1、Designation: D5420 10Standard Test Method forImpact Resistance of Flat, Rigid Plastic Specimen by Meansof a Striker Impacted by a Falling Weight (Gardner Impact)1This standard is issued under the fixed designation D5420; the number immediately following the designation indicates the year oforiginal
2、adoption or, in the case of revision, the year of last revision. 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 relativeranking of
3、 materials according to the energy required to crackor break flat, rigid plastic specimens under various specifiedconditions of impact of a striker impacted by a falling weight.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonl
4、y.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 limitations prior to use.NOTE 1There i
5、s no similar or equivalent ISO standard.2. Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD1600 Terminology for Abbreviated Terms Relating toPlasticsD2794 Test Method for Resistance of Organic Coatings tothe Effects of
6、Rapid Deformation (Impact)D3763 Test Method for High Speed Puncture Properties ofPlastics Using Load and Displacement SensorsD4066 Classification System for Nylon Injection and Ex-trusion Materials (PA)D4226 Test Methods for Impact Resistance of Rigid Poly-(Vinyl Chloride) (PVC) Building ProductsD56
7、28 Test Method for Impact Resistance of Flat, RigidPlastic Specimens by Means of a Falling Dart (Tup orFalling Mass)D5947 Test Methods for Physical Dimensions of SolidPlastics SpecimensE171 Specification for Atmospheres for Conditioning andTesting Flexible Barrier MaterialsE691 Practice for Conducti
8、ng an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 DefinitionsFor definitions of plastics terms used inthis test method, see Terminologies D883 and D1600.3.2 Definitions of Terms Specific to This Standard:3.2.1 failure (of test specimen)the presence of any cracko
9、r split created by the impact of the falling weight that can beseen by the naked eye under normal laboratory lightingconditions.3.2.1.1 DiscussionFailure shall include the following:(1) complete shattering of the plaque; (2) any crack radiatingout toward the edges of the plaque on either surface of
10、theplaque; (3) any radial crack within or just outside the impactarea of the striker; (4) any hole in the plaque, whether due tobrittle or ductile puncture, where unobstructed light or watercould pass through; (5) any brittle splitting of the bottomsurface of the plaque; and (6) any glassy-type chip
11、 dislodgedfrom or loosened from the plaque.3.2.1.2 DiscussionSince the interpretation of failure maybe slightly different between material types, refer to theappropriate material specification for guidance.3.2.1.3 DiscussionCracks usually start at the surface op-posite the one that is struck. For ex
12、ample, in some casesincipient cracking in glass-reinforced polymers is difficult todifferentiate from the reinforcing fibers. In such cases, apply apenetrating dye such as gentian violet to the stressed surface todetermine the onset of crack formation.3.2.2 mean-failure energy (mean impact resistanc
13、e)theenergy required to produce 50 % failures, equal to the productof the constant mass and mean failure height.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 July 1
14、, 2010. Published July 2010. Originally approvedin 1993. Last previous edition approved in 2004 as D5420 - 04. DOI: 10.1520/D5420-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume infor
15、mation, 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 Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.3 mean-failure height (impact-failure heigh
16、t)theheight at which a standard mass, when dropped on testspecimens, will cause 50 % failures.4. Summary of Test Method4.1 In this test method, a weight falls through a guide tubeand impacts a striker resting on top of a supported specimen.The fixed weight is dropped from various heights (see Fig. 1
17、).4.2 The procedure determines the energy(mass 3 gravity 3 height) that will cause 50 % of the speci-mens tested to fail (mean-failure energy).4.3 The technique used to determine mean-failure energy iscommonly called the Bruceton Staircase Method, or theUp-and-Down Method (1).3Testing is concentrate
18、d near themean, reducing the number of specimens required to obtain areasonably precise estimate of the impact resistance.4.4 This test method permits the use of different strikerdiameters and specimen support plate geometries to obtaindifferent modes of failure, permit easier sampling, or testlimit
19、ed amounts of material. There is no known means forcorrelating the results of tests made by different methods orprocedures.5. Significance and Use5.1 Plastics are viscoelastic it is and therefore possible thatthey are sensitive to changes in velocity of weights falling ontheir surfaces. However, the
20、 velocity of a free-falling object isa function of the square root of the drop height. A change of afactor of two in the drop height will cause a change of only 1.4in velocity. Hagan, et al (2) found that the mean-failure energyof sheeting was constant at drop heights between 0.30 and 1.4m. Differen
21、t materials respond differently to changes in thevelocity of impact.5.2 The test conditions used in Geometry GA are the sameas those used in Geometry FA of Test Method D5628 (seeTable 1).5.3 The test conditions of Geometry GB are equivalent tothe geometry used for the Gardner Variable Height Impact
22、Test(3).5.4 The test conditions of Geometry GC cause a punch-shear type of failure because the support-plate hole is close tothe diameter of the striker.5.5 The test conditions of Geometry GD are the same asthose in Test Method D3763.5.6 The test conditions of Geometry GE are the same asthose in Tes
23、t Method D4226, impactor head configurationH.25.5.7 Because of the nature of impact testing, the selection ofa test method and striker must be somewhat arbitrary. Considerthe end use environment and requirements when choosing fromthe available striker geometries. However, the selection of anyone of
24、the striker geometries is permitted, after such consider-ation.NOTE 2Material processing can have a significant affect on thedevelopment of a plastics physical properties. Consult relevant materialstandards for processing guidelines6. Interferences6.1 Falling-weight-impact test results are dependent
25、 on thegeometry of the falling weight, striker, and the support. Thus,use impact tests only to obtain relative rankings of materials.Impact values cannot be considered absolute unless the geom-etry of the test equipment and specimen conform to the end-userequirement. Data obtained with different geo
26、metries, cannot,in general, be compared directly with each other.6.1.1 Falling-weight-impact types of tests are not suitablefor predicting the relative ranking of materials at impactvelocities differing greatly from those imposed by these testmethods.6.2 As cracks usually start at the surface opposi
27、te the onethat is struck, the results obtained can be greatly influenced bythe surface characteristics of the test specimens. Therefore,3The boldface numbers in parentheses refer to the list of references found at theend of this test method.FIG. 1 Impact TesterTABLE 1 Striker and Specimen-Support-Pl
28、ate DimensionsGeometryStriker Diameter,mm (in.)Support Plate Inside Diameter, mm(in.)GA 15.86 6 0.10 76.06 3.0(0.625 6 0.004) (3.00 6 0.12)GB 15.86 6 0.10 31.756 0.025(0.625 6 0.004) (1.25 6 0.001)GC 15.86 6 0.10(0.625 6 0.004)16.26 6 0.025(0.640 6 0.001)GD 12.70 6 0.10(0.500 6 0.004)76.0 6 3.0(3.00
29、 6 0.12)GE 12.70 6 0.10(0.500 6 0.004)16.26 6 0.025(0.640 6 0.001)D5420 102factors including surface features (flaws, texturing, and soforth), surface composition, orientation due to specimen prepa-ration, and so forth, are important variables and will influenceresults.6.3 Impact properties of plast
30、ic materials can be verysensitive to temperature. This test can be carried out at anyreasonable temperature and humidity, thus representing actual-use environments. However, this test method is intendedprimarily for rating materials under specific impact conditions.6.4 It is possible that the appara
31、tus used in this test methodwill not have sufficient energy available to cause failure ofsome specimens under the conditions of this procedure.7. Apparatus7.1 Testing MechanismThe apparatus is shown in Fig. 1.Adapt the apparatus from Test Method D2794 for use in thistest method or obtain the apparat
32、us commercially. The appa-ratus shall consist of the following: suitable base to withstandthe impact shock; steel-rod impact mass, weighing 0.9 kg (2lb), 1.8 kg (4 lb), or 3.6 kg (8 lb); a hardened steel strikerhaving a round nose with diameter described in 7.1.1 and 7.1.2and Table 1; a slotted guid
33、e tube 1.0 m (40 in.) in length, inwhich the impact mass slides, having graduations in newton-metres (inch-pound increments) or multiples thereof. Use abracket to hold the tube in a vertical position by attaching it tothe base and also to hold the hand knob, which is a pivot armalignment for the str
34、iker, about 50 mm (2 in.) under the tube.Mount this instrument firmly to a rigid table or bench. Roundthe top edge of the opening in each specimen-support plate toa 1.0 6 0.2-mm (0.039 6 0.008-in.) radius, except in Geom-etry GE which has a radius of 0.75 mm (0.031 in.).7.1.1 For Geometries GA, GB,
35、and GC, the striker shallhave a rounded nose with a diameter of 15.86 6 0.10 mm(0.625 6 0.004 in.).7.1.2 For Geometries GD and GE the striker shall have arounded nose with a diameter of 12.70 6 0.1 mm (0.500 60.004 in.).7.1.3 With Geometries GA and GD, a specimen-supportplate with a hole 76.0 6 3.0
36、mm (3.00 6 0.12 in.) in diameteris mounted in the apparatus.Asuggested design is given in Fig.2.7.1.4 With Geometry GB, the specimen-support plate has a31.75 6 0.025-mm (1.25 6 0.001-in.) diameter hole. Thisgeometry can be achieved by removing the removable supportring on the standard Gardner instru
37、ment.7.1.5 With Geometries GC and GE, the standard removablespecimen-support plate, with a hole 16.26 6 0.025 mm (0.6406 0.001 in.) in diameter, is mounted in the specimen supportanvil (see Fig. 3 for Geometry GC and Fig. 4 for GeometryGE).7.2 Supporting BaseIn order to minimize the energyabsorption
38、, compression, and deflection of the support, affixthe tester to a dense, solid block or base weighing a minimumof 400 lb (see Appendix X2). The main body of the block orbase shall have maximum dimensions of 16 by 30 by 30 in.(height by width by depth). Place this block or base at a heightsuitable f
39、or ease of operation. It is not necessary to bolt blocksor bases of this weight to the floor. Alternatively, affix testersdirectly to the floor. Use of rubber mats either directly underthe tester or supporting apparatus is prohibited.7.2.1 Bolt supporting bases or tables lighter than 400 lb to aconc
40、rete floor. For each different material tested, make com-parisons between mean failure energy data generated using thissupport and one where the tester is fixed directly to theconcrete floor. If mean failure energy differences between twoFIG. 2 Specimen-Support Plate Used for Geometries GA and GDFIG
41、. 3 Striker/Specimen/Support Plate Configuration forGeometries GB and GC (Geometry GC Shown)D5420 103types of supports are found to be statistically nonsignificant,use of the lighter support shall be allowed.NOTE 3Such block dimensions conform to commercially availablebutcher block tables.7.3 Microm
42、eter, for measurement of specimen thickness.Ensure that the accuracy is 1 % of the average thickness of thespecimens used. See Test Methods D5947 for descriptions ofsuitable micrometers.8. Sampling8.1 Sample using a statistically acceptable procedure.9. Test Specimens9.1 The diameter or width of fla
43、t test specimens shall be atleast 25 mm (1.00 in.) greater than the diameter of the hole inthe support plate. The specimens shall be free of obviousimperfections, unless the imperfections constitute a variableunder study.9.2 The thickness of any specimen in a sample shall notdiffer by more than 5 %
44、from the average specimen thicknessof that sample. However, if variations greater than 5 % areunavoidable in a sample that is obtained from parts, the sampleshall be permitted to be tested, but the data shall not be used forreferee purposes. Machining specimens to reduce thicknessvariation is not pe
45、rmissible.9.3 When the approximate mean-failure height for a givensample is known, 20 specimens will usually yield sufficientlyprecise results. If the approximate mean-failure height isunknown, six or more additional specimens shall be used todetermine the appropriate starting point of the test.9.4
46、Visually examine the specimens to ensure they are freeof cracks or other obvious imperfections or damages, unlessthese imperfections constitute variables under study. For speci-fication purposes, do not test samples known to be defective.Production parts shall be tested in the as-received condition
47、todetermine conformance to specified standards.9.5 Select a suitable method for making the specimen thatwill minimize the effect of specimen preparation on the impactresistance of the material. Refer to the appropriate materialspecification for requirements for specimen preparation.NOTE 4As few as t
48、en specimens often yield sufficiently reliableestimates of the mean-failure height. However, in such cases the estimatedstandard deviation will be relatively large (1).10. Conditioning10.1 Unless otherwise specified by contract or relevantmaterial specification, condition the test specimens in accor
49、-dance with Procedure A of Practice D618 or SpecificationE171, for those tests where conditioning is required. Tempera-ture and humidity tolerances shall be in accordance withSection 7 of Practice D618, unless otherwise specified bycontract or relevant ASTM material specification.10.1.1 Note that for some hygroscopic materials, such asnylons, the material specifications (for example, SpecificationD4066) call for testing “dry as-molded specimens.” Suchrequirements take precedence over the above routine precon-ditioning to 50 % relative humidity and require sealing thesp
