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Acoustic Emission Parameters of Three Gorges Sandstone during Shear Failure

Xu J., Liu Y., Peng S.

Acta Geophysica

2016

Vol. 64, no. 6

2410--2429

In this paper, an experimental investigation of sandstone samples from the Three Gorges during shear failure was conducted using acoustic emission (AE) and direct shear tests. The AE count rate, cumulative AE count, AE energy, and amplitude of the sandstone samples were determined. Then, the relationships among the AE signals and shearing behaviors of the samples were analyzed in order to detect micro-crack initiation and propagation and reflect shear failure. The results indicated that both the shear strength and displacement exhibited a logarithmic relationship with the displacement rate at peak levels of stress. In addition, the various characteristics of the AE signals were apparent in various situations. The AE signals corresponded with the shear stress under different displacement rates. As the displacement rate increased, the amount of accumulative damage to each specimen decreased, while the AE energy peaked earlier and more significantly. The cumulative AE count primarily increased during the post-peak period. Furthermore, the AE count rate and amplitude exhibited two peaks during the peak shear stress period due to crack coalescence and rock bridge breakage. These isolated cracks later formed larger fractures and eventually caused ruptures.

Influence of High Pressure and High Temperature Hydrogen on Fracture Toughness of Ni-Containing Steels and Alloys

Balitskii A., Ivaskevich L., Mochulskyi V., Eliasz J., Skolozdra O

Archive of Mechanical Engineering

2014

Vol. LXI, nr 1

129--138

The effect of hydrogen on short-term strength, low-cycle durability and planestress fracture toughness of 10Cr15Ni27 steel, 04Cr16Ni56 and 05Cr19Ni55 alloys at pressure up to 35 MPa and temperature 293. . . 773 K was investigated. The modes of hydrogen action for which the elongation , reduction of area , low-cycle durability N and crack resistance parameters Kc of alloys are minimal were established: hydrogen pressure above 10 MPa (non-hydrogenated specimens of 04Cr16Ni56 alloy) and above 15 MPa (hydrogenated specimens of 10Cr15Ni27 steel and 05Cr19Ni55 alloy, hydrogen concentration 15 and 19 wppm, respectively).

W ramach przeprowadzonych badan określono wpływ wodoru na krótkotrwałą wytrzymałość i płasko-naprężeniową ciągliwość stali 10Cr15Ni27 oraz stopów niklu 04Cr16Ni56, 05Cr19Ni55 przy wielkościach ciśnienia do 35 MPa i zakresie temperatury od 293 do 773 K. Wpływ wodoru wysokiego ciśnienia powoduje, że wydłużenie, plastyczność, wytrzymałość nisko cyklowa N i parametr odporności na pękanie Kc przyjmują minimalne wartości dla próbek stopu 04Cr16Ni56 przy ciśnieniu wynoszącym 10 MPa, natomiast dla nasyconych wodorem próbek stali 10Cr15Ni27 i stopu 05Cr19Ni55 minimum wartości tych parametrów występuje przy ciśnieniu 15 MPa, dla koncentracji wodoru wynoszącej odpowiednio 15 i 19 wppm.