ANSI ASTM F1473-2016 Standard Test Method for Notch Tensile Test to Measure the Resistance to Slow Crack Growth of Polyethylene Pipes and Resins.pdf

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1、Designation: F1473 16Standard 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 oforiginal adoption or, in the

2、 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-ylene materials to slow crack gr

3、owth 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 failure andthereby eventually i

4、nduce 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 tospecimens from pipe.1.4 The va

5、lues 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 standard to establish appro-priate s

6、afety 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 Test Specimens, Plaques, or She

7、etsF412 Terminology Relating to Plastic Piping Systems3. Terminology3.1 Definitions are in accordance with Terminology F412.Abbreviations are in accordance with Terminology D1600,unless otherwise indicated.3.2 Definitions:3.2.1 brittle failurea pipe failure mode which exhibits novisible (to the nake

8、d eye) permanent material deformation(stretching, elongation, or necking down) in the area of thebreak (Terminology F412).3.3 Definitions of Terms Specific to This Standard:3.3.1 slow crack growththe slow extension of the crackwith time.4. Summary of Test Method4.1 Specimens are prepared from compre

9、ssion 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 time before failure requirements

10、 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 sharp notch.5.2 The testing time or

11、 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 test shall bespecified.6. Appar

12、atus6.1 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 under the jurisdiction of ASTM Com

13、mittee F17 on PlasticPiping Systems and is the direct responsibility of Subcommittee F17.40 on TestMethods.Current edition approved Aug. 15, 2016. Published August 2016. Originallyapproved in 1997. Last previous edition approved in 2013 as F1473 13. DOI:10.1520/F1473-16.2Lu, X., and Brown, N., “ATes

14、t 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 ASTMStandards volume information, r

15、efer 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 serrated to prevent slippage.

16、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 respect to the set point.6.4 Temp

17、erature-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, which aligns the gripsand the speci

18、men 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 razor blade intothe specimen a

19、t 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 the razor blade isapproximately

20、 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 asdetergents.8. Test Specimens8.1 Specim

21、ens 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 plaquethicknesses.8.3.2 The overall

22、 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 Compression Molded Plaques8.4.1 Po

23、lyethylene 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 temperature to170 to 190C for 10 to 15

24、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 voids. Turnoff the heat and apply p

25、ressure. 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 NotchingThe specimen has two types ofn

26、otches, the main notch and two side notches. The side notchesFIG. 1 Alignment JigFIG. 2 Notching MachineF1473 162are 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 blade into the specimen at aspeed

27、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 shall be notched at roomtemperature

28、.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 follows:P 5 3 w 3 t (1)where:

29、= stress,w = specimen width, andt = specimen thickness.The variables w and t are based on the specimens prior tonotching.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 to pounds, multiply by 0.2

30、25.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 the grips. When the grips ar

31、etightened, 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 machine, take care that the not

32、ch 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 orthermometer near the notche

33、d 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 SpecimenTABLE 1 Notch Depth as

34、 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 4.8818.00 4.9519.00 5.0920.00

35、 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 16310.5 When testing is stopped before failure or when thespecimen fails, record the time on test, or the time to failure.Failur

36、e 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 number.11.2 Stress based on the

37、 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 PrecisionA round robin was co

38、nducted 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 because thereis no established r

39、eference 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 respect to the results at theUn

40、iversity 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(Mandatory Information)A1. MEASURE

41、MENT 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 DocumentsA1.2.1 ASTM Standards:2D618 P

42、ractice 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 standard for theproduct being t

43、ested.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 ofeach specimen.A1.5.2 If the th

44、ickness 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 report theprecision of the app

45、aratus 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 164APPENDIX(Nonmandatory Information)X1. TESTING SPECIM

46、ENS 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 polyethylene moleculesparallel to

47、 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 values obtained from tests ofs

48、pecimens 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 slow crackgrowth resistance, w

49、hen 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, and processingconditions