1.1 本规程涵盖了结构工程固体（如单片陶瓷、增韧陶瓷和陶瓷基复合材料）中超声波速度的测量程序。 1.2 这种做法是基于宽带脉冲回波接触超声方法。该程序涉及一种计算机实现的频域方法，用于精确测量试样或零件背面返回的回波对之间的时间延迟。 1.3 本规程描述了使用数字互相关算法进行速度测量的过程。互相关函数产生任意两个回波波形之间的时间延迟 ( 1. ) 。 2. 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ====意义和用途====== 4.1 本实践中描述的速度测量可用于表征影响机械或物理性能的材料变化。该程序可用于测量单片陶瓷中微观结构特征的变化，如晶粒结构、孔隙分数和密度变化。 4.2 本文所述的速度测量可以评估给定材料或部件内孔隙率的细微变化，例如，在陶瓷超导体和结构陶瓷样品中 ( 2. ， 3. ) 。 4.3 除了陶瓷和陶瓷复合材料外，本文所述的速度测量还可应用于多晶和单晶金属、金属基复合材料和聚合物基复合材料。 4.4 实践中给出了另一种速度测量技术 E494 。

1.1 This practice covers a procedure for measurement of ultrasonic velocity in structural engineering solids such as monolithic ceramics, toughened ceramics, and ceramic matrix composites. 1.2 This practice is based on the broadband pulse-echo contact ultrasonic method. The procedure involves a computer-implemented, frequency-domain method for precise measurement of time delays between pairs of echoes returned by the back surface of a test sample or part. 1.3 This practice describes a procedure for using a digital cross-correlation algorithm for velocity measurement. The cross-correlation function yields a time delay between any two echo waveforms ( 1 ) . 2 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 ====== 4.1 The velocity measurements described in this practice may be used to characterize material variations that affect mechanical or physical properties. This procedure is useful for measuring variations in microstructural features such as grain structure, pore fractions, and density variations in monolithic ceramics. 4.2 Velocity measurements described herein can assess subtle variations in porosity within a given material or component, as, for example, in ceramic superconductors and structural ceramic specimens ( 2 , 3 ) . 4.3 In addition to ceramics and ceramic composites, the velocity measurements described herein may be applied to polycrystalline and single crystal metals, metal matrix composites, and polymer matrix composites. 4.4 An alternative technique for velocity measurement is given in Practice E494 .