ASTM C714-2017 Standard Test Method for Thermal Diffusivity of Carbon and Graphite by Thermal Pulse Method《采用热脉冲法测定碳和石墨热扩散性的标准试验方法》.pdf
《ASTM C714-2017 Standard Test Method for Thermal Diffusivity of Carbon and Graphite by Thermal Pulse Method《采用热脉冲法测定碳和石墨热扩散性的标准试验方法》.pdf》由会员分享,可在线阅读,更多相关《ASTM C714-2017 Standard Test Method for Thermal Diffusivity of Carbon and Graphite by Thermal Pulse Method《采用热脉冲法测定碳和石墨热扩散性的标准试验方法》.pdf(5页珍藏版)》请在麦多课文档分享上搜索。
1、Designation: C714 05 (Reapproved 2015)C714 17 An American National StandardStandard Test Method forThermal Diffusivity of Carbon and Graphite by ThermalPulse Method1This standard is issued under the fixed designation C714; the number immediately following the designation indicates the year oforigina
2、l adoption or, in the 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.1. Scope Scope*1.1 This test method covers the determination of the thermal di
3、ffusivity of carbons and graphite to 65 % at temperatures up to500 C. It requires only a small easily fabricated specimen. Thermal diffusivity values in the range from 0.04 cm2/s to 2.0 cm2/sare readily measurable by this test method; however, for the reason outlined in Section 57, for materials out
4、side this range this testmethod may require modification.1.2 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 and health practices and determine the applicabilit
5、y of regulatorylimitations prior to use.1.3 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 issuedby the World Tra
6、de Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2C781 Practice for Testing Graphite and Boronated Graphite Materials for High-Temperature Gas-Cooled Nuclear ReactorComponentsD7775 Guide for Measurements on Small Graphite SpecimensE1461 Test Metho
7、d for Thermal Diffusivity by the Flash Method3. Terminology3.1 Definitions:3.1.1 thermal conductivity, nthe rate at which heat passes through a material, expressed as the amount of heat that flows perunit time through a unit area with a temperature gradient of one degree per unit distance.3.1.2 ther
8、mal diffusivity, na measure of the ability of a material to conduct thermal energy relative to its ability to store thermalenergy; it is equal to the thermal conductivity divided by density and specific heat capacity at constant pressure.4. Summary of Test Method4.1 A high-intensity short-duration t
9、hermal pulse from a flash lamp is absorbed on the front surface of a specimen; and the rearsurface temperature change as a function of time is observed on an oscilloscope. The pulse raises the average temperature of thespecimen only a few degrees above its initial value. The ambient temperature of t
10、he specimen is controlled by a furnace or cryostat.Thermal diffusivity is calculated from the specimen thickness and the time required for the temperature of the back surface to riseto one half of its maximum value (1).34.2 The critical factors in this test method are:4.2.1 /t12 must be 0.02 or less
11、. is the pulse time as defined in Fig. 1 and t12 is the time for the rear surface temperature to riseto one half of its maximum value (see Fig. 2).1 This test method is under the jurisdiction ofASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
12、 SubcommitteeD02.F0 on Manufactured Carbon and Graphite Products.Current edition approved Oct. 1, 2015May 1, 2017. Published December 2015May 2017. Originally approved in 1972. Last previous edition approved in 20102015 asC714 05 (2010).(2015). DOI: 10.1520/C0714-05R15.10.1520/C0714-17.2 For referen
13、cedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 The boldface numbers in parentheses refer to the list of references at t
14、he end of this test method.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 made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends t
15、hat 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.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West
16、 Conshohocken, PA 19428-2959. United States14.2.2 Heat losses from the specimen via radiation, convection, or conduction to the specimen holder must be small. Whetheror not this condition is violated can be determined experimentally from the oscilloscope trace, an example of which is shown inFig. 2.
17、 If T(10 t12)/ T(t12) 1.98, the heat losses are assumed to be zero.4.2.3 The oscilloscope trace must be such that Tmax, T(10 t12), and t12can be determined to 62 %.4.2.4 The other conditions are less critical, and the experimenter is left to his discretion.FIG. 1 Flash Tube ResponseFIG. 2 Example of
18、 Oscilloscope Trace Showing Parameters Used to Calculate Thermal DiffusivityC714 1725. Significance and Use5.1 Thermal diffusivity is an important property required for such purposes as design applications under transient heat flowconditions, determination of safe operating temperature, process cont
19、rol, and quality assurance.5.2 The flash method is used to measure values of thermal diffusivity () of a wide range of solid materials. It is particularlyadvantageous because of the simple specimen geometry, small specimen size requirements, rapidity of measurement, and ease ofhandling materials hav
20、ing a wide range of thermal diffusivity values over a large temperature range with a single apparatus. Theshort measurement times involved reduce the chances of contamination and change of specimen properties due to exposure to hightemperature environments.5.3 Thermal diffusivity results in many cas
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