Fracture Mode of High Strength Steel Thin Plates with Elliptical Hole

In the simple tension fracture experiment of thin plates with elliptical hole fabricated from high strength steel Q345, the effect of the ratio of the major axis to the minor axis of the elliptical hole on the fracture mode was studied. The experiment results showed that the macroscopic crack was initiated at the tip of the major axis of the elliptical hole. For the specimens with sharp elliptical hole, the first crack quickly expanded along the path vertical the loading direction until it ruptured. For the specimens with blunt elliptical hole, it was difficult to observe the process of the first crack, and the specimens ruptured at the critical section almost at the same time. The location of fracture load lay at the necking phase of load-displacement curve. The fracture ductility is lower and the ultimate strength is slight higher for the specimens with sharper elliptical hole.