1、Designation: F1473 13 An American National StandardStandard Test Method forNotch Tensile Test to Measure the Resistance to Slow CrackGrowth of Polyethylene Pipes and Resins1This standard is issued under the fixed designation F1473; the number immediately following the designation indicates the year
2、oforiginal 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 determines the resistance of polyeth-yl
3、ene materials to slow crack growth under conditions speci-fied within.NOTE 1This test method is known as PENT (Pennsylvania NotchTest) test.1.2 The test is generally performed at 80C and at 2.4 MPa,but may also be done at temperatures below 80C and withother stresses low enough to preclude ductile f
4、ailure andthereby eventually induce brittle type of failure. Generally,polyethylenes will ultimately fail in a brittle manner by slowcrack growth at 80C if the stress is below 2.4 MPa.1.3 The test method is for specimens cut from compressionmolded plaques.2See Appendix X1 for information relating to
5、specimens from pipe.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 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 standa
6、rd to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D1600 Terminology forAbbreviated Terms Relating to Plas-ticsD4703 Practice for Compression Molding ThermoplasticMaterials into T
7、est Specimens, Plaques, or SheetsF412 Terminology Relating to Plastic Piping Systems3. Terminology3.1 Definitions:3.1.1 Definitions are in accordance with Terminology F412.Abbreviations are in accordance with Terminology D1600,unless otherwise indicated.3.1.2 brittle failurea pipe failure mode which
8、 exhibits novisible (to the naked eye) permanent material deformation(stretching, elongation, or necking down) in the area of thebreak (Terminology F412).3.2 Definitions of Terms Specific to This Standard:3.2.1 slow crack growththe slow extension of the crackwith time.4. Summary of Test Method4.1 Sp
9、ecimens are prepared from compression moldedplaques, precisely notched and then exposed to a constanttensile stress at elevated temperatures in air. Time on test isrecorded for tests conducted against a minimum time beforefailure requirement or the time to complete failure is recorded.NOTE 2Minimum
10、time before failure requirements are found inmaterial or product specifications, codes, etc.5. Significance and Use5.1 This test method is useful to measure the slow crackgrowth resistance of molded plaques of polyethylene materialsat accelerated conditions such as 80C, 2.4-MPa stress, andwith a sha
11、rp notch.5.2 The testing time or time to failure depends on thefollowing test parameters: temperature; stress; notch depth; andspecimen geometry. Increasing temperature, stress, and notchdepth decrease the time to failure. Thus, in reporting the testtime or time to failure, all the conditions of the
12、 test shall bespecified.6. Apparatus6.1 Lever Loading Machine, with a lever arm ratio of about5:1. The tensile load may also be applied directly using deadweights or any other method for producing a constant load.Thepull rods on the grips shall have universal action to prevent1This test method is un
13、der the jurisdiction of ASTM Committee F17 on PlasticPiping Systems and is the direct responsibility of Subcommittee F17.40 on TestMethods.Current edition approved Aug. 1, 2013. Published August 2013. Originallyapproved in 1997. Last previous edition approved in 2011 as F1473 11. DOI:10.1520/F1473-1
14、3.2Lu, X., and Brown, N., “ATest for Slow Crack Growth Failure in PolyethyleneUnder a Constant Load,” Journal of Polymer Testing, Vol 11, pp. 309319, 1992.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM
15、Standards 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 C700, West Conshohocken, PA 19428-2959. United States1bending. The grips shall be
16、 serrated to prevent slippage. Theload on the specimen shall be accurate to at least 60.5 %.6.2 Furnace, heated by ordinary incandescent light bulbscovered with aluminum foil or any other suitable heatingelement.6.3 Temperature Controller, shall be able to control thetemperature within 60.5C with re
17、spect to the set point.6.4 Temperature-Measuring Device, a thermometer or athermocouple which can measure the temperature with anaccuracy better than 0.5C.6.5 Timer, shall have an accuracy of at least 1 % and shallautomatically stop when the specimen fails.6.6 Alignment Jig, as shown in Fig. 1, whic
18、h aligns the gripsand the specimen when the specimen is being tightened in thegrips.Alignment jigs which produce the same function may beused.6.7 Notching Machine , for notching the specimen is shownin Fig. 2 or other machines which produce the same resultsmay be used. The notching machine presses a
19、 razor blade intothe specimen at a speed less than 0.25 mm/min. The depth ofthe notch is controlled within 60.01 mm. The machine isdesigned so that the main notch and the side notches will becoplanar and the plane of the notching is perpendicular to thetensile axis of the specimen. The thickness of
20、the razor blade isapproximately 0.2 mm.7. Precautions7.1 The load shall be carefully added to avoid shocking thespecimen. When the specimen is inserted in the grips, bendingand twisting shall be avoided in order to prevent the prematureactivation of the notch. Avoid exposure to fluids such asdeterge
21、nts.8. Test Specimens8.1 Specimens are machined from a compression moldedplaque of the polyethylene material.8.2 Specimen GeometryA representative geometry forcompression molded plaque specimens is shown in Fig. 3.8.3 Dimensional Requirements:8.3.1 The side groove shall be 1.0 6 0.10 mm for all plaq
22、uethicknesses.8.3.2 The overall length is not critical except that thedistance between the notch and the end of a grip should bemore than 10 mm. Thicker specimens should have a greateroverall length so that the gripped area will be greater in orderto avoid slippage in the grip.8.4 Preparation of Com
23、pression Molded Plaques8.4.1 Polyethylene resins shall be evaluated by usingspecimens that are machined from compression moldedplaques using Practice D4703, except for the following proce-dures. After the resin is heated to 140 to 160C, apply andremove the pressure three times. Increase the temperat
24、ure to170 to 190C for 10 to 15 min without pressure. Then applyand remove the pressure three times. The specific temperaturesthat are used depend on the melt index of the resin, that is, ahigher temperature for a lower melt index. The purpose ofapplying and removing the pressure is to eliminate void
25、s. Turnoff the heat and apply pressure. The time to cool between 130and 90C shall be greater than 80 min. Alternatively, the timeto cool from the molding temperature to about room tempera-ture shall be greater than 5 h. During cooling the pressure isallowed to decrease naturally.8.5 Specimen Notchin
26、gThe specimen has two types ofnotches, the main notch and two side notches. The side notchesFIG. 1 Alignment JigFIG. 2 Notching MachineF1473 132are usually referred to as “side grooves.” The depth require-ments for these notches are given in Table 1. The main notchis produced by pressing a razor bla
27、de into the specimen at aspeed of less than 0.25 mm/min. A fresh razor blade shall notbe used for more than three specimens and shall be used withinone day. The rate of notching for the side grooves is notimportant. It is important to make the side grooves coplanarwith the main notch. Specimens shal
28、l be notched at roomtemperature.9. Conditioning9.1 Unless otherwise specified, hold the test specimens forat least1hatthetest temperature prior to loading. The lengthof time between notching and testing is not important.10. Procedure10.1 Calculation of Test Load:10.1.1 Calculate the test load, P, as
29、 follows:P 5 3 w 3 t (1)where: = stress,w = specimen width, andt = specimen thickness.The variables w and t are based on the unnotched crosssection.10.1.2 If has the units of megapascals and w and t are inmillimetres, and A is in square millimetres, then P has the unitsof Newtons. To convert Newtons
30、 to pounds, multiply by 0.225.If a lever-loaded machine is used, divide P by the lever armratio. The load on the specimen shall be 60.5 % of thecalculated load.10.2 Gripping the SpecimenUsing an alignment jig (Fig.1), center the specimen in the grips so that the axis of thespecimen is aligned with t
31、he grips. When the grips aretightened, it is important not to activate the notch by bendingor twisting the specimen. The ends of the grips shall be at least10 mm from the notch.10.3 Loading the SpecimenWhen the specimen in thegrips is removed from the alignment jig and transferred to thetesting mach
32、ine, take care that the notch is not activated bybending the specimen. Apply the load after the specimen hasbeen held for at least1hatthetest temperature.Apply the loadgradually within a period of about 5 to 10 s without any impacton the specimen.10.4 Temperature MeasurementPlace the thermocouple or
33、thermometer near the notched part of the specimen. Periodi-cally record the temperature with a frequency that depends onthe length of the test.Legend:Arrows designate direction of tensile stress.t = thickness.All dimensions are in millimetres.FIG. 3 Representative Geometry for Compression-Molded Spe
34、cimenTABLE 1 Notch Depth as a Function of Specimen ThicknessAThis table is based on the stress intensity being the same for allthicknesses.Thickness, mm Notch Depth, mm4.00 1.905.00 2.286.00 2.507.00 2.808.00 3.099.00 3.3010.00 3.5011.00 3.7012.00 3.9013.00 4.1814.00 4.3915.00 4.4816.00 4.6517.00 4.
35、8818.00 4.9519.00 5.0920.00 5.20AFor an intermediate thickness, linearly interpolate to obtain the notch depth. Thenotch depth in the specimen shall be within 0.05 mm of the interpolated value.F1473 13310.5 When testing is stopped before failure or when thespecimen fails, record the time on test, or
36、 the time to failure.Failure occurs when the two halves of the specimen separatecompletely or extensive deformation occurs in the remainingligament.11. Report11.1 Compression-molded test specimens shall be identifiedby the polyethylene material source (resin manufacturer orother source) and lot numb
37、er.11.2 Stress based on the unnotched area.11.3 Depth of main notch and side grooves.11.4 Calculated load and cross-sectional dimensions of thespecimen.11.5 Test temperature.11.6 Time on test or time to failure.11.7 Date and time for the beginning and ending of the test.12. Precision and Bias12.1 Pr
38、ecisionA round robin was conducted with sevenlaboratories and used three resins from different producers. Thestandard deviation of the average values within laboratories is616 %. The standard deviation of the average values betweenlaboratories is 626 %.12.2 BiasNo statement on bias can be made becau
39、se thereis no established reference value. The test method originated atthe University of Pennsylvania. If the test results from abouteight years of testing at the University of Pennsylvania can beused as reference values, then there is no bias in the resultsfrom the different laboratories with resp
40、ect to the results at theUniversity of Pennsylvania. If the test results from the Univer-sity of Pennsylvania can be used as a reference, then there is nobias for the round robin starting with pellets.413. Keywords13.1 fracture; notch testing; pipes; polyethylene; resin; slowcrack growthANNEX(Mandat
41、ory Information)A1. MEASUREMENT OF SPECIMEN THICKNESS DIMENSIONA1.1 ScopeA1.1.1 The following procedures for measurement shall beused when required by the standard for the product beingtested. These requirements are in addition to those in the mainbody of this test method.A1.2 Referenced DocumentsA1
42、.2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingA1.3 ConditioningA1.3.1 Conditioning Temperature and HumidityCondition the test specimens in accordance with Practice D618Procedure A without regard for humidity unless otherwisespecified by contract or when required by the stan
43、dard for theproduct being tested.A1.4 ApparatusA1.4.1 The following apparatus shall be usedFlat-AnvilMicrometer with an accuracy of at least 6 0.001 in. (6 0.025mm).A1.5 DimensioningA1.5.1 Measure the thickness of each specimen prior tonotching to the nearest 0.001 in. (0.025 mm) at the center ofeac
44、h specimen.A1.5.2 If the thickness dimension has a required value in thestandard for the product being tested, then report the thicknessto the same decimal place required by that standard.A1.5.3 If the thickness dimension has a required precisionin the standard for the product being tested, then rep
45、ort theprecision of the apparatus used for measurement.4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:F17-1043. This report is based on around robin of seven laboratories starting with pellets.F1473 134APPENDIX(Nonmandatory Inf
46、ormation)X1. TESTING SPECIMENS FROM PIPEX1.1 ScopeTest Method F1473 has been used to measurethe slow crack growth resistance of specimens from pipe.X1.1.1 Test results are affected by size, specimen geometry,molecular orientation, and other processing effects.X1.1.2 Extrusion generally aligns polyet
47、hylene moleculesparallel to the extrusion direction. Notching perpendicular tothe extrusion direction (Fig. X1.1(a) generally gives higherresults than notching parallel to the extrusion direction (Fig.X1.1(b).X1.1.3 Values obtained from tests of specimens cut frompipe can vary significantly from val
48、ues obtained from tests ofspecimens machined from a compression molded plaque of theresin.X1.2 Significance and UseTest results may be useful forresearch, or for comparison or evaluation of resin or processingeffects on slow crack growth resistance.X1.2.1 While the resin is the primary factor in slo
49、w crackgrowth resistance, when tests are conducted on specimens frompipe, pipe size, pipe wall thickness, extrusion equipment, andprocessing can affect test results. These influences can beaddressed by consistency and uniformity in preparing, loading,and notching specimens. This is especially important whentesting is for the purpose of evaluation or comparison.NOTE X1.1Many combinations of different types of extrusionequipment, tooling, and processing conditions are used to extrude poly-ethylene pipe. Differences in extrusion equipment, tooling
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