1.1 本试验方法包括通过使用承受单轴力的试样来测定名义均匀材料的疲劳性能。本手册旨在为材料研发、机械设计、过程和质量控制、产品性能和故障分析等活动提供支持，作为疲劳试验的指南。虽然本试验方法主要用于应变控制疲劳试验，但某些章节可能为力控制或应力控制试验提供有用信息。 1.2 本试验方法的使用仅限于试样，不包括全尺寸部件、结构或消费品的试验。 1.3 本试验方法适用于与时间相关的非弹性应变幅值相同或小于与时间无关的非弹性应变幅值的温度和应变率。环境因素（如温度、压力、湿度、介质等）不受限制，前提是在整个试验过程中对其进行控制，不会导致尺寸随时间的损失或变化，并在数据报告中详细说明。 注1: 术语 非弹性 此处用于指所有非弹性应变。术语 塑料 此处仅指非弹性应变的与时间无关（即非蠕变）分量。为了真正确定与时间无关的应变，必须瞬时施加力，这是不可能的。当应变率超过某个值时，可以获得与时间无关的应变的有用工程估计。例如，应变率为1 × 10 −3. 证券交易委员会 −1. 通常用于此目的。该值应随着试验温度的升高而增加。 1.4 本试验方法仅限于测试承受轴向力的均匀规截面试样，如所示 图1 （a） 。测试仅限于应变控制循环。试验方法可适用于沙漏试样，见 图1 （b） ，但用户应注意数据分析和解释中的不确定性。测试主要在恒定振幅循环下进行，可能包含重复间隔的间隔保持时间。试验方法可适用于指导更一般情况下的试验，其中应变或温度可能根据应用特定历史而变化。 在这种情况下，数据分析可能不遵循此测试方法。 图1 推荐的低周疲劳试样 注1: * 建议尺寸d为6.35 mm[0.25 in]。看见 7.1 . 允许的中心** 根据材料硬度，该直径可以大于或小于2d。在典型的韧性材料中，通常使用小于2d的直径，在典型的脆性材料中，可能需要大于2d的直径。 注2: 螺纹连接更容易出现较差的轴向对准，并且有更大的反冲可能性，尤其是当与把手的连接设计不当时。 1.5 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。 1.6 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《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====== 4.1 应变控制疲劳是一种受影响力控制疲劳的相同变量影响的现象。应变控制疲劳的性质对疲劳试验方法提出了独特的要求。特别是，应测量循环总应变，并确定循环塑性应变。此外，这两种应变中的任何一种通常用于建立循环极限；总应变通常在整个循环中得到控制。该试验方法的唯一性及其产生的结果是在试验期间的任何时间测定循环应力和应变。 与恒定振幅结果相比，恒定振幅以外的应变历史差异会改变疲劳寿命（例如，周期性过应变和块或频谱历史）。同样，与恒定振幅、完全反向疲劳试验相比，非零平均应变的存在和变化的环境条件可能会改变疲劳寿命。在分析和解释此类案例的数据时必须小心。在变幅或频谱应变历史的情况下，可以实际进行循环计数 E1049号 . 4.2 应变控制疲劳是工业产品设计中的一个重要考虑因素。对于部件或部件的一部分承受机械或热诱导循环塑性应变的情况，这一点很重要，这些应变在相对较少的范围内（即约<10）导致失效 5. )周期。从应变控制疲劳试验中获得的信息可能是制定设计标准以防止部件疲劳失效的一个重要因素。 4.3 应变控制疲劳试验结果在机械设计、材料研发、过程和质量控制、产品性能和失效分析等领域非常有用。 应变控制疲劳试验程序的结果可用于制定应力、总应变、塑性应变和疲劳寿命循环变量之间的经验关系。它们通常用于数据关联，例如循环应力或应变与寿命的曲线，以及从材料寿命的某一部分（通常为一半）的磁滞回线获得的循环应力与循环塑性应变的曲线。对循环应力-应变曲线的检查及其与单调应力-应变曲线的比较提供了有关材料循环稳定性的有用信息，例如，硬度、屈服强度、极限强度、应变值是否为- 硬化指数和强度系数将因循环塑性应变而增加、减少或保持不变（即材料是否硬化、软化或稳定） ( 1. ) . 3. 在高温试验期间，随时间变化的非弹性应变的存在为研究这些应变对疲劳寿命和材料循环应力应变响应的影响提供了机会。有关应变率效应、松弛行为和蠕变的信息也可以从这些测试中获得。如果可以确定应变，并且应力或应变的多轴状态及其梯度与单轴应变数据正确相关，则简单几何形状试样的单轴试验结果可以应用于具有缺口或其他复杂形状的部件的设计。

1.1 This test method covers the determination of fatigue properties of nominally homogeneous materials by the use of test specimens subjected to uniaxial forces. It is intended as a guide for fatigue testing performed in support of such activities as materials research and development, mechanical design, process and quality control, product performance, and failure analysis. While this test method is intended primarily for strain-controlled fatigue testing, some sections may provide useful information for force-controlled or stress-controlled testing. 1.2 The use of this test method is limited to specimens and does not cover testing of full-scale components, structures, or consumer products. 1.3 This test method is applicable to temperatures and strain rates for which the magnitudes of time-dependent inelastic strains are on the same order or less than the magnitudes of time-independent inelastic strains. No restrictions are placed on environmental factors such as temperature, pressure, humidity, medium, and others, provided they are controlled throughout the test, do not cause loss of or change in dimension with time, and are detailed in the data report. Note 1: The term inelastic is used herein to refer to all nonelastic strains. The term plastic is used herein to refer only to the time-independent (that is, noncreep) component of inelastic strain. To truly determine a time-independent strain the force would have to be applied instantaneously, which is not possible. A useful engineering estimate of time-independent strain can be obtained when the strain rate exceeds some value. For example, a strain rate of 1 × 10 −3 sec −1 is often used for this purpose. This value should increase with increasing test temperature. 1.4 This test method is restricted to the testing of uniform gage section test specimens subjected to axial forces as shown in Fig. 1 (a). Testing is limited to strain-controlled cycling. The test method may be applied to hourglass specimens, see Fig. 1 (b), but the user is cautioned about uncertainties in data analysis and interpretation. Testing is done primarily under constant amplitude cycling and may contain interspersed hold times at repeated intervals. The test method may be adapted to guide testing for more general cases where strain or temperature may vary according to application specific histories. Data analysis may not follow this test method in such cases. FIG. 1 Recommended Low-Cycle Fatigue Specimens Note 1: * Dimension d is recommended to be 6.35 mm [0.25 in.]. See 7.1 . Centers permissible. ** This diameter may be made greater or less than 2d depending on material hardness. In typically ductile materials diameters less than 2d are often employed and in typically brittle materials diameters greater than 2d may be found desirable. Note 2: Threaded connections are more prone to inferior axial alignment and have greater potential for backlash, particularly if the connection with the grip is not properly designed. 1.5 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. 1.6 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 Strain-controlled fatigue is a phenomenon that is influenced by the same variables that influence force-controlled fatigue. The nature of strain-controlled fatigue imposes distinctive requirements on fatigue testing methods. In particular, cyclic total strain should be measured and cyclic plastic strain should be determined. Furthermore, either of these strains typically is used to establish cyclic limits; total strain usually is controlled throughout the cycle. The uniqueness of this test method and the results it yields are the determination of cyclic stresses and strains at any time during the tests. Differences in strain histories other than constant-amplitude alter fatigue life as compared with the constant amplitude results (for example, periodic overstrains and block or spectrum histories). Likewise, the presence of nonzero mean strains and varying environmental conditions may alter fatigue life as compared with the constant-amplitude, fully reversed fatigue tests. Care must be exercised in analyzing and interpreting data for such cases. In the case of variable amplitude or spectrum strain histories, cycle counting can be performed with Practice E1049 . 4.2 Strain-controlled fatigue can be an important consideration in the design of industrial products. It is important for situations in which components or portions of components undergo either mechanically or thermally induced cyclic plastic strains that cause failure within relatively few (that is, approximately <10 5 ) cycles. Information obtained from strain-controlled fatigue testing may be an important element in the establishment of design criteria to protect against component failure by fatigue. 4.3 Strain-controlled fatigue test results are useful in the areas of mechanical design as well as materials research and development, process and quality control, product performance, and failure analysis. Results of a strain-controlled fatigue test program may be used in the formulation of empirical relationships between the cyclic variables of stress, total strain, plastic strain, and fatigue life. They are commonly used in data correlations such as curves of cyclic stress or strain versus life and cyclic stress versus cyclic plastic strain obtained from hysteresis loops at some fraction (often half) of material life. Examination of the cyclic stress–strain curve and its comparison with monotonic stress–strain curves gives useful information regarding the cyclic stability of a material, for example, whether the values of hardness, yield strength, ultimate strength, strain-hardening exponent, and strength coefficient will increase, decrease, or remain unchanged (that is, whether a material will harden, soften, or be stable) because of cyclic plastic straining ( 1 ) . 3 The presence of time-dependent inelastic strains during elevated temperature testing provides the opportunity to study the effects of these strains on fatigue life and on the cyclic stress-strain response of the material. Information about strain rate effects, relaxation behavior, and creep also may be available from these tests. Results of the uniaxial tests on specimens of simple geometry can be applied to the design of components with notches or other complex shapes, provided that the strains can be determined and multiaxial states of stress or strain and their gradients are correctly correlated with the uniaxial strain data.