Some Experiments on the Brittle Fracture in Ships

Abstract

As a first step of research on brittle fracture in ship structure, first the effect of notch sharpness on brittle fracture in wide width plate, and secondly the radius of opening corners in semi-box type girder were tested.Boodberg's experiments(5) on the wide width effect show the decrease of maximum breaking stress at wide width plate having constant notch sharpness. The author's experiment treated the effect of notch sharpness on the bending strength of wide width plates. The shape of test pieces is shown in Fig. 1. In Fig. 3, the transition temperatures are shown. The nominal maximum stress of wide width specimen (21×63mm) with sharp notch (rad. 0.05 mm) decreases in brittle fracture as shown in Fig. 4. In Fig. 6, the absorbed energy per unit volume at low temperature decreases in the wide width specimen with sharp notch as increase of width.Fig. 8 shows the effect of notch depth on the nominal maxinum stress and absorbed energy.Next, the semi-box type girders of rimmed and killed steel, perforated at the centre with round, square, notched, and slit shape, shown in Fig. 9, were tested under tension. The nominal maximum stress and absorbed energy are shown in Fig. 11 and 12. The strength of test pieces of several opening shape are nearly equal at room temperature (30°C), but at low temperature (-30°C), the sharp notch or the defect of welding at opening corners has more remarkable effect in their maximum stress and energy absorption rather than the square corner. The test pieces of killed steel show the parallel increase in their strength.