Effects of U-notches on the dynamic fracture and fragmentation of explosively driven cylinders

• Fragments of cylinders are sorted into four categories according to fracture mode.
• The shear fracture is pronounced in low notch depth.
• Mass distribution of fragments appears more affected by notch depth than width.
• A revised fragmentation model is suggested to adapt the notch effect.

Metal cylinder specimens are explosively expanded to fragmentation and the effect of U-notches in walls are investigated on fragmentation behaviors and failure mechanisms of the cylinders experimentally and numerically. Fragments were recovered by sawdust and sorted into four categories according to fragment morphology and fracture mode. The shear fracture is pronounced in the low notch depth condition, while tensile fracture plays a leading role in higher notch depth. Moreover, mass percentage distribution of the fragments appears more affected by the notch depth than width. In addition, fragmentation energy and fragmentation toughness, considered as material properties, are discussed using Grady’s energy-based theory. A suitable correction factor related to the width and depth of the notch is proposed to depict the effects of the U-notch. The effects of U-notches on the deformation and fracture behavior of cylinders are discussed with numerical simulations, indicating the stress concentration was noticeable at the notch tip, and the dynamic stress concentration factor (SCF) of the U-notch was less than that of the V-notch.