He Hong-Liang

Dynamic Failure of Shock-Loaded Glass

Failure wave generations on both impacted surface and internal surface inside the sample have been observed for K9 glass under planar shock wave loading, which demonstrates that formation of failure wave is a process related to the surface microcracks nuclei developing. Based on these observations, a hypothesis is suggested that the large local strains resulting from the rearrangement of SiO4 tetrahedral within the permanent densification region behind the shock wave front and then strains releasing due to the surface microcracks developing could be responsible for the failure wave generation.

Crystal-Orientation Dependent Evolution of Edge Dislocations from a Void in Single Crystal Cu

The micro-void growth by dislocation emission under tensile loading is explored with focus on the influence of crystal orientations. Based on the elastic theory, a dislocation emission criterion is formulated. It is predicted that the preferential location of dislocation nucleation and its threshold stress are dependent on the crystal orientation. Large-scale molecular dynamics (MD) simulations are also performed for single crystal copper to illustrate the dislocation evolution pattern associated with a nano-void growth. The results are in line with those given by the theoretical prediction. As revealed by MD simulations, the characteristics of void growth at micro-scale depend greatly on the crystal-orientation.

Microscopic Characteristics of Damage Evolution in Ultrapure Aluminum under Tensile Loading

A series of plate-experiments are carried out to acquire ultrapure aluminum (purity, 99.999%) samples with damage. Based on the metallographic of all ?soft-recovered samples, the characteristics of damage evolution and spallation damage mechanism in ultrapure aluminum are analyzed in detail. Results show that the damage will increase regularly with increasing loading strength. Most of voids appear in the grain boundary and grow alone under tensile loading before they coalesce each other to form big irregular voids. These analysis results are helpful to understand the evolution process of ductile metal dynamic fracture and establish the damage evolution model.

Design and Parameter Analysis for Explosive-Driven Demagnetization Pulsed Power Source

We design a pulsed power source based on the technique for explosive-driven demagnetization. The physical process and geometry structure of this power source are described in detail and several formulae are deduced to predict some important properties of the power source. With a Φ 40 mm×20 mm×10 mm cylindrical magnet, the maximum output voltage and current reaches 125.5 V and 862.9 A, respectively. The rise time of the front edge of the output voltage is about 264 ns. On the 0.05 Ω simulative load, the net power is 37 kW.

A STUDY OF THE CRITICAL FRACTURE BEHAVIOR OF HIGH PURITY ALUMINUM IN THE DYNAMIC LOADING

One‐dimensional strain impact experiments were performed for the High Purity Aluminum—HPA (99.999%). The measurement of free‐surface velocity profile and the soft‐recovery of the shocked specimen has been obtained at the same time and for the same piece of sample. The critical behavior of HPA in the dynamic tensile fracture has been discussed according to the quantitative metallographic analysis results for the shocked samples. By defining the product of the tensile stress and the time as a parameter called Tensile Impulse, the statistic results indicate that an obvious critical behavior for the damage evolution appears with the increasing of Tensile Impulse. When the Tensile Impulse is low, the damage grows slowly with a linear increment. While once the Tensile Impulse reaches a critical value, the damage grows rapidly and an increment as a power exponential function is observed. Our preliminary results indicate that the critical value of Tensile Impulse for HPA is about 0.34 GPa⋅μs. Such a critical tran...

Effect of Temperature on the Void Growth in Pure Aluminium at High Strain-Rate Loading

With the environment temperature varying from 273 K to 773 K, the dynamic process of void growth in pure aluminium at high strain-rate loading is calculated based on the dynamic growth equation of a void with internal pressure. The result shows that the effect of temperature on the growth of void should be emphasized. Because the initial pressure of void with gas will increase and the viscosity of materials will decrease with the rising of temperature, the growth of void is accelerated. Furthermore, material inertia restrains the growth of void evidently when the diameter exceeds 10 μm. The effect of surface tension is very weak in the whole process of void growth.

SHOCK-INDUCED CRYSTALLIZATION OF METALLIC GLASS Fe40Ni40P12B8

Shock induced crystallization of metallic glass Fe40Ni40P12B8 has been studied using a two-stage light-gas gun under pressures ranging from 13.4 to 62.2 GPa. The shocked samples were recovered and characterized by the analyses of X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray energy dispersive spectrum (EDS). The results of the analyses indicate that the crystallization occurs at the edge of the sample at the pressure of 29.3 GPa, and covers the whole sample as the pressure increases to 49.2 GPa. The analyses also show that there are two different structures in the crystallized samples: the fcc type Fe-Ni solid solution and the Fe3P type compound—(Fe,Ni)3(P,B). Furthermore, EDS analysis demonstrates that Fe-Ni solid solution contains different amounts of Fe and Ni in different places for the same crystallized sample, and does so for the (Fe, Ni)3(P,B) compound.