Issue 30

P. Lorenzino et alii, Frattura ed Integrità Strutturale, 30 (2014) 369-374; DOI: 10.3221/IGF-ESIS.30.44 372 Fig. 6 shows the target surface (both specimen sides). The inside of the notch was filled with plasticine in order to avoid light from one microscope interfering with the photographs acquired by the other. Figure 6 : View of the notch during the test as acquired with the microscopes. T EST ests were conducted on a Rumul Testronic 100 KN testing machine using loads of the tensile–tensile type (R = 0.1). The target material was 2 mm thick aluminum alloy 1050 cut into 300×42 mm sheets. Notches were 1, 2 or 4 mm in size. Some specimens were subjected to a thermomechanical treatment described elsewhere [6] to obtain abnormally large grains (8.22 mm) in order to detect microstructural interactions with the plastic zones around the cracks. R ESULTS ig. 7 shows an event of crack growth as examined by DIC. The target specimen had a grain size of 0.07 mm and a cylindrical notch 2 mm in diameter. The figure shows 6 photographs taken at different crack growth stages. Propagation of the resulting plastic zone is clearly apparent. These results are quite promising as they confirm that the DIC technique allows the above-described experimental difficulties to be overcome simply by altering the way the cameras are arranged. Figure 7 : Crack growth as determined by digital image correlation (DIC). Number of cycles (N): (a) 100 000, (b) 130 000, (c) 160 000, (d) 180 000, (e) 210 000, (f) 230 000. T F