Tensile and shear fracture behavior of maraging steel with defective expansion rings: A phase field study

In military applications, the structural integrity of missile and warhead shells, as well as gun barrels, is of paramount importance as they undergo high-strain-rate deformation and fracture under explosive loads. Despite advances, a comprehensive model for the fracture mechanisms under such conditions remains elusive. This study investigates the dynamic fracture behavior of metal rings, representing a 120 mm gun barrel, under explosive impact loading using a thermo-elastic-plastic phase field model. The model examines the effects of defects and peak load on the expansion ring fracture process, revealing that both tensile and shear failures occur during the explosive-driven expansion. Notably, shear cracks precede tensile cracks in this context. When load magnitude and defect configuration align with the material's properties, fracture occurs in two distinct phases: primary fracture dominated by explosive load and secondary fracture driven by residual internal forces. The primary fracture is completed in the first 20–30 μs, and the secondary fracture lasts for 100 μs until it ends, resulting in eight square fragments and several triangular fragments with sizes less than or equal to those of the defects, which provides insights into controlled fragmentation patterns for structural design.