PSI - Issue 13

Guiyun Gao / Procedia Structural Integrity 13 (2018) 51–56

54

Guiyun Gao/ Structural Integrity Procedia 00 (2018) 000 – 000

4

t = 20 μs

t =1 20 μs

t =20 0 μs

t =24 0 μs t =40 0 μs Fig. 2 Typical u y deformation fields at different time ticks (gas pressure: 10psi, compression: 0MPa) t =280 μs

1200

3

Crack propagation velocity Fracture toughness

Fracture toughness (MPa m 1/2 )

1100

2.5

1000

2

900

1.5

Crack propagation velocity (m/s)

800

1

8

10

12

14

16

18

20

Loading speed (m/s)

Fig. 3 Crack propagation velocity and fracture toughness at different loading speed

The hydraulic compressive pressure was implemented unidirectional in vertical direction by using the hydraulic pump. The fracture behavior will be different from that stress free before being subjected to dynamic loading. The opening displacement u y first increases with time. Then the crack initiates and propagates under dynamic loading and confining stress when the crack reaches to its critical state. However, the crack opening displacement is limited due to the confinement and the crack arrests. The crack propagation velocities at different confining stresses are showed in Fig. 4. If the plate is free of confining stress before dynamic loading, the crack propagation velocity is about 965.0 m/s. The crack propagation velocity decreases with the increase of hydraulic pressure, and it reduces to about 452.4 m/s at confining stress of 10.6 MPa. The finial crack length also decrease with confining stress as shown in Fig. 4. Micro cracks could be observed near the crack path and the crack tip when the rock plate subjected to hydraulic compression and dynamic loading. The specimen was broken into two parts at confinement-free state under dynamic loading, while the plate does not been departed into two when subjected to hydraulic compression stress. The final crack length decreases with