EN ISO 899-2:1996

SLOVENSKI STANDARD
SIST EN ISO 899-2:1999
01-maj-1999
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Plastics - Determination of creep behaviour - Part 2: Flexural creep by three-point
loading (ISO 899-2:1993)
Kunststoffe - Bestimmung des Kriechverhaltens - Teil 2: Zeitstand-Biegeversuch bei
Dreipunkt-Belastung (ISO 899-2:1993)
Plastiques - Détermination du comportement au fluage - Partie 2: Fluage en flexion par
mise en charge en 3 points (ISO 899-2:1993)
Ta slovenski standard je istoveten z: EN ISO 899-2:1996
ICS:
83.080.01 Polimerni materiali na Plastics in general
splošno
SIST EN ISO 899-2:1999 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 899-2:1999

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SIST EN ISO 899-2:1999

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SIST EN ISO 899-2:1999

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SIST EN ISO 899-2:1999

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SIST EN ISO 899-2:1999

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SIST EN ISO 899-2:1999
Is0
INTERNATIONAL
899-2
STANDARD
First edition
1993-l 2-15
- Determination of creep
Plastics
behaviour -
Part 2:
Flexural creep by three-point loading
- Ddtermination du comportement au fluage -
P/as tiques
Partie 2: Fluage en flexion par mise en charge en trois points
Reference number
IS0 899-2:1993(E)

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SIST EN ISO 899-2:1999
IS0 899=2:1993(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation-of national standards bodies (IS0 member bodies). The work
of preparing International Standards is normally carried out through IS0
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. IS0
collaborates closely with the International Electrotechnical Commission
(I EC) on all matters of electrotechnical standardization.
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.
International Standard IS0 899-2 was prepared by Technical Committee
lSO/TC 61, Plastics, Sub-Committee SC 2, Mechanical properties.
Together with IS0 899-1, it cancels and replaces IS0 899:1981 and
IS0 6602:1985, which have been technically revised.
IS0 899 consists of the following parts, under the general title
P/as tics - Determination of creep behaviour:
- Part 1: Tensile creep
. - Part 2: Flexural creep by three-point loading
Annexes A and B of this part of IS0 899 are for information only.
0 IS0 1993
All rights resewed. No part of this publication may be reproduced or utilized in any form or
by any means, electronic or mechanical, including photocopying and microfilm, without per-
mission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii

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SIST EN ISO 899-2:1999
INTERNATIONAL STANDARD IS0 899=2:1993(E)
Plastics - Determination of creep behaviour -
Part 2:
Flexural creep by three-point loading
Part 2: Determination of flexural
Flexural tests -
1 Scope
properties).
1.1 This part of IS0 899 specifies a method for de-
termining the flexural creep of plastics in the form of
2 Normative references
standard test specimens under specified conditions
such as those of pretreatment, temperature and hu-
The following standards contain provisions which,
midity. It applies only to a simple freely supported
through reference in this text, constitute provisions
beam loaded at mid-span (three-point-loading test).
of this part of IS0 899. At the time of publication, the
editions indicated were valid. All standards are subject
to revision, and parties to agreements based on this
1.2 The method is suitable for use with rigid and
part of IS0 899 are encouraged to investigate the
semi-rigid non-reinforced, filled and fibre-reinforced
possibility of applying the most recent editions of the
plastics materials (see IS0 472 for definitions) in the
standards indicated below. Members of IEC and IS0
form of rectangular bars moulded directly or cut from
maintain registers of currently valid International
sheets or moulded articles.
Standards.
NOTE 1 The method may be unsuitable for certain fibre-
reinforced materials due to differences in fibre orientation.
IS0 178:1993, Plastics - Determination of flexural
properties.
1.3 The method is intended to provide data for
- Standard atmospheres for
IS0 291 :I 977, Plastics
engineering-design and research and development
conditioning and testing.
purposes.
IS0 47211988, Plastics - Vocabulary.
1.4 Flexural creep may vary significantly with differ-
ences in specimen preparation and dimensions and in
the test environment. The thermal history of the test
3 Definitions
specimen can also have profound effects on its creep
behaviour (see annex A). Consequently, when precise
For the purposes of this part of IS0 899, the defi-
comparative results are required, these factors must
nitions given in IS0 472 and the following definitions
be carefully controlled.
apply*
1.5 If flexural-creep properties are to be used for
3.1 creep: The increase in strain with time when a
engineering-design purposes, the plastics materials
constant stress is applied.
should be tested over a broad range of stresses,
times and environmental conditions.
3.2 flexural stress, 0: The surface stress in the
mid-span section of the test specimen. It is calculated
from the relationship given in 7.1.2.
1.6 The method may not be suitable for determining
the flexural creep of rigid cellular plastics (attention is
3.3 deflection, s,: The distance, in millimetres,
drawn in this respect to IS0 1209-I :1990, Cellular
through which the top or bottom surface of the test
plastics, rigid - Flexural tests - Part 1: Bending
specimen at mid-span deviates, during flexure, from
test, and IS0 1209-2:1990, Cellular plastics, rigid -
1

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SIST EN ISO 899-2:1999
IS0 899=2:1993(E)
its position before application of the test load to its
The radius R, of the loading edge and the radius R2
position at time t. of the supports shall conform to the values given in
table 1.
3.4 flexural-creep strain, Ed: The strain at the sur-
face of the test specimen produced by a stress at any
Table 1
given time t during a creep test, calculated in accord-
Values in millimetres
ance with 7.1.3. It is expressed as a dimensionless
Radius of Radius of
ratio or as a percentage.
Thickness of
loading edge supports
test specimen
3.5 flexural-creep modulus, E,: The ratio of flexural
4 R2
stress to flexural-creep strain, calculated as in 7.1.1.
<3 2 + - 0,2
5 f RI
3.6 isochronous stress-strain curve: A Cartesian
>3 5 & 0,2
5 * O,l
plot of stress versus creep strain, at a specific time
after application of the test load.
4.2 Loading system, capable of ensuring that the
3.7 time to rupture: The period of time which
load is applied smoothly, without causing transient
elapses between the point in time at which the
overloading, and that the load is maintained to within
specimen is fully loaded and the rupture point.
+ 1 % of the desired load. In creep-to-rupture tests,
provision shall be made to prevent any shocks which
3.8 creep-strength limit: That initial stress which
occur at the moment of rupture being transmitted to
will just cause rupture (Q J or will produce a specified
adjacent loading systems. The loading mechanism
strain (Q) at a specified ti’me t, at a given temperature
shall allow rapid, smooth and reproducible loading.
and relative humidity.
4.3 Deflection-measuring device, comprising any
contactless or contact device capable of measuring
the deflection of the specimen under load without in-
4 Apparatus
fluencing the specimen behaviour by mechanical ef-
fects (e.g. undesirable deformations, notches), other
physical effects (e.g. heating of the specimen) or
4.1 Test rack, comprising a rigid frame with two
chemical effects. The accuracy of the deflection-
supports, one for each end of the test specimen, the
measuring device shall be within & 1 % of the final
distance between the supports being adjustable to
deflection.
(16 + 1) times the thickness (height) of the specimen
(see figure 1) for normal specimens or greater than
4.4 Time-measurement device, accurate to 0,l %.
17 times the thickness (height) of the specimen for
very thick, unidirectional specimens (see 6.2). The
4.5 Micrometer, reading to 0,Ol mm or closer, for
test rack shall be level, and sufficient space shall be
allowed below the specimen for the specimen to flex measuring the thickness and width of the test speci-
men.
under dead-weight loading at mid-span.
Applied force F
Figure 1 - Characteristics of flexural-creep apparatus

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SIST EN ISO 899-2:1999
IS0 899=2:1993(E)
4.6 Vernier calipers, accurate to 0,l % of the span
6.4 Selection of stress value
between the test supports or better, for determining
the span.
Select a stress value appropriate to the application
envisaged for the material under test, and calculate,
using the equation given in 7.1.2, the test load to be
5 Test specimens applied to the test specimen.
Choose the stress such that the deflection is not
Use test specimens of the same shape and dimen-
greater than 0,l times the distance between the
sions as specified for the determination of flexural
supports at any time during the test.
properties (see IS0 178).
65 . Loading procedure
6 Procedure
6.5.1 Preloading
6.1 Conditioning and test atmosphere
When it is necessary to preload the test specimen
prior to increasing the load to the test load, take care
Condition the test specimens as specified in the In-
to ensure that the preload does not influence the test
ternational Standard for the material under test. In the
results. Do not apply the preload until the temperature
absence of any information on conditioning, use the
and humidity of the test specimen (positioned in the
most appropriate set of conditions specified in
test apparatus) correspond to the test conditions.
IS0 291, unless otherwise agreed upon by the inter-
ested parties.
Set the deflection-measuring device to zero after
application of the preload; the preload shall act during
NOTE 2 The creep behaviour will be affected not only by
the whole duration of the test.
the thermal history of the specimen under test, but also by
the temperature and (where applicable) humidity used in
conditioning.
6.5.2 Loading
Conduct the test in the same atmosphere as used for
Load the test specimen progressively so that full
conditioning, unless otherwise agreed upon by the
loading of the test specimen is reached between 1 s
interested parties, e.g. for testing at elevated or low
and 5 s after the beginning of the application of the
temperatures. Ensure that the variation in tempera-
load. Use the same rate of loading for each of a series
ture during the duration of the test remains within
of tests on one material.
+ 2 “C.
-
Take the total load (including the preload) to be the
test load.
6.2 Measurement of test-specimen
dimensions and distance between supports
66 . Deflection-measurement schedule
Measure the dimensions of the conditioned test
specimens. Record the point in time at which the specimen is
fully loaded as t = 0. Unless the deflection is auto-
For normal test specimens, adjust the distance L be-
matically and/or continuously recorded, choose the
tween the test-specimen supports to
times for making individual measurements as a func-
tion of the creep cuNe obtained from the particular
(16 + 1)h
material under test. It is preferable to use the follow-
ing measurement schedule:
where h is the thickness of the specimen.
In the case of very thick, unidirectional fibre-reinforced
1 min, 3 min, 6 min, 12 min and 30 min;
test specimens, a distance between the supports
may be adjusted to a value > 17h if necessary to avoid
1 h, 2 h, 5 h, 10 h, 20 h, 50 h, 100 h, 200 h,
delamination in shear.
500 h, 1 000 h, etc.
Mea
...