1.1 本试验方法提供了确定疲劳寿命（失效循环次数，N f )沥青混合料的动态模量（|E*|）随加载循环的降低。该试验获得的结果可用于校准粘弹性连续损伤（VECD）模型，以获得损伤特征曲线，进而可用于获得疲劳寿命（N f )在各种温度、应变水平和频率下（正在为该程序起草单独的标准规程）。 尽管该试验方法主要用于位移（应变）控制疲劳试验，但某些章节可能为力控制试验提供有用信息。 1.2 试验方法描述了确定沥青混凝土失效循环次数所需的试验设备、仪器、试样制作和分析程序。 1.3 本测试方法的文本引用了提供说明材料的注释和脚注。这些注释和脚注（不包括表和图中的注释和脚注）不应视为试验方法的要求。 1.4 单位- 以国际单位制表示的数值应视为标准。本标准不包括其他测量单位。 1.5 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建立适当的安全、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（TBT）委员会发布的《国际标准、指南和建议制定原则决定》中确立的国际公认标准化原则制定的。 =====意义和用途====== 5.1 该试验方法可用于测定沥青混合料的抗疲劳性能。测试方法通常适用于在中间温度下测试的试样。三点弯曲圆柱体试验样品是通过从直径为150mm的旋转压实样品的中心取68 mm直径圆柱体的芯，或从现场岩芯或从现场段切割的板上取水平芯而获得的。取芯后，样品准备好进行测试，不需要进一步的样品制备步骤。 直径68 mm的三点弯曲圆柱体样品的两端不需要切片。 5.2 Timoshenko梁理论用于计算每个加载循环的动态模量降低。该试验可用于研究沥青混合料在不同应变水平、温度和频率下的疲劳行为。结果可用于比较疲劳寿命（N f )对于不同的沥青混合料。N f 值可以计算为50 % 动态模量降低。N f 该值是沥青混合料疲劳性能的指标，包括各种混合料设计特性、沥青粘合剂类型和改性、级配和再生材料。 通常，较高的N f 该值表示更好的疲劳性能。N f 该值可用于在基于性能的混合料设计或施工验收程序中或两者中识别易开裂的混合料。 注1: 该测试方法产生的结果质量取决于执行程序的人员的能力以及所用设备的能力、校准和维护。符合规范标准的机构 第3666页 通常认为能够胜任和客观的测试、取样、检验等。 本试验方法的使用者应注意遵守规范 第3666页 单独使用并不能完全确保可靠的结果。可靠的结果可能取决于许多因素；遵循规范的建议 第3666页 或一些类似的可接受准则提供了评估和控制这些因素的方法。

1.1 This test method provides a procedure to determine the fatigue life (number of cycles to failure, N f ) of asphalt mixtures, and also the reduction in dynamic modulus (|E*|) with loading cycles, using cylindrical samples subjected to three-point cyclic bending. The results obtained from this test can be used to calibrate Viscoelastic Continuum Damage (VECD) models to obtain a damage characteristic curve, which in turn can be used to obtain fatigue lives (N f ) at a variety of temperatures, strain levels, and frequencies (a separate standard practice is being drafted for this procedure). Even though this test method is intended primarily for displacement (strain) controlled fatigue testing, certain sections may provide useful information for force-controlled tests. 1.2 The test method describes the testing apparatus, instrumentation, specimen fabrication, and analysis procedures required to determine the number of cycles to failure of asphalt concrete. 1.3 The text of this test method references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the test method. 1.4 Units— The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard. 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 ====== 5.1 This test method can be utilized to determine the fatigue resistance of asphalt mixtures. The test method is generally valid for specimens that are tested at intermediate temperatures. The three-point bending cylinder test samples are obtained by coring a 68 mm diameter cylinder from the center of a 150 mm diameter gyratory compacted sample, or horizontal coring from field cores or slabs cut from field sections. After coring, the sample is ready for testing and no further sample preparations steps are required. The two ends of the 68 mm diameter three-point bending cylinder sample do not need to be sliced. 5.2 The Timoshenko beam theory is used to calculate the reduction in dynamic modulus for each loading cycle. The test can be used to investigate the fatigue behavior of asphalt mixtures at various strain levels, temperatures, and frequencies. The results can be used to compare the fatigue life (N f ) for different asphalt mixtures. The N f value can be calculated as the 50 % reduction in dynamic modulus. The N f value is an indicator of fatigue performance of asphalt mixtures containing various mix design properties, asphalt binder types and modifications, gradations, and recycled materials. Typically, a higher N f value indicates better fatigue performance. The N f value may be used to identify crack-prone mixtures in performance-based mix design or in construction acceptance procedures, or both. Note 1: The quality of the results produced by this test method are dependent on the competence of the personnel performing the procedure and the capability, calibration, and maintenance of the equipment used. Agencies that meet the criteria of Specification D3666 are generally considered capable of competent and objective testing, sampling, inspection, etc. Users of this test method are cautioned that compliance with Specification D3666 alone does not completely ensure reliable results. Reliable results may depend on many factors; following the suggestions of Specification D3666 or some similar acceptable guideline provides a means of evaluating and controlling some of those factors.