1、Designation: F1473 11An 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 o
2、foriginal 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-yle
3、ne 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 fa
4、ilure 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 tos
5、pecimens 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 standar
6、d 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 for Abbreviated Terms Relating toPlasticsD4703 Practice for Compression Molding ThermoplasticMaterials into Tes
7、t 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 e
8、xhibits 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 Spec
9、imens 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 ti
10、me 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 sharp
11、 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 t
12、est 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 und
13、er the jurisdiction of ASTM Committee F17 on PlasticPiping Systems and is the direct responsibility of Subcommittee F17.40 on TestMethods.Current edition approved May 1, 2011. Published May 2011. Originallyapproved in 1997. Last previous edition approved in 2007 as F1473 07. DOI:10.1520/F1473-11.2Lu
14、, 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 ASTMStand
15、ards volume information, 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.bending. The grips shall be se
16、rrated 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 respe
17、ct 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, which a
18、ligns 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 r
19、azor 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 th
20、e 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 asdetergent
21、s.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 plaque
22、thicknesses.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 Compr
23、ession Molded PlaquesPolyethylene resins shall be evaluated by using specimens thatare machined from compression molded plaques using PracticeD4703, except for the following procedures. After the resin isheated to 140 to 160C, apply and remove the pressure threetimes. Increase the temperature to 170
24、 to 190C for 10 to 15min without pressure. Then apply and remove the pressurethree times. The specific temperatures that are used depend onthe melt index of the resin, that is, a higher temperature for alower melt index. The purpose of applying and removing thepressure is to eliminate voids. Turn of
25、f the heat and applypressure. The time to cool between 130 and 90C shall begreater than 80 min. Alternatively, the time to cool from themolding temperature to about room temperature shall begreater than 5 h. During cooling the pressure is allowed todecrease naturally.8.5 Specimen NotchingThe specime
26、n has two types ofnotches, the main notch and two side notches. The side notchesare 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 aFIG. 1 Alignment JigFIG. 2 Notching Mac
27、hineF1473 112speed 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
28、 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 follows:P 5
29、s3w 3 t (1)where:s = stress,w = specimen width, andt = specimen thickness.The variables w and t are based on the unnotched crosssection.10.1.2 If s 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
30、, 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 the grips.
31、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 machine, take
32、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 thermocoupleor thermomete
33、r near the notched part of the specimen. Peri-odically record the temperature with a frequency that dependson the length of the test.10.5 When testing is stopped before failure or when thespecimen fails, record the time on test, or the time to failure.Failure occurs when the two halves of the specim
34、en separatecompletely or extensive deformation occurs in the remainingligament.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 a Function of Specimen ThicknessAThi
35、s 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 5.20AFor an intermediate thickness,
36、linearly interpolate to obtain the notch depth.The notch depth in the specimen shall be within6 0.05 mm of the interpolatedvalue.F1473 11311. Report11.1 Compression-molded test specimens shall be identifiedby the polyethylene material source (resin manufacturer orother source) and lot number.11.2 St
37、ress 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 PrecisionA r
38、ound 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 because thereis
39、 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 respect to the
40、 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 growthAPPENDIX(Nonmandatory
41、Information)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 pol
42、yethylene 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
43、values 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
44、slow 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 imp
45、ortant whentesting is for the purpose of evaluation or comparison.NOTE X1.1Many combinations of different types of extrusion equip-ment, tooling, and processing conditions are used to extrude polyethylenepipe. Differences in extrusion equipment, tooling, and processing condi-tions are known to affec
46、t the results when specimens cut from pipe aretested in accordance with this test method.X1.3 Specimen Preparation:X1.3.1 When a section of the pipe wall is to be tested, cutsections or strips from the pipe. Sections or strips should be cut4 to 6 mm wider than the required specimen width, thendeburr
47、ed, and machined to the specimen width.X1.3.2 Fig. X1.1(a) illustrates a specimen cut from 4 in. IPSSDR 11 pipe where the load direction axis is parallel to theextrusion direction and the main notch is perpendicular to theextrusion direction. Fig. X1.1(b) illustrates a specimen from 4in. IPS SDR 11
48、pipe where the load direction axis is perpen-dicular to the extrusion direction axis (parallel to the hoopdirection) and the main notch is parallel to the extrusiondirection. Fig. X1.1(c) illustrates a specimen for pipe diametersless than 25 mm.X1.3.3 Sawing, cutting, machining, or milling operation
49、sshould be carefully performed to avoid overheating the speci-men.X1.3.4 RemodelingPipe may be remolded by cuttingchips from the pipe, then preparing a compression moldedplaque in accordance with 8.4 or by flattening a section of pipe,then heating, pressing, and cooling the flattened section inaccordance with 8.4. When remolded, most extrusion process-ing effects will be removed, therefore, the results obtained fromremolded plaques will differ from the results obtained fromas-extruded pipe.X1.4 Specimen Dimensions:X1.4.1 The overall length of the specim
