PSI - Issue 2_A

Shaowei Hu et al. / Procedia Structural Integrity 2 (2016) 2818–2832 S. Hu et al./ Structural Integrity Procedia 00 (2016) 000–000

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appear small macro cracks. When the load increases to a maximum, specimen is unstability failure, load begins to decline and CMOD rises quickly. In Fig.8, curves were intercepted from test beginning to unstability failure, which can express the trend in every stage more clearly. As can be seen from Fig.8, for the specimens with different initial seam height ratios, there are some differences in P-CMOD curves. The smaller initial seam height ratio of the specimen, the external load P for unstability failure and the energy for specimen damage will be larger, it suggests that the ability to resist failure of the specimen is stronger, and the toughness of specimen is also better.

Fig.7 State chart diagram of typical specimen failure

30

25

20

15

WS-020 WS-025 WS-030 WS-035 WS-040

P /kN

10

5

0

0,00

0,02

0,04

0,06

0,08

0,10

CMOD /mm

Fig.8 Curves of P-CMOD

4.3. Fracture parameters analysis Taking the experiment measured unstable fracture load P un and critical crack mouth opening displacement c CMOD of each specimen into formula (3) to (5), to calculate the critical effective crack length c a and unstable fracture toughness un IC K , then calculate the cohesive toughness c IC K by formula (8) to (11). Taking the calculated