Surface Crack Growth from Small Indentations in a Silicon Nitride Square Bar under Cyclic Reversed Torsion

2012 ◽  
Vol 566 ◽  
pp. 65-69
Author(s):  
Katsuyuki Kida ◽  
Takashi Honda ◽  
Edson Costa Santos
Keyword(s):  
Silicon Nitride ◽  
Crack Growth ◽  
Stress Ratio ◽  
Fatigue Testing ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Mode Ii ◽  
Surface Cracks ◽  
Silicon Nitride Ceramic ◽  
Surface Crack Growth

In order to investigate the mechanism of surface cracks in silicon nitride ceramic (HIP-Si3N4) from the viewpoint of shear stress, the authors focused on torsion fatigue testing and observed the crack growth behavior under conditions where the stress ratio was R = - 1. Furthermore the residual stresses around the cracks were measured. Based on these results, mode II growth of surface cracks is discussed and it was concluded that under stress ratio R = -1, surface cracks grow slowly in mode II, for ΔKⅡ less than 3.6MPam1/2.

Experimental Study on Crack Growth Behavior for Austenitic Stainless Steel in High Temperature Pure Water

1986 ◽  
Vol 108 (2) ◽  
pp. 226-233 ◽  
Author(s):  
M. Hishida ◽  
M. Saito ◽  
K. Hasegawa ◽  
K. Enomoto ◽  
Y. Matsuo
Keyword(s):  
Stainless Steel ◽  
Crack Propagation ◽  
Stress Corrosion ◽  
Crack Growth ◽  
Stress Corrosion Cracking ◽  
Surface Crack ◽  
Stress Ratio ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Surface Crack Growth

Crack growth behavior of Type 304 stainless steel in a simulated BWR water environment was investigated for the quantitative characterization of subcritical flaw growth in BWR piping systems. Crack propagation rates under corrosion fatigue and stress corrosion cracking were generated using compact specimens. The effects of several parameters on the rates were discussed. Furthermore, surface crack growth behavior was examined under different modes of cyclic loading, and results were discussed in comparison with compact specimen data. The corrosion fatigue crack propagation rates strongly depended on the frequency and the stress ratio. The rates became higher as the frequency lowered and the stress ratio increased. No effect from dissolved oxygen concentration and heat treatment of the steel was observed in tests, where transgranular cracking mainly took place. Stress corrosion cracking rate data indicated KISCC was above 15 MPa•m1/2. On the other hand, surface crack growth behavior included scattered crack propagation rates. However, the relationship between da/dN and ΔK was basically similar to that obtained in the compact specimens, except under given test conditions, where the acceleration for the crack growth rate at a crack tip on the panel surface was different from that at the deepest point.

Effect of Stress Ratio on Fatigue Crack Growth in 95Pb-5Sn Solder

1999 ◽  
Vol 123 (3) ◽  
pp. 311-315 ◽  
Author(s):  
J. Zhao and ◽  
Y. Mutoh ◽  
T. Ogawa
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Stress Ratio ◽  
High Stress ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Threshold Region ◽  
Test Conditions

The stress ratio effect on the fatigue crack growth behavior of 95Pb-5Sn solder has been investigated. It is found that both ΔJ and ΔK can correlate fatigue crack growth data well, which means that the crack growth behavior of the 95Pb-5Sn solder under the frequency of 10 Hz was dominantly cyclic dependent. The da/dN-ΔJ relationship can be expressed as: da/dN=1.1×10−11s˙ΔJ1.45. Low level of crack closure was found only in the near-threshold region. Except in this region, no crack closure was observed in the present test conditions. Both transgranular and intergranular fractures were observed on fracture surfaces: the former was dominant in most test conditions and the latter was dominant at the high stress ratio of 0.7. Striations and striation-like features were also found. Many slip bands and cavities along the grain boundary were observed on the crack wake and ahead of the crack tip in the high crack growth rate region.

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