Papers by Author: Hong Liang He

Abstract: Knowledge of damage distribution is important and essential for understanding the dynamic failure behavior of solid material under the high velocity impact. For the High Purity Aluminum (99.999%), disk sample was shock impacted by a light gun and its damage distribution has been carefully characterized. The recovered sample was cut symmetrically along the impact direction and the damage on the cross section has been statistically studied. Unlike the previous work as Lynn Seaman et al. reported, a new computation treatment has been established in terms of the Schwartz-Saltykov method, which gives an easy and simple transformation from the two-dimensional size distribution to three-dimensional size distribution. We demonstrated the variation of damage distribution of High Purity Aluminum under different dynamic tensile loading, and discussed the damage evolution characteristics associated with the micro-voids nucleation, growth and coalescence. Results provide physical basis for the theoretical modeling and numerical simulation of spall fracture.

Abstract: In the frame of shock-induced depoling, PZT 95/5 ferroelectric ceramics with niobium doped has been assembled for the pulsed power supply, and the electrical current output has been investigated under the action of shock wave in a "normal mode". The electrical response of LRC load especially for the small resistance (R) and small inductance (L) load was studied. Plane-shock-wave tests were conducted, and the PZT 95/5 ceramics stacked in parallel were devised to generate high-power electrical pulse. An output current of 7 kA has been obtained, and the corresponding rise time of the front edge is under 500 ns. Theoretical calculations were conducted and a good agreement with the experiment presented.

Abstract: In the framework of percolation theory, a simple void-coalescence model combined with the constitutive relations for describing the stress relaxation and material softening during the void-coalescence process, name as the percolation-relaxation (P-R) model, is proposed to describe the dynamic tensile spallation of ductile metals. A critical damage is introduced and coupled into the model to identify the onset of the void coalescence. Mesoscopically, the critical damage corresponds to the critical intervoid ligament distance (ILD), indicating the start of transition from the void-growth to the void-coalescence.