EN ISO 7539-2:1995
(Main)Corrosion of metals and alloys - Stress corrosion testing - Part 2: Preparation and use of bent-beam specimen (ISO 7539-2:1989)
Corrosion of metals and alloys - Stress corrosion testing - Part 2: Preparation and use of bent-beam specimen (ISO 7539-2:1989)
Covers procedures for designing, preparing and using bent-beam test specimens. These specimens may be used to test a variety of product forms (i. e. sheet, plate, flat extruded material, wire or rod). They are espesially suitable for multiple testing and for atmospheric stress corrosion tests; they are usually tested under nominally constant strain conditions. Bent-beam specimens made from high strength materials may fracture rapidly and can be dangerous.
Korrosion der Metalle und Legierungen - Prüfung der Spannungsrißkorrosion - Teil 2: Vorbereitung und Anwendung von Biegeproben (ISO 7539-2:1989)
Der vorliegende Teil von ISO 7539 behandelt Verfahren zur Gestaltung, Vorbereitung und Anwendung von Biegeproben zur Untersuchung der Anfälligkeit eines Metalles für Spannungsrißkorrosion. In diesem Teil von ISO 7539 werden mit der Benennung "Metall" auch Legierungen erfaßt. Biegeproben können zum Prüfen einer Vielzahl von Erzeugnisformen verwendet werden. Grundsätzlich werden sie für Band, Blech oder flaches, stanggepreßtes Material verwendet, aus welchem leicht flache Proben mit rechteckigem Querschnitt zu fertigen sind.
Corrosion des métaux et alliages - Essais de corrosion sous contrainte - Partie 2: Préparation et utilisation des éprouvettes pour essais en flexion (ISO 7539-2:1989)
1.1 La présente partie de l'ISO 7539 couvre les procédures de définition, de préparation et d'utilisation d'éprouvettes pour essais en flexion, servant à évaluer la sensibilité d'un métal à la corrosion sous contrainte. Pour les besoins de la présente partie de l'ISO 7539, le terme « métal » inclut également les alliages. 1.2 Les éprouvettes pour essais en flexion peuvent être utilisées pour tester une multitude de formes de produits. Elles sont principalement utilisées pour les tôles, plaques ou matériaux profilés, qui fournissent facilement des éprouvettes plates de section rectangulaire, mais peuvent être employées également pour les matériaux moulés, les fils métalliques ou les barres, sous la forme d'éprouvettes usinées de section circulaire. Elles peuvent aussi être utilisées pour des pièces assemblées par soudage. 1.3 La préparation des éprouvettes et l'appareillage servant à les tester sous contrainte étant simple et peu coûteux, les éprouvettes pour essais en flexion sont tout à fait adaptées aux essais multiples et aux essais atmosphériques sous contrainte. 1.4 Les éprouvettes pour essais en flexion sont normalement testées dans des conditions nominales de déformation constante, mais on peut également les soumettre à des conditions nominales de charge constante. Dans les deux cas, une modification locale de la 244 courbure de l'éprouvette, au moment de la fissuration entraîne une variation des conditions pendant la propagation de la fissure. La « contrainte d'essai » s'entend comme la contrainte de traction maximale en début d'essai.
Korozija kovin in zlitin - Ugotavljanje pokanja zaradi napetostne korozije - 2. del: Priprava in uporaba upogibnih preskušancev (ISO 7539-2:1989)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-oktober-1999
Korozija kovin in zlitin - Ugotavljanje pokanja zaradi napetostne korozije - 2. del:
Priprava in uporaba upogibnih preskušancev (ISO 7539-2:1989)
Corrosion of metals and alloys - Stress corrosion testing - Part 2: Preparation and use of
bent-beam specimen (ISO 7539-2:1989)
Korrosion der Metalle und Legierungen - Prüfung der Spannungsrißkorrosion - Teil 2:
Vorbereitung und Anwendung von Biegeproben (ISO 7539-2:1989)
Corrosion des métaux et alliages - Essais de corrosion sous contrainte - Partie 2:
Préparation et utilisation des éprouvettes pour essais en flexion (ISO 7539-2:1989)
Ta slovenski standard je istoveten z: EN ISO 7539-2:1995
ICS:
77.060 Korozija kovin Corrosion of metals
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
ISO
INTERNATIONAL
7539-2
STANDARD
First edition
1989-12-15
Corrosion of metals and alloys - Stress
corrosion testing -
Part 2:
Preparation and use of bent-beam specimens
Essais de corrosion sous contrainte -
Corrosion des mhtaux et alliages -
Partie 2: Prkparation et utilisation des kprouvettes pour essais en flexion
Reference number
ISO 7539-2 : 1989 (EI
ISO 7539-2 : 1989 (E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of
national Standards bodies (ISO member bedies). The work of preparing International
Standards is normally carried out through ISO technical committees. Esch 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, govern-
mental 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.
Draft International Standards adopted by the technical committees are circulated to
the member bodies for approval before their acceptance as International Standards by
the ISO Council. They are approved in accordance with ISO procedures requiring at
least 75 % approval by the member bodies voting.
International Standard ISO 7539-2 was prepared by Technical Committee ISO/TC 156,
Corrosion of metals and alloys.
general title Corrosion of me tals
ISO 7539 consists of the following Parts, under the
and alloys - S tress corrosion tes ting :
Part 7: General guidance on testing procedures
-
Part 2: Preparation and use of bent-beam specimens
Part 3: Preparation and use of U-bend specimens
-
Part 4: Preparation and use of uniaxialfy loaded tension specimens
Part 5: Preparation and use of C-ring specimens
Part 6: Preparation and use of pre-cracked specimens
- Part 7: Slow strain rate testing
-
Part 8: Preparation and use of welded specimens
0 ISO 1989
All rights reserved. No patt of this publication may be reproduced or utilized in any form or by any
means, electronie or mechanical, including photocopying and microfilm, without Permission in
writing from the publisher.
International Organization for Standardization
Case postale 56 l CH-121 1 Geneve 20 l Switzerland
Printed in Switzerland
ii
ISO 7539-2 : 1989 (E)
Introduction
This part of ISO 7539 is one of a series giving procedures for designing, preparing and
using various forms of test specimen to carry out tests to establish a metals resistance
to stress corrosion.
Esch of the Standards in the series needs to be read in association with ISO 7539-1.
This helps in the choice of an appropriate test procedure to suit particular
circumstances as well as giving guidance towards assessing the significance of the
results of the tests.
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INTERNATIONALSTANDARD ISO 7539-2 : 1989 (E)
Corrosion of metals and alloys - Stress corrosion
testing -
Part 2:
Preparation and use of bent-beam spec imens
WARNING - Bent-beam specimens made from high strength materials may fracture rapidly; pieces may fly off at high
velocity and tan be dangerous. Personne1 installing and examining specimens must be made aware of this possiblity and
be protected against injury.
1 Scope were valid. All Standards are subject to revision, and Parties to
agreements based on this part of ISO 7539 are encouraged to
investigate the possibility of applying the most recent editions
1 .l This part of ISO 7539 covers procedures for designing,
of the Standards indicated below. Members of IEC and ISO
preparing and using bent-beam test specimens for investigating
maintain registers of currently valid International Standards.
the susceptibility of a metal to stress corrosion.
The term “metal” as used in this part of ISO 7539 includes ISO 7539-1 : 1987, Corrosion of metals and alloys - stress cor-
alloys. Part 7: General guidance on testing pro-
rosion testing -
cedures.
1.2
Bent-beam specimens may be used to test a variety of
ISO 7539-4 : 1989, Corrosion of metals and alloys - Stress
product forms. They are used principally for sheet, plate or flat
corrosion testing - Part 4 : Preparation and use of uniaxially
extruded material, which conveniently provides flat specimens
loaded tension specimens.
of rectangular Cross-section, but may also be employed for cast
material, wire or rod, or for machined specimens of circular
Cross-section. They tan also be used for Parts joined by
3 Definitions
welding.
For the purposes of this part of ISO 7539, the definitions given
1.3 Since the preparation of the specimens and the
in ISO 7539-1 are applicable.
apparatus used for stressing them are both simple and in-
expensive, bent-beam specimens are especially suitable for
multiple testing and for atmospheric stress corrosion tests.
4 Principle
1.4 Bent-beam specimens are usually tested under nominally
4.1 The test consists of applying a bending stress to a beam
constant strain conditions but nominally constant load con-
specimen of rectangular or circular section and exposing the
ditions may be employed. In either case local Change of
stressed specimen to a specified test environment.
curvature in the specimen when cracking occurs results in
changing conditions during Crack propagation. The “test
4.2 The magnitude of the resultant applied tensile stress in
stress” is taken as the highest surface tensile stress existing at
the outer fibres of the bent-beam specimen is calculated from
the statt of the test.
the dimensions and modulus of elasticity of the specimen and
the bending deflection, as described in 5.4.
2 Normative references
4.3 Bent-beam specimens are used only for testing at stress
levels below the elastic limit since the formulae used for
The following Standards contain provisions which, through
reference in this text, constitute provisions of this part of calculating stress in bent beams apply only within the elastic
ISO 7539. At the time of publication, the editions indicated range.
ISO 7539-2 : 1989 (E)
studying the structure of the material as shown in an etched
4.4 The time required for Cracks to appear after exposure of
stressed specimens to the test environment or the threshold metallographic section. lt is desirable to remove the required
stress below which Cracks do not appear tan be used as a amount of metal in several Steps by alternatively machining or
measure of the stress corrosion resistance of the material in the grinding opposite surfaces. This practice minimizes warping
test environment at the stress level employed. due to unequal residual Stresses introduced by machining. All
edges should be similarly ground or machined to remove any
cold worked material remaining from shearing.
4.5 Wide variations in test results may be obtained for a
given metal and environment even when testing nominally
5.3.3 Chemical or electrochemical treatments are generally
identical specimens and the replication of tests is frequently
inappropriate for flat rectangular section specimens as attack at
necessary.
the edges tends to be greater and less easy to control than on
the faces.
4.6 The possiblity of relaxation during the exposure period
should be considered especially when specimens are exposed
5.3.4 If Chemical or electrochemical treatments are employed,
at elevated temperatures. Relaxation tan be estimated if creep
care must be taken to ensure that the conditions used do not
data are available for a simultaneous effect of the test environ-
result in selective Phase attack on the metal or leave a deposit
ment. The differente in thermal expansion should also be con-
of undesirable residues on the surface.
sidered.
5.3.5 Chemical or electrochemical treatments that generate
hydrogen on the specimen surface must not be used on
5 Spetimens
materials that are susceptible to hydrogen-induced darnage.
5.1 General
5.3.6 Before testing, the specimens should be degreased to
remove surface contamination; they should then be tested im-
5.1.1 Identification marks or numbers should be permanently
mediately, or stored in such a way as to avoid contamination or
inscribed at each end of the specimen. This is the region of
deterioration until they tan be tested.
lowest stress and the identification marks will therefore not
initiate cracking.
5.4 Methods of stressing
5.1.2 Spetimens for determination of mechanical proper-Ges
5.4.1 Constant strain methods
shall be taken from the same heat treatment batch, and
preferably from the same piece of material, as the stress cor-
5.4.1.1 Modes of loading
rosion specimens.
Figure 1 Shows six methods of stressing specimens under
5.2 Types of specimens
nominally constant strain conditions. The two-Point loaded,
three-Point loaded and four-Point loaded specimens represent
the three basic modes of loading used for bent-beam speci-
5.2.1 Bent-beam stress corrosion specimens are usually flat
mens. The double-beam specimen, fully supported specimen
Strips of metal of uniform rectangular Cross-section and
and lever-loaded specimen may be regarded as special cases of
uniform thickness. They may alternatively be lengths of wire or
four-Point loading.
rod of uniform circular Cross-section.
5.4.1.2 Two-Point loading
5.2.2 Bent-beam stress corrosion tests may also be carrried
out on specimens having a gauge length of uniform rectangular
5.4.1.2.1 The maximum stress in a two-Point loaded
or circular Cross-section with threaded ends of larger cross-
specimen occurs at the mid-Point of its convex surface and
section as described in ISO 7539-4.
decreases to zero at the specimen ends.
5.3 Surface finish
5.4.1.2.2 Flat two-Point loaded specimens should be approxi-
mately 15 mm to 25 mm wide by 110 mm to 255 mm long as
5.3.1 Wire or rod specimens and flat specimens tut from
shown in figure 1 a). The specimen thickness, t, exact length,
sheet, plate and extruded sections may be tested with the
L, and holder span, H, are selected to give the required stress
original surface retained. This is often desirable as the structure
calculated according to 5.4.1.2.4 and to give a value for
of the original surface may be different from that of the layers
(L - HUH between 0,Ol and 0,50 to keep the error in
of metal beneath.
calculating stress within acceptable limits. A specimen of
thickness 0,8 mm to 1,8 mm with a holder span of 175 mm to
215 mm has proved convenient when working with very high
5.3.2 If it is desired to exclude the effects of variations in the
strength steels and with aluminium alloys, with test Stresses
original surface conditions for a comparison of different alloys,
ranging from about 200 MN/mzfor aluminium to 1 500 MN/m2
the specimens should be finished by grinding or machining to a
for steel.
depth of at least 025 mm. This is usually sufficient to eliminate
original surface imperfections without completely removing
any outer recrystallized layer. The maximum depth of machin- 5.4.1.2.3 Care should be taken when fitting specimens into
their holders to avoid overstressing, distortion or misalignment.
ing or grinding of the surface should be decided after
ISO 7539-2 : 1989 (EI
Dimensions in millimetres
Specimen
a) Two-Point loaded specimen
(9 Assembly
b) Three-Point ioaded specimen
c) Four-Point loaded specimen
i) Specimen
H
h
I
Weld
Weld
d) Double-beam specimen
h
Y
4 ‘1 u
h Il
h II
4 (>
II II
v - IIII
J
4 c
4 b
(iii) Lever
e) Fully supported specimen
fl Lever-loaded specimen
Figure 1 - Constant strain loading test specimens
ISO 7539-2 : 1989 (El
5.4.1.2.4 The approximate elastic stress at the mid-Point of t is the thickness of specimen in metres;
the convex surface is calculated from the relationship
is the maximum deflection in metres;
Y
L= (ktE/a) sin -1 (HalktE)
H is the distance between outer supports in metres.
where
5.4.1.4 Four-Point loading
L is the specimen length in metres;
0 is the maximum stress in newtons per Square metre;
5.4.1.4.1 Four-Point loading gives a uniform longitudinal
tensile stress in the convex surface of the part of the specimen
E is the modulus of elasticity in newtons per Square
between the inner supports.
metre;
H is the holder span in metres;
The stress decreases linearly to zero from the inner supports to
the outer supports. The relatively large area of uniformly
t is the thickness of specimen in metres;
stressed material makes four-Point loaded specimens generally
preferable to two or three-Point loaded specimens and
k = 1,280, an empirical constant.
particularly suitable for tests of welded material and for studies
The equation should be used only with of protection by sprayed metal or organic coatings.
HalktE = 1,O
5.4.1.4.2 Four-Point loaded specimens are commonly flat
Strips 15 mm to 50 mm wide and 110 mm to 250 mm long. The
This equation tan be solved by Computer, by trial and error, or
thickness of the specimen is usually dictated by the mechanical
by using a series expansion of the si
...
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