Position of four transducers in the multianvil box. Four acoustic sensors (1–4) are attached to the outer truncated edges of the tungsten carbide (WC) cubes. The upper most truncated edge is shown by arrow. Cables carrying acoustic signals are shown as thick lines.
(Color online) A multianvil apparatus (Presnall press) (1) Top pressure ram (2) Bottom pressure ram. (a) Loaded sample at room pressure. Sample assembly is located at the center. (b) Pressurized sample to .
(Color online) Cross section of sample assembly for the truncations (Octahedron edge length / truncated edge length of WC cube).
Schematic drawings of starting materials which have a dimension of the length of 7.5 mm and the diameter of 3.1 mm. (a)–(c) Saw cut of WC rod. (d) Natural serpentinite sample with Ni evaporations to be used as a passive marker of a fault offset. (e) Backscattered electron images showing a typical microstructure of the natural serpentinite.
(a)–(c) Backscattered electron images showing the broken carbide samples near the top, center, and bottom. Scale bars represent 1 mm.
(a) Acoustic signals with four channels of a shear event when a specimen, tungsten carbide rod, was broken near the center at (M529). (b) Magnified view of (a). Please note that the polarity of the first arrival is different at different channels. Arrival time difference between the first and the last arrived signal is . Note also that the resolution in the wave form is better than .
(a) An example of acoustic emission with four channels when a tungsten carbide rod was broken near the bottom (M528). (b) Magnified view of (a). The arrival time at the channel 4 is earlier than those at the other channels.
(a) An example of acoustic emission occurred outside the sample area. Both channels 1 and 3 show a large amplitude whereas both channels 2 and 4 show a small amplitude. (b) Magnified view of (a). Please note that arrival time difference between the first and the last arrived signal is . This event may be caused due a frictional slip of the pressure media between the two anvils on which transducers 1 and 3 are attached.
(a) An example of acoustic emission at the pressure of 0.3 GPa and room temperature (M528) showing a low-frequency event. (b) An example of acoustic emission at the pressure of 3.3 GPa and at the temperature of 500 °C (M513) showing a high-frequency event. The two plots show that the system resolves well the frequency range in about three orders (10 kHz–8 MHz).
Experimental conditions and results.
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