PSI - Issue 13

Yuki Nishizono et al. / Procedia Structural Integrity 13 (2018) 1817–1827 —‹ ‹•Š‹œ‘‘ Ȁ –”—…–—”ƒŽ –‡‰”‹–› ”‘…‡†‹ƒ ͲͲ ሺʹͲͳͺሻ ͲͲͲ – ͲͲͲ

ͻ

1825

Specimen No.1

Specimen No.3 Fig. 11. Temperature history before the brittle crack initiation.

Notch processing 0

Stroke [mm]

Table 6. Results of the main experiments.

T [ °C ] -60 -80

No.

[kN]

[mm]

1 2 3

B A B

619 681 515

67 82 39

-

11.2

-40

9.4

Specimen No.1

Specimen No.3

Fig. 12. Fracture surface. 4.2. Arrest toughness evaluation by Figure 13 shows the generals of dynamic 3D elasto-plastic FEM model simulating the main experiments. Details of the model are as introduced in Section 3.3 . Figure 14 shows the d transitions of the main experiments calculated by FEA. For all analysis results, the authors confirmed that d decreases monotonically regardless of crack velocity, as well as the preliminary experiments. Fig. 15 shows the evaluation results of [ d ] critical by the main experiments and the evaluation results of ca by the ESSO tests. [ d ] critical by the main experiments shows a strong Arrhenius type temperature dependence and these results have high correlation with ca by ESSO tests. There has never been any simplified evaluation method by which we can accurately evaluate ca of at least 6000 N/mm 3/2 using test specimen and test load as small as this evaluation method. Thus, this evaluation method developed in this study can be said to be a groundbreaking evaluation method in terms of the characterization of physical mechanism in brittle crack propagation and the high correlation with ca by ESSO tests.