PSI - Issue 42

Zeng Chen et al. / Procedia Structural Integrity 42 (2022) 180–188 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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uniaxial bending simulations, the load-displacement curves of the loading punches are drawn to be compared with experimental data in Figure 6. The loads were obtained by the reaction forces at the reference points of the loading punches. It is found that the FEA curves agree well with the experimental curves. Their load-line compliances of the elastic region are the same. Comparisons between the stress contour diagrams and the fractured specimens are also shown in Figure 7 . The “S” shape fracture trajectory observed on the 5PB specimen, which was stated as an effect of biaxiality, shows the biaxiality was captured successfully in the experiments (Leevers et al., 1976). From Figure 7, it can be found that the maximum stress distributions starting from the crack tips (except loading area) are consistent with the fracture trajectories of two specimens, which indicates the numerical modelling is correct. All simulated J -integral of 3PB and 5PB models were the maximum values through the thicknesses and also from the 10th contour when the load displacement reached to the failure values. Due to the lack of standard procedure for these two bending specimens, the simulation results were used in the following calculations and discussions. For convenience of comparison, these simulated J -integral were also converted into K JC with the Eq. (3).

Figure 6. Comparisons of load-displacement curves between FEA results and experimental results

Crack tips

Crack tips

Maximum stress distribution

Maximum stress distribution

Loading area

Loading area

Crack tip

Crack tip

Figure 7. Comparisons between stress contour diagrams and fractured specimens (1_U_1 and 1_B_2)

4.2. Results of different constraint parameters To obtain the parameter Q , the opening stress along the line ahead of the crack tip was extracted from FEA. For