PSI - Issue 18

Fokion Oikonomidis et al. / Procedia Structural Integrity 18 (2019) 142–162 Dr Fokion Oikonomidis/ Structural Integrity Procedia 00 (2019) 000 – 000

19

160

Fig. 26. Higher magnification of the region indicating possible crack extension in two steps. Magnification indicated by the scale marker.

Fig. 27. Sketch of the EDM notch and crack from measurements made after fracture.

Fig. 28 shows the K values along the crack front for each of the step loads when the crack geometry is as observed after the fracture test. The maximum K values at the centre of the crack, obtained from this elastic analysis at 7035kN, 8109kN, and 15250kN were 3620MPa√m m , 4204MPa√m m , and 7840MPa√m m respectively. The negative K value due to the compressive residual stress needs to be added to the above values to obtain the total K value that was applied to the crack front. The total K values that take into account the presence of residual stresses are listed in the 4th column