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Failure Waves in Rock under Shock Wave Loading

Author: ChenDengPing
Tutor: LiMingFa；HeHongLiang
School: Wuhan University of Technology
Course: Solid Mechanics
Keywords: Shockwave Destroy wave Heterogeneous brittle media Relaxation destruction AOW rock
CLC: TU452
Type: Master's thesis
Year: 2006
Downloads: 216
Quote: 3
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Abstract


Heterogeneous brittle materials contain a large number of micro-cracks, holes and other micro-micro-defects in the shock wave compression, these micro-defects may be due to the role of local shear stress activation, expansion. Compared with ductile materials, brittle materials in shock compression conditions showed many unusual mechanical response characteristics. Paper reviews the damage in brittle materials wave of progress and problems, and to use \In shock Hugoniot elastic limit stress below (σ HEL ) compression failure stress zone characteristics of the destruction of wave phenomena of a more systematic study. Following major elements: (1) Use thick copper flyer plate impact AOW rock samples, were in shock loading stress 0.8 ± 0.2GPa, 3.9 ± 0.1GPa conditions, for the first time explicitly measured which is different from the glass medium destroy wave phenomena. Reduces shock loading stress, measured by observing the history of the sample free surface velocity of the secondary load signal to determine the AOW rock impact stress waves generated damage threshold is about 0.1 ~ 0.6GPa, far below the rocky σ HEL < / sub> (~ 7.8GPa). Meanwhile, fly by appropriately changing the thickness, contrast AOW rock samples were measured within the compression damage zone and undamaged area spall strength, the results showed that the undamaged area spall strength of about 316.4MPa, while compression spall damage zone intensity is approximately zero, to further support and pressure rock samples confirmed the presence of damaged areas. (2) Through the unique design of experiments to study the AOW rock samples destroy wave formation, dissemination and evolution. Maintaining constant stress shock loading, by changing the thickness of the rock samples were measured again and the compressed signal appears the moment the thickness of the damage zone, thereby determining the type of the damage within the sample thickness boundary. At 0.8 ± 0.2GPa, 3.9 ± 0.1GPa two kinds of loading stress, the three thicknesses (6mm, 8mm, 10mm) thickness destruction zone within the sample x and time t, respectively relation t = 0.15x 1.2, t = 0.15x 0.5. This two fronts destruction zone connecting line passes through the origin, indicating that the destruction of the sample after the shock front there is a clear relaxation time. When the impact stress was 0.8 ± 0.2GPa, the damage zone is formed relaxation time 1.2μs, with the impact of the relaxation time decreases with increasing loading stress, when the impact stress reaches 3.9 ± 0.1GPa (about material σ HEL half), the relaxation time was reduced to 0.5μs. Approximate damage zone front parallel with the shock front, indicating that the AOW rock destroy waves close to the speed of the shock wave is propagated to the sample, much larger than the destruction of the glass wave velocity. (2) According to the experimental results, the medium of rock destruction physical mechanism of wave formation analyzed, within a sample of native micro-defects by the action of shear stress \The main mechanism that the glass with the existing literature on the media to explain the \Thesis results further validate and support our research group proposed earlier glass and rocks that may exist in the media

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CLC: > Industrial Technology > Building Science > Soil mechanics,foundation engineering > Rock ( rock ) mechanics and rock testing > Rock mechanical properties and stress theory
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