1.1 本规程涵盖了使用脉冲激励法（IEM）的一般程序，以便于自然频率测量和检测金属和非金属零件中的缺陷和材料变化。这种测试方法也被称为脉冲激励技术（IET）、声共振测试（ART）、ping测试、抽头测试和其他名称。IEM被列为共振超声光谱学（RUS）方法。该方法应用脉冲负载来激励并记录零件的共振频率。将这些记录的共振频率与参考总体或同一零件的实例的子组/族内或建模频率或两者进行比较。 1.2 绝对频移、共振阻尼和共振模式差异可用于区分可接受零件和具有材料差异和缺陷的零件。 这些缺陷和材料差异包括裂纹、孔隙、孔隙率、材料弹性性能差异和残余应力。IEM可应用于采用制造工艺制造的零件，包括但不限于粉末金属烧结、铸造、锻造、机加工、复合材料叠层和增材制造（AM）。 1.3 本规程适用于能够激励、测量、记录和分析声学或超声波频率范围内的多个全身机械振动共振频率或两者兼有的仪器。本规程未提供零件的检验验收标准。然而，它确实讨论了建立脉冲测试特定验收标准的过程。 这些标准包括绝对频率偏移的频率可接受性窗口、统计分析方法的评分标准（Z-score）、诊断共振模式的量具重复性和再现性（R&R），以及制造过程和环境变化的检查标准调整（补偿）。 1.4 这种做法使用英寸磅单位作为主要单位。国际单位制单位包含在括号中仅供参考，是主要单位的数学转换。 1.5 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。 1.6 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 IEM应用程序和功能-- IEM已成功应用于金属和非金属零件的制造、维护和维修中的广泛无损检测应用。检测到的异常示例在 1.1 和 6.2 IEM已被证明可以在几乎所有的制造、维护或维修模式中提供快速、经济高效和准确的无损检测解决方案。 成功应用重点的例子包括但不限于:烧结粉末金属、铸件、锻件、冲压件、陶瓷、玻璃、木材、焊接件、热处理、复合材料、增材制造、机械加工产品和钎焊产品。 4.2 IEM的一般方法和设备要求: 4.2.1 IEM系统由硬件和软件组成，能够感应振动，记录部件对感应振动的响应，并对收集的数据进行分析。 4.2.2 硬件要求-- 桌面冲击激励系统和生产级跌落激励系统的示例如所示 图1 和 图2 分别地IEM系统包括: 向物体提供脉冲激励的激励装置（例如，模态锤/冲击装置/下落系统）、振动检测器（例如，麦克风）、信号放大器、模数转换器（ADC）、嵌入式逻辑和数据用户界面（UI）。测试零件通常可以在任何表面类型上，但考虑到可能的阻尼影响，也可以对其进行支撑（例如，泡沫支撑，用弹性材料固定）。以下示意图显示了冲击激励方法的基本部分( 图3 )和液滴激励方法( 图4 )。 图1 使用非仪器冲击器的IEM桌面测试系统 图2 生产级跌落励磁系统 图3 冲击激励方法示意图 图4 跌落激励方法示意图 4.3 限制和限制: 4.3.1 IEM需要改变结构完整性，以正确地对不同的部分进行分类。这意味着，只有外观问题的零件，如视觉表面异常，仍需要通过集中的视觉检查进行检查。 4.3.2 缺陷的位置或特定缺陷类型的表征具有挑战性。由于IEM测量零件的全身响应，缺陷的定位和分类通常需要额外的数据（如额外的无损和破坏性评估）和分析。 4.3.3 大的原材料或工艺变化，或两者兼而有之，可能会限制IEM的灵敏度，而没有一些方法来补偿这些变化。 4.3.4 如果没有一些补偿这些变化的方法，具有宽物理温度范围的零件组就不是IEM的好对象。温度会影响固有频率，因此零件测试需要温度的稳定。只要零件在测试过程中稳定，就可以在很大的温度范围内获取数据。 4.3.5 IEM是一种体积检查方法。对缺陷的敏感性将由缺陷的大小相对于零件的大小和质量来驱动。例如，在0.5磅的零件中可以检测到的特定长度的细小发际裂纹在100磅的零件上可能无法检测到。 4.3.6 在选择和配置IEM检查时，必须考虑待测试零件的预期有用频率范围。 许多IEM系统仅限于检测高达50kHz的频率，但更现代的系统已经证明在某些部件上检测高达150kHz的频率。尺寸较小的零件或由某些材料制成的零件，或两者兼有，其共振谱可能部分或完全超出某些IEM系统的频率范围。来自脉冲的能量分布和来自干扰谐波模式的衰减的物理特性也可以导致IEM频率范围的高端的信噪比降低。 4.3.7 共振不良或阻尼振动的材料通常不适合IEM考试。

1.1 This practice covers a general procedure for using the Impulse Excitation Method (IEM) to facilitate natural frequency measurement and detection of defects and material variations in metallic and non-metallic parts. This test method is also known as Impulse Excitation Technique (IET), Acoustic Resonance Testing (ART), ping testing, tap testing, and other names. IEM is listed as a Resonance Ultrasound Spectroscopy (RUS) method. The method applies an impulse load to excite and then record resonance frequencies of a part. These recorded resonance frequencies are compared to a reference population or within subgroups/families of examples of the same part, or modeled frequencies, or both. 1.2 Absolute frequency shifting, resonance damping, and resonance pattern differences can be used to distinguish acceptable parts from parts with material differences and defects. These defects and material differences include, cracks, voids, porosity, material elastic property differences, and residual stress. IEM can be applied to parts made with manufacturing processes including, but not limited to, powdered metal sintering, casting, forging, machining, composite layup, and additive manufacturing (AM). 1.3 This practice is intended for use with instruments capable of exciting, measuring, recording, and analyzing multiple whole body, mechanical vibration resonance frequencies in acoustic or ultrasonic frequency ranges, or both. This practice does not provide inspection acceptance criteria for parts. However, it does discuss the processes for establishing acceptance criteria specific to impulse testing. These criteria include frequency acceptability windows for absolute frequency shifting, scoring criteria for statistical analysis methods (Z-score), Gage Repeatability & Reproducibility (R&R) for diagnostic resonance modes, and inspection criteria adjustment (compensation) for manufacturing process and environmental variations. 1.4 This practice uses inch pound units as primary units. SI units are included in parentheses for reference only and are mathematical conversions of the primary units. 1.5 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. 1.6 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 IEM Applications and Capabilities— IEM has been successfully applied to a wide range of NDT applications in the manufacture, maintenance, and repair of metallic and non-metallic parts. Examples of anomalies detected are discussed in 1.1 and 6.2 . IEM has been proven to provide fast, cost-effective, and accurate NDT solutions in nearly all manufacturing, maintenance, or repair modalities. Examples of the successful application focuses include, but are not limited to: sintered powder metals, castings, forgings, stampings, ceramics, glass, wood, weldments, heat treatment, composites, additive manufacturing, machined products, and brazed products. 4.2 General Approach and Equipment Requirements for IEM: 4.2.1 IEM systems are comprised of hardware and software capable of inducing vibrations, recording the component response to the induced vibrations, and executing analysis of the data collected. 4.2.2 Hardware Requirements— Examples of a tabletop impact excitation system and a production-grade drop excitation system are shown in Fig. 1 and Fig. 2 , respectively. IEM systems include: an excitation device (for example, modal hammer / impact device / dropping system) providing an impulse excitation to the object, a vibration detector (for example., microphone), a signal amplifier, an Analog-to-Digital Converter (ADC), an embedded logic, and a data User Interface (UI). Tested parts can typically be on any surface type, but they can also be supported (for example, foam support, held with an elastic) in consideration of possible damping influences. The following schematics show the basic parts for an impact excitation approach ( Fig. 3 ) and a drop excitation approach ( Fig. 4 ). FIG. 1 IEM Tabletop Testing System Using a Non-Instrumented Impactor FIG. 2 Production-Grade Drop Excitation System FIG. 3 Schematic of Impact Excitation Approach FIG. 4 Schematic of Drop Excitation Approach 4.3 Constraints and Limitations: 4.3.1 IEM needs a change in structural integrity to properly sort different parts. This means that parts with only cosmetic issues, such as a visual surface anomaly would still need be inspected with a focused visual inspection. 4.3.2 The location of a flaw or specific flaw type characterization is challenging. As IEM measures the whole-body response of a part, location and categorization of defects usually requires additional data (such as additional nondestructive and destructive evaluation) and analysis. 4.3.3 Large raw material or process variation, or both, may limit the sensitivity of IEM without some method for compensating for those variations. 4.3.4 Groups of parts with a wide range of physical temperatures are not good subjects for IEM without some method for compensating for those variations. Temperature affects the natural frequencies, so stabilization of temperature is desired for parts testing. Data can be taken over a large range of temperatures, as long as the parts are stable during the testing. 4.3.5 IEM is a volumetric inspection method. Sensitivity to defects will be driven by the size of the defect relative to the size and mass of the part. For example, a small hairline crack of a certain length that may be detectable in a 0.5 lb part may not be detectable in a 100 lb part. 4.3.6 The expected useful frequency range of the part to be tested must be considered when selecting and configuring an IEM examination. Many IEM systems are limited to detecting frequencies up to 50 kHz, but more modern systems have demonstrated detection of frequencies up to 150 kHz on some parts. Parts with small dimensions or parts made from certain materials, or both, may have resonance spectra that fall partially or entirely outside of the frequency range of some IEM systems. The physics of energy distribution from the impulse and attenuation from interfering harmonic modes can also cause a reduction in signal-to-noise ratio at the higher end of IEM frequency ranges. 4.3.7 Materials that resonate poorly or dampen vibrations are typically not good candidates for IEM examination.