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导热系数测试标准ASTM E 1461-01

更新时间:2016/10/30 18:08:08 点击: 来源:www.daoreceshi.com
  • 产品品牌ASTM E 1461-01
  • 产品型号ASTM E 1461-01
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    导热系数测试标准ASTME1461-01StandardTestMethodforThermalDiffusivitybytheFlashMethodThisstandardisissuedunderthefixeddesignationE1461;thenumberimmed...

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导热系数测试标准ASTM E 1461-01

Standard Test Method for Thermal Diffusivity 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.

 

1. 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 m2/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.
2. Referenced Documents
2.1 ASTM Standards:
C 714 Test Method for Thermal Diffusivity of Carbon and
Graphite by a Thermal Pulse Method2
E 230 Temperature-Electromotive Force (EMF) Tables for
Standardized Thermocouples3
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 thermal conductivity, l, of a solid material—the time
rate of steady heat flow through unit thickness of an infinite
slab of a homogeneous material in a direction perpendicular to
the surface, induced by unit temperature difference. The
property must be identified with a specific mean temperature,
since it varies with temperature.
3.1.2 thermal diffusivity, a, of a solid material—the property
given by the thermal conductivity divided by the product
of the density and heat capacity per unit mass.3.2 Description of Symbols and Units Specific to This
Standard:
3.2.1 D—diameter, meters.
3.2.2 k—constant in solution to diffusion equation.
3.2.3 L—specimen thickness, meters.
3.2.4 t—response time, seconds.
3.2.5 t*—dimensionless time (t* = 4as t/DT
2).
3.2.6 T—temperature, Kelvin.
3.2.7 a—thermal diffusivity, m2/s.
3.2.8 l—thermal conductivity, W/m·K.
3.2.9 b—fraction of pulse duration required to reach maximum
intensity.
3.2.10 Dt5—T (5t1⁄2) /T (t1⁄2).
3.2.11 Dt10—T (10t1⁄2) /T (t1⁄2).
3.3 Description of Subscripts Specific to This Standard:
3.3.1 o—ambient.
3.3.2 s—specimen.
3.3.3 T—thermocouple.
3.3.4 x—percent rise.
3.3.5 C—Cowan.
3.3.6 R—ratio.
3.3.7 m—maximum.
3.3.8 t—time.
4. Summary of Test Method
4.1 A small, thin disc specimen is subjected to a highintensity
short duration radiant energy pulse. The energy of the
pulse is absorbed on the front surface of the specimen and the
resulting rear face temperature rise (thermogram) is recorded.
The thermal diffusivity value is calculated from the specimen
thickness and the time required for the rear face temperature
rise to reach certain percentages of its maximum value (Fig. 1).
When the thermal diffusivity of the sample is to be determined
over a temperature range, the measurement must be repeated at
each temperature of interest. This test method is described in
detail in a number of publications (1, 2)4 and review articles (3,
4, 5). A summary of the theory can be found in Appendix X5.
5. Significance and Use
5.1 Thermal diffusivity is an important property, required
for such purposes as design applications under transient heat
flow conditions, determination of safe operating temperature,
process control, and quality assurance.5.2 The flash method is used to measure values of thermal
diffusivity, a, of a wide range of solid materials. It is
particularly advantageous because of simple specimen geometry,
small specimen size requirements, rapidity of measurement
and ease of handling, with a single apparatus, of materials
having a wide range of thermal diffusivity values over a large
temperature range.
5.3 Under certain strict conditions, specific heat capacity of
a homogeneous isotropic opaque solid sample can be determined
when the method is used in a quantitative fashion (see
Appendix X4).
5.4 Thermal diffusivity results, together with specific heat
capacity (Cp) and density (r) values, can be used in many cases
to derive thermal conductivity (l), according to the relationship:
l 5 a Cp r. (1)
6. Interferences
6.1 In principle, the thermal diffusivity is obtained from the
thickness of the sample and from a characteristic time function
describing the propagation of heat from the front surface of the
sample to its back surface. The sources of uncertainties in the
measurement are associated with the sample itself, the temperature
measurements, the performance of the detector and of
the data acquisition system, the data analysis and more
specifically the finite pulse time effect, the nonuniform heating
of the sample and the radiative heat losses. These sources of
uncertainty can be considered systematic, and should be
carefully considered for each experiment. Errors random in
nature (noise, for example) can be best estimated by performing
a large number of repeat experiments and comparing their
results. The relative standard deviation of the obtained results
is a good representation of the random component of the
uncertainty associated with the measurement. Guidelines in
performing a rigorous evaluation of these factors are given in
(31).
7. Apparatus
The essential components of the apparatus are shown in Fig.
2. These are the flash source, sample holder, environmental
enclosure (optional), temperature response detector and recording
device.
7.1 The flash source may be a pulse laser, a flash lamp, or
other device capable to generate a short duration pulse of
substantial energy. The duration of the energy flash should be
less than 2 % of the time required for the rear face temperature
rise to reach one half of its maximum value (see Fig. 1).
7.1.1 The pulse hitting the sample’s surface must be spatially
uniform in intensity. Most pulse lasers exhibit hot spots
and a substantially higher intensity in the center region of the
beam than in the periphery. For this reason, systems using
unmodified beams directly from a pulse laser should use beams
somewhat larger in diameter than the largest diameter of the
samples to be tested. The use of an optical fiber between the
laser and the sample improves substantially uniformity of the
beam (up to 95 %). Since this method produces almost no edge
effects, a larger portion of the energy can be directed to the
sample than for natural beam lasers.
7.1.2 Most commonly used lasers are: ruby (visible red),

 

 

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导热系数测试标准ASTM E 1461-01