1、Designation: E 831 06Standard Test Method forLinear Thermal Expansion of Solid Materials byThermomechanical Analysis1This standard is issued under the fixed designation E 831; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r 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.1. Scope1.1 This test method determines the apparent coefficient oflinear thermal expansion of solid materials using thermom
3、e-chanical analysis techniques. Related information can be foundin Refs. (1, 2)2.1.2 This test method is applicable to solid materials thatexhibit sufficient rigidity over the test temperature range suchthat the sensing probe does not produce indentation of thespecimen.1.3 The recommended lower limi
4、t of coefficient of linearthermal expansion measured with this test method is 5 m/(mC). The test method may be used at lower (or negative)expansion levels with decreased accuracy and precision (seeSection 11).1.4 This test method is applicable to the temperature rangefrom 120 to 900 C. The temperatu
5、re range may be extendeddepending upon the instrumentation and calibration materialsused.1.5 Computer or electronic based instruments, techniques,or data treatment equivalent to this test method may also beused.NOTE 1Users of this test method are expressly advised that all suchinstruments or techniq
6、ues may not be equivalent. It is the responsibility ofthe user to determine the necessary equivalency prior to use.1.6 SI values are the standard.1.7 This test method is related to ISO 11359-2 but issignificantly different in technical detail.1.8 This standard does not purport to address all of thes
7、afety problems, if any, associated with its use. It is 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.2. Referenced Documents2.1 ASTM Standards:3D 696 Test Method for Coeffic
8、ient of Linear Thermal Ex-pansion of Plastics Between 30C and 30C with aVitreous Silica DilatometerD 3386 Test Method for Coefficient of Linear ThermalExpansion of Electrical Insulating Materials4E 228 Test Method for Linear Thermal Expansion of SolidMaterials With a Vitreous Silica Dilatometer4E 47
9、3 Terminology Relating to Thermal Analysis and Rhe-ologyE 1142 Terminology Relating to Thermophysical PropertiesE 1363 Test Method for Temperature Calibration of Ther-momechanical AnalyzersE2113 Test Method for Length Change Calibration ofThermomechanical Analyzers2.2 ISO Standards:5ISO 11359-2 Plas
10、ticsThermomechanical Analysis(TMA)Part 2: Determination of Coefficient of LinearThermal Expansion and Glass Transition Temperature3. Terminology3.1 DefinitionsThermal analysis terms in TerminologiesE 473 and E 1142 shall apply to this test method.3.2 Definitions of Terms Specific to This Standard:3.
11、2.1 apparent coeffcient of linear thermal expansion,(am)the change in length, relative to the specimen length at1This test method is under the jurisdiction ofASTM Committee E37 on ThermalMeasurements and is the direct responsibility of Subcommittee E37.01 on TestMethods and Recommended Practices.Cur
12、rent edition approved March 15, 2006. Published April 2006. Originallyapproved in 1981. Last previous edition approved in 2005 as E 831 05.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For referenced ASTM standards, visit the ASTM website, www.astm.
13、org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Withdrawn.5Available from theAmerican National Standards Institute, 11 W. 42nd St., 13thFloor, New York, NY 10036.1Copyright
14、ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.ambient temperature, accompanying a unit change in tempera-ture identified by the midpoint temperature of the temperaturerange of measurement4. Summary of Test Method4.1 This test method uses a th
15、ermomechanical analyzer orsimilar device to determine the linear thermal expansion ofsolid materials when subjected to a constant heating rate.4.2 The change of the specimen length is electronicallyrecorded as a function of temperature. The coefficient of linearthermal expansion can be calculated fr
16、om these recorded data.5. Significance and Use5.1 Coefficients of linear thermal expansion are used, forexample, for design purposes and to determine if failure bythermal stress may occur when a solid body composed of twodifferent materials is subjected to temperature variations.5.2 This test method
17、 is comparable to Test Method D 3386for testing electrical insulation materials, but it covers a moregeneral group of solid materials and it defines test conditionsmore specifically. This test method uses a smaller specimenand substantially different apparatus than Test Methods E 228and D 696.6. App
18、aratus6.1 Thermomechanical Analyzers (TMA)The essential in-strumentation required providing minimum thermomechanicalanalytical or thermodilatometric capability for this test methodincludes:6.1.1 Rigid Specimen Holder, of inert, low expansivitymaterial (# 0.5 m/(m C) to center the specimen in thefurn
19、ace and to fix the specimen to mechanical ground.6.1.2 Rigid Expansion Probe, of inert, low expansivitymaterial (#0.5 m/(m C) that contacts the specimen with anapplied compressive force.6.1.3 Sensing Element, linear over a minimum range of 2mm to measure the displacement of the rigid expansion probe
20、to within 6 50 nm resulting from changes in length of thespecimen.6.1.4 Weight or Force Transducer, to generate a constantforce of 1 to 100 mN (0.1 to 10 g) that is applied through therigid expansion probe to the specimen.6.1.5 Furnace, capable of providing uniform controlledheating (cooling) of a s
21、pecimen to a constant temperature or ata constant rate between 2 and 10 C/min within the applicabletemperatures range of between 150 and 1000 C.6.1.6 Temperature Controller, capable of executing a spe-cific temperature program by operating the furnace betweenselected temperature limits at a rate of
22、temperature change of2 to 10 C/min constant to within 6 0.1 C/min or at anisothermal temperature constant to 6 0.5 C.6.1.7 Temperature Sensor, that can be attached to, in contactwith, or reproducibly positioned in close proximity to thespecimen capable of indicating temperature to 6 0.5 C.6.1.8 A me
23、ans of sustaining an environment around thespecimen of inert gas at a purge gas rate of 10 to 50 mL/min.NOTE 2Typically, greater than 99 % pure nitrogen, argon, or heliumis used when oxidation in air is a concern. Unless effects of moisture areto be studied, use of dry purge gas is recommended and i
24、s essential foroperation at subambient temperatures.6.1.9 Recording Device, capable of recording and display-ing any fraction of the specimen dimension signal (TMAcurve), including signal noise, on theY-axis versus any fractionof the temperature signal, including noise, on the X-axis.6.2 Cooling Cap
25、ability, to sustain a subambient specimentemperature (if subambient measurements are to be made) or tohasten cool down of the specimen from elevated temperatures.6.3 Micrometer, or other length-measuring device with arange of up to 10 mm to determine specimen dimensions towithin 6 25 m.7. Test Speci
26、mens7.1 Specimens shall be between 2 and 10 mm in length andhave flat and parallel ends to within 6 25 m. Lateraldimensions shall not exceed 10 mm. Other lengths may beused, but shall be noted in the report.NOTE 3It has been found with some materials that this level offlatness and parallelness canno
27、t be attained. Specimens that do not meetthese requirements may result in increased imprecision.7.2 The specimens are ordinarily measured as received.Where some heat or mechanical treatment is applied to thespecimen prior to test, this should be noted in the report.NOTE 4Some materials, particularly
28、 composites, may require heattreatment to condition the specimen prior to test to relieve stresses ordistortions. Such heat treatment must be included in the report.8. Calibration8.1 Prepare the instrument for operation according to theprocedures in the manufacturers operation manual.8.2 Calibrate t
29、he temperature signal using Test MethodE 1363.8.3 Calibrate the length change signal using Test MethodE2113at the same heating rate as that to be used for the testspecimens. The observed expansion must be corrected for thedifference in expansion between the specimen holder and probeobtained from a b
30、lank run in which no sample or a specimen ofthe material of construction of the probe is run. (see 10.1).9. Procedure9.1 Measure the initial specimen length in the direction ofthe expansion test to 6 25 m at 20 to 25 C.NOTE 5Direct readout of zero position and specimen length using theanalyzer sensi
31、ng element, where available, with a sufficient range has beenfound to be an accurate means of length determination.9.2 Place the specimen in the specimen holder under theprobe. Place the specimen temperature sensor in contact withthe specimen or as near to the specimen as possible.9.3 Move the furna
32、ce to enclose the specimen holder. Ifmeasurements at subambient temperature are to be made, coolthe specimen to at least 20 C below the lowest temperature ofinterest. The refrigerant used for cooling shall not come intodirect contact with the specimen.9.4 Apply an appropriate load force to the sensi
33、ng probe toensure that it is in contact with the specimen. Depending on thecompressibility of the specimen and the temperature range tobe investigated, a force of between 1 and 100 mN (0.1 to 10 g)E831062is adequate. The actual incremental force, mass, or stress abovethat required to make contact wi
34、th zero force shall be noted inthe report.9.5 Select appropriate ordinate and abcissa range sensitivitysettings on the graphical representation.NOTE 6Normally, the expansion increases with the increase intemperature as shown in the schematic diagram of Fig. 1. An abruptchange in slope of the expansi
35、on curve indicates a transition of thematerial from one state to another.9.6 Heat the specimen at a constant heating rate of 5 C/minover the desired temperature range and record the changes inspecimen length and temperature to all available decimalplaces. Other heating rates may be used but shall be
36、 noted inthe report.NOTE 7For best results, specimen temperature gradients should besmall. High heating rates, large specimen sizes, and low specimen thermalconductivity may lead to large specimen temperature gradients. Theeffects of specimen temperature gradients may be compensated for bycorrection
37、 found through the use of suitable reference materials whosesize and thermal conductivity are close to that of the test specimen.NOTE 8Intralaboratory testing indicates that no detectable increase inimprecision is observed for specimen sizes from 2 to 10 mm in length, forheating rates from 2 to 10 C
38、/min, and for thermal conductivities from 0.2to 400 W/(mC) if only one parameter is changed.9.7 Measure the measurement instrument baseline by re-peating 9.3 through 9.6 using the same test parameters butwithout a test specimen, that is, with the probe in contact withthe specimen holder. The measure
39、d DL for the specimen shouldnormally be corrected for this instrument baseline, especiallyfor low expansion specimens.9.8 Test at least three specimens of the same material. Retestof a specimen may be used only as reference and shall not betreated as an independent test of a new specimen.10. Calcula
40、tion10.1 Calculate the mean coefficient of linear thermal expan-sion rounded to the nearest 0.1 m/(mC) for a desiredtemperature range as follows:am5DLsp3 kL 3DT(1)k 5aref3 Lref3DTrefDLref(2)where:amm(T) = mean coefficient of linear thermalexpansion,m/(mC),aref= mean coefficient of linear thermal exp
41、ansion,for reference material, m/(mC) (see 8.3),k = calibration coefficient, from Test MethodE 2113,L = specimen length at room temperature, m,DLref= change of reference material length due toheating, m,Lref= reference material length at room tempera-ture, m,DLsp= change of specimen length, m,DTref=
42、 temperature difference over which thechange in reference material length is mea-sured, C, typically 100 C,DT = temperature difference over which thechange in specimen length is measured, C,T = midpoint temperature of the temperaturerange DT, andNOTE 9For low-expansion specimens, DL should be correc
43、ted for theexpansion of the sample holder displaced by the specimen.DLspor DLref! 5DLobs1 L DT aholder2DLblank(3)where:DLobs= measured change in length, m,aholder= mean coefficient of linear thermal expansion forholder, m/(mC), andDLblank= change of baseline due to heating, m.If the holder is compos
44、ed of vitreous silica, aholder= 0.52 60.02 m/(mC) from 20 to 700 C.10.2 Select a DT from a smooth portion of the thermalcurves in the desired temperature range symmetically aroundthe temperature of interest; then obtain DL as depicted in Fig.1. The amshall not be calculated from a temperature range
45、inwhich a transition point is noted.NOTE 10Values for DT generally range between 50 and 100 C.Values less than 50 C may lead to poor precision; values greater than 100C may mask small change in the expansion coefficient.11. Report11.1 The report shall include the following:11.1.1 Designation of the
46、material, including the name ofthe manufacturer and information on lot number and chemicalcomposition when known,11.1.2 Specimen orientation with respect to the original partor the direction of the oriented fiber fillers if a compositematerial is used,11.1.3 Method of test specimen preparation,11.1.
47、4 Dimensions of the specimen,FIG. 1 Specimen Expansion Versus TemperatureE83106311.1.5 Description of the thermomechanical analysis appa-ratus, including manufacturer and model number,11.1.6 Purge gas and cooling medium, if used,11.1.7 The midpoint temperature (T) and the temperaturerange (DT) at wh
48、ich the coefficient of linear thermal expansionhas been determined,11.1.8 Average value of the coefficient of linear thermalexpansion in m/(mC) as determined from three specimens,11.1.9 Expansion curves obtained, and11.1.10 The specific dated version of this test method used.12. Precision and Bias61
49、2.1 Precision of thermal expansion measurements dependson the length of the specimen, the temperature range ofinterest, and the change in the specimen length. Maximumimprecision in the calculated coefficient of linear thermalexpansion may be estimated from the imprecisions in theindividual measurements by the following equation.da/am5 dDL/ 6DL!21 dL/L!21 dDT/DT!2#1/2(4)where:am= mean coefficient of linear thermal expansion, m/(mC),da= imprecision in the measurement of a, m/(mC),DL = change of
