However, due to defects in the material itself and randomness during the sample processing and experimental loading, even though the experiment process is strictly followed and controlled according to the experiment standard, the test results of the fracture toughness inevitably exhibit considerable statistical dispersion 13.

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Institute for Strength and Vibration of Mechanical Structures, Yangtze University, Jingzhou 434023, Peoples Republic of China.

Mechanical Engineering Academy, Yangtze University, Jingzhou 434023, Peoples Republic of China.

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 J IC obtained by the two standards was about 5.

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It is used widely in the structural design and fatigue life predictions of structures with defects 1, 2.

An accurate and reliable determination of the fracture toughness is of great importance for the failure assessment of equipment.

At present, the fracture toughness tests are performed mainly following the ISO 12135:2016 and ASTM E1820-2013 standards, which are the most accurate methods for measuring the fracture toughness 3, 4.

For different materials and working conditions, different kinds of specimens and experimental procedures have been proposed in the literature to measure the fracture toughness.

This technique was extensively developed by many researchers to estimate the potential for residual life assessment of components during service 5 8.

The Charpy impact test was proposed to avoid the disadvantages of traditional CT(Compact Tension) and SENB(Single Edge Notch Beam) samples.

In contrast, this test requires smaller specimens and simpler experimental equipment.

However, its result only shows the susceptibility of steel to brittle fractures instead of providing the value of fracture toughness 9.

Chen et al. proposed a method to accurately estimate the fracture toughness for 16MnDR steel in the transition region under different test conditions using the master curve method 1, 10.

The spherical indentation test (SIT) was proposed to measure the fracture toughness for ductile metals 2.

Jelitto et al proposed an experimental method to measure the fracture toughness values of porous materials.

However, the CT and three-point bending specimens are the two most common specimens 12.

In particular, CT samples require smaller dimensions and are more suitable for tests of high fracture toughness values.

Beijing 2008 Pc Crack Iso