1.1 本规程描述了一种使用传统脉冲回波超声波探伤设备测量具有平坦平行表面的材料或部件中超声波的表观衰减的程序，其中反射指示显示在a扫描显示中。 1.2 测量程序很容易适用于确定材料之间的相对衰减。对于指示材料固有性质的绝对（真实）衰减测量，有必要校正样本几何形状、声束发散、仪器和程序效应。 这些结果可以通过更专业的超声波设备和技术获得。 1.3 以国际单位制或英寸-磅单位表示的数值应单独视为标准值。每个系统中规定的值可能不是精确的等效值；因此，每个系统应相互独立使用。将两个系统的值合并可能会导致不符合标准。 1.4 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。 1.5 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 材料表观衰减的测量在各种应用中非常有用，例如比较不同批次材料的热处理或评估材料因环境引起的降解。 5.2 固体中可以传播几种不同的波振动模式。本规程涉及与浸入法引入试样的纵波相关的衰减。 5.3 这种做法允许比较几何相似试样的表观衰减。 5.4 对于表观衰减的测定，本文所述程序仅适用于超声波束远场的测量。

1.1 This practice describes a procedure for measuring the apparent attenuation of ultrasound in materials or components with flat, parallel surfaces using conventional pulse-echo ultrasonic flaw detection equipment in which reflected indications are displayed in an A-scan presentation. 1.2 The measurement procedure is readily adaptable for the determination of relative attenuation between materials. For absolute (true) attenuation measurements, indicative of the intrinsic nature of the material, it is necessary to correct for specimen geometry, sound beam divergence, instrumentation, and procedural effects. These results can be obtained with more specialized ultrasonic equipment and techniques. 1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. 1.4 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. 1.5 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 The measurement of apparent attenuation in materials is useful in applications such as the comparison of heat treatments of different lots of material or the assessment of the degradation of materials due to environment. 5.2 Several different modes of wave vibration can be propagated in solids. This practice is concerned with the attenuation associated with longitudinal waves introduced into the specimen by the immersion method. 5.3 This practice allows for the comparison of the apparent attenuations of geometrically similar specimens. 5.4 For the determination of apparent attenuation, the procedures described herein are valid only for measurements in the far field of the ultrasonic beam.