1.1 本规程描述了先进结构陶瓷材料超声衰减系数的测量程序。该程序基于脉冲回波接触模式中使用的宽带缓冲压电探针，并发射纵波或横波。该实践的主要目标是材料表征。 1.2 该程序要求将超声波探头连接到板状样品的表面，并恢复连续的前表面和后表面回波（参见 图3 )。回波的功率谱用于计算样品材料的衰减谱（衰减系数作为超声频率的函数）。选择换能器带宽和光谱响应以覆盖与固体试样中感兴趣的微观结构特征相互作用的一系列频率和相应波长。 1.3 本规程的目的是建立超声波衰减系数测量的基本程序。这些测量应区分和量化固体样品之间的微观结构差异，从而有助于建立一个参考数据库，用于比较材料和校准超声衰减测量设备。 1.4 这种做法适用于单片陶瓷和多晶金属。该实践可应用于晶须增强陶瓷、颗粒增韧陶瓷和陶瓷复合材料，前提是满足本文所述的单片陶瓷对样品尺寸、形状和光洁度的类似约束。 1.5 本规程规定了样本大小、形状和光洁度的限制条件，以确保有效的衰减系数测量。 本规程还描述了完成测量的仪器、方法和数据处理程序。 1.6 这种做法不建议用于高度衰减的材料，如非常厚、非常多孔、表面粗糙的单片或复合材料。对于高度不均匀、不均匀、有裂纹、有缺陷或其他缺陷的样品，不建议采用此做法，因为这些样品不能代表所检查材料的性质或固有特性。 1.7 本标准并不旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者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。 1.8 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====== 5.1 此实践可用于表征材料微观结构或测量由于材料加工条件和热、机械或化学暴露而发生的微观结构变化 ( 3. ) 当应用于单片或复合陶瓷时，该程序应显示由于密度、孔隙率和晶粒变化而产生的微观结构梯度。这种做法也可以应用于多晶金属，以评估晶粒尺寸、孔隙率和多相成分的变化。 5.2 该实践可用于测量和比较相同材料的不同样品之间的微观结构变化，或用于感测和测量给定样品内的细微微观结构变化。 5.3 这种做法有助于绘制衰减系数和衰减光谱的变化，因为它们与单片陶瓷、陶瓷复合材料和金属的微观结构和相关性能的变化有关。 5.4 这种做法有助于建立一个参考数据库，用于比较材料和校准超声波衰减测量设备。 5.5 对于厚度大、高度多孔或表面粗糙或高度纹理化的高衰减单片或复合材料，不建议采用此做法。对于这些材料，练习 E664/E664M 可能是适当的。指导 E1495/E1495米 建议用于评估复合材料板和层压板之间的衰减差异，例如，除了具有复杂的纤维结构或热机械退化外，还可能表现出普遍的基体孔隙率或基体裂纹 ( 3. ) 提出的ASTM测量高级陶瓷中超声波速度的标准实施规程( C1331 )建议用于表征具有显著孔隙率或孔隙率变化的单片陶瓷 ( 4 ) .

1.1 This practice describes a procedure for measurement of ultrasonic attenuation coefficients for advanced structural ceramic materials. The procedure is based on a broadband buffered piezoelectric probe used in the pulse-echo contact mode and emitting either longitudinal or shear waves. The primary objective of this practice is materials characterization. 1.2 The procedure requires coupling an ultrasonic probe to the surface of a plate-like sample and the recovery of successive front surface and back surface echoes (refer to Fig. 3 ). Power spectra of the echoes are used to calculate the attenuation spectrum (attenuation coefficient as a function of ultrasonic frequency) for the sample material. The transducer bandwidth and spectral response are selected to cover a range of frequencies and corresponding wavelengths that interact with microstructural features of interest in solid test samples. 1.3 The purpose of this practice is to establish fundamental procedures for measurement of ultrasonic attenuation coefficients. These measurements should distinguish and quantify microstructural differences among solid samples and therefore help establish a reference database for comparing materials and calibrating ultrasonic attenuation measurement equipment. 1.4 This practice applies to monolithic ceramics and also polycrystalline metals. This practice may be applied to whisker reinforced ceramics, particulate toughened ceramics, and ceramic composites provided that similar constraints on sample size, shape, and finish are met as described herein for monolithic ceramics. 1.5 This practice sets forth the constraints on sample size, shape, and finish that will assure valid attenuation coefficient measurements. This practice also describes the instrumentat- ion, methods, and data processing procedures for accomplishing the measurements. 1.6 This practice is not recommended for highly attenuating materials such as very thick, very porous, rough-surfaced monolithics or composites. This practice is not recommended for highly nonuniform, heterogeneous, cracked, defective, or otherwise flaw-ridden samples that are unrepresentative of the nature or inherent characteristics of the material under examination. 1.7 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. 1.8 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 This practice is useful for characterizing material microstructure or measuring variations in microstructure that occur because of material processing conditions and thermal, mechanical, or chemical exposure ( 3 ) . When applied to monolithic or composite ceramics, the procedure should reveal microstructural gradients due to density, porosity, and grain variations. This practice may also be applied to polycrystalline metals to assess variations in grain size, porosity, and multiphase constituents. 5.2 This practice is useful for measuring and comparing microstructural variations among different samples of the same material or for sensing and measuring subtle microstructural variations within a given sample. 5.3 This practice is useful for mapping variations in the attenuation coefficient and the attenuation spectrum as they pertain to variations in the microstructure and associated properties of monolithic ceramics, ceramic composites and metals. 5.4 This practice is useful for establishing a reference database for comparing materials and for calibrating ultrasonic attenuation measurement equipment. 5.5 This practice is not recommended for highly attenuating monolithics or composites that are thick, highly porous, or that have rough or highly textured surfaces. For these materials Practice E664/E664M may be appropriate. Guide E1495/E1495M is recommended for assessing attenuation differences among composite plates and laminates that may exhibit, for example, pervasive matrix porosity or matrix crazing in addition to having complex fiber architectures or thermomechanical degradation ( 3 ) . The proposed ASTM Standard Practice for Measuring Ultrasonic Velocity in Advanced Ceramics ( C1331 ) is recommended for characterizing monolithic ceramics with significant porosity or porosity variations ( 4 ) .