1、Designation: D256 101Standard Test Methods forDetermining the Izod Pendulum Impact Resistance ofPlastics1This standard is issued under the fixed designation D256; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last rev
2、ision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1NOTEEditorially corrected Figure 2 in October 2015.
3、1. Scope*1.1 These test methods cover the determination of theresistance of plastics to “standardized” (see Note 1) pendulum-type hammers, mounted in “standardized” machines, in break-ing standard specimens with one pendulum swing (see Note 2).The standard tests for these test methods require specim
4、ensmade with a milled notch (see Note 3). In Test Methods A, C,and D, the notch produces a stress concentration that increasesthe probability 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. T
5、he results ofall test methods are reported in terms of energy absorbed perunit of specimen width or per unit of cross-sectional area underthe 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
6、 fixed height of hammer fall that results in a substantially fixedvelocity of the hammer at the moment of impact. However, hammers ofdifferent initial energies (produced by varying their effective weights) arerecommended for use with specimens of different impact resistance.Moreover, manufacturers o
7、f the equipment are permitted to use differentlengths and constructions of pendulums with possible differences inpendulum rigidities resulting. (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 l
8、ength, one fixed depth,and one particular design of milled notch. The width of the specimens ispermitted to vary between limits.NOTE 2Results 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
9、manually or digitally encoded testers thatmeasure the energy remaining in the pendulum after impact.NOTE 3The notch in the Izod specimen 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 t
10、hus reduced.However, because of differences in the elastic and viscoelastic propertiesof plastics, response to a given notch varies among materials. A measureof a plastics “notch sensitivity” may be obtained with Test Method D bycomparing the energies to break specimens having different radii at the
11、base of the notch.NOTE 4Caution must be exercised in interpreting the results of thesestandard test methods. The following testing parameters may affect testresults significantly:Method of fabrication, including but not limited to processingtechnology, molding conditions, mold design, and thermaltre
12、atments;Method of notching;Speed of notching tool;Design of notching apparatus;Quality of the notch;Time between notching and test;Test 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
13、in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its 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 l
14、imitations prior to use.NOTE 5These test methods resemble ISO 180:1993 in regard to titleonly. The contents are significantly different.2. Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD3641 Practice for Injection Mold
15、ing Test Specimens ofThermoplastic Molding and Extrusion MaterialsD4066 Classification System for Nylon Injection and Extru-sion Materials (PA)D5947 Test Methods for Physical Dimensions of SolidPlastics Specimens1These test methods are under the jurisdiction of ASTM Committee D20 onPlastics and are
16、the direct responsibility of Subcommittee D20.10 on MechanicalProperties.Current edition approved May 1, 2010. Published June 2010. Originallyapproved in 1926. Last previous edition approved in 2006 as D256 - 06a1. DOI:10.1520/D0256-10.2For referenced ASTM standards, visit the ASTM website, www.astm
17、.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.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box
18、C700, West Conshohocken, PA 19428-2959. United States1D6110 Test Method for Determining the Charpy ImpactResistance of Notched Specimens of PlasticsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standard:ISO 180:1993 PlasticsDetermination of I
19、zod ImpactStrength of Rigid Materials33. Terminology3.1 DefinitionsFor definitions related to plastics see Ter-minology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 cantilevera projecting beam clamped at only oneend.3.2.2 notch sensitivitya measure of the variation of impactenergy a
20、s 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 results from the different test methods.NOTE 6Previous versions
21、of this test method contained Test MethodB for Charpy. It has been removed from this test method and has beenpublished as D6110.4.1.1 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
22、 fromthe 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 ne
23、t Izod 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
24、 impact 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. Sinc
25、e the 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
26、 0.03 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
27、” results. 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
28、,are relatively 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 sim
29、ilar to Test 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
30、resistance 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
31、being tested.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.3Available from American National
32、 Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.4Supporting data giving results of the interlaboratory tests are available fromASTM Headquarters. Request RR:D20-1021.5Supporting data giving results of the interlaboratory tests are available fromASTM Head
33、quarters. Request RR:D20-1026.FIG. 1 Relationship of Vise, Specimen, and Striking Edge toEach Other for Izod Test Methods A and CD256 10125.2 The pendulum impact test indicates the energy to breakstandard test specimens of specified size under stipulatedparameters of specimen mounting, notching, and
34、 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 Energy to propagate the fracture across the specimen;5.3.3 Energy to throw the free end (or ends) of the brokenspecim
35、en (“toss correction”);5.3.4 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 overcom
36、e windage(pendulum air drag);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
37、fracture propa-gation energy 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
38、relatively dense and brittlematerials. 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 a
39、nd rectilinear velocities may not 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-laminatedmaterials, the fracture pr
40、opagation energy (see 5.3.2) may belarge compared to the fracture initiation energy (see 5.3.1).When testing these materials, factors (see 5.3.2, 5.3.5, and5.3.9) can become quite significant, even when the specimen isaccurately machined and positioned and the machine is in goodcondition with adequa
41、te capacity. (See Note 7.) Bending (see5.3.4) and indentation losses (see 5.3.8) may be appreciablewhen testing soft 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
42、design must ensure that thecenter 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 thepen
43、dulum, will occur with tough 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 ar
44、e tested in machines ofinsufficient 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-ener
45、gyabsorption, and above which 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-energybrea
46、k or a ductile, high energy break 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 thatdiff
47、er by more than a few mils.5.8 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 itsel
48、f abovethe horizontal when the 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 hasfractured at least 90 % of the distance betweenthe vertex of the notch and the opposite side.NB = Non-BreakAn incomp
49、lete break where thefracture extends less than 90 % of the distancebetween 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 considered a departure from stan-dard and shall not be reported as a standard result. ImpactFIG. 2 Relationship of Vise, Specimen, and Striking Edge toEach Other for Test Method ED256 1013resistance cannot be directly compared for any two
