Relation Between Crack Velocity and the Stress Intensity Factor in Birefringent Polymers

2009 ◽  
pp. 257-257-17 ◽  
Author(s):  
T Kobayashi ◽  
JW Dally
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Velocity

Slow crack-growth behavior of alumina ceramics

2000 ◽  
Vol 15 (1) ◽  
pp. 142-147 ◽  
Author(s):  
M. E. Ebrahimi ◽  
J. Chevalier ◽  
G. Fantozzi
Keyword(s):  
Stress Intensity Factor ◽  
Grain Size ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Growth ◽  
Crack Velocity ◽  
Slow Crack Growth ◽  
Velocity Versus ◽  
Water Molecules ◽  
Alumina Ceramics

The fracture behavior of high-purity alumina ceramics with grain sizes ranging from 2 to 13 μm is studied by means of the double torsion method. Crack-propagation tests conducted in air, water, and silicon oil, for crack velocities from 10−7 to 10−2 m/s, show that slow crack growth is due to stress corrosion by water molecules. An increase of the grain size leads to enhanced crack resistance, which is indicated by a shift of the V–KI (crack velocity versus applied stress intensity factor) plot toward high values of KI. Moreover, the slope of the curve is apparently higher for coarse grain alumina. However, if the R-curve effect is substracted from the experimental results, a unique V–KItip (crack velocity versus stress intensity factor at the crack tip) law is obtained for all alumina ceramics, independently of the grain size. This means that the crack-growth mechanism (stress corrosion by water molecules) is the same and that the apparent change of the V–KI law with grain size is a direct effect of crack bridging.

Dynamic Emission of Dislocations From a Moving Crack

1985 ◽  
Vol 107 (4) ◽  
pp. 277-281 ◽  
Author(s):  
Rui-Huan Zhao ◽  
J. C. M. Li
Keyword(s):  
Stress Intensity Factor ◽  
Steady State ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Applied Stress ◽  
Critical Stress ◽  
Crack Velocity ◽  
Plastic Zone Size ◽  
Critical Stress Intensity Factor ◽  
Dislocation Emission

The emission of dislocations from a propagating crack in the mode II or III situations is studied by computer simulation. While the crack is moving the steady state number of dislocations is smaller than the saturation number which could be emitted from a stationary crack and such a steady state number decreases with increasing crack velocity. The effect on the emission process of the applied stress, the lattice friction for dislocation motion and the critical stress intensity factor for dislocation emission is studied. The results include also the plastic zone size, the dislocation distribution, the dislocation-free zone, and the instantaneous crack velocity. The average crack velocity does not depend on the applied stress but depends only on the critical stress intensity factor for dislocation emission. When such a factor is zero as assumed in some theories, the crack does not move at all.

Lifetime Control and Prediction of ZrO2/CePO4 Composites

2007 ◽  
Vol 336-338 ◽  
pp. 2505-2506
Author(s):  
Hai Yan Du ◽  
Xiu Juan Ou ◽  
Jing Han ◽  
Yu Ling Wang
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Environmental Conditions ◽  
Crack Velocity ◽  
Grain Sizes ◽  
Prediction And Control ◽  
Two Phases ◽  
And Control ◽  
The Relationship

Based on the relation between the stress intensity factor Ki and the crack velocity V, lifetime prediction and control were discussed and studied for machinable Ce-ZrO2/CePO4 ceramics. The relationship among lifetime, starting cracks and grain sizes were investigated by a set of designed simulation setting with a definite actual environmental conditions. It was concluded that crack started from larger weak interfaces of two phases and linking of cracking weak interfaces each other, and the lifetime of Ce-ZrO2/CePO4 composites could be controlled and predicted by adjusting of grain sizes of CePO4, which was depended on design of composites.

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