PSI - Issue 45

Dylan Agius et al. / Procedia Structural Integrity 45 (2023) 4–11 Dylan Agius et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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4.2. Region of interest reconstruction The ROI is the area of the microstructure used in the DIC investigation. The simulation domain however must be larger than the ROI, reducing the unrealistic influence of boundary conditions. The region used in the simulation is provided in Fig. 1 (b), with the ROI highlighted by the black square. A thickness was added to the reconstructed region of a size comparable to the average grain size of the microstructure. A substrate layer built using the microstructure statistics extracted from the EBSD scan of the larger area shown in Fig. 1 (b) was also added to the simulation domain. Adding the substrate was aimed at incorporating the local grain environment effects of the subsurface grains. Five layers of Fourier points (assigned infinite compliance) were added to the surface. This was done to ensure a free surface was modelled using periodic boundary conditions. The complete simulation domain is provided in Fig. 1 (c).

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Fig. 1 (a) The homogenised stress-strain response obtained from calibration simulations and the experimental monotonic tensile results; (b) the reconstructed volume (where colours represent different grains) with the ROI outlined; (c) the complete simulation domain including the top surface Fourier points. 5. Experimental results and discussion The measured effective shear strain ( ) map calculated using the DIC approach over the ROI is provided in Fig. 2 (a). Two different grain boundaries are highlighted: grain boundaries (solid grey lines) and prior grain boundaries (black dotted lines). is calculated from the total strain tensor ( ): =√( − 2 ) 2 + 2 (8) a

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From the DIC results, it is evident that significant slip bands have formed during deformation. These include both intergranular and transgranular slip banding. The transgranular slip banding is expected due to the grain clusters of similar crystallographic orientation within prior grains. When considering the three large prior grains, the one in the top left corner has the most activity. This is confirmed from analysis of the magnitude of strain across the Fig. 2. (a) The mapped to the ROI, measured using DIC; (b) the simulated ROI, with grain boundaries (solid grey lines) and prior grain boundaries (black dotted lines) highlighted.