Issue 33

M.-L. Zhu et alii, Frattura ed Integrità Strutturale, 33 (2015) 67-72; DOI: 10.3221/IGF-ESIS.33.09 70 the selected points were averaged over a square domain of 14  14 pixels (9.52  9.52  m), centred at each tracking point. This is illustrated in Fig. 4, where the normal strain value at Point 1 is obtained by averaging the strain data from the square. 0.00 0.02 0.04 0.06 0.08 0.10 V y , wake V y , front Standard deviation of displacement (  m) V x , wake V x , front (b) 0.0 0.1 0.2 0.3 0.4  yy , wake  yy , front  xy , wake  xy , front Standard deviation of strain (%)  xx , wake  xx , front (c) Figure 2: Error analysis of displacements and strains for both ahead of (front) and behind (wake) the crack tip under zero load: (a) An image of the region of interest (1mm  0.5mm) near the crack tip; (b) standard deviation of the displacement components and (c) standard deviation of the strain components. Figure 3: A fatigue crack path with the initial and final crack tips indicated. The last stage of the crack growth was considered in the strain analysis using DIC.