1、Designation:E258509(Reapproved 2015)Standard Practice forThermal Diffusivity by the Flash Method1This standard is issued under the fixed designation E2585;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A nu
2、mber in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice covers practical details associated with thedetermination of the thermal diffusivity of primarily homoge-neous isotropic solid
3、materials.Thermal diffusivity valuesranging from 10-7to 10-3m2/s are readily measurable by thisfrom about 75 to 2800 K.1.2 This practice is adjunct to Test Method E1461.1.3 This practice is applicable to the measurements per-formed on materials opaque to the spectrum of the energypulse,but with spec
4、ial precautions can be used on fully orpartially transparent materials.1.4 This practice is intended to allow a wide variety ofapparatus designs.It is not practical in a document of this typeto establish details of construction and procedures to cover allcontingencies that might offer difficulties t
5、o a person withoutpertinent technical knowledge,or to stop or restrict researchand development for improvements in the basic technique.This practice provides guidelines for the constructionprinciples,preferred embodiments and operating parametersfor this type of instruments.1.5 This practice is appl
6、icable to the measurements per-formed on essentially fully dense materials;however,in somecases it has shown to produce acceptable results when usedwith porous specimens.Since the magnitude of porosity,poreshapes,and parameters of pore distribution influence thebehavior of the thermal diffusivity,ex
7、treme caution must beexercised when analyzing data.Special caution is advisedwhen other properties,such as thermal conductivity,arederived from thermal diffusivity obtained by this method.1.6 The flash can be considered an absolute(or primary)method of measurement,since no reference materials arereq
8、uired.It is advisable to use only reference materials toverify the performance of the instrument used.1.7 This method is applicable only for homogeneous solidmaterials,in the strictest sense;however,in some cases it hasbeen shown to produce data found to be useful in certainapplications:1.7.1 Testin
9、g of Composite MaterialsWhen substantialnon-homogeneity and anisotropy is present in a material,thethermal diffusivity data obtained with this method may besubstantially in error.Nevertheless,such data,while usuallylacking absolute accuracy,may be useful in comparing mate-rials of similar structure.
10、Extreme caution must be exercisedwhen related properties,such as thermal conductivity,arederived,as composite materials,for example,may have heatflow patterns substantially different than uniaxial.In caseswhere the particle size of the composite phases is smallcompared to the specimen thickness(on t
11、he order of 1 to 25%of thickness)and where the transient thermal response of thespecimen appears homogenous when compared to the model,this method can produce accurate results for composite mate-rials.Anisotropic materials can be measured by varioustechniques,as long as the directional thermal diffu
12、sivities(twodimensional or three dimensional)are mutually orthogonal andthe measurement and specimen preparation produce heat flowonly along one principle direction.Also,2D and 3D modelsand either independent measurements in one or two directions,or simultaneous measurements of temperature response
13、atdifferent locations on the surface of the specimen,can beutilized.1.7.2 Testing LiquidsThis method has found an especiallyuseful application in determining thermal diffusivity of moltenmaterials.For this technique,specially constructed specimenenclosures must be used.1.7.3 Testing Layered Material
14、sThis method has alsobeen extended to test certain layered structures made ofdissimilar materials,where the thermal properties of one of thelayers are considered unknown.In some cases,contact con-ductance of the interface may also be determined.1This practice is under the jurisdiction of ASTM Commit
15、tee E37 on ThermalMeasurements and is the direct responsibility of Subcommittee E37.05 on Thermo-physical Properties.Current edition approved Sept.1,2015.Published September 2015.Originallyapproved in 2009.Last previous edition approved in 2009 as E2585 09.DOI:10.1520/E2585-09R15.Copyright ASTM Inte
16、rnational,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 1.8 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.9 This standard does not purport to address all of thesafety concerns,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.Re
