Issue 35

S. Morita et alii, Frattura ed Integrità Strutturale, 35 (2016) 82-87; DOI: 10.3221/IGF-ESIS.35.10 84 Figure 2 : IPF map. Single edge notched tension specimens with a width ( W ) of 12 mm, a thickness ( B ) of 4 mm, a initial crack length ( a ) of 1 mm, and a length ( L ) of 50 mm were machined from a rolled as shown in Fig.3. Loading axes were parallel to the rolling direction; fatigue crack propagated parallel to the transverse direction (L-T specimen), parallel to the short transverse direction (L-S specimen). On the other hand, loading axis was normal to the rolling direction; fatigue cracks propagated parallel to the transverse direction (S-T specimen). Fatigue crack propagation tests were performed on an electro-hydraulic testing machine (capacity: 9.8 kN) at a stress ratio of R = P min /P max = 0.1 (tension-tension) and a frequency of 10 Hz at room temperature in air. Here, P max and P min are the maximum and minimum applied load, respectively. The fatigue crack length was determined using a microscope. The stress intensity factor range (  K ) was calculated using the following equation: 3 2 tan 2 0.752 2.02 0.37 1 sin 2 cos 2                                     a P a a W K a W W B W W (1) where P is the applied load, and W , B and a are the width, thickness, and crack length, respectively. The fracture surface of the fatigue tested specimens were observed by SEM. Figure 3 : Shape and dimensions of SENT specimen (in mm). 300μm