Influence of the notch curvature on the impact fracture of the three-point bending beam

Studies show that sharp and blunt notches can be classified in the same research system. In the present study, the virtual-real caustics experimental method is applied to investigate the influence of the notch curvature on the impact fracture behavior of the three-point bending beam with a notch. Moreover, the loading characteristics of the drop hammer impact and the dynamic process of specimen fracture are analyzed in detail. Obtained results demonstrate that the drop hammer impact under the experimental conditions is a process of multiple loadings. It is found that as the notch curvature decreases, the moment of the crack initiation gradually postpones and the whole crack propagation time increases at first and then decreases. The initiation behavior of the notch under the impact loading of the drop hammer is an energy-controlled process rather than a loading force-controlled process. Furthermore, it is found that as the notch curvature decreases, both the peak value of the dynamic stress intensity factor and the corresponding peak value of the propagation velocity of the crack tip increase significantly after the initiation. Obtained results from the extended finite element method (XFEM) show that as the crack initiating gradually decreases, the stress σ_y at the notch end decreases with the decrease of the notch curvature. Meanwhile, the peak position of the stress gradually shifts to both sides of the notch end as the curvature decreases.