PSI - Issue 42

Toru Yagi et al. / Procedia Structural Integrity 42 (2022) 702–713 Author name / Structural Integrity Procedia 00 (2019) 000 – 000 specimens at 0 ℃ experiences pop-ins. The maximum load drop ratio at 0 ℃ is 16.6%. Therefore, pop-ins with 16.6% of the load drop ratio or below could be judged as insignificant. Based on the results of the experiments, it would be safe to change the critical load drop ratio for the pop-in judgement from the current 5% to 10%. 707 6

Fig. 2.3 Specimen configuration

Fig. 2.4 Results comparison of (a) section notch vs. surface notch and (b) standard specimen vs. shallow specimen

3. Stress Intensity Factor Approach 3.1. FEM analysis

To find out where the stress wave reflects and see the difference of the loading mode of bending and tensile test, the finite element method, FEM, analysis has been performed. The condition of the FEM analysis is shown in Fig. 3.1. This is a three-dimensional, elastic, dynamic-implicit analysis with a nodal release method. The minimum element size is 0.2 mm. The shape of the crack front is straight two-dimensional shape. The dynamic stress intensity factor d is used for the evaluation of this analysis. d value shows the driving force of the propagating crack. d is