................................................... 5

7.3 Strain amplitude.................................................................................................................................... 5

7.4 Testing under non-relaxed conditions ............................................................................................... 5

8 Procedure.............................................................................................................................................. 5

8.1 Determination of strain energy density.............................................................................................. 5

8.2 Determination of tearing energy ......................................................................................................... 5

8.3 Measurement of crack growth............................................................................................................. 6

9 Expression of results........................................................................................................................... 7

10 Precision................................................................................................................................................ 8

11 Test report............................................................................................................................................. 8

Bibliography ..................................................................................................................................................... 10

© ISO 2008 – All rights reserved iii
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ISO 27727:2008(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 27727 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee

SC 2, Testing and analysis.
iv © ISO 2008 – All rights reserved
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INTERNATIONAL STANDARD ISO 27727:2008(E)
Rubber, vulcanized — Measurement of fatigue crack growth
rate
1 Scope

This International Standard specifies a method for the determination of the fatigue crack growth rate of

vulcanized rubber under repeated loading over an extended period of time. The crack starts from the tip of a

cut made in the test piece before the test, and grows progressively until it finally becomes large enough for

complete fracture to occur. Using a pure-shear test piece, measurements are made to monitor the crack

growth under the cyclic loading in order to obtain the crack growth rate, i.e. the increase in crack length per

cycle. Tests are carried out at various tearing energies by varying the strain energy density in the test piece.

This is done by changing the strain amplitude.
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 23529, Rubber — General procedures for preparing and conditioning test pieces for physical test

methods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
strain energy density

elastic energy stored in unit volume of the test piece when in a state of strain and resulting from the work done

in deforming the test piece
NOTE It is measured in joules per cubic metre.
3.2
tearing energy
amount of energy required to propagate a tear/crack in a test piece

NOTE The tearing energy is expressed as the ratio of the total work done to the surface area of the crack. It is

measured in joules per square metre.
© ISO 2008 – All rights reserved 1
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ISO 27727:2008(E)
3.3
strain-range parameter

〈test cycles in which the test piece is always in a strained state〉 ratio of the minimum distance from the

relaxed (zero strain) position to the maximum distance from the relaxed position in each cycle

NOTE The strain-range parameter is expressed as P = d /d , where d is the minimum distance from the

R min max min
relaxed position and d is the maximum distance from the relaxed position.
max
4 Principle

A pure-shear geometry test piece with a deliberately introduced cut is subjected to cyclic loading during which

the length of the crack produced grows with the number of deformation cycles. The crack length is measured

by means of an in situ monitoring device as a function of the number of cycles carried out, and the measured

data are processed by digital analysis to establish the rate of crack growth. The crack growth rate is then

interpreted in terms of the tearing energy of the test piece, determined from its strain energy density.

5 Apparatus
5.1 Fatigue crack growth rate test machine

A suitable test machine for measuring fatigue crack growth rate, which operates with constant displacement

cycles, is shown in Figure 1. The grips hold the test piece in a temperature-controlled chamber, with the upper

grip connected to the load cell fixed to a cr
...