PSI - Issue 37

Cheng Qian et al. / Procedia Structural Integrity 37 (2022) 926–933 Cheng Qian et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 2. SE(B) and SE(T) fracture toughness resistance curves (a)  J -conversion – R curves, (b)  ExxonMobil – R curves and (c) J – R curves.

4.2. FEA results

FEA results showed that the stress state near the crack tip was the superposition of the HRR field dependent on J value and a hydrostatic stress that decreased the constraint. A single J field was not able to uniquely describe the stress distribution in the area of interest. The distribution of   /  0 for deeply-cracked SE(B) model was almost linear at r  0 / J > 1 and J /( b  0 ) > 0.020 caused by the significant influence of the global bending stress, while as a 0 / W decreased, the influence of bending on opening stress became less significant. Comparing the distributions of   /  0 at same load levels, the opening stress at the same normalized distance from the crack tip for shallow-cracked model was lower than that for deeply-cracked model, due to the loss of constraint. The expected trend of the SE(T) model exhibiting a greater loss of constraint compared to the SE(B) model was also demonstrated. 4.3. Constraint analysis results The eleven constraint parameters (i.e. Q HRR , Q SSY , Q LM , Q BM , A 2 , A 2 BM , h , T z , C p , A p , V p ) introduced in the previous section were calculated at J = J 0.2 BL for all specimens based on the aforementioned finite element models. For these correlations the J and  ExxonMobil0.2 BL were superior to the  J -conversion0.2 BL based on the following linear relationship according to Zhu et al. (2006) and Huang et al. (2014), and different constraint parameters Y are plotted in Figure 3. For brevity, only representative results for the Q HRR and A p constraint parameters are presented.