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TECHNICAL PAPERS

[+] Author and Article Information
Guowen Yao

School of Civil Engineering and Architecture, Chongqing Jiaotong University, Chongqing, 400074, China

Zhanfang Liu

Department of Engineering Mechanics, Chongqing University, Chongqing, 400044, China

J. Appl. Mech 74(5), 990-995 (Jan 07, 2007) (6 pages) doi:10.1115/1.2722777 History: Received February 14, 2006; Revised January 07, 2007

## Abstract

Plate impact experiments and impact recovery experiments were performed on $92.93wt.%$ aluminas using a $100mmdia$ compressed-gas gun. Free surface velocity histories were traced by a velocity interferometry system for any reflector (VISAR) velocity interferometer. There is a recompression signal in free surface velocity, which shows evidence of a failure wave in impacted alumina. The failure wave velocities are $1.27km∕s$ and $1.46km∕s$ at stresses of $7.54GPa$ and $8.56GPa$, respectively. It drops to $0.21km∕s$ after the material released. SEM analysis of recovered samples showed the transit of intergranular microcracks to transgranular microcracks with increasing shock loading. A failure wave in impacted ceramics is a continuous fracture zone, which may be associated with the damage accumulation process during the propagation of shock waves. Then a progressive fracture model was proposed to describe the failure wave formation and propagation in shocked ceramics. The governing equation of the failure wave is characterized by inelastic bulk strain with material damage and fracture. Numerical simulation of the free surface velocity was performed in good agreement with the plate impact experiments. And the longitudinal, lateral, and shear stress histories upon the arrival of the failure wave were predicted, which present the diminished shear strength and lost spall strength in the failed layer.

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## Figures

Figure 1

Plate impact experimental schematic with VISAR

Figure 2

Free surface velocity profiles showing small recompression for shots 405 and 425

Figure 3

Free surface velocity profiles of glass monitored by VISAR (9,19-20)

Figure 4

Propagation and interaction of compression, rarefaction and failure waves

Figure 5

Expanded region of free surface velocity profile showing second small recompression signal from shot 425

Figure 6

SEM micrographs of (a) initial and recovered alumina samples under (b) 5.76GPa, and (c) 8.65GPa shock loading

Figure 7

Schematic of the failure wave and elastic precursor for the conservation of mass, momentum, and energy

Figure 8

Figure 9

Longitudinal, lateral, and shear stresses histories of specimens under shock loading simulated by progressive fracture model

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