Calculation and comparison on fracture toughness of specific reliability between ASTM and ISO standards

Fracture toughness, as a crucial mechanical property, is essential in the research of fatigue crack propagation and fatigue life. Considering the enormous data scatter of the fracture toughness in experiments, a data processing method is proposed to calculate the fracture toughness for the specified reliability. Based on the traditional data processing method shown in the relative standards, the two-dimensional, one-sided tolerance factor is introduced to calculate the influence of the reliability. In addition, by comparing the data processing methods of the fracture toughness presented in the ISO12135:2016 and ASTM E1820-2013 standards, the differences between them were mainly the range of the qualified data, the function of the construction line, and the equation of the regression line. Because the construction lines of the two standards are based on two different material constitutive models, if the constitutive model of material is more aligned with that of the ideal elastic plastic material, the ASTM E1820-2013 standard is recommended; otherwise, the ISO12135:2016 standard is recommended. For 30CrNi2MoVA, the ISO 12135:2016 standard was more suitable, and the error of the JIC obtained by the two standards was about 5%.