PSI - Issue 13

Atsuhisa Kitade et al. / Procedia Structural Integrity 13 (2018) 1845–1854 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

1852

8

By using the method of [Kawabata et al. 2012, Kawabata et al.2015], brittle fracture is judged by local critical stress and ductile fracture by strain criterion, and when reaching the limit condition, node separation or element deletion shall be performed respectively. Also, when brittle fracture occurs, some energy dissipation is set to occur. The analysis results is being exhibit by the way that the brittle fracture surface was red, the ductile fracture area surface was gray, and the unbroken surface was shown in blue. Fig.14 is shown as an example. Fig 15 shows the temperature transition of the ductile fracture rate under the production condition of "850-75". From this graph, it is understood that substantially all ductile fractures occur at 0 ° C. under this manufacturing condition, but almost all fracture surface is brittle fracture at -40 ° C. Fig.16 is a photograph of the fracture surface after the DWTT test. In this paper, we analyzed the conditions of these two temperatures and examined whether the temperature transition can be correctly expressed.

Fig. 14 Example of analysis result

Fig. 15 Temperature transition of the ductile fracture rate

Fig. 16 DWTT test result

Fig.17 the shape of the specimen after the experiment

3.2. Various constitutive equation and various parameters

From Fig.13, it is necessary to introduce various constitutive formulas and parameters in this analysis. Regarding the static stress strain relationship, low temperature tensile test was carried out and fitting was performed using the Swift equation as shown in (3), determining 0.008 for α , 0.17 for n . Regarding the dynamic stress strain relationship,