1.1 本试验方法涵盖了测量人造碳和石墨中纵向和横向（剪切）声速的程序，可用于获得弹性常数的近似值:杨氏模量( E )，剪切模量( G )，和泊松比( v ). 1.2 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.3 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 声速测量有助于比较具有类似弹性特性、尺寸和微观结构的材料。 5.2 等式1 仅为各向同性、非各向同性材料提供准确的杨氏模量值- 无限维衰减非色散材料。对于非各向同性石墨 等式1 可以修改以考虑所有方向上的泊松比。由于石墨是一种强衰减材料，使用 等式1 取决于试样长度。如果与传播脉冲的波长相比，试样的横向尺寸不大，则使用 等式1 取决于试样的横向尺寸。根据以下公式计算的杨氏模量的精度: 等式1 还将取决于泊松比的不确定性及其对中泊松因子评估的影响 公式2 . 然而，杨氏模量的值 等式1 或 公式7 )可以在许多应用中获得，这通常与其他更精确的方法（如测试方法）获得的值非常一致 C747 . STP 1578详细讨论了相应不确定性的技术问题和典型值。 6. 5.3 如果碳或石墨的粒度大于或约等于声脉冲的波长，则该方法可能无法提供代表大块材料的杨氏模量值。 因此，最好测试较低的频率（较长的波长），以证明获得的速度值范围在可接受的精度水平内。当材料的晶粒尺寸大于或约等于传输的声脉冲的波长，或材料比制造的石墨更多孔时，应预期信号会显著衰减。 注1: 由于石墨中的频率依赖衰减，通过试样的声脉冲波长不一定与发射换能器的波长相同。 5.4 如果样品只有几粒厚，则应通过最初在一系列虚拟试样上进行测量来证明该方法应用的可接受性，该虚拟试样涵盖拟议试样长度和包含足够颗粒以充分代表散装材料的试样长度之间的一系列长度。

1.1 This test method covers a procedure for measuring the longitudinal and transverse (shear) sonic velocities in manufactured carbon and graphite which can be used to obtain approximate values for the elastic constants: Young’s modulus ( E ), the shear modulus ( G ), and Poisson’s ratio ( v ). 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 Sonic velocity measurements are useful for comparing materials with similar elastic properties, dimensions, and microstructure. 5.2 Eq 1 provides an accurate value of Young’s modulus only for isotropic, non-attenuative, non-dispersive materials of infinite dimensions. For non-isotropic graphite Eq 1 can be modified to take into account the Poisson’s ratios in all directions. As graphite is a strongly attenuative material, the value of Young’s modulus obtained with Eq 1 will be dependent on specimen length. If the specimen lateral dimensions are not large compared with the wavelength of the propagated pulse, then the value of Young’s modulus obtained with Eq 1 will be dependent on the specimen lateral dimensions. The accuracy of the Young’s modulus calculated from Eq 1 will also depend upon uncertainty in Poisson’s ratio and its impact on the evaluation of the Poisson’s factor in Eq 2 . However, a value for Young’s modulus Eq 1 or Eq 7 ) can be obtained for many applications, which is often in good agreement with the value obtained by other more accurate methods, such as in Test Method C747 . The technical issues and typical values of corresponding uncertainties are discussed in detail in STP 1578. 6 5.3 If the grain size of the carbon or graphite is greater than or about equal to the wavelength of the sonic pulse, the method may not provide a value of the Young’s modulus representative of the bulk material. Therefore it would be desirable to test a lower frequency (longer wavelength) to demonstrate that the range of obtained velocity values are within acceptable levels of accuracy. Significant signal attenuation should be expected when grain size of the material is greater than or about equal to the wavelength of the transmitted sonic pulse or the material is more porous than would be expected for as-manufactured graphite. Note 1: Due to frequency dependent attenuation in graphite, the wavelength of the sonic pulse through the test specimen is not necessarily the same wavelength of the transmitting transducer. 5.4 If the sample is only a few grains thick, the acceptability of the method’s application should be demonstrated by initially performing measurements on a series of dummy specimens covering a range of lengths between the proposed test specimen’s length and a specimen length incorporating sufficient grains to adequately represent the bulk material.