Fatigue Crack Growth and Coalescence Algorithm Starting from Multiple Surface Cracks

2014 ◽  
Vol 891-892 ◽  
pp. 1003-1008 ◽  
Author(s):  
John Hock Lye Pang ◽  
You Xiang Chew
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Surface Crack ◽  
Crack Depth ◽  
Surface Cracks ◽  
Growth Data ◽  
Aspect Ratios ◽  
Weld Toe ◽  
Fatigue Crack Propagation Life

Fatigue crack growth and propagation analysis in welded joints have to deal with the complexity of modeling multiple weld toe surface cracks originating from weld toes. Fitness-For-Service (FFS) assessments for weld toe surface cracks employ a fracture mechanics and Paris Law approach to predict the fatigue crack propagation life of a semi-elliptical surface crack (SESC) to failure. A fatigue crack growth algorithm for assessing multiple surface crack growth, coalescence and propagation life was initially validated with previuously report crack growth data for a fillet shoulder specimen. Next a parametric study for single, double, and triple SESCs located along the weld toe line of a fillet weld was investigated with three starting crack depth sizes (0.1mm, 0.5mm, 1.0mm) coupled with three different crack aspect ratios (a/c = 1.0, a/c = 0.5 and 0.25) giving a total of 27 cases studied.

Experimental Study and Prediction of Fatigue Crack Growth in Girth Welded Pipes

2002 ◽  
Author(s):  
Yan H. Zhang ◽  
Stephen J. Maddox ◽  
G. Reza Razmjoo
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Large Diameter ◽  
Accurate Solution ◽  
Growth Data ◽  
3D Fea ◽  
Weld Toe ◽  
Stress Concentration Effect

Fracture mechanics fatigue crack growth analysis is widely used in the Engineering Critical Assessment of welded structures. An important requirement is an accurate solution for the stress intensity factor, K, for the particular type and geometry of crack under consideration. A case commonly encountered is the weld toe crack. A solution incorporating the stress intensity magnification factor, MK, to allow for the stress concentration effect of the welded joint, based on 2D FEA has been in use for many years. A new solution from 3D FEA has recently become available. However, in both cases, little has been done to validate the solutions against actual fatigue crack growth data. The results from a recent investigation of fatigue in large diameter (609mm OD × 20mm WT) girth-welded pipes provided an opportunity to do this. This paper presents a comparison of these crack growth data based on beachmarking information with predictions based on the 2D and 3D MK solutions. It was found that the 2D MK solution tended to over-estimate the crack growth rate, while the 3D solution provided better correlation between predicted and actual crack propagation behaviour. It is therefore recommended that the 3D MK solution should be used in the calculation of K for weld toe cracks.

An Investigation of the Effects of Microstructure on Fatigue Crack Growth in Ti-6242

2005 ◽  
Vol 127 (1) ◽  
pp. 46-57 ◽  
Author(s):  
F. McBagonluri ◽  
E. Akpan ◽  
C. Mercer ◽  
W. Shen ◽  
W. O. Soboyejo
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Surface Crack ◽  
Rate Data ◽  
Aspect Ratios ◽  
Crack Growth Rates

Surface and subsurface crack nucleation and growth mechanisms are elucidated for equiaxed (microstructure 1), elongated (microstructure 2), and colony (microstructure 3) microstructures of Ti6242. Prominent cleavage facets, indicative of a Stroh-type dislocation-pile phenomenon characterize the nucleation sites. Beachmarking and scanning electron microscopy (SEM) techniques are used to study fatigue crack growth rates and crack shape evolution in the short and long crack regimes. The studies reveal that surface crack growth rate data are generally comparable to the through-crack growth rate data in the long crack growth regime. However, the depth crack growth rates are somewhat slower than the through-crack growth rates. Surface crack evolution profiles are shown to exhibit a tendency towards “Preferred Propagation Paths” (PPPs). However, the magnitudes of the aspect ratios along the PPPs are different from those reported for square or rectangular cross sections subjected to cyclic tension or bending loads. Finally, the measured crack lengths and aspect ratios are compared with predictions obtained from a fracture mechanics model.

Effect of Hardness and Tensile Mean Stress on Fatigue Crack Growth in Beryllium Copper

1969 ◽  
Vol 11 (3) ◽  
pp. 343-349 ◽  
Author(s):  
L. P. Pook
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Residual Stresses ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Mean Stress ◽  
Growth Data ◽  
Beryllium Copper

Some fatigue crack growth data have been obtained for age-hardened beryllium copper. The fatigue crack growth rate was found to be very dependent on the hardness and tensile mean stress. This dependence is believed to be associated with the intense residual stresses surrounding Preston-Guinier zones.

Fatigue crack growth of filament wound GRP pipes with a surface crack under cyclic internal pressure

2008 ◽  
Vol 43 (16) ◽  
pp. 5569-5573 ◽  
Author(s):  
Ahmet Samanci ◽  
Ahmet Avci ◽  
Necmettin Tarakcioglu ◽  
Ömer Sinan Şahin
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Internal Pressure ◽  
Crack Growth ◽  
Surface Crack ◽  
Filament Wound

A Method for the Analysis of the Growth of Short Fatigue Cracks

1995 ◽  
Vol 117 (4) ◽  
pp. 408-411 ◽  
Author(s):  
A. J. McEvily ◽  
Y.-S. Shin
Keyword(s):  
Experimental Data ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Material Constant ◽  
Plastic Zone Size ◽  
Surface Cracks ◽  
Zone Size ◽  
Short Cracks

A method for the analysis of the fatigue crack growth rate for short cracks has been developed and is applied to the case of fatigue crack growth of short surface cracks in a 1045 carbon steel. The method entails three modifications to standard LEFM procedures. These modifications include the use of a material constant to bridge between smooth and cracked specimen behavior, consideration of the plastic zone size to crack length ratio, and incorporation of the development of crack closure. Comparisons are made between calculations based upon this approach and experimental data.

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