Fenghua Zhou

Characteristic fragment size distributions in dynamic fragmentation

The one-dimensional fragmentation of a dynamically expanding ring (Mott’s problem) is studied numerically to obtain the fragment signatures under different strain rates. An empirical formula is proposed to calculate an average fragment size. Rayleigh distribution is found to describe the statistical properties of the fragment populations.

Three-dimensional numerical simulations of dynamic fracture in silicon carbide reinforced aluminum

The three-point bending test by Kolsky-bar apparatus is a convenient technique to test the dynamic fracture properties of materials. This paper presents detailed three-dimensional finite element simulations of a silicon particle reinforced aluminum (SiCp/Al) experiment (Li et al., [Proceedings of the US Army Symposium on Solid Mechanics]). In the simulations, the interaction between the input bar and the specimen is modeled by coupled boundary conditions. The material model includes large plastic deformations, strain-hardening and strain-rate hardening mechanisms. Furthermore, crack initiation and propagation processes are simulated by a cohesive element model. The simulation results quantitatively agree with the experimental measurements on three fronts: (1) the structural response of the specimen, (2) the time of unstable crack propagation, and (3) the local deformations at the crack-tip zone. The simulations reveal crack propagation characteristics, including crack-tip plastic deformation, crack front curving, and crack velocity profile. The effectiveness of Kolsky-bar type fracture tests is verified. It is shown that a rate-independent cohesive model can describe the complicated dynamic elastic-plastic fracture process in the SiCp/Al material

Numerical convergence of the cohesive element approach in dynamic fragmentation simulations

The cohesive element approach is getting increasingly popular for simulations in which a large amount of cracking occurs. Naturally, a robust representation of fragmentation mechanics is contingent to an accurate description of dissipative mechanisms in form of cracking and branching. This paper addresses the issue of energy convergence of the finite‐element solution for high‐loading rate fragmentation problems. These results provide new insight for choosing mesh sizes and size distributions in two and three‐dimensional fragmentation.