1、Designation: D2519 07 (Reapproved 2012)D2519 18Standard Test Method forBond Strength of Electrical Insulating Varnishes by theHelical Coil Test1This standard is issued under the fixed designation D2519; the number immediately following the designation indicates the year oforiginal adoption or, in th
2、e 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.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope*1.1
3、 This test method covers determination of the bond strength of an electrical insulating varnish when applied to a helical coil.The helical coil can be made from bare aluminum or copper wire or from film or fiber-insulated magnet wire. Helical coils madefrom bare aluminum or bare copper wire will yie
4、ld values of bond strength for the varnish when applied to bare metal conductors.The use of film or fiber-insulated magnet wire will show values for that particular combination of insulation and varnish.1.2 The values stated in SI units are to be regarded as the standard. The values given in parenth
5、eses are for information only.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicabili
6、ty of regulatory limitations prior to use. See Section 7.1.4 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issue
7、dby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D115 Test Methods for Testing Solvent Containing Varnishes Used for Electrical InsulationD1711 Terminology Relating to Electrical InsulationD6054 Practice for Conditioning Electric
8、al Insulating Materials for Testing (Withdrawn 2012)3E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 For definitions of other terms relating to electrical insulation, see Terminology D1711.3.1.2 bond strengtha measu
9、re of the force required to separate surfaces which have been bonded together.3.2 Definitions of Terms Specific to This Standard:3.2.1 event timethe time between initial application of a physical or electrical stress and failure of the specimen under test.3.2.2 response timethe time required for an
10、indicating or recording device to react to change in stress on a specimen undertest.4. Summary of Test Method4.1 Flexural strength tests are made on varnish-treated helical coils to determine the force required to break the coil underspecified conditions.1 This test method is under the jurisdiction
11、of ASTM Committee D09 on Electrical and Electronic Insulating Materials and is the direct responsibility of SubcommitteeD09.01 on Electrical Insulating Varnishes, Powders and Encapsulating CompoundsProducts.Current edition approved April 1, 2012Nov. 1, 2018. Published April 2012November 2018. Origin
12、ally approved in 1966. Last previous edition approved in 20072012 asD2519 07.D2519 07 (2012). DOI: 10.1520/D2519-07R12.10.1520/D2519-18.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume inf
13、ormation, refer to the standards Document Summary page on the ASTM website.3 The last approved version of this historical standard is referenced on www.astm.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been
14、made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*
15、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 States15. Significance and Use5.1 Values obtained by flexural tests can provide information with regard to the bond strength of t
16、he particular varnish, incombination with a particular wire, when measured under conditions described in this test method.6. Apparatus6.1 Tensile Testing MachineUse an adjustable-speed drive and a suitable instrument for measuring force to break thespecimen. Available tensile testing machines or an
17、accurate spring gauge and a separate adjustable-speed drive are suitable. Tocover the range of load strength values which are commonly encountered it is recommended that a multirange tester be used.6.1.1 It has been found that gages rated 5, 25, 150, and 500 N (1, 5, 30, and 100 lbf) are adequate to
18、 cover the range of varnishes.6.2 Test FixtureThe test fixture consists of two rollers, attached to a common frame, and a 90 V-block. One part, either therollers or the V-block, is held stationary while the other part is moved. No friction contact which will affect this movement isallowed. The gener
19、al shape and the relative position of these parts are shown in Fig. 1. The rollers have a diameter of 9.5 mm(0.375 in.) at the center and are parallel having a center-to-center distance of 44.5 mm (1.75 in.). The 90 V-block has a radiusat the apex of 0.8 mm (0.03 in.).6.3 Test Fixture EnclosureFor t
20、ests at other than room temperature, use an insulated heat-resistant enclosure, designed to fitaround the test fixture and connected to the tension testing machine. This enclosure permits a frictionless connection between thetest fixture and the instrument that measures the breaking force. The enclo
21、sure is designed with a suitable location for holding sixor more specimens. It is heated or cooled by a separate source of uniformly circulating hot or cold air. The temperature controlsystem is capable of returning the test specimens and the chamber to the test temperature in less than 10 min. A th
22、ermostaticcontrol, with the measuring thermocouple located within 25 mm (1.0 in.) of the center of the coil being tested, is set to maintainthe temperature of the chamber to within 6 2C62C of the desired temperature after the temperature has stabilized.7. Safety Precautions7.1 It is unsafe to use va
23、rnish at temperatures above the flash point without adequate ventilation, especially if the possibilityexists that flames or sparks are present. Store varnish in sealed containers.8. Test Specimens8.1 The test specimens are 75 mm (3 in.) long coils of No. 18AWG wire, cut from a helix of convenient l
24、ength which has beenwound without space between turns on a 6 mm (0.25 in.) diameter mandrel. Bend the last loop on each end of the coil toapproximately 90 to the coil to provide a means of support. Treat the coil with the varnish to be tested. Make the helical coilsas agreed to by interested parties
25、 from one of the following:8.1.1 Bare aluminum wire,8.1.2 Bare copper wire,8.1.3 Film-coated magnet wire, or8.1.4 Fiber-insulated magnet wire.FIG. 1 Test Fixture for Bond Strength TestD2519 182NOTE 1A practical method of winding a tight helical coil is to guide the wire from the rotating reel betwee
26、n folds of a clean cloth onto the rotatingmandrel using moderate hand tension. Maintain a trailing angle of 1 to 5 from a perpendicular to the mandrel. When the wire is cut, the coil must berestrained to avoid rapid spring back.8.2 Prepare six or more specimens for each condition to be investigated.
27、8.3 Adjust the viscosity of the varnish to be tested, by trial, to produce a dry film build of 0.043 to 0.053 mm (0.0017 to 0.0021in.) on a metal panel double coated in accordance with Test Methods D115.8.4 Use solventless varnish in the “as received” condition.8.5 Immerse coils made from bare wire
28、in a solvent of 50 % toluene and 50 % denatured alcohol by weight for 30 min. Removeand dry for 15 min at 100 C 100C before treating with varnish. Do not clean coils made from insulated wire before treating withvarnish.8.6 Attach several coils to a rack and immerse vertically in the varnish until bu
29、bbling stops. Withdraw them at 100 65mm/min65 mmmin (460.2 in./min)60.2 in.min) and allow them to drain 10 to 30 min at the Standard LaboratoryAtmospherein accordance with Practice 30 min, 23 6 2C, and less than 55 % RH. D6054. Place the coils in an oven in the same positionas dipped at the temperat
30、ure and for the time specified by the manufacturer. For solvent containing varnishes, reverse dip and bakethe coils, following the above procedure.9. Procedure9.1 Rate of LoadingAdjust the testing machine to a crosshead speed of 50 mm/min (2 in./min).9.1.1 Position the coils in the test fixture with
31、 the center of the coils below the V-block. Each coil is broken only once.9.2 Number of SpecimensTest a minimum of five specimens for each condition. It is allowable to use one of the original sixspecimens for adjusting the testing machine.9.3 Selection of Test RangeSelect the proper test range whic
32、h corresponds to the specified rate of loading. The proper testrange is the one where the anticipated bond strength will be reached in the middle or upper portion of the test range, wheneverpossible. For testers with chart recorders it is essential that the test range be selected in such a manner th
33、at the event time is greaterthan the response time of the recorder.9.4 Tests at Other than Room Temperature:9.4.1 Adjust the temperature control until the temperature of the chamber becomes constant within 6 2C62C of the specifiedtest temperature.9.4.2 Place one specimen in the test fixture. Place t
34、he remaining specimens in the enclosure. Allow the enclosure to stabilizefor 5 6 1 min at the test temperature. Break the specimen in the test fixture as described in 9.1 9.3.9.4.3 Replace broken specimen with an untested specimen from within the enclosure. Allow the enclosure to stabilize forapprox
35、imately 1 min at the test temperature. Break the specimen in the test fixture as described in 9.1 9.3.9.4.4 Repeat 9.4.3 for the remaining specimens.10. Report10.1 Report the following information:10.1.1 Description of varnish,10.1.2 Identification of wire used,10.1.3 Cure time and temperature for e
36、ach coat and number of dips used to prepare the coils, and10.1.4 The individual values in newtons (pounds-force) of bond strength and their averages at each test condition.11. Precision and Bias11.1 PrecisionTable 1 lists the results based on a round robin test conducted in accordance with Practice
37、E691 involving sixlaboratories and three materials. Each test result was the average of five specimens. Each laboratory obtained two test results foreach material.11.2 BiasThis test method has no bias because the value for bond strength of electrical insulating varnishes by the helical coiltest is d
38、etermined solely in terms of this test method.TABLE 1 Results in NewtonsMaterial Average StandardDeviationRepeatabilityStandardDeviationReproducibilityStandard DeviationRepeatabilityLimitReproducibilityLimitSolvent Varnish 97.21 13.92 1.75 12.81 4.90 35.87UnsaturatedPolyester166.76 34.03 6.26 31.59
39、17.53 88.45Epoxy 208.43 37.45 10.41 35.48 29.15 99.34D2519 183Combined data from six laboratories:Mean = 220.6 N (49.6 lbf)Standard deviation = 41.99 N (6.96 lbf)95 % Confidence level = 82.25 N (13.64 lbf)12. Keywords12.1 bond strength; helical coil; varnishSUMMARY OF CHANGESCommittee D09 has identi
40、fied the location of selected changes to this test method standard since the last issue,issue (D2519 02D2519 07 (2012),) that may impact the use of this test method. standard. (Approved May 1,2007Nov. 1, 2018).)(1) Revised Sections 6, 8, and 9.(1) Revised 8.6 to revise humidity conditions.ASTM Inter
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