Fatigue Crack Growth Threshold Stress Intensity Determination via Surface Flaw (Kb Bar) Specimen Geometry

2008 ◽  
pp. 445-445-12
Author(s):  
KR Bain ◽  
DS Miller
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Threshold Stress ◽  
Surface Flaw ◽  
Specimen Geometry ◽  
Threshold Stress Intensity ◽  
Growth Threshold

Some Applications of Fractal Fracture Mechanics to Describe the Fatigue Behaviour of Materials

2008 ◽  
Vol 378-379 ◽  
pp. 355-370 ◽  
Author(s):  
Andrea Carpinteri ◽  
Andrea Spagnoli ◽  
Sabrina Vantadori
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Limit ◽  
Threshold Stress ◽  
Threshold Stress Intensity ◽  
Stress Intensity Range

As is well-known, fatigue limit, threshold stress intensity range and fatigue crack growth rate are influenced by the specimen or structure size. Limited information on size effect is available in the literature. In the present paper, by employing some concepts of fractal geometry, new definitions of fatigue limit, fracture energy and stress intensity factor, based on physical dimensions different from the classical ones, are discussed. Then, size-dependent laws for fatigue limit, threshold stress intensity range and fatigue crack growth rate are proposed. Some experimental results are examined in order to show how to apply such theoretical scaling laws.

Experimental Study and Numerical Simulation on Fatigue Crack Growth Behavior of GH4133B Superalloy

2012 ◽  
Vol 512-515 ◽  
pp. 980-988
Author(s):  
Rong Guo Zhao ◽  
Xiu Juan Li ◽  
Yong Zhou Jiang ◽  
Xi Yan Luo ◽  
Jun Fei Li ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Threshold Stress ◽  
Threshold Stress Intensity ◽  
Intensity Factors

The fatigue crack growth tests for nickel-based GH4133B superalloy used in turbine disk of a type of aero-engine are carried out at room temperature. The stress intensity factor ranges and the fatigue crack growth rates at various stress ratios are measured, and the corresponding threshold stress intensity factor ranges are determined. Using the Paris formula, the experiment data of fatigue crack growth are analyzed. It is shown that the fatigue crack growth rate increasing with increasing stress intensity factor range and stress ratio, and a modified Paris formula considering threshold stress intensity factor range can describe the fatigue crack growth behavior precisely. The fracture surface morphologies are investigated using a scanning electron microscope. It is shown that in the crack initiation region, steady growth region and rapid growth region, the fracture surface exhibits a cleavage fracture mode, fatigue striations and an intergranular fracture mode, respectively. Finally, the von Mises stresses and stress intensity factors at the crack tip of specimen of GH4133B superalloy at various external loads and crack lengths are simulated using the finite element method, and the threshold stress intensity factors under different maximal external loads at a certain crack length are calculated. The comparison between test and simulation indicates that the stress intensity factors at the crack tip calculated by the finite element method agree well with experimental data.

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