SIST EN ISO 179-2:2000

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Kunststoffe - Bestimmung der Charpy-Schlageigenschaften - Teil 2: Instrumentierte Schlagzähigkeitsprüfung (ISO 179-2:1997)Plastiques - Détermination des caractéristiques au choc Charpy - Partie 2: Essai de choc instrumenté (ISO 179-2:1997)Plastics - Determination of Charpy impact properties - Part 2: Instrumented impact test (ISO 179-2:1997)83.080.01Polimerni materiali na splošnoPlastics in generalICS:Ta slovenski standard je istoveten z:EN ISO 179-2:1999SIST EN ISO 179-2:2000en01-maj-2000SIST EN ISO 179-2:2000SLOVENSKI
STANDARD



SIST EN ISO 179-2:2000



SIST EN ISO 179-2:2000



SIST EN ISO 179-2:2000



AReference numberISO 179-2:1997(E)INTERNATIONALSTANDARDISO179-2First edition1997-12-15Plastics — Determination of Charpy impactproperties —Part 2:Instrumented impact testPlastiques — Détermination des caractéristiques au choc Charpy —Partie 2: Essai de choc instrumentéSIST EN ISO 179-2:2000



ISO 179-2:1997(E)©
ISO 1997All rights reserved. Unless otherwise specified, no part of this publication may be reproducedor utilized in any form or by any means, electronic or mechanical, including photocopying andmicrofilm, without permission in writing from the publisher.International Organization for StandardizationCase postale 56 · CH-1211 Genève 20 · SwitzerlandInternetcentral@iso.chX.400c=ch; a=400net; p=iso; o=isocs; s=centralPrinted in SwitzerlandiiForewordISO (the International Organization for Standardization) is a worldwidefederation of national standards bodies (ISO member bodies). The work ofpreparing International Standards is normally carried out through ISOtechnical committees. Each member body interested in a subject for whicha technical committee has been established has the right to be representedon that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISOcollaborates closely with the International Electrotechnical Commission(IEC) on all matters of electrotechnical standardization.Draft International Standards adopted by the technical committees arecirculated to the member bodies for voting. Publication as an InternationalStandard requires approval by at least 75 % of the member bodies castinga vote.International Standard ISO 179-2 was prepared by Technical CommitteeISO/TC 61, Plastics, Subcommittee SC 2, Mechanical properties.ISO 179 consists of the following parts, under the general title Plastics —Determination of Charpy impact properties:—Part 1: Non-instrumented impact test—Part 2: Instrumented impact testAnnexes A to C of this part of ISO 179 are for information only.SIST EN ISO 179-2:2000



INTERNATIONAL STANDARD
© ISOISO 179-2:1997(E)1Plastics — Determination of Charpy impact properties —Part 2:Instrumented impact test1
Scope1.1
This part of ISO 179 specifies a method for determining Charpy impact properties of plastics from force-deflection diagrams. Different types of rod-shaped test specimen and test configuration, as well as test parametersdepending on the type of material, the type of test specimen and the type of notch are defined in part 1 of ISO 179.Dynamic effects such as load-cell/striker resonance, test specimen resonance and initial-contact/inertia peaks aredescribed (see figure 1, curve b, and annex A).1.2
For the comparison between Charpy and Izod test methods, see ISO 179-1, clause 1.ISO 179-1 is suitable for characterizing the impact behaviour by the impact strength only and for using apparatuswhose potential energy is matched approximately to the particular energy to break to be measured (see ISO 13802,annex C). This part of ISO 179 is used if a force-deflection or force-time diagram is necessary for detailedcharacterization of the impact behaviour, and for developing automatic apparatus, i.e. avoiding the need, mentionedabove, to match energy.1.3
For the range of materials which may be tested by this method, see ISO 179-1, clause 1.1.4
For the general comparability of test results, see ISO 179-1, clause 1.1.5
The method may not be used as a source of data for design calculations on components. However, thepossible use of data is not the subject of this part of ISO 179. Any application of data obtained using this part ofISO 179 should be specified by a referring standard or agreed upon by the interested parties.Information on the typical behaviour of materials can be obtained by testing at different temperatures, by varying thenotch radius and/or specimen thickness and by testing specimens prepared under different conditions.It is not the purpose of this part of ISO 179 to give an interpretation of the mechanism occurring at every point onthe force-deflection diagram. These interpretations are a task for on-going scientific research.1.6
The test results are comparable only if the conditions of test specimen preparation, as well as the testconditions, are the same. Comprehensive evaluation of the reaction to impact stress requires that determinations bemade as a function of deformation rate and temperature for different material variables such as crystallinity andmoisture content. The impact behaviour of finished products cannot, therefore, be predicted directly from this test,but test specimens may be taken from finished products for testing by this method.1.7
Impact strengths determined by this method may replace those determined using ISO 179-1 if comparabilityhas been established by previous tests.SIST EN ISO 179-2:2000



ISO 179-2:1997(E)© ISO22
Normative referencesThe following standards contain provisions which, through reference in this text, constitute provisions of this part ofISO 179. At the time of publication, the editions indicated were valid. All standards are subject to revision, andparties to agreements based on this part of ISO 179 are encouraged to investigate the possibility of applying themost recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently validInternational Standards.ISO 179-1:—1), Plastics — Determination of Charpy impact properties — Part 1: Non-instrumented impact test.ISO 13802:—2), Plastics — Verification of pendulum impact-testing machines — Charpy, Izod and tensile impacttesting.3
DefinitionsFor the purposes of this part of ISO 179, the definitions given in part 1 apply, together with the following:3.1
impact velocity, v0: The velocity of the striker relative to the test specimen supports at the moment of impact.It is expressed in metres per second (m/s).3.2
inertial peak: The first peak in a force-time or force-deflection diagram. It arises from the inertia of that part ofthe test specimen accelerated after the first contact with the striker (see figure 1, curve b, and annex A).3.3
impact force, F: The force exerted by the striking edge on the test specimen in the direction of impact.It is expressed in newtons (N).3.4
deflection, s: The displacement of the striker relative to the test specimen supports after impact, starting atfirst contact between striker and test specimen.It is expressed in millimetres (mm).3.5
impact energy, W: The energy expended in accelerating, deforming and breaking the test specimen duringthe deflection s.It is expressed in joules (J).It is measured by integrating the area under the force-deflection curve from the point of impact to the deflection s.3.6
maximum impact force, FM: The maximum value of the impact force in a force-time or force-deflectiondiagram (see figure 1).It is expressed in newtons (N).3.7
deflection at maximum impact force, sM: The deflection at which the maximum impact force FM occurs (seefigure 1).It is expressed in millimetres (mm).___________1)
To be published. (Revision of ISO 179:1993)2)
To be published.SIST EN ISO 179-2:2000



© ISOISO 179-2:1997(E)3Figure 1 — Typical force-deflection (N and t) and force-time (b) curves(for the types of failure, see figure 2)SIST EN ISO 179-2:2000



ISO 179-2:1997(E)© ISO4N=no break: yielding followed by plastic deformation up to the deflection limit sL;P=partial break: yielding followed by stable cracking, resulting in a force at the deflection limit sL which is greater than5 % of the maximum force;t=tough break: yielding followed by stable cracking, resulting in a force at the deflection limit sL which is less than orequal to 5 % of the maximum force;b=brittle break: yielding followed by unstable cracking;s=splintering break: unstable cracking followed by yielding;sL=deflection limit; beginning of pull-through.NOTE —
Due to the different modes of deformation, force-deformation curves obtained using this part of ISO 179 show features which aredifferent from those obtained using ISO 6603-2 [1]. In particular, the first damage event in instrumented puncture tests frequently appears as aslight sudden force decrease (crack initiation), followed by a gradual force increase. Force increases after crack initiation are never observed ininstrumented three-point-bending impact tests. Furthermore, inertial effects are not as pronounced in plate impact tests as they are in bendingimpacts tests (see annex A).Figure 2 — Typical force-deflection curves showing different failure modesfor type 1 specimens tested edgewise3.8
energy to maximum impact force, WM: The energy expended up to the deflection at maximum impact force.It is expressed in joules (J).3.9
deflection at break, sB: The deflection at which the impact force is reduced to less than or equal to 5 % of themaximum impact force FM (see figure 1).SIST EN ISO 179-2:2000



© ISOISO 179-2:1997(E)5It is expressed in millimetres (mm).It is necessary to differentiate between the deflection at break sB and the deflection limit sL at the beginning of pull-through (see figure 1, curve N) which is determined by the length l and width b of the test specimen and thedistance L between the specimen supports. For type 1 specimens in the edgewise position, sL is in the range 32 mmto 34 mm.NOTE —
Using type 1 specimens tested edgewise, apparent deflection limits are sometimes observed, i.e. unexpectedly lowvalues (down to only 20 mm) at which the impact force drops to zero, but the specimens do not break. Carrying out the testslowly shows that, in such cases, the specimen changes from the edgewise to the more stable flatwise position by a combinedbending-twisting deformation. This can easily be confirmed by checking the specimen after the test: it is bent with respect to anaxis not parallel, but inclined to, the specimen width.This behaviour is caused by the high ratio between the edgewise and the flatwise flexural rigidity of the specimen and istriggered by a small asymmetry feature e.g. the draft angle.This phenomenon may be avoided by fitting guide elements in front of, but not connected to, the instrumented striking edge,thus preventing the central part of the specimen from twisting to any great extent.3.10
impact energy at break, WB: The impact energy up to the deflection at break sB.It is expressed in joules (J).3.11
Charpy (notched) impact strength, acU (acN): The impact energy at break relative to the initial centralcross-sectional area A (AN) of the unnotched (notched) specimen (see 8.4 and ISO 179-1, 3.1 and 3.2).It is expressed in kilojoules per square metre (kJ/m2).3.12
type of failure: The type of deformation behaviour of the material under test (see figure 2). It may be eitherno break (N), partial break (P), tough (t), brittle (b) or splintering (s).Types t, b and s represent subgroups of the complete break C and hinge break H defined in part 1 of ISO 179. Forthese types, values of the impact energy at break WB, and thus for the Charpy impact strength, may be averaged togive a common mean value. For specimens giving a partial break P and for materials exhibiting interlaminar shearfracture, see ISO 179-1, subclause 7.6. For specimens showing more than one failure type, see ISO 179-1,subclause 7.7.NOTE —
As can be seen from figure 2, the deflection and the impact energy at maximum force are identical to the deflectionand impact energy at break in the case of splintering failure (see curve s) and brittle failure (see curve b), where unstablecracking takes place at the maximum impact force.4
PrincipleA rod-shaped test specimen, supported near its ends as a horizontal beam, is impacted perpendicularly, with theline of impact midway between the supports, and bent at a high, nominally constant velocity. The impact geometryis described in ISO 13802, clause 5. During the impact, the impact force is recorded. Depending on the method ofevaluation, the deflection of the specimen may be either measured directly by suitable measuring devices or, in thecase of energy carriers which give a frictionless impact, calculated from the initial velocity and the force as afunction of time. The force-deflection diagram obtained in these tests describes the high-bending-rate impactbehaviour of the specimen from which several aspects of the material properties may be inferred.5
Apparatus5.1
Test machine5.1.1
Basic componentsThe basic components of the test machine are the energy carrier, the striker and the frame with its specimensupports. The energy carrier may be of the inertial type (e.g. a pendulum or free-falling dart, which may be spring orpneumatically assisted before impact) or of the hydraulic type.SIST EN ISO 179-2:2000



ISO 179-2:1997(E)© ISO6The test machine shall ensure that the specimen is bent by the impact at a nominally constant velocityperpendicular to the specimen length. The force exerted on the specimen shall be measurable, and its deflection inthe direction of impact shall be derivable or measurable.5.1.2
Energy carrierFor the low-energy pendulum types specified in ISO 179-1 (see also ISO 13802, subclause 5.2.3), the impactvelocity v0 is 2,90 m/s ± 0,15 m/s and for the high-energy types it is 3,8 m/s ± 0,2 m/s. For the purposes ofcomparing impact strength data obtained using this method with data obtained in accordance with ISO 179-1, theimpact velocity used in this part of ISO 179 shall be 2,90 m/s ± 0,15 m/s, although it may be desirable to also usethe impact velocity v0 = 3,8 m/s ± 0,2 m/s (see also notes 1 and 2 below).To avoid obtaining results which cannot be compared due to the viscoelastic behaviour of the material under test,the decrease in the velocity during impact shall not be greater than 10 % (see note 3 below).The hydraulic-type energy carrier is a high-speed impact-testing machine with suitable attachments. Any inaccuracyin the velocity of the striker relative to the specimen supports during impact shall be checked, e.g. by recording thedeflection-time curve and checking the slope.In the case of gravitationally accelerated energy carriers, the above impact velocities correspond to drop heights of43 cm ± 5 cm and 74 cm ± 7 cm, respectively, the latter representing an increase by a factor of 1,54 in the kineticenergy E at impact if the same energy carrier is used at both impact velocities.The maximum permitted decrease in velocity during impact of 10 % specified above means that the kinetic energyE, in joules, at impact must satisfy the conditionEW*>5. . . (1)where W* is the highest value, in joules, of the energy to be measured (see ISO 13802, annex C, and note 2).The mass mC, in kilograms, of the energy carrier must therefore satisfy inequalities (2) and (3):mWvC>1002*. . . (2)mWvCwhen2,9ms>120,*=. . . (3)e.g.mWCkgwhen10J>12*=NOTES1
The height of the inertial peak FI (see figure 1, curve b), and also the amplitudes of the subsequent vibrations of thespecimen, increase with increasing impact velocity. For basic information about these vibrations, see annex A and references[1] and [2] in annex C. For further information about the interpretation of the inertial peak and the damping of vibrations, seeannex A.2
For special applications, e.g. testing precracked test specimens to obtain data on fracture properties, it may be useful to usea lower impact velocity of e.g. 1 m/s ± 0,05 m/s to reduce the vibrations mentioned in note 1.3
This condition is in accordance with the conditions given in ISO 179-1, subclause 7.3 (see ISO 13802, annex C). It ensuresthat the change in velocity during impact is comparable to that in conventional impact testing, and consequently the values ofimpact strength are comparable. This is important, because plastics are bending-rate-sensitive, especially at temperaturesclose to transition temperatures.5.1.3
Striking edgeSee ISO 13802, subclause 5.8.1 and table 3.Any material with sufficient resistance to wear and sufficiently high strength to prevent it from being deformed, aswell as being capable of transmitting the forces exerted upon the specimen to the load-measuring device, can beused for the striking edge.SIST EN ISO 179-2:2000



© ISOISO 179-2:1997(E)7NOTE —
Experience shows that steel is generally suitable. However, a material of lower density, e.g. titanium, can be used toincrease the natural frequency of the load-measuring system.5.1.4
PendulumThe pendulum shall conform to ISO 13802, subclause 5.2 and table 3.5.1.5
Test specimen supportsThe test specimen supports shall conform to ISO 13802, subclause 5.7.1.5.1.6
FrameThe frame of the test machine shall be capable of being levelled so that the striker and the specimen supportsconform to 5.1.3 and 5.1.5.When calculating deflections from the kinetic energy of the energy carrier, the ratio mF/mC of the mass of the frameto the mass of the energy carrier shall be at least 1
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