ASTM B1008-2018 Standard Test Method for Stress-Strain Testing for Overhead Electrical Conductors.pdf

1、Designation: B1008 18Standard Test Method forStress-Strain Testing for Overhead Electrical Conductors1This standard is issued under the fixed designation B1008; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis

2、ion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the measurement of the elasticand short-term creep characteristics of conductors for overheadpower lines

3、.1.2 Stress-strain data from tests performed in accordancewith IEC 61089 are compliant with this standard.1.3 Stress-strain data from prior Aluminum Associationtesting procedures are compliant with this standard.1.4 The values stated in either SI units or inch-pound unitsare to be regarded separatel

4、y as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.5 This standard does not purport to address all of thesafety concerns, if

5、 any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internat

6、ionally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E4 Pract

7、ices for Force Verification of Testing MachinesE83 Practice for Verification and Classification of Exten-someter SystemsE220 Test Method for Calibration of Thermocouples ByComparison Techniques2.2 Aluminum Association Document:3Aluminum Association Guide for Stress-Strain and CreepTesting of Conduct

8、ors, 19992.3 IEC Document:4IEC 61089:1991 Appendix B, Stress-strain Test Method3. Terminology3.1 Definitions:3.1.1 banding clamps, nany of several means for lockingtogether all strands of a conductor or core sample.3.1.2 composite conductor, na conductor made of twodistinct elements, a single wire o

9、r stranded core primarily usedfor reinforcement or support and an outer stranded componentof a second, more conductive material.3.1.3 conductor stress-strain, nelastic and short-termcreep behavior of a conductor.3.1.4 creep, npermanent elongation of a material understress, for a given temperature an

10、d time.3.1.5 elastic strain, nelongation caused by stress that iscompletely recovered when the stress is released.3.1.6 final modulus, na linear relationship between stressand strain after the conductor has experienced its maximumstrain.3.1.7 gauge length (gauge section), nthe distance overwhich the

11、 strain is measured.3.1.8 gauge rod, nthe rigid frame used to set the gaugelength.3.1.9 homogeneous conductor, na conductor made of asingle wire or stranded using strands of the same material.3.1.10 initial modulus, na fitted curve through test datathat describes the expected behavior of the conduct

12、or duringloading.3.1.11 modulus of elasticity (MOE, elastic modulus, E),nthe slope of the linear, elastic portions of the stress-straindata for a conductor or conductor component.1This test method is under the jurisdiction of ASTM Committee B01 onElectrical Conductors and is the direct responsibilit

13、y of Subcommittee B01.02 onMethods of Test and Sampling Procedure.Current edition approved Nov. 1, 2018. Published January 2019. DOI: 10.1520/B1008-18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStan

14、dards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Aluminum Association, 1400 Crystal Dr., Suite 430, Arlington,VA 22202, http:/www.aluminum.org.4Available from International Electrotechnical Commission (IEC), 3, rue deVaremb, 1st Floor, P.O. Bo

15、x 131, CH-1211, Geneva 20, Switzerland, http:/www.iec.ch.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established

16、in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.1.11.1 virtual stress (for composite conductors), nstressin a conductor component multiplied by the area fract

17、ion ofthat component.3.1.12 one-hour creep, npermanent elongation of theconductor sample after holding it for an hour at various stresslevels.3.1.13 one-hour modulus, nsee initial modulus.3.1.14 plastic strain, npermanent deformation after thestress is removed.3.1.15 rated breaking strength (RBS), n

18、a minimum theo-retical tensile value assigned to a conductor calculated from therelevant product specifications.3.1.16 rated tensile strength (RTS), nsee RBS.3.1.17 sample length, noverall length of the conductor,inclusive of the end sections used for gripping.3.1.18 core,ninitial load target, in ps

19、i (MPa), for the corestress-strain test.3.1.19 composite,ninitial load, in psi (MPa), applied dur-ing the composite stress-strain test.3.1.20 strainfractional change in the original length of aconductor.3.1.21 stress, ntension in a conductor or conductorcomponent, divided by the solid area of that c

20、onductor orconductor component.3.1.22 yield, npermanent elongation that occurs at andabove the nominal yield strength of the conductor or conductorcomponent.4. Summary of Test Method4.1 Conductor and, if present, the conductor core are sub-jected to a series of loading and unloading at progressively

21、higher stress levels to determine the elastic and short-timecreep characteristics of composite and homogeneous conduc-tors.5. Significance and Use5.1 To model the mechanical characteristics of overheadelectrical conductor, stress-strain characteristics must be deter-mined. The most accurate method f

22、or determination of thesecharacteristics is a laboratory stress-strain test. These mechani-cal characteristics can then be used to determine the strainresponse of a conductor to mechanical loads, and thus predictthe sag of the conductor. This can then be used to determine therequired installation pa

23、rameters to provide safe clearance andtension for the conductor usage.6. Interferences6.1 Error Due to Ambient Temperature ChangeMagnitudeof the error depends on the ambient temperature profile of thelab and the materials and the relative thermal response timesfor the gauge rod and the sample. Provi

24、ded the laboratory istemperature-controlled per the requirements of this standard,the typical strain measurement error from this source is 5strain-ppm (0.0005 strain%).6.2 Errors in the Tension MeasurementStrain is approxi-mately linear with tension. Therefore the 1 % of readingallowed in the tensio

25、n measurement translates directly to anadditional 1 % of reading error in the strain measurement.6.3 Error in Straightening the Sample Prior to TestErrorfrom slack due to conductor sag may be considered negligibleprovided the conductor is supported as specified in 7.7.6.4 Even with the best possible

26、 test accuracy, users shouldrecognize that there are sag prediction errors due to differencesin test sample properties versus the properties of the conductorfollowing handling and installation. Prudent line designersprovide a safety factor to allow for known uncertainties in sagpredictions, includin

27、g uncertainties in the stress-strain mea-surement and normal variation in the properties of differentconductor lots.7. Apparatus7.1 Acontrolled actuator shall be used to load the conductorin the sequence described in this standard. The actuator may behydraulic, mechanical lead screw, or any other me

28、thod capableof ramping smoothly to a target load. Upon reaching the targetload, any over-shoot shall be less than 1 % of the target load.See Fig. 1.FIG. 1 Elements of the Stress-strain Test ApparatusB1008 1827.2 The frame shall be long enough to test samples withlengths specified in 9.3.7.3 Temperat

29、ure measurements shall be taken of ambient,sample surface and gauge rod.7.4 Strain shall be measured with an accuracy of 60.001strain% (10 strain-ppm). Resolution of the recorded data shallbe 0.00005 strain% (0.5 strain-ppm) or lower.NOTE 1This issue has caused confusion because the measurement(stra

30、in) and the error are both expressed in percent or ppm. To be clear: theallowable error values in this section are absolute error in strain%, andstrain-ppm, and not percent error on the measured value of strain.7.5 Actuator displacement shall be measured using aninstrument meeting the specifications

31、 of 11.4.7.6 Time, tension, strain, actuator position, and all tempera-ture channels must be recorded, as a minimum, at frequency ofonce per second. During hold periods, the frequency can bereduced to once per five minutes.7.7 The sample shall be supported in a straight line with amaximum sag of14 i

32、n. (6 mm) between any two supports. SeeX2.5 for best practices.7.8 The ambient temperature during the test shall be be-tween 15 and 40C, and preferably stable at or near 23C(73F). The ambient temperature shall be stable within 61Cfor the duration of the test.8. Hazards8.1 Standard industrial safety

33、precautions are appropriateduring sample handling and preparation. Coiled samples maywhip unexpectedly, and therefore the ends should be restrained.Eye protection is recommended during all phases of samplepreparation and testing.8.2 Chemical and respiratory hazards may exist when han-dling potting c

34、ompounds for cast resin end fittings.8.3 Sample rupture is possible during loading tests.Therefore, safety cages for the testing machine are recom-mended.9. Sampling, Test Specimens, and Test Units9.1 Conductor Samples:9.1.1 The test samples shall be taken from standard produc-tion and representativ

35、e of the production process.9.1.2 Samples removed from the production line shall havetemporary clamps applied inboard of each cut to preventshifting of any strand or layer relative to the core.9.1.3 Samples removed from shipping reels shall not in-clude end sections if there is evidence that any str

36、and or layerhas shifted and the manufacturing pre-stress has been released.9.1.4 The end termination used for testing shall preventshifting on any conductor component. Appendix X2 containsacceptable methods.9.1.5 The conductor manufacturer, at their sole discretion,may direct the acceptable design f

37、or the end terminationsuitable for their product.9.1.6 The method used to cut the conductor shall not causethe conductor core or any strand to slip inside the clamp(s).9.1.7 Samples shall be transported as straight sections,preferably inside a protective tube, or coiled with a coildiameter not less

38、than 40 times the conductor diameter.9.2 Core Samples:9.2.1 The core sample shall be either taken from a compos-ite sample prepared in accordance with 9.1 (with the aluminumremoved), or taken directly from the core pay-off reel.9.2.2 End Preparation:9.2.2.1 The core sample may be prepared identical

39、to thecomposite sample, and the aluminum layers removed prior tothe test. Alternately, the aluminum may be removed first, andthe bare core prepared for the test.9.2.2.2 The core sample may be taken directly from theoriginal payout reel.9.3 Sample Gauge Length:9.3.1 The gauge length where strain is m

40、easured may notinclude the 12 in. (30 cm) nearest to the fitting. Minimumgauge length shall be 400 the sample diameter not to exceed500 in. Shorter gauge lengths may be used provided thelaboratory provides justification, demonstrating the accuracyrequirements are met.10. Preparation of Apparatus10.1

41、 Calibration status and proper operation of the controlsshall be verified prior to the start of the test.11. Calibration and Standardization11.1 Calibration of the tension instrument shall conform tothe requirements of Practices E4.11.2 Calibration of the strain instrument shall conform tothe requir

42、ements of Practice E83.11.3 Calibration of temperature instruments shall be inaccordance with Test Method E220, and temperature shall berecorded with a resolution of 0.1C.11.4 Actuator displacement shall be measured using aninstrument with an accuracy of 60.004 in (0.1 mm) andresolution of 0.0005 in

43、 (0.01 mm).12. Conditioning12.1 The sample, the gauge rod, and all instruments shall beat thermal equilibrium with a stable lab ambient during allphases of the stress-strain test.13. Procedure13.1 Composite Conductor:13.1.1 Install the sample and apply an initial load of 8 % ofthe conductor RBS or 1

44、000 lb (4.45 kN), whichever is less.13.1.2 Remove sag by supporting the weight of the sample(see 7.7).13.1.3 Install the extensometer and set to zero strain whilethe conductor is at initial load.13.1.4 Increase load smoothly to 30 % of the conductorRBS within two minutes but not less than one minute

45、. Holdload at 30 % RBS for 30 6 0.25 min,13.1.5 Return to the initial load at the same rate as usedduring the increase to load (Note 2).B1008 183NOTE 2Initial load may be modified to 50 % of the prior load holdtarget, if necessary, to avoid excessive bird caging of the aluminumstrands for conductors

46、 with annealed aluminum strands and a low-modulus core.13.1.6 Increase load smoothly to 50 % of the conductorrating at the same rate used for the ramp to 30 % RBS. Hold for60 6 0.25 min.13.1.7 Return to the initial load (Note 2).13.1.8 Increase load smoothly to 70 % of the conductorrating at the sam

47、e rate used for the ramp to 30 % RBS. Hold for60 6 0.25 min.13.1.9 Return to the initial load (Note 2).13.1.10 Increase load smoothly to 85 % of the conductorrating at the same rate used for the ramp to 30 % RBS. Hold for60 6 0.25 min.13.1.11 Return to the initial load (Note 2).13.1.12 Remove the te

48、mperature and strain instruments.Inspect the sample and its end fittings and document anyunusual conditions (bird caging, broken strands, or movementof any strand in the end grips, for example).13.1.13 After documentation and disposition of any findingsunder 13.1.12, pull the sample to rupture at a

49、rate of not greaterthan 50 % RBS/min and not less than 10 % RBS/min. Simul-taneous recording of tension and actuator position are required,as a minimum, every 2.5 % of RBS during the final tensile test.The maximum load reached prior to rupture shall be recorded.See Fig. 2.NOTE 3Load hold times are designed to simulate creep duringshort-time load events during transmission line operation. Long-termcreep effects are simulated by creep testing.13.2 Conductor Core:13.2.1 Determine the initial tension using Eq 1 (the goal isto stress the core as c