ASTM E1461-92
(Test Method)Standard Test Method for Thermal Diffusivity of Solids by the Flash Method
Standard Test Method for Thermal Diffusivity of Solids by the Flash Method
SCOPE
1.1 This test method covers the determination of the thermal diffusivity of primarily homogeneous isotropic solid materials. Thermal diffusivity values ranging from 10-7 to 10-3 m 2/s are readily measurable by this test method from about 75 to 2800 K.
1.2 This test method is a more detailed form of Test Method C 714, but has applicability to much wider ranges of materials, applications, and temperatures, with improved accuracy of measurements.
1.3 This test method is applicable to the measurements performed on materials opaque to the spectrum of the energy pulse, but with special precautions can be used on fully or partially transparent materials (see Appendix X1).
1.4 This test method is intended to allow a wide variety of apparatus designs. It is not practical in a test method of this type to establish details of construction and procedures to cover all contingencies that might offer difficulties to a person without pertinent technical knowledge, or to stop or restrict research and development for improvements in the basic technique.
1.5 This test method is applicable to the measurements performed on essentially fully dense materials; however, in some cases it has shown to produce acceptable results when used with porous samples. Since the magnitude of porosity, pore shapes, sizes and parameters of pore distribution influence the behavior of the thermal diffusivity, extreme caution must be exercised when analyzing data. Special caution is advised when other properties, such as thermal conductivity, are derived from thermal diffusivity obtained by this method.
1.6 This test method can be considered an absolute (or primary) method of measurement, since no reference standards are required. It is advisable to use reference materials to verify the performance of the instrument used.
1.7 This method is applicable only for homogeneous solid materials, in the strictest sense; however, in some cases it has shown to produce data which may be useful in certain applications.
1.7.1 Testing of Composite Materials--When substantial inhomogeneity and anisotropy is present in a material, the thermal diffusivity data obtained with this method may be substantially in error. Nevertheless, such data, while usually lacking absolute accuracy, may be useful in comparing materials of similar structure. Extreme caution must be exercised when related properties, such as thermal conductivity, are derived, as composites may have heat flow patterns substantially different than uniaxial.
1.7.2 Testing Liquids--This method has found an especially useful application in determining thermal diffusivity of molten materials. For this technique, specially constructed sample enclosures must be used.
1.7.3 Testing Layered Materials--This method has also been extended to test certain layered structures made of dissimilar materials, where one of the layers is considered unknown. In some cases, contact conductance of the interface may also be determined.
1.8 The values stated in SI units are to be regarded as the standard.
1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E 1461 – 92
Standard Test Method for
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Thermal Diffusivity of Solids by the Flash Method
This standard is issued under the fixed designation E 1461; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
,
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1. Scope parison Techniques
E 230 Temperature-Electromotive Force (EMF) Tables for
1.1 This test method covers the determination of the thermal
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Thermocouples
diffusivity of homogeneous solid materials. Thermal diffusivity
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values ranging from 0.1 to 1000 mm /s are readily measurable
3. Terminology
by this test method and measurements can be made from about
3.1 Definitions:
100 to 2500 K normally in a vacuum or inert gas environment.
3.1.1 thermal conductivity, l, of a solid material—the time
1.2 This test method is a more detailed form of Test Method
rate of steady heat flow through unit thickness of an infinite
C 714 but has applicability to much wider ranges of materials,
slab of a homogeneous material in a direction perpendicular to
applications, and temperatures with improved accuracy of
the surface, induced by unit temperature difference.
measurement.
3.1.1.1 Discussion—Where other modes of heat transfer are
1.3 This test method is applicable to the measurement of a
present in addition to conduction, this property is often referred
wide variety of homogeneous opaque materials and, with
to as apparent or effective thermal conductivity, e or app.
special precautions, can be used on transparent and some
3.1.1.2 Discussion—For practical purposes, the lateral ex-
porous and composite materials.
tent of a slab is considered to be infinite when heat flow
1.4 This test method is intended to allow a wide variety of
laterally is less than 2 % of the transverse flow.
apparatus design and design accuracies to satisfy the require-
3.1.1.3 Discussion—The property must be identified with
ments of specific measurements problems. It is not practical in
both a specific mean temperature, since it varies with tempera-
a test method of this type to establish details of construction
ture, and for a direction and orientation of thermal transmission
and procedures to cover all contingencies that might offer
since some bodies are not isotropic with respect to the thermal
difficulties to a person without pertinent technical knowledge
conductivity.
or to stop or restrict research and development for improve-
3.1.2 thermal diffusivity, a, of a solid material—the prop-
ments in the basic technique.
erty given by the thermal conductivity divided by the product
1.5 This test method can be considered an absolute (or
of the density and heat capacity per unit mass.
primary) method of measurement since no heat flux reference
3.2 Definitions:
standards are required except for verification purposes and to
3.2.1 a—1/(1 + 0.667 l /l ).
T s
confirm accuracy statements.
3.2.2 D—diameter, meters.
1.6 The values stated in SI units are to be regarded as the
3.2.3 k—constants in solution to diffusion equation.
standard.
3.2.4 L—specimen thickness, meters.
1.7 This standard does not purport to address all of the
3.2.5 t—response time, seconds.
safety problems, if any, associated with its use. It is the
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3.2.6 t*—dimensionless time ( t*=4a t/D T).
s
responsibility of the user of this standard to establish appro-
3.2.7 T—temperature, Kelvins.
priate safety and health practices and determine the applica-
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3.2.8 a—thermal diffusivity, m /s.
bility of regulatory limitations prior to use.
3.2.9 l—thermal conductivity, W/m.K.
2. Referenced Documents 3.2.10 b—fraction of pulse duration required to reach
maximum intensity.
2.1 ASTM Standards:
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3.2.11 Dt —T (5t ⁄2 /T (t ⁄2)).
C 714 Test Method for Thermal Diffusivity of Carbon and 5
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3.2.12 Dt —T (10t ⁄2/T (t ⁄2 )).
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Graphite by a Thermal Pulse Method
3.3 Definitions:
E 220 Method for Calibration of Thermocouples by Com-
3.3.1 o—ambient.
3.3.2 s—specimen.
3.3.3 T—thermocouple.
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This test method is under the jurisdiction of ASTM Committee E-37 on
3.3.4 x—percent rise.
Thermal Measurements and is the direct responsibility of Subcommittee E37.05 on
Thermophysical Properties.
Current edition approved Feb. 15, 1992. Published April 1992.
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Annual Book of ASTM Standards, Vol 15.01. Annual Book of ASTM Standards, Vol 14.03.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
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E 1461
3.3.5 C—Cowan. 6. Interferences
3.3.6 R—ratio.
6.1 Experimental results are subject to two general types of
3.3.7 m—maximum.
errors:
3.3.8 t—time.
6.1.1 Measurement errors associated with uncertainties that
exis
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