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IS0
I NT ERN AT I ON AL ORGAN I ZATl O N FOR STAND AR D I2 AT1 O N
IS0 R E COM MEN DATl O N
R 604
PLASTICS
DETERM NATION OF COMPRESSIVE PROPERT ES
OF PLASTICS
1st EDITION
August 1967
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The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized bherefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 604, Plastics-Determination of Compressive Properties
of Plastics, was drawn up by Technical Committee ISO/TC 61, Plastics, the Secretariat
of which is held by the United States of America Standards Institute (USASI).
Work on this question by the Technical Committee began in 1961 and led, in 1963,
to the adoption of a Draft IS0 Recommendation.
In March 1964, this Draft IS0 Recommendation (No. 747) was circulated to all the
IS0 Member Bodies for enquiry. It was approved, subject to a few modifications of an
editorial nature, by the following Member Bodies :
Argentina Romania
Germany
Australia Hungary Spain
Austria India Sweden
Switzerland
Belgium Israel
Turkey
Bulgaria Italy
Japan U.A.R.
Canada
Czechoslovakia Korea, Rep. of United Kingdom
Denmark Netherlands U.S.A.
Finland New Zealand U.S.S.R.
Yugoslavia
France Poland
No Member Body opposed the approval of the Draft.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0
Council, which decided, in August 1967, to accept it as an IS0 RECOMMENDATION.
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IS0 / R 604 - 1967 (E)
IS0 Recommendation R 604 August 1967
PLASTICS
DETERMINATION OF COMPRESSIW PROPERTIES
OF PLASTICS
1. SCOPE
This IS0 Recommendation describes a method intended for use in determining the compressive
properties of plastics in the form of standard test specimens when tested under defined conditions
of pre-treatment, temperature, humidity and testing machine speed.
.
2. DEFINITIONS
2.1 Compressive stress (nominal). The compressive load per unit area of original cross-section
carried by the test specimen at any time during the compressive test. It is expressed in kilo-
grammes-force per square centimetre.
2.2 Compressive deformation. The change in length produced in a longitudinal section of the
test specimen by a compressive load. It is expressed in centimetres.
2.3 Compressive strain (unit compressive deformation). The change in length per unit of original
length. It is expressed as a dimensionless ratio.
2.4 Compressive yield stress. The compressive stress (nominal) at the first observable point in
a compression test where, on the load-deformation curve, an increase in strain or deforma-
tion occurs without an increase in load. It is expressed in kilogrammes-force per square
centimetre.
2.5 Compressive offset yield stress. The compressive stress (nominal) in a compression test
where the load-deformation curve departs from linearity by a specified percentage of defor-
mation (offset). It is expressed in kilogrammes-force per square centimetre.
2.6 Compressive strength. The maximum compressive stress (nominal) carried by a test specimen
during a compressive test. It may or may not be the compressive stress (nominal) carried
by the specimen at the moment of rupture. It is expressed in kilogrammes-force per square
centimetre.
2.7 Percentage compressive strain. The compressive strain times one hundred.
2.8 Percentage compressive strain at compressive yield stress. The compressive strain at the
first observable point in a compression test where, on the load-deformation curve, the
compressive strain is increasing without increase in load. It is expressed as a percentage of
the original length of the measured compressed section.
I
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IS0 / R 604 - 1967 (E)
2.9 Percentage compressive strain at rupture. A compressive deformation of the test specimen
at the moment of rupture, expressed as a percentage of the original length of the measured
compressed section.
2.10 Compressive load-deformation curve. The curve obtained by plotting compressive loads
as ordinates against corresponding deformation as abscissae for the entire course of a com-
pression test.
2.11 Slenderness ratio. The ratio of the length of a solid of uniform cross-section (column) to
its least radius of gyration.
The slenderness ratio is used as the basis for the calculation of dimensions of the test specimen
as follows:
h
A=-
I
where
X = slenderness ratio,
h = height of the test specimen,
i = least radius of gyration.
NOTE. - The least radius of gyration i is given by the formula:
where
Z = least main moment of gyration of cross-section area,
F = cross-section area.
(a) For a right prism
Square prisms
F= a2
Rectangular prisms
ab3
I=-
12
F=ab
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e
IS0 / R 604 - 1967 (E)
(b) For right cylinders
1 rr d4
= - Ip = -
2 64
d
(c) For a right circular crown tube
1 rr
I = - Ip = - (O4 - df)
2 64
7r
F = - (O2 - d:)
4
i = - 1 JOz + d:
4
where
a = width of the right prism,
b = thickness of the rectangular prism,
d = diameter of right cylinder,
dl = inner diameter of tube,
D = outer diameter of tube,
Ip = polar moment of gyration.
3. SIGNIFICANCE OF TEST
3.1 Compressive properties determined by this method include compressive yield stress, com-
pressive strength, offset yield strength, percentage compressive strain at compressive yield
stress and percentage compressive strain at rupture.
3.2 Compressive tests may provide data for research and development, engineering design,
quality control, acceptance or rejection under specifications and for special purposes. The
tests cannot be considered significant for applications differing widely from the loadtime
scale of the standard test. Such applications require appropriate tests such as impact, creep
and fatigue.
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IS0 / R 604 - 1967 (E)
4. APPARATUS
The apparatus should consist of:
Testing machine of the constant-rate-of-crosshead-movement type and comprising essentially the
following :
4.1 Compression tool, a hardened steel compression plate for applying the load to the test
specimen so constructed that the compressive loading is truly axial and so that the load is
applied through polished surfaces which are flat and parallel to each other. A self-aligning
device should be interposed between the compression tool plunger and the testing machine
plate.
4.2 Load indicator, a load-indicating mechanism capable of showing the total compressive load
carried by the test specimen. The mechanism should be essentially free from inertia lag at
the specified rate of testing and should indicate the load value with an accuracy of & 1 % of
the indicated value, or better.
4.3 Deformation indicator, a suitable instrument for determining the distance between the
contact surfaces of the compression tool, or the distance between two fixed points on the
test specimen at any time during the test. It is desirable, but not essential, that this instrument
automatically record this distance (or any change in it) as a function of the load on the test
specimen or of the elapsed time from the start of the test, or both. This instrument should be
essentially free from inertia lag at the specified rate o
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