PSI - Issue 5

Kaveh Samadian et al. / Procedia Structural Integrity 5 (2017) 1245–1252 Kaveh Samadian/ Structural Integrity Procedia 00 (2017) 000 – 000

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α 2 in Figure 2), and average curvature analysis in which best fitting circles were defined. In the latter case, strain band curvature was characterized as the inverse of the circle radii ( R 1 and R 2 in Figure 2). These characteristics were then used to identify the presence or absence of interaction between both notches, as discussed below.

4. Results and discussion

4.1. Equivalent strain patterns

Full field deformation patterns are studied in this paper to identify the interaction between two non-co-planar side edge notches by employing equivalent strain measurements. Figure 3 shows the equivalent strain patterns of the six tested samples at maximum force. Note that the magnitude of maximum force varies for the different specimens due to differences in notch out of plane distance. It is seen that, by increasing the out of plane distance ( H / W ), the strain patterns evolve from quasi-circular symmetric patterns in H / W= 0 to a pattern with a maximum strain value at the core of the strain band connecting the notch tips around H/W , after which the strain concentrations start to separate at H / W= 2 and eventually disconnect when H / W= 3.

Fig. 3. Equivalent strain patterns in various notches out of plane distances.

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Fig. 4. (a) Band of maximum strain trajectory in specimen with H/W=1 and (b) equivalent strain magnitude on the band; (c) band of maximum strain trajectory in specimen with H/W=2 and (d) equivalent strain magnitude on the band; (e) band of maximum strain trajectory in specimen with H/W=3 and (f) equivalent strain magnitude on the band. The visual appearance of the strain patterns reveals valuable qualitative information about the interaction between the notches. However, it is hard to judge on subtle differences in flaw interaction, e.g. between H / W = 2/3 and H / W = 4/3. A more quantitative interpretation has been obtained by applying the methodology introduced in Figure 2, based on bands of maximum equivalent strain. Figure 4 compares trajectories of maximum strain for three different cases; the upper graphs show the maximum strain trajectories and the lower graphs show the magnitude of equivalent strain