1、Designation: D4812 11Standard Test Method forUnnotched Cantilever Beam Impact Resistance of Plastics1This standard is issued under the fixed designation D4812; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi
2、on. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of the resis-tance of plastics to breakage by flexural shock, as indicated bythe energ
3、y extracted from standardized pendulum-type ham-mers, mounted in standardized machines, in breaking standardspecimens with one pendulum swing. The result of this testmethod is reported as energy absorbed per unit of specimenwidth.NOTE 1The pendulum-type test instruments have been standardizedin that
4、 they must comply with certain requirements, including a fixedheight of hammer fall that results in a substantially fixed velocity of thehammer at the moment of impact. Pendulums of different initial energies(produced by varying their effective weights) are recommended for usewith specimens of diffe
5、rent impact strengths. Moreover, manufacturers ofthe equipment are permitted to use different lengths and constructions ofpendulums (with resulting possible differences in pendulum rigidities (seeSection 5), and other differences in machine design).1.2 The values stated in SI units are to be regarde
6、d asstandard. The values given 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
7、 applica-bility of regulatory limitations prior to use.NOTE 2This standard and ISO 180, Method U address the samesubject matter, but differ in technical content.2. Referenced Documents2.1 ASTM Standards:2D256 Test Methods for Determining the Izod PendulumImpact Resistance of PlasticsD618 Practice fo
8、r Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD5947 Test Methods for Physical Dimensions of SolidPlastics SpecimensE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 DefinitionsDefinitions used in this test meth
9、od are inaccordance with Terminology D883.4. Summary of Test Method4.1 This test method differs from others of similar characterin that unnotched test specimens are used (see Test MethodsD256 for procedures using notched test specimens). The lackof a notch makes this test method especially useful fo
10、rreinforced materials where a notch may mask the effects oforientation. It may also be used with other filled or unrein-forced materials where a stress-concentrating notch is notdesired. It is not valid for materials that twist when subjectedto this test.5. Significance and Use5.1 The pendulum-impac
11、t test indicates the energy to breakstandard test specimens of specified size under stipulatedconditions of specimen mounting and pendulum velocity atimpact.5.2 The energy lost by the pendulum during the breakage ofthe specimen is the sum of the energies required to produce thefollowing results:5.2.
12、1 To initiate fracture of the specimen,5.2.2 To propagate the fracture across the specimen,5.2.3 To throw the free end (or pieces) of the brokenspecimen (toss correction),5.2.4 To bend the specimen,5.2.5 To produce vibration in the pendulum arm,5.2.6 To produce vibration or horizontal movement of th
13、emachine frame or base,5.2.7 To overcome friction in the pendulum bearing and inthe indicating mechanism, and to overcome windage (pendu-lum air drag),5.2.8 To indent or deform plastically the specimen at theline of impact, and5.2.9 To overcome the friction caused by the rubbing of thestriking nose
14、(or other part of the pendulum) over the face ofthe bent specimen.1This test method is under the jurisdiction ofASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.10 on Mechanical Properties.Current edition approved Dec. 1, 2011. Published January 2012. Originallyappr
15、oved in 1988. Last previous edition approved in 2006 as D4812 - 06. DOI:10.1520/D4812-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summ
16、ary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.3 For relatively brittle materials for which fracture propa-gation energy is small in com
17、parison with the fracture initiationenergy, the indicated impact energy absorbed is, for allpractical purposes, the sum of items given in 5.2.1 and 5.2.3.The toss correction (5.2.3) may represent a very large fractionof the total energy absorbed when testing relatively dense andbrittle materials.5.4
18、 For materials for which the fracture propagation energy(5.2.2) may be large compared to the fracture initiation energy(5.2.1), factors (5.2.2, 5.2.5, and 5.2.9) can become quitesignificant, even when the specimen is accurately machinedand positioned and the machine is in good condition withadequate
19、 capacity (Note 3). Bending (5.2.4) and indentationlosses (5.2.8) may be appreciable when testing soft materials.NOTE 3Although the frame and base of the machine should besufficiently rigid and massive to handle the energies of tough specimenswithout motion or excessive vibration, the pendulum arm c
20、annot be madevery massive because the greater part of its mass must be concentratednear its center of percussion at the striking nose. Locating the striking noseprecisely at the center of percussion reduces vibration of the pendulumarm when used with brittle specimens. However, some losses due topen
21、dulum-arm vibration, the amount varying with the design of thependulum, will occur with tough specimens even when the striking noseis properly positioned.5.5 In a well-designed machine of sufficient rigidity andmass the losses due to the items given in 5.2.6 and 5.2.7 shouldbe very small. Vibrationa
22、l losses (5.2.6) can be quite largewhen specimens of tough materials are tested in machines ofinsufficient mass which are not securely fastened to a heavybase.5.6 This test method requires that the type of failure for eachspecimen be recorded as one of the three coded categoriesdefined as follows:5.
23、6.1 C (Complete Break)A break in which the specimenis separated into two or more pieces.5.6.2 P (Partial Break)An incomplete break that hasfractured at least 90 % of the depth of the specimen.5.6.3 NB (Non-Break)An incomplete break where thefracture extends less than 90 % of the depth of the specime
24、n.5.6.3.1 For tough materials the pendulum may not have theenergy necessary to completely break the extreme outermostfibers and toss the broken piece or pieces. Results obtainedfrom “non-break” specimens shall be considered a departurefrom standard and shall be reported as “NB” only and anumerical v
25、alue shall not be reported. Impact values cannot bedirectly compared for any two materials that experiencedifferent types of failure as defined by this code.5.6.4 Averages reported must likewise be derived fromspecimens contained within a single failure category. Thisletter code will be included wit
26、h the reported impact identify-ing the types of failure associated with the reported value. Ifmore than one type of failure is observed for a sample material,then the report will indicate the average impact value for eachtype of failure, followed by the percent of the specimens failingin that manner
27、 and identified by the letter code.5.7 The value of this impact test method lies mainly in theareas of quality control and materials specification. The factthat a material shows twice the energy absorption of anotherunder these conditions of test does not indicate that this samerelationship will exi
28、st under another set of test conditions. Theranking of materials may even be changed under differenttesting conditions.5.8 Before proceeding with this test method, referenceshould be made to the specification of the material being tested.Any test specimen preparation, conditioning, dimensions, ortes
29、ting parameters, or combination thereof, covered in thematerial specification shall take precedence over those men-tioned in this test method except in cases where to do so wouldconflict with the purpose for conducting testing. If there are nomaterial specifications, then the default conditions appl
30、y.6. Apparatus6.1 Impact Machine, consisting of a massive base on whichis mounted a vise for holding the specimen and to which isconnected, through a rigid frame and antifriction bearings, oneof a number of pendulum-type hammers (or one basic hammerto which extra weights may be attached) having an i
31、nitialenergy suitable for use with the particular specimen to betested, plus a pendulum holding and releasing mechanism anda mechanism for indicating the breaking energy of the speci-men. A jig for positioning the specimen in the vise and graphsor tables to aid in the calculation of the correction f
32、or frictionand windage should be included. See Fig. 1 for one type ofmachine that may be used. The type of machine that is depictedcan also be used for the testing of notched specimens usingTest Methods D256. Detailed requirements are given in 6.2-6.5. See Appendix X1 for general methods for checkin
33、g andcalibrating the machine. Additional instructions for adjusting aparticular machine should be supplied by the manufacturer.6.2 Pendulum, consisting of a single or multimembered armwith a bearing on one end and a head, containing the strikingnose, on the other. Although a large proportion of the
34、mass ofthe pendulum should be concentrated in the head, the arm mustFIG. 1 Cantilever Beam Impact Test EquipmentD4812 112be sufficiently rigid to maintain the proper clearances andgeometric relationships between the machine parts and thespecimen and to minimize vibrational losses which are alwaysinc
35、luded in the measured impact value.6.2.1 Striking Nose (of the Pendulum), of hardened steel andcylindrical surface having a radius of curvature of 0.80 6 0.20mm (0.031 6 0.008 in.) with its axis horizontal and perpen-dicular to the plane of swing of the pendulum.6.2.1.1 The line of contact of the st
36、riking nose shall belocated at the center of percussion of the pendulum within62.54 mm (60.100 in.) (Note 4). Those portions of thependulum adjacent to the cylindrical striking edge shall berecessed or inclined at a suitable angle so that there will be nochance for other than this cylindrical surfac
37、e coming intocontact with the specimen during the break.6.2.2 Pendulum Holding and Releasing Mechanism,inaposition such that the vertical height of fall of the striking noseshall be 610 6 2 mm (24.0 6 0.1 in.); this will produce avelocity of the striking nose at the moment of impact ofapproximately
38、3.46 m (11.35 ft)/s. The mechanism shall be soconstructed and operated that it will release the pendulumwithout imparting acceleration or vibration to it.6.2.3 The effective length of the pendulum shall be between0.325 and 0.406 m (12.8 and 16.0 in.) so that the aboverequired elevation of the striki
39、ng nose may be obtained byraising the pendulum to an angle between 60 and 30 above thehorizontal.NOTE 4The distance from the axis of support to the center ofpercussion may be determined experimentally from the period of smallamplitude oscillations of the pendulum, as follows:L 5 g/4p2!p2(1)where:L =
40、 distance from the axis of support to the center of percussion, m(ft),g = local gravitational acceleration (known to an accuracy of one partin one thousand), m/s2(ft/s2),p = 3.1416 (4p2= 39.4786), andp = period, s, of a single complete swing (to and fro) determined fromat least 20 consecutive and un
41、interrupted swings (known to onepart in two thousandths). The angle of swing shall be less than 5each side of center.6.2.4 The machine shall be provided with a basic pendulumcapable of delivering an energy of 2.710 6 0.135 J (2.00 60.10 ft-lbf). This pendulum shall be used with all specimensthat ext
42、ract less than 85 % of this energy. Heavier pendulumsshall be provided for specimens that require more energy tobreak. These may be separate interchangeable pendulums orone basic pendulum to which extra pairs of equal calibratedweights may be attached rigidly to opposite sides of thependulum at its
43、center of percussion. It is imperative that theextra weights shall not change the position of the center ofpercussion of the free-hanging rest point of the pendulum.6.2.4.1 Arange of pendulums having energies from 2.710 to21.680 J (2 to 16 ft-lbf) has been found to be sufficient for usewith most pla
44、stic specimens and may be used with mostmachines. A series of pendulums such that each has twice theenergy of the next lighter one will be found convenient. Eachpendulum shall have an energy within 60.5 % of its nominalcapacity.6.2.5 When the pendulum is free-hanging, the strikingsurface shall come
45、within 0.2 % of scale of touching the frontface of a standard specimen. During an actual swing thiselement shall make initial contact with the specimen on a line22.00 6 0.05 mm (0.866 6 0.002 in.) above the top surface ofthe vise.6.2.6 Means shall be provided for determining the energyexpended by th
46、e pendulum in breaking the specimen. This isaccomplished using either a pointer and dial mechanism or anelectronic system consisting of a digital indicator and sensor(typically an encoder or resolver). In either case, the indicatedbreaking energy is determined by detecting the height of rise ofthe p
47、endulum beyond the point of impact in terms of energyremoved from that specific pendulum. Since the indicatedenergy must be corrected for pendulum-bearing friction,pointer friction, pointer inertia, and pendulum windage, in-structions for making these corrections are included in 9.3 andAnnex A1 and
48、Annex A2. If the electronic display does notautomatically correct for windage and friction, it shall beincumbent for the operator to determine the energy lossmanually. (See Note 5)NOTE 5Many digital indicating systems automatically correct forwindage and friction. The equipment manufacturer may be c
49、onsulted fordetails concerning how this is performed, or if it is necessary to determinethe means for manually calculating the energy loss due to windage andfriction.6.3 Vise, for clamping the specimen rigidly in position sothat the long axis of the specimen is vertical and at right anglesto the top plane of the vise. The top edges of the jaws of thevise shall have a radius of 0.25 6 0.12 mm (0.010 6 0.005 in.)(see Fig. 2).NOTE 6It is especially important that the correct radius be maintainedFIG. 2 Diagram Showing Proper Radius for Vise Jaw EdgesD4812 113on the moveable
