Improvements of the Crack Extension Algorithm Based on the Maximum Energy Release Rate Criterion

2016 ◽  
Vol 52 (10) ◽  
pp. 91 ◽  
Author(s):  
Youli ZHU
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Crack Extension ◽  
Maximum Energy ◽  
Energy Release Rate Criterion ◽  
Rate Criterion ◽  
Maximum Energy Release

Analysis of Branched Interface Cracks

1990 ◽  
Vol 57 (4) ◽  
pp. 887-893 ◽  
Author(s):  
D. J. Mukai ◽  
R. Ballarini ◽  
G. R. Miller
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Interface Crack ◽  
Finite Length ◽  
Release Rate ◽  
Rate Ratio ◽  
Maximum Energy ◽  
Crack Branching ◽  
Maximum Energy Release ◽  
Branch Crack

A solution is presented for the problem of a finite length crack branching off the interface between two bonded dissimilar isotropic materials. Results are presented in terms of the ratio of the energy release rate of a branched interface crack to the energy release rate of a straight interface crack with the same total length. It is found that this ratio reaches a maximum when the interface crack branches into the softer material. Longer branches tend to have smaller maximum energy release rate ratio angles indicating that all else being equal, a branch crack will tend to turn back parallel to the interface as it grows.

Crack Tunneling in Cement Sheath of Hydrocarbon Well

2015 ◽  
Vol 83 (1) ◽  
Author(s):  
Zhengjin Wang ◽  
Yucun Lou ◽  
Zhigang Suo
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Maximum Energy ◽  
Large Area ◽  
Annular Gap ◽  
Small Cracks ◽  
Cement Sheath ◽  
Well Cement ◽  
Maximum Energy Release

In a hydrocarbon well, cement fills the annular gap between two steel casings or between a steel casing and rock formation, forming a sheath that isolates fluids in different zones of the well. For a well as long as several kilometers, the cement sheath covers a large area and inevitably contains small cracks. The cement sheath fails when a small crack grows and tunnels through the length of the well. We calculate the energy release rate at a steady-state tunneling front as a function of the width of the tunnel. So long as the maximum energy release rate is below the fracture energy of the cement, tunnels of any width will not form. This failsafe condition requires no measurement of small cracks, but depends on material properties and loading conditions. We further show that the critical load for tunneling reduces significantly if the cement/casing and cement/formation interfaces slide.

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