1、Designation: D 256 06aStandard Test Methods forDetermining the Izod Pendulum Impact Resistance ofPlastics1This standard is issued under the fixed designation D 256; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last r
2、evision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 These test methods cover the determination of theresistance of plastics to “standardized” (see Note 1) pendulum-type hamme
3、rs, mounted in “standardized” machines, in break-ing standard specimens with one pendulum swing (see Note 2).The standard tests for these test methods require specimensmade with a milled notch (see Note 3). In Test Methods A, C,and D, the notch produces a stress concentration that increasesthe proba
4、bility of a brittle, rather than a ductile, fracture. InTest Method E, the impact resistance is obtained by reversingthe notched specimen 180 in the clamping vise. The results ofall test methods are reported in terms of energy absorbed perunit of specimen width or per unit of cross-sectional area un
5、derthe notch. (See Note 4.)NOTE 1The machines with their pendulum-type hammers have been“standardized” in that they must comply with certain requirements,including a fixed height of hammer fall that results in a substantially fixedvelocity of the hammer at the moment of impact. However, hammers ofdi
6、fferent initial energies (produced by varying their effective weights) arerecommended for use with specimens of different impact resistance.Moreover, manufacturers of the equipment are permitted to use differentlengths and constructions of pendulums with possible differences inpendulum rigidities re
7、sulting. (See Section 5.) Be aware that otherdifferences in machine design may exist. The specimens are “standard-ized” in that they are required to have one fixed length, one fixed depth,and one particular design of milled notch. The width of the specimens ispermitted to vary between limits.NOTE 2R
8、esults generated using pendulums that utilize a load cell torecord the impact force and thus impact energy, may not be equivalent toresults that are generated using manually or digitally encoded testers thatmeasure the energy remaining in the pendulum after impact.NOTE 3The notch in the Izod specime
9、n serves to concentrate thestress, minimize plastic deformation, and direct the fracture to the part ofthe specimen behind the notch. Scatter in energy-to-break is thus reduced.However, because of differences in the elastic and viscoelastic propertiesof plastics, response to a given notch varies amo
10、ng materials. A measureof a plastics “notch sensitivity” may be obtained with Test Method D bycomparing the energies to break specimens having different radii at thebase of the notch.NOTE 4Caution must be exercised in interpreting the results of thesestandard test methods. The following testing para
11、meters may affect testresults significantly:Method of fabrication, including but not limited to processingtechnology, molding conditions, mold design, and thermaltreatments;Method of notching;Speed of notching tool;Design of notching apparatus;Quality of the notch;Time between notching and test;Test
12、 specimen thickness,Test specimen width under notch, andEnvironmental conditioning.1.2 The values stated in SI units are to be regarded asstandard. The values given in brackets are for information only.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with i
13、ts use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE 5These test methods resemble ISO 180:1993 in regard to titleonly. The contents are significantly different.2
14、. Referenced Documents2.1 ASTM Standards:2D 618 Practice for Conditioning Plastics for TestingD 883 Terminology Relating to PlasticsD 3641 Practice for Injection Molding Test Specimens ofThermoplastic Molding and Extrusion MaterialsD 4066 Classification System for Nylon Injection and Ex-trusion Mate
15、rials (PA)D 5947 Test Methods for Physical Dimensions of SolidPlastics SpecimensE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standard:ISO 180:1993 PlasticsDetermination of Izod Impact1These test methods are under the jurisdiction of ASTM Co
16、mmittee D20 onPlastics and are the direct responsibility of Subcommittee D20.10 on MechanicalProperties.Current edition approved Dec. 1, 2006. Published December 2006. Originallyapproved in 1926. Last previous edition approved in 2006 as D 256 - 06.2For referenced ASTM standards, visit the ASTM webs
17、ite, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor
18、 Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Strength of Rigid Materials33. Terminology3.1 Definitions For definitions related to plastics seeTerminology D 883.3.2 Definitions of Terms Specific to This Standard:3.2.1 cantilevera projecting beam clamped at only oneend.3.2.2 no
19、tch sensitivitya measure of the variation of impactenergy as a function of notch radius.4. Types of Tests4.1 Four similar methods are presented in these test meth-ods. (See Note 6.) All test methods use the same testingmachine and specimen dimensions. There is no known meansfor correlating the resul
20、ts from the different test methods.NOTE 6Test Method B for Charpy has been removed and is beingrevised under a new standard.4.1.1 In Test Method A, the specimen is held as a verticalcantilever beam and is broken by a single swing of thependulum. The line of initial contact is at a fixed distance fro
21、mthe specimen clamp and from the centerline of the notch and onthe same face as the notch.4.1.2 Test Method C is similar to Test Method A, except forthe addition of a procedure for determining the energy ex-pended in tossing a portion of the specimen. The value reportedis called the “estimated net I
22、zod impact resistance.” TestMethod C is preferred over Test Method A for materials thathave an Izod impact resistance of less than 27 J/m 0.5ftlbf/in. under notch. (See Appendix X4 for optional units.)The differences between Test Methods A and C becomeunimportant for materials that have an Izod impa
23、ct resistancehigher than this value.4.1.3 Test Method D provides a measure of the notchsensitivity of a material. The stress-concentration at the notchincreases with decreasing notch radius.4.1.3.1 For a given system, greater stress concentrationresults in higher localized rates-of-strain. Since the
24、 effect ofstrain-rate on energy-to-break varies among materials, a mea-sure of this effect may be obtained by testing specimens withdifferent notch radii. In the Izod-type test it has been demon-strated that the function, energy-to-break versus notch radius,is reasonably linear from a radius of 0.03
25、 to 2.5 mm 0.001 to0.100 in., provided that all specimens have the same type ofbreak. (See 5.8 and 22.1.)4.1.3.2 For the purpose of this test, the slope, b (see 22.1),of the line between radii of 0.25 and 1.0 mm 0.010 and 0.040in. is used, unless tests with the 1.0-mm radius give “non-break” results
26、. In that case, 0.25 and 0.50-mm 0.010 and0.020-in. radii may be used. The effect of notch radius on theimpact energy to break a specimen under the conditions of thistest is measured by the value b. Materials with low values of b,whether high or low energy-to-break with the standard notch,are relati
27、vely insensitive to differences in notch radius; whilethe energy-to-break materials with high values of b is highlydependent on notch radius. The parameter b cannot be used indesign calculations but may serve as a guide to the designerand in selection of materials.4.2 Test Method E is similar to Tes
28、t Method A, except thatthe specimen is reversed in the vise of the machine 180 to theusual striking position, such that the striker of the apparatusimpacts the specimen on the face opposite the notch. (See Fig.1, Fig. 2.) Test Method E is used to give an indication of theunnotched impact resistance
29、of plastics; however, results ob-tained by the reversed notch method may not always agree withthose obtained on a completely unnotched specimen. (See28.1.)4,55. Significance and Use5.1 Before proceeding with these test methods, referenceshould be made to the specification of the material being teste
30、d.Any test specimen preparation, conditioning, dimensions, andtesting parameters covered in the materials specification shalltake precedence over those mentioned in these test methods. Ifthere is no material specification, then the default conditionsapply.5.2 The pendulum impact test indicates the e
31、nergy to breakstandard test specimens of specified size under stipulatedparameters of specimen mounting, notching, and pendulumvelocity-at-impact.5.3 The energy lost by the pendulum during the breakage ofthe specimen is the sum of the following:5.3.1 Energy to initiate fracture of the specimen;5.3.2
32、 Energy to propagate the fracture across the specimen;3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.4Supporting data giving results of the interlaboratory tests are available fromASTM Headquarters. Request RR: D20-1021.5Supporting data giv
33、ing results of the interlaboratory tests are available fromASTM Headquarters. Request RR: D20-1026.FIG. 1 Relationship of Vise, Specimen, and Striking Edge to EachOther for Izod Test Methods A and CD 256 06a25.3.3 Energy to throw the free end (or ends) of the brokenspecimen (“toss correction”);5.3.4
34、 Energy to bend the specimen;5.3.5 Energy to produce vibration in the pendulum arm;5.3.6 Energy to produce vibration or horizontal movementof the machine frame or base;5.3.7 Energy to overcome friction in the pendulum bearingand in the indicating mechanism, and to overcome windage(pendulum air drag)
35、;5.3.8 Energy to indent or deform plastically the specimen atthe line of impact; and5.3.9 Energy to overcome the friction caused by the rubbingof the striker (or other part of the pendulum) over the face ofthe bent specimen.5.4 For relatively brittle materials, for which fracture propa-gation energy
36、 is small in comparison with the fracture initiationenergy, the indicated impact energy absorbed is, for allpractical purposes, the sum of factors 5.3.1 and 5.3.3. The tosscorrection (see 5.3.3) may represent a very large fraction of thetotal energy absorbed when testing relatively dense and brittle
37、materials. Test Method C shall be used for materials that havean Izod impact resistance of less than 27 J/m 0.5 ftlbf/in.(See Appendix X4 for optional units.) The toss correctionobtained in Test Method C is only an approximation of the tosserror, since the rotational and rectilinear velocities may n
38、ot bethe same during the re-toss of the specimen as for the originaltoss, and because stored stresses in the specimen may havebeen released as kinetic energy during the specimen fracture.5.5 For tough, ductile, fiber filled, or cloth-laminated mate-rials, the fracture propagation energy (see 5.3.2)
39、may be largecompared to the fracture initiation energy (see 5.3.1). Whentesting these materials, factors (see 5.3.2, 5.3.5, and 5.3.9) canbecome quite significant, even when the specimen is accuratelymachined and positioned and the machine is in good conditionwith adequate capacity. (See Note 7.) Be
40、nding (see 5.3.4) andindentation losses (see 5.3.8) may be appreciable when testingsoft materials.NOTE 7Although the frame and base of the machine should besufficiently rigid and massive to handle the energies of tough specimenswithout motion or excessive vibration, the design must ensure that thece
41、nter of percussion be at the center of strike. Locating the strikerprecisely at the center of percussion reduces vibration of the pendulumarm when used with brittle specimens. However, some losses due topendulum arm vibration, the amount varying with the design of thependulum, will occur with tough
42、specimens, even when the striker isproperly positioned.5.6 In a well-designed machine of sufficient rigidity andmass, the losses due to factors 5.3.6 and 5.3.7 should be verysmall. Vibrational losses (see 5.3.6) can be quite large whenwide specimens of tough materials are tested in machines ofinsuff
43、icient mass, not securely fastened to a heavy base.5.7 With some materials, a critical width of specimen maybe found below which specimens will appear ductile, asevidenced by considerable drawing or necking down in theregion behind the notch and by a relatively high-energyabsorption, and above which
44、 they will appear brittle asevidenced by little or no drawing down or necking and by arelatively low-energy absorption. Since these methods permit avariation in the width of the specimens, and since the widthdictates, for many materials, whether a brittle, low-energybreak or a ductile, high energy b
45、reak will occur, it is necessarythat the width be stated in the specification covering thatmaterial and that the width be reported along with the impactresistance. In view of the preceding, one should not makecomparisons between data from specimens having widths thatdiffer by more than a few mils.5.
46、8 The type of failure for each specimen shall be recordedas one of the four categories listed as follows:C= Complete BreakA break where the specimenseparates into two or more pieces.H= Hinge BreakAn incomplete break, such that onepart of the specimen cannot support itself abovethe horizontal when th
47、e other part is held vertically(less than 90 included angle).P= Partial BreakAn incomplete break that does notmeet the definition for a hinge break but has frac-tured at least 90 % of the distance between thevertex of the notch and the opposite side.NB = Non-BreakAn incomplete break where the frac-t
48、ure extends less than 90 % of the distance be-tween the vertex of the notch and the oppositeside.For tough materials, the pendulum may not have the energynecessary to complete the breaking of the extreme fibers andtoss the broken piece or pieces. Results obtained from “non-break” specimens shall be
49、considered a departure from stan-dard and shall not be reported as a standard result. Impactresistance cannot be directly compared for any two materialsthat experience different types of failure as defined in the testmethod by this code. Averages reported must likewise bederived from specimens contained within a single failurecategory. This letter code shall suffix the reported impactidentifying the types of failure associated with the reportedvalue. If more than one type of failure is observed for a samplematerial, then the report will indicate the aver
