1、Designation: D348 13Standard Test Methods forRigid Tubes Used for Electrical Insulation1This standard is issued under the fixed designation D348; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number i
2、n parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope*1.1 These test methods cover the testing of rigid tubes used
3、in electrical insulation. These tubes include many types madefrom fibrous sheets of basic materials, such as cellulose, glass,or nylon, in the form of paper, woven fabrics, or mats, bondedtogether by natural or synthetic resins or by adhesives. Suchtubes include vulcanized fiber and thermosetting la
4、minates, aswell as tubes made from cast, molded, or extruded natural orsynthetic resins, with or without fillers or reinforcing materials.1.2 Tubes tested by these test methods are most commonlycircular in cross section; however, noncircular shapes are alsoin commercial use. To the extent that the i
5、ndividual methodsare compatible with a particular noncircular shape, these testmethods are applicable to these other shapes. For tests onnoncircular tubes, appropriate comments shall be included inthe test report, including details of orientation of test specimenswith respect to the cross section of
6、 the tube.1.3 The procedures appear in the following sections:Procedure SectionsASTM TestMethodReferenceCompressive Strength (Axial and Diametral) 12 to 17 E4Conditioning. 4 .Density 20 to 24 .Dielectric Strength 25 to 32 D149Dimensional Measurements 5 D668Dissipation Factor and Permittivity 33 to 3
7、5 D150Tensile Strength 6 to 11 E4Water Absorption 18 to 19 D5701.4 The values stated in inch-pound units are to be regardedas the standard. SI units in parentheses are for informationonly.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is
8、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. For a specifichazard statement, see 27.1.1.2. Referenced Documents2.1 ASTM Standards:2D149 Test Method for Dielectric Breakdow
9、n Voltage andDielectric Strength of Solid Electrical Insulating Materialsat Commercial Power FrequenciesD150 Test Methods for AC Loss Characteristics and Permit-tivity (Dielectric Constant) of Solid Electrical InsulationD570 Test Method for Water Absorption of PlasticsD668 Test Methods of Measuring
10、Dimensions of Rigid Rodsand Tubes Used for Electrical InsulationD1711 Terminology Relating to Electrical InsulationE4 Practices for Force Verification of Testing Machines3. Terminology3.1 DefinitionsFor definitions of terms used in these testmethods, refer to Terminology D1711.4. Conditioning4.1 In
11、order to eliminate the effects of previous history ofhumidity exposure and to obtain reproducible results (Note 1),the test specimens in all cases of dispute, shall be given aconditioning treatment for physical tests as follows:4.1.1 Tensile Strength, Compressive Strength (Axial andDiametral), and D
12、ensityCondition the machined specimensprior to test by drying in an air-circulating oven for 48 h at 506 3 C, followed by cooling to room temperature in adesiccator. In either case, all specimens shall be tested at roomtemperature maintained at 23 6 2 C, 50 % relative humidity.NOTE 1The following ar
13、e potential reasons to undertake conditioningof specimens: (a) for the purpose of bringing the material into equilibriumwith standard laboratory atmospheric conditions of 23 C and 50 %relative humidity; (b) simply to obtain reproducible results, irrespective ofprevious history of exposure; or (c) to
14、 subject the material to abnormalconditions of temperature or humidity in order to predict its servicebehavior.1These test methods are under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and are the direct responsibility ofSubcommittee D09.07 on Flexible and
15、 Rigid Insulating Materials.Current edition approved Nov. 1, 2013. Published November 2013. Originallyapproved in 1932. Last previous edition approved in 2007 as D348 07. DOI:10.1520/D0348-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at ser
16、viceastm.org. For Annual Book of ASTMStandards 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. Unit
17、ed States1The conditions given here to obtain reproducible results will givephysical values which could be somewhat higher or somewhat lower thanvalues under equilibrium at normal conditions, depending upon theparticular material and test. To ensure substantial equilibrium undernormal conditions of
18、humidity and temperature, however, will requirefrom 20 to 100 days or more depending upon thickness and type ofmaterial and its previous history. Consequently, conditioning for repro-ducibility must of necessity be used for general purchase specificationsand product control tests.4.1.2 Conditioning
19、of specimens for electrical tests is alsonecessary to obtain consistent results. In order to securecomparative results, specimens shall be conditioned at thesame temperature and humidity.5. Dimensional Measurements5.1 Dimensional measurements of tube shall be made inaccordance with Test Methods D668
20、.TENSILE STRENGTH6. Significance and Use6.1 Tension tests, properly interpreted, provide informationwith regard to the tensile properties of rigid tubing, whenemployed under conditions approximating those under whichthe tests are made. It is possible that the tensile strength valueswill vary with th
21、e size of the tube and with the temperature andatmospheric conditions. Tension tests provide data potentiallyuseful for research and development and for engineeringdesign, and quality control purposes.7. Apparatus7.1 Any universal testing machine is acceptable for useprovided it is accurate to 1 % o
22、f the lowest breaking load to beapplied. Jaws that tighten under load, such as wedge-grip jaws,shall be used with the specimen properly aligned.7.2 The machine shall be verified in accordance withPractices E4.8. Test Specimens8.1 The test specimens shall be as shown in Fig. 1. Thelength, L, shall be
23、 as shown in Table 1. A groove shall bemachined around the outside of the specimen at the center of itslength so that the wall section after machining shall be 60 % ofthe original nominal wall thickness. This groove shall consistof a straight section 2.25 in. (57 mm) in length with a radius of3 in.
24、(76 mm) at each end joining it to the outside diameter.Steel or brass plugs having diameters such that they will fitsnugly inside the tube, and having a length equal to the full jawlength plus 1 in. (25 mm) shall be placed in the ends of thespecimen to prevent crushing. They can be located in the tu
25、beconveniently by separating and supporting them on a threadedmetal rod. Details of plugs and test assembly are shown in Fig.1.9. Procedure9.1 Test five specimens. Measure the average inside andoutside diameters, determined from at least two measurements90 apart, at the groove to the nearest 0.001 i
26、n. (0.03 mm) andcalculate the cross-sectional area from these dimensions. As-semble the metal plugs with the tube as shown in Fig. 1. Graspthis assembly in the V-notched jaws of the testing machine.9.2 Speed of TestingThe crosshead speed of the testingmachine shall be such that the load can be accur
27、ately weighed,but shall not exceed 0.05 in./min (1.3 mm/min) when themachine is running idle.10. Report10.1 Report the following information:10.1.1 The average inside and outside diameters of thespecimen expressed to the nearest 0.001 in. (0.03 mm), eachdetermined from at least two measurements 90 a
28、part,10.1.2 The average outside diameter of the reduced sectionexpressed to the nearest 0.001 in. (0.03 mm),10.1.3 The full wall thickness of the specimen,10.1.4 The net area of the test section, in.2or mm2,10.1.5 The breaking load of each specimen, lbf or N,10.1.6 The tensile strength of each speci
29、men, psi or MPa,and10.1.7 The room temperature.11. Precision and Bias11.1 PrecisionThis test method has been in use for manyyears, but no information has been presented to ASTM uponwhich to base a statement of precision. No activity has beenplanned to develop such information.11.2 BiasThis test meth
30、od has no bias because the valuefor tensile strength is determined solely in terms of this testmethod.FIG. 1 Diagram Showing Location of Tube Tension Test Speci-men in Testing MachineD348 132COMPRESSIVE STRENGTH (AXIAL ANDDIAMETRAL)12. Significance and Use12.1 Compressive tests, properly interpreted
31、, provide infor-mation with regard to the compressive properties of rigidtubing when employed under conditions approximating thoseunder which the tests are made. Compressive strength valueshave the potential to vary with the size of the tube, and withtemperature and atmospheric conditions. Compressi
32、on testsprovide data which could be useful for research anddevelopment, engineering design, quality control, and accep-tance or rejection under specifications.13. Apparatus13.1 Any universal testing machine is acceptable for useprovided it is accurate to 1 % of the lowest breaking load to beapplied,
33、 in accordance with Practices E4. One end of thespecimen for axial loading or the side of the specimen fordiametral loading shall bear upon an accurately centeredspherical bearing block, located whenever practicable at thetop. The metal bearing plates shall be directly in contact withthe test specim
34、en.NOTE 2Off-center loading of the diametral compressive test has thepotential to cause the tube to push to one side.14. Test Specimens14.1 Unless otherwise specified, the material shall be testedin the as-received condition.14.2 Test specimens shall consist of 1-in. (25-mm) longsections of the tubi
35、ng.14.3 When cutting the test specimens for the axial tests, takecare to have the ends of the specimens cut accurately andsmoothly at right angles to the axis of the tube.14.4 If the tubing is too large in diameter, or is too high inbreaking strength to be tested with the available testingequipment,
36、 it is acceptable to substitute a segment of the testspecimen specified in 14.2 and 14.3 for axial tests. Suchsegments shall not be used for testing tubes less than 2 in. (51mm) in outside diameter. Unless otherwise specified, usesegments having a circumferential length of 2 in. (51 mm).15. Procedur
37、e15.1 Test five specimens axially, with the load appliedperpendicular to the faces or ends of the specimen, or test fivespecimens diametrically, with the load applied perpendicular tothe tangent at point of application.15.2 Discard specimens that break at some obvious fortu-itous flaw and retest, un
38、less such flaws constitute a variable, theeffect of which it is desired to study.15.3 Retain results (on specimens) that deviate markedlyfrom the mean value of all tests unless 15.2 applies. In this caserun additional tests, the exact number to be fixed by the desired(statistical) significance level
39、.15.4 Speed of TestingThe crosshead speed of the testingmachine shall be 0.050 in./min (1.3 mm/min) when themachine is running idle. In cases of diametral loading ofcertain tubing, especially the larger diameter tubes, it will benecessary, in some cases, to operate the crosshead at a speed ofloading
40、 greater than 0.050 in./min. In this event the speed shallbe stated in the report.16. Report16.1 Report the following information:16.1.1 The average inside and outside diameters of thespecimen expressed to the nearest 0.001 in. (0.03 mm), eachdetermined from at least two measurements 90 apart,16.1.2
41、 The average wall thickness of the specimen ex-pressed to the nearest 0.001 in. (0.03 mm),16.1.3 The segment length, if segmental specimens are usedfor axial tests,16.1.4 The direction of application of the load,16.1.5 The load on each specimen at the first sign of rupture,lbf or N, and16.1.6 The ul
42、timate compressive strength in force per unitarea for axial loading and force for diametral loading.17. Precision and Bias17.1 PrecisionSame as 11.1.17.2 BiasSame as 11.2 except for the property of com-pressive strength.TABLE 1 Dimensions of Tension Specimens, in. (mm)Nominal Wall Thickness Length o
43、f Radial Sections, 2R.S.Total Calculated Minimum Length ofSpecimenStandard Length, L, of Specimen tobe Used for 312-in. (89-mm) JawsA132 (0.79) 0.547 (13.9) 13.80 (350.0) 15 (381.0)364 (1.2) 0.670 (17.0) 13.92 (354.0) 15 (381.0)116 (1.6) 0.773 (19.6) 14.02 (356.0) 15 (381.0)332 (2.4) 0.946 (24.0) 14
44、.20 (361.0) 15 (381.0)18 (3.2) 1.091 (27.7) 14.34 (364.0) 15 (381.0)316 (4.8) 1.333 (33.9) 14.58 (370.0) 15 (381.0)14 (6.4) 1.536 (39.0) 14.79 (376.0) 15.75 (400.0)516 (7.9) 1.714 (43.5) 14.96 (380.0) 15.75 (400.0)38 (9.5) 1.873 (47.6) 15.12 (384.0) 15.75 (400.0)716 (11.1) 2.019 (51.3) 15.27 (388.0)
45、 15.75 (400.0)12 (12.7) 2.154 (54.7) 15.40 (391.0) 16.5 (419.0)AFor other jaws greater than 312 in. (89 mm), the standard length shall be increased by twice the length of the jaws minus 7 in. (178 mm). The standard length permitsa slippage of approximately14 to12 in. (6.4 to 12.7 mm) in each jaw whi
46、le maintaining maximum length of jaw grip.D348 133WATER ABSORPTION18. Significance and Use18.1 The moisture content of a rigid tube has a definiteinfluence on the electrical properties, as well as on mechanicalstrength, dimensional stability, and appearance. The effectupon these properties of change
47、s in moisture content, due towater absorption, depends largely upon the inherent propertiesof the rigid tube. It is possible that the rate of water absorptionwill be widely different through each edge and surface.Awaterabsorption determination will provide data useful for researchand development, en
48、gineering design, quality control, andacceptance or rejection under specifications.19. Procedure19.1 Determine and report the rate of water absorption inaccordance with Test Method D570, immersing specimens for24 h in distilled water at 23 C after preliminary conditioningfor1hat105C.19.2 For some ty
49、pes of materials, or for special applications,it is desirable to employ longer periods of water immersion inorder to evaluate performance. In these cases, the report shallindicate the exact conditioning procedure.DENSITY20. Significance and Use20.1 A density measurement will provide data useful forresearch and development, engineering design, quality control,and acceptance or rejection under specifications.21. Test Specimens21.1 Use any suitable size specimen. The specimen 1 in. (25mm) in length used for the water absorption test (Sections 18and 19
