ISO 22889:2013规定了通过对塑性变形表现出低约束的裂纹试样进行准静态加载来确定均质金属材料的裂纹张开位移δ 5和临界裂纹尖端张开角ψ c的稳定裂纹扩展阻力的方法。紧凑和中等裂纹的拉伸试样被缺口，疲劳预裂，并在缓慢增加的位移下进行测试。 ISO 22889:2013描述了涵盖对不满足尺寸不敏感断裂特性要求的试样进行测试的方法；即相对较薄规格中的致密试样和中裂纹拉伸试样。 给出了确定裂纹扩展阻力曲线（R曲线）的方法。根据ISO 12135测定致密试样的断裂韧性点值。给出了中裂纹拉伸试样断裂韧性点值的确定方法。 使用多样本或单样本方法确定抗裂纹扩展性。多样本方法要求将几个名义上相同的样本中的每一个加载到指定的位移水平。标记延性裂纹扩展的程度，然后将试样破开以测量裂纹扩展。基于卸载柔度或电位跌落技术的单试样方法可用于测量裂纹扩展，前提是它们满足指定的精度要求。ISO 12135中描述了单样本技术的建议。使用任一技术，目标是确定足够数量的数据点以充分描述材料的抗裂纹扩展行为。δ 5的测量相对简单且已得到充分证实。δ 5结果用阻力曲线表示，该阻力曲线已被证明在指定的裂纹扩展极限内是唯一的。超过这些限制，致密试样的δ 5 R曲线显示出对试样宽度的强依赖性，而中裂纹拉伸试样的δ 5 R曲线显示出弱依赖性。 CTOA更难通过实验确定。临界CTOA表示为一定量的裂纹扩展后达到的恒定值。CTOA概念已被证明适用于非常大量的裂纹扩展，并且可以应用于超出δ 5应用的当前限制。 这两种抗裂纹扩展措施都适用于结构评估。δ 5概念已经很好地建立，可以通过现有评估程序中的简单裂纹驱动力公式应用于结构完整性问题。CTOA概念通常更准确。其结构应用需要数值方法，即有限元分析。 研究表明，对于最大载荷下的致密和中等裂纹拉伸试样，恒定CTOA的概念与独特的R曲线之间有着非常密切的关系。需要进一步研究以建立δ 5 R曲线和临界CTOA值之间的解析或数值关系。

ISO 22889:2013 specifies methods for determining the resistance to stable crack extension in terms of crack opening displacement, δ₅, and critical crack tip opening angle, ψ_c, for homogeneous metallic materials by the quasistatic loading of cracked specimens that exhibit low constraint to plastic deformation. Compact and middle-cracked tension specimens are notched, precracked by fatigue, and tested under slowly increasing displacement. ISO 22889:2013 describes methods covering tests on specimens not satisfying requirements for size-insensitive fracture properties; namely, compact specimens and middle-cracked tension specimens in relatively thin gauges. Methods are given for determining the crack extension resistance curve (R-curve). Point values of fracture toughness for compact specimens are determined according to ISO 12135. Methods for determining point values of fracture toughness for the middle-cracked tension specimen are given. Crack extension resistance is determined using either the multiple-specimen or single-specimen method. The multiple-specimen method requires that each of several nominally identical specimens be loaded to a specified level of displacement. The extent of ductile crack extension is marked and the specimens are then broken open to allow measurement of crack extension. Single-specimen methods based on either unloading compliance or potential drop techniques can be used to measure crack extension, provided they meet specified accuracy requirements. Recommendations for single-specimen techniques are described in ISO 12135. Using either technique, the objective is to determine a sufficient number of data points to adequately describe the crack extension resistance behaviour of a material. The measurement of δ₅ is relatively simple and well established. The δ₅ results are expressed in terms of a resistance curve, which has been shown to be unique within specified limits of crack extension. Beyond those limits, δ₅ R-curves for compact specimens show a strong specimen dependency on specimen width, whereas the δ₅ R-curves for middle-cracked tension specimens show a weak dependency. CTOA is more difficult to determine experimentally. The critical CTOA is expressed in terms of a constant value achieved after a certain amount of crack extension. The CTOA concept has been shown to apply to very large amounts of crack extension and can be applied beyond the current limits of δ₅ applications. Both measures of crack extension resistance are suitable for structural assessment. The δ₅ concept is well established and can be applied to structural integrity problems by means of simple crack driving force formulae from existing assessment procedures. The CTOA concept is generally more accurate. Its structural application requires numerical methods, i.e. finite element analysis. Investigations have shown a very close relation between the concept of constant CTOA and a unique R-curve for both compact and middle-cracked tension specimens up to maximum load. Further study is required to establish analytical or numerical relationships between the δ₅ R-curve and the critical CTOA values.