PSI - Issue 2_A

Takuhiro Hemmi et al. / Procedia Structural Integrity 2 (2016) 2230–2237 Author name / Structural Integrity Procedia 00 (2016) 000–000

2235

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Table3. Valid results and arrest toughness

P 0 (MPa)

a 0 (mm)

a a (mm)

K ca (N/mm

3/2 )

T (K)

type SA1 SA1 SA1 SA1 SA2 SA2 SA2 SA3 SA3 SA3

170 219 210 229 189 200 183

18 25 15 22 18 25 18 15 15 15

72 72 64 69 73 72 52 65 66 65

907

283 293 303 313 293 303 313 243 253 263

1520 1810 1890

706

1390 2600

95

780

150 142

1180 1170

8000

SA1 SA2 SA3

4000

2000

Kca

1000

500

Fig.5. ܭ ୡୟ Plot From these results, smaller grain steel shows better arrest toughness and this trend made consistent with empirical knowledge. Therefore, it is necessary to revise effective surface energy distribution in the model. 4. Simulation of experiments and identification of effective surface energy We simulated the crack arrest tests stated in previous section by using the multiscale model. We calculated effective surface energy 1000 times by microscopic model, when average grain size was 40μm. We multiply the distribution by coefficient C and we used it. Effective surface energy distributions multiplied coefficient C= 0.7, 0.8, 1.0 were shown in Fig.6. We fitted crack arrest length with simulation results by changing coefficient C and examined exact energy distribution. 3,0 3,5 4,0 4,5 1000/ T [K -1 ]

0 0,2 0,4 0,6 0,8 1

Effective surface energy Coefficient C

γ: × 0.7 γ: × 0.8 γ: × 1.0

Cumulative probability

0

2000 4000 6000 8000 10000

Effective surface energy γ [J/m 2 ]

Fig.6.Effective surface energy distribution