ISO 179-2:1997 download free.Plastics-Determination of charpy impact properties Part 2 : Instrumented impact test.
1.1 This part of SO 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 parameters depending on the type of rnatenal, the type of test specimen and the type of notch are defined part I of ISO 179.
Dynamic effects such as toad-celVstriker resonance, test specimen resonance and initial-contact/inertia peaks are described (see figure 1, curve b. and annex A).
1.2 For the comparison between Charpy and hod 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 apparatus whose 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 detaded characterization of the impact behaviour, and for developing automatic apparatus, ie. avoiding the need, mentioned above, 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 cakulalions on components. However, the possible use of data is not the subect of this part of ISO 179. Any application of data obtained using this pan of ISO 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 the notch 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 on the force-deflection diagram. These interpretations are a task for on-going scientific research.
1.6 The test results are comparable only if the conditions attest specimen preparation, as well as the test conddions, are the same. Comprehensive evaluation of the reaction to impact stress requires that determinations be made as a function of deformation rate and temperature for different material variables such as crystallinity and moisture 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.
2 Normaflve references
The following standards contain provisions which. ttwough reference in this text. constitute provisions of this part of 150179. At the tim. of put5cation. the editions indicated wire vakd. All standards are subject to revision, arxl parties to agreements based on this pall of ISO 179 are encouraged to irwestigate the possibdity of applymg the most recent ecteions ci the standards indicated below. Members of lEG and ISO maintain registers ci currently valid International Standards.
ISO 179.1:—’). Plastics — DtemW,.tion of Charpy lrriact pmpeitl.s — Part 1: ha -iistnamented ln’çact test.
ISO 13$O2:.2), Plastics — Verthcalxn of pendulum hipact-lestlng mactwies — Charpy. ?zod and tensile impact teshn
3 Definit)ons
For the purposes of this pail of ISO 179. th. definitions given in part I apply, together with the following:
3.1 impact velocity, : The velocity 01 the striker relative to the test specimen supports at the moment of impact.
it ii expressed in metres per second (mm).
3.2 kierlIal peek: The first peak in a force-tIme or lorce-dellection diagram. it arises from the Inertia of that pail of the test specimen acoeleraled after th. first contact with the striker (see fIgure 1, curve b, and arviex A).
3.3 Impact force. F The force exeiled by the striking edge on the test specimen in the dEection of impact. Ills expressed In newtons (N).
3.4 defh.ctlon, s The displacement 01 the striker relative to the test specimen supports after impact, starting at tWit contact between str*er and lest specimen.
It is expressed li rrdlimetres (run).
3.5 Impact energy, W The energy expended in acoelemating. delormang and breaking the lest specimen duflng the deflection,.
It Is expressed in oules (.1).
It is measured by integrating the area und.r the force-deflectIon curve from th. point of Impact to the deflection,.
3.6 maxImum Impact force, Fu: The maximum value of the impact force in a force-time or force-deflection diagram (see fIgure 1).
It Is expressed in newtons (N).
3.7 deflectIon it maxImum Impact fore,, sU: The dellaction at which the maximum Impact force FM ocours (see figure 1).
It is expressed In intllimetres (mm).
It Is necessary to cftfterenhiat. between the deffection at break s and the deftechon timit i at the beginrwng of puitthrou (see figure 1 curve N) which is detetmined by the lengTh 1 and wicith S of the test specimen and the distance L between the specimen supports. For type I specimens inthe edgewise position, 5L in the range 32 mm to 34 mm
NOTE — using type 1 epecanens tested edgewise, apparent deflection bnits era sometimes observed, I.- unexpectedly low vduea (down to only 20 mm) at *hich the Impect force drcps to zero, but the specimens do not break. Canying out the test ilowly shoes that. m sud cases. the specimen changes from the edgewis. to lie note stable ttalwiee position byc coiabEied benr*ig.hestliig deformation. This t easily be conffrmed by checking the specimen after the test C is bent with respect to an axis not parale& but incined to. the specinen widlh.
This behaviour is caused by the lagh ratio between the edgewise and the Itatwise flexural ngidtty of lie specimen and is triggered by a emafi asynwnelry features g. the draft angle.
This phenomenon may be avoided by fitting guide elements in front of. but not connected to, the lnshm’ienfed suilung edge. thus preventing the central pan of the specimen Irvin heating to any great extent.
3.10 impact energy at break. w: The impact energy up to the deflection at break ra, It is expressed in Joutes (J).
3.11 Cherpy (notched) Impact strength, a (adi): The impact energy at break relative to the initial central cross •sactionat area A (t) of ttw unnotched (nOtched) specimen (see 8.4 and ISO 179-1. 3.1 and 32).
It is expressed in lulOfoules per square metre (kilrn2).
3.12 type of failure The type of deformation behaviour of the material under test (see figure 2). It may be either no break (N), partial break (P), tough (I), briote (b) or splintetmg (s).
Types t, b and a represent subgroups of the complete break C and hinge break H defined in pail I of ISO 179. For these types, values of the impact energy at break WB, and thus for the Charpy impact strength, may be averaged to give a common mean value For specimens giving a partial break P and for matenals exh.tAng interleminar shear fracture, see ISO 179-I, subcleuse 7.6. For specimens showing more than one failure type, see 150179-1 subdause 77.
NOTE — As can be seen Irom fIgure 2, the delecf on and the Impact energy at maxinum tome are Identical to the deflection and impact energy at break in the case of spbntering tallure (see curve a) and brittle lailure (see curve ti). where unstable cracking Lakes place at the maxiim,n impact force.
4 Prlnc(ple
A rod-shaped test specimen, supported near iii ends as a hoflzonlai beam, is impacted perpendiouterty, with the tine of impact midway between the supports, and bent at a high, noninally constant velocity The impact geometry is described in ISO 13802, clause 5. Dunng the impact, the impact force is recorded. Depending on the method of evaluation, Ihe deflection of the specimen may be either measured directly by suitable meeaunng devices or, in the case of energy carriers which give a trictionless impact. calculated from the artiuial velocity and the force as a function of lime The force-defiection diagram obtained in these tests describes the lilgh-bendang.rate wspact behaviour of the specimen from which several aspects of the malenal properties may be inferred.
5 Apparatus
5.1 Vest mach)ne
5.1.1 Basic components
Th. basic components of the test machine are the energy carrier, the striker and the frame with it specimen supports. The energy carrier may be of the inertial type (e.g a pendulum or Ireeiaikng dart, which may be spnng or pneumatically assisted before Impact) or of the hydraulic type.