1、Designation: F 725 03e1An American National StandardStandard Practice forDrafting Impact Test Requirements In Thermoplastic PipeAnd Fittings Standards1This standard is issued under the fixed designation F 725; the number immediately following the designation indicates the year oforiginal adoption or
2、, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEKeywords editorially added in November 2003.1. Scope1.1 This practice describes a pr
3、ocedure for setting up impacttest requirements on the basis of test data obtained by TestMethod D 2444.1.2 This practice is applicable to thermoplastic pipe andfittings.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility o
4、f the user of this standard 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:D 2444 Test Method for Impact Resistance of Thermoplas-tic Pipe and Fittings by Means of a Tup (Falling
5、Weight)23. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 binomial probability equationthe equation that de-fines the chance for exactly r specimens to pass, when n aretested, given p, the chance that a single specimen chosen atrandom will pass. It is expressed as follows:rPn5n!
6、r!nr!pr1 2 p!n2r(1)NOTE 1The factorial of zero is one.3.1.2 binomial testa test that has only two possible results(for example, pass or fail, heads or tails, true or false).3.1.3 mean strengththe average strength of the totalpopulation (see Note 2).3.1.4 OC curve (operating characteristic curve)a gr
7、aphthat illustrates the chance of success or failure when a givenspecification format is employed, given any quality level from0 to 1 (0 to 100 % passing in the lot from which test specimensare selected).3.1.5 probability graph papercommercially availablegraph paper that provides straight-line plots
8、 when the distribu-tion of attributes is normal. For a discussion on the use ofproability graph paper, see Test Method D 2444 Appendix X2.3.1.6 specification formatthe rules set forth by the testrequirement, including the number of specimens to be testedand the minimum acceptable number of passes.3.
9、1.7 standard deviationa statistical term that relates tothe size of the expected variation in test results.NOTE 2The terms “mean,” “normal distribution,” and “standarddeviation” are dealt with in elementary statistics textbooks.4. Summary of Practice4.1 Round-robin tests of representative pipe and f
10、ittingsspecimens are performed to identify the energy levels at which90 % or more of the specimens in acceptable lots will pass. Apreferred test format is listed. The B-tup and the V-blockholder, and room-temperature conditioning and tests are pre-ferred choices.5. Significance and Use5.1 This pract
11、ice is used for drafting impact test specifica-tion requirements, and it presupposes no special familiaritywith statistical methods. It provides for specification valuesthat will pass acceptable lots with a high degree of certainty.The impact test requirement is intended to discriminate be-tween acc
12、eptable materials and manufacturing methods andthose which are not; it is not a simulated service test.6. Procedure6.1 Test thermoplastic pipe or fittings specimens in accor-dance with Test Method D 2444, and plot the test results onprobability graph paper.1This practice is under the jurisdiction of
13、 ASTM Committee F17 on PlasticPiping Systems and is the direct responsibility of Subcommittee F17.40 on TestMethods.Current edition approved April 10, 2003. Published May 2003. Originallyapproved in 1981. Last previous edition approved in 1996 as F 725 89 (1996).2Annual Book of ASTM Standards, Vol 0
14、8.04.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.2 It will be clear, from the probability paper plot, that theenergy level where 98 % or 99 % of all specimens would passwill be low. On the one hand, when the test format require
15、s thatfive of five, or six of six, or nine or ten of ten tested shall pass,or the lot rejected, then the specified energy levels mustcorrespond to these levels (see Fig. 1, the operating character-istic (OC) curve for the “nine or ten of ten” test format). On theother hand, five of five, six of six,
16、 and nine or ten of ten testsat low energy levels will not screen marginal or poor lotseffectively. (See Fig. 1 again).6.3 A format which will accept reliably when 90 % or moreof the specimens in acceptable lots would pass, and rejectreliably when 60 % or fewer would pass, is as follows:6.3.1 “X.X T
17、est ten specimens. When nine or ten pass,accept the lot. When six or fewer pass, reject the lot. Whenseven or eight pass, test ten additional specimens. When 17 ormore of 20 pass, accept the lot. When 13 or fewer of 20 pass,reject the lot. When 14, 15, or 16 pass, test 20 additionalspecimens. When 3
18、2 or more of 40 pass, accept the lot. When31 or fewer pass, reject the lot.”6.3.2 The OC curve for this format is illustrated in Fig. 2.6.4 Specimen LengthThe pipe specimen length should be6 in. (150 mm) 614 in. (6mm).6.5 Choice of Tup and HolderThe B tup is preferred. Itprovides a good compromise b
19、etween energy concentration inthe specimen (and therefore reduced test energy levels), andresistance to damage in service. The V-block holder is pre-ferred for pipe specimens; it provides for greater energyconcentration, and for failures in a range of thin-walledspecimens which would merely flatten
20、on the flat-plate holder.6.6 Test ConditionsRoom-temperature tests are preferred.They can be performed by the manufacturer on a timely basis,so that the size of questionable or defective inventories isminimized. Binomial tests are relatively crude, unless largenumbers of specimens are subjected to t
21、est. The expense andinconvenience of low-temperature conditioning render it a poorchoice (study Fig. 1 together with a data plot performed inaccordance with Test Method D 2444 to fully grasp the meritsof this statement).7. Multiple-Product Standards7.1 Many thermoplastic pipe and fittings specificat
22、ions listlarge numbers of products. Test Method D 2444 requires that atleast 100 test specimens shall be employed for each single testrun in order that the impact properties can be measured withuseful accuracy. The cost of round-robin tests on each size ofthe products in the standard may approach or
23、 exceed the valueof the information to be obtained.7.2 Testing costs can be significantly reduced by performingpreliminary tests on the largest sizes listed, to determinewhether or not a cut-off point exists above which all specimenswill pass at an energy level of 300 ftlbf (407 J) (ordinarily thehi
24、ghest test energy level listed in a thermoplastic pipe orfittings impact test requirement).7.2.1 Following these tests, a limited number of represen-tative sizes can be selected, and round-robin testing performed.7.2.2 The results of these tests are analyzed. List the energylevels where the failure
25、level was 10 % for each size tested, anddivide the energy levels by the specimen volumes in cubicinches. Plot the results against the specimen outside diameters,and label the points if it is a multiple SDR specification. In aspecification which included 25 sizes of pipe, and seven SDRseries, for exa
26、mple, three sizes each of three different SDRseries of pipe might be tested preliminarily. The points for eachSDR series would be connected with a curve, and from theplots the appropriate trial energy levels for six untested sizesand SDRs calculated.7.3 One hundred test specimens of each of the six
27、untestedsizes would be prepared, and subjected to test. If 85 to 95specimens in each lot passed, the degree of correlation wouldbe good.7.4 Depending upon the degree of correlation obtained,proceed to calculate the test energy levels for each untestedsize, factor all energy levels back by an appropr
28、iate amount anddraft the test specification proposal, or else conduct additionaltests.7.5 The tup weight and style listed in the proposal should bethe same as that used for the preliminary tests.FIG. 1 O.C. Curve for Nine or Ten of TenFIG. 2 O.C. Curve for Section 6.3F72503e128. Special Consideratio
29、ns8.1 FittingsThe flat-plate holder is employed for fittingsimpact tests. Shims may be required, depending on fittingsconfiguration. Fittings should be impacted on a horizontalsurface, as close to the center of mass as is practical. Ordi-narily, the specification will require that half the fittings
30、beimpacted on one side, and half on the other.8.2 Thin-Walled PipeThin-walled pipe may undergo com-plete closure without failure (particularly if the flat-plate holderis employed). Impact testing may still serve a useful purpose,however, since the energy levels required to flatten acceptablespecimen
31、s may result in failure of improperly manufacturedspecimens.8.3 Yard-Aged PipeThe impact test is not ordinarilyspecified on yard-aged pipe since many thermoplastic pipematerials are subject to reduction in impact strength as theresult of exposure to ultraviolet rays.9. Keywords9.1 drafting impact; d
32、rafting impact requirements; impact;plastic pipe; plastic tubing; thermoplastic pipe; thermoplastictubingAPPENDIXES(Nonmandatory Information)X1. THE OPERATING CHARACTERISTIC (OC) CURVEX1.1 PurposeThe OC curve gives and accurate picture ofthe impact-test realtionship between a particular test samplea
33、nd the total population. Specifically, the curve provides thechance of success of a sample when given testing regimen isemployed. This relationship is ordinarily too complex to bearrived at on the basis of guesswork.X1.2 Constructing the OC CurveStart by listing thenumber of ways in which success ca
34、n be achieved (Forexample, in a “7 or more out of 10” specification format, the lotis accepted when 7, 8, 9, or 10 out of 10 specimens pass.) Usethe binomial probability equation to obtain an expression forthe chance that each of these events will occur. (See example.)Evaluate the chances, substitut
35、ing values for p ranging from 0to 1. Sum the chances of success, for each chosen value of p.Plot the results (chance of success, against p) to obtain thecurve.Example: OC Curve for a “7 or more out of 10” specificationformat.The chance that 7 out of 10 will pass equals,10!7!3!p71 2 p!3or 120 p71 2 p
36、!3(X1.1)Substitute values ranging from 0.1 to 0.9 for p, and tabulatethe results:p7P100.10.0000.20.0010.30.0090.40.0420.50.1170.60.2150.70.2670.80.2010.90.057In like manner, tabulate the chance that 8, 9, or 10 will pass.p 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9Odds of: 7 0.000 0.001 0.009 0.042 0.117 0
37、.215 0.267 0.201 0.0578 0.000 0.000 0.001 0.011 0.044 0.121 0.233 0.302 0.1949 0.000 0.000 0.000 0.002 0.010 0.040 0.121 0.268 0.38710 0.000 0.000 0.000 0.000 0.001 0.006 0.028 0.107 0.349Totals: 0.000 0.001 0.010 0.055 0.172 0.382 0.649 0.878 0.987When the totals are plotted against p, the OC curve
38、 results.Note that calculation increments smaller than 0.1 will providemore accuracy. A spreadsheet is useful in evaluating thebinomial probability equation.F72503e13X2. MEASURING CONFORMANCE TO EXISTING TEST REQUIREMENTSX2.1 A variety of impact test specification formats are incurrent use. The info
39、rmation provided in the OC curve for eachof them can be expressed in mathematical terms. To identifythe chance that a given manufacturing process will pass the testrequirement, select at least 100 test specimens, and subjectthem to the impact test listed. Express the decimal percentpassing as p, and
40、 substitute in the appropriate equation:For a 5 out of 5 test requirement, Psuccess= p5For a 6 out of 6 test requirement, Psuccess= p6For a 10 out of 10 test requirement, Psuccess= p10For a 12 out of 12 test requirement, Psuccess= p12Fora5of5or9of10test, Psuccess= p5(1+5p45p5)Fora6of6or11of12test, P
41、success= p6(1+6p56p6)Fora9ormore out of 10 test, Psuccess= p9(109p)Fora7ormore out of 10 test, Psuccess= 120p7 315p8+ 280p984p10For the procedure listed in 6.3, the formula is: 3 225p36(1 p)4+75300p35(1 p)5+ 828 750p34(1 p)6+ 5 728 500p33(1 p)7+ 62 312 400p32(1 p)8+ 570p17(1 p)3+45p18(1 p)2+10p9(1 p
42、)+p10X2.2 The results from a 100-specimen test may notcorrelate accurately with the quality level in the population.The standard error for a 100-specimen test is approximately0.05 (68 % of the time the measured results will not be in errorby more than 0.05, and 95.5 % of the time they will not be in
43、error by more than 0.10). If better accuracy is required thenmore specimens should be tested. The approximate equationfor the standard error is (P (1 P)/N)1/2.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this stand
44、ard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be review
45、ed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible
46、 technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).F72503e14
