PSI - Issue 13

Fuminori Yanagimoto et al. / Procedia Structural Integrity 13 (2018) 116–122 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

4

119

500

400

0 Crack arrest toughness [MPa m] 100 200 300 3.4

Temp. Grad. Arrest Tests Conv. Model

1000/ [ −1 ]

3.6

3.8

4.0

Fig. 3 Crack arrest toughness of the steel employed

2.4. Determination of the experimental conditions In order to determine the experimental temperatures, the above model was employed to predict the crack arrest length for each temperature. Here, the applied stress for the long crack experiments was set to 315 MPa. The results of the predicted arrest crack length for each temperature are shown in Fig. 4. Due to the limitation of the distance between pins and the fact that the isothermal region started 280 mm from the top, the crack arrest length had to be in the range from 280 mm to 600 mm from the top of the specimen. In this study, the temperatures for the experiments were determined to be −3 and − 13 ℃ according to calculation shown in Fig. 4.

1000 1200

0 200 400 600 800

280mm

Fig. 4 Predicted crack arrest length by model simulation Temperature of the isothermal region [ ℃ ] -30 -25 -20 -15 -10 -5

Arrest crack length [mm]

0

3. Experiment Two experiments were carried out under −3 and − 13 ℃ , named “Wide2016” and “Wide2017”, respectively. The applied stresses were 315 MPa along the crack path. The crack behavior was measured by using strain gauges and crack gauges connected to the high speed acquisition system. The crack was arrested in Wide2016, but it penetrated the specimen in Wide2017. Figure 5 shows the fracture surface of Wide2016. The crack arrest length was 303 mm.

Crack arrest position Arrest length: 303mm

Fig. 5 Fracture surface (Wide2016)