As mentioned previously, five different notch radii of 0.1, 0.3,
0.5, 1.0 and 2.0 mm were machined however, a later analysis by
means of optical microscopy revealed that the actual radii differed
slightly from the values initially targeted. A Nikon Metaphot optical microscope, linked with a Jenoptik ProgRes C5 digital camera,was used for this measurement. With this equipment, four images of the notch tip were taken from each specimen. Then, the radius at the notch tip for each image was obtained with the help of the ImageJ software. For the calibration of the images, an optical grid with a resolution of 0.01 mm was used. The actual radius of each specimen was obtained as the average value of the radii measured from the four images taken from each specimen. The results of these actual notch radiuses are gathered in Table 1.