本CWA描述了通过EWF方法评估薄韧性金属板的平面应力断裂韧性的程序。该文件提供了样本制备、测试和数据后处理的指南，以及该方法的局限性。 注1:本文件中提出的试验方法适用于呈现平面应力条件的相对较薄的金属板材料，其不符合ISO 12135:2016中所述的厚度要求。值得注意的是，通过本方法获得的韧性值为厚度- 依赖的。因此，它们不能被视为固有材料特性，而是特定板材厚度的几何无关常数。 注2:推荐的试样为双面缺口拉伸（凹痕），因为其对称性以及试验期间试样的最小旋转和屈曲。试样有缺口，疲劳预裂，并以恒定位移率进行断裂试验。或者，描述了用于获得尖锐缺口凹痕试样的机械开槽工艺。研究表明，通过这种机械开槽工艺制备的试样获得的EWF结果与通过疲劳预处理获得的结果相当- 一系列AHS的开裂试样。需要进一步分析，以确认该程序在其他强度较低材料中制备试样的可靠性。 注3:该方法要求测试具有相同几何形状但不同裂纹长度的多个试样。通过试验，得到了两个特征参数；断裂的特定基本功we和非基本塑性功wp乘以形状几何因子β。我们独立于平面内尺寸，表示薄韧性板材的平面应力断裂韧性。 由于它是从完整断裂的平均能量值中获得的，因此它被视为稳定裂纹扩展的总阻力值，即它包含裂纹萌生和扩展阻力的能量贡献。还可以确定单个萌生韧性值wei，该值表示材料对裂纹扩展萌生的抵抗力。参数βwp取决于试样尺寸，因此，它不是材料常数。 注4:稳定裂纹扩展阻力也可用临界裂纹张开位移（δc）表示。 建立了we、δc与流动特性之间的经验关系。

This CWA describes the procedure for the evaluation of the plane stress fracture toughness of thin ductile metallic sheets by means of the EWF methodology. The document provides the guidelines for specimen preparation, testing and data post-processing as well as the limitations of the method. NOTE 1 The test method proposed in this document is intended to relatively thin metallic sheet materials presenting plane stress conditions, which do not fulfil the thickness requirements described in ISO 12135:2016. It is important noting that toughness values obtained by the present method are thickness-dependent. Therefore, they cannot be considered as an intrinsic material property but a geometry-independent constant for a specific sheet thickness. NOTE 2 The recommended specimen is the Double Edge Notched Tension (DENT) because of its symmetry and minimal specimen rotation and buckling during the test. The specimens are notched, fatigue pre-cracked and tested up to fracture at a constant displacement rate. Alternatively, a mechanical notching process is described for obtaining sharp-notched DENT specimens. Investigations have shown that EWF results obtained with specimens prepared by means of this mechanical notching process are equivalent to those obtained with fatigue pre-cracked specimens for a range of AHSS. Further analysis is required to confirm the reliability of this procedure for specimen preparation in other materials of lower strength. NOTE 3 The method requires testing multiple specimens with the same geometry but different crack lengths. From the test, two characteristic parameters are obtained; the specific essential work of fracture, we, and the non-essential plastic work, wp, multiplied by a shape geometry factor β. we is independent of in-plane dimensions and represents the plane stress fracture toughness of thin ductile sheet materials. Since it is obtained from an average of energy values for the complete fracture, it is considered an overall resistance value to stable crack extension, i.e. it contains energetics contributions from crack initiation and propagation resistance. It is also possible determining a single initiation toughness value, wei, which represents the material resistance to crack growth initiation. The parameter βwp depends upon specimen dimensions and, therefore, it is not a material constant. NOTE 4 Resistance to stable crack extension can be also expressed in terms of a critical crack opening displacement (δc). An empirical relationship between we, δc and flow properties is established.