PSI - Issue 5

Sameera Naib et al. / Procedia Structural Integrity 5 (2017) 1417–1424 Naib et al./ Structural Integrity Procedia 00 (2017) 000 – 000

1420

4

gauges as per BS 8571:2014 , (2014). In addition to ‘conventional’ instrumentation, digital image correlation (DIC) was used to depict full field plastic deformations. The detailed procedure is put forward by Verstraete et al., (2013). In brief, a stereoscopic system consisting of two synchronized monochromatic cameras captures pictures at predefined intervals of time (6 seconds here) during the process of testing. The obtained pictures were correlated using the commercial software package VIC 3D (version 7) to obtain contours of in-plane strain values on the surface of the specimen.

Figure 2: Plot of hardness traverses showing the variation in hardness along the weld in overmatching (OM) and undermatching (UM) region.

2.2. SE(T) numerical model Similar to the experimental tests, two three-dimensional side grooved SE(T) specimens were modelled using the commercial finite element software package Abaqus® (version 6.11). Modelled specimens were given the same dimensions (overall, notch tip radius, side groove geometry) as those extracted from the welded plate (see section 2.2). The model geometry was chosen accordance with the procedure suggested by Verstraete et al., (2014). The specimen had length L=200mm, in accordance with the daylight length between the grips of the experimental tests and width W and thickness B equal to 20mm. The complex weld properties were incorporated in the finite element model by assigning element specific properties using hardness values as input and converting them to material properties ( 02 , and ). The detailed technique of assigning element specific properties is explained by Hertelé et al., (2015) and the optimal transfer function to calculat material strength properties from hardness map is given by Naib et al., (2016). Figure 3(a) shows the detailed FE model with the B being the thickness and W being the width of the specimen. Isotropic J 2 type plasticity obeying Ramberg-Osgood(RO) strain hardening with finite strain assumptions was implemented. The geometry of the applied side grooves and notch is also shown. Figure 3(b) shows the outcome of using experimentally determined hardness values and assigning them to individual element in FE model.

L

W

Side groove

Notch

B

(a)

(b)

Figure 3: The finite element model (a) global model and (b) element specific properties