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.

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.

Effective Modeling of Fatigue Crack Growth in Pipelines

2012 ◽  
Author(s):  
Steven J. Polasik ◽  
Carl E. Jaske
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Growth Models ◽  
Critical Parameters ◽  
Operating Pressure ◽  
Mechanics Model ◽  
Key Variables

Pipeline operators must rely on fatigue crack growth models to evaluate the effects of operating pressure acting on flaws within the longitudinal seam to set re-assessment intervals. In most cases, many of the critical parameters in these models are unknown and must be assumed. As such, estimated remaining lives can be overly conservative, potentially leading to unrealistic and short reassessment intervals. This paper describes the fatigue crack growth methodology utilized by Det Norske Veritas (USA), Inc. (DNV), which is based on established fracture mechanics principles. DNV uses the fracture mechanics model in CorLAS™ to calculate stress intensity factors using the elastic portion of the J-integral for either an elliptically or rectangularly shaped surface crack profile. Various correction factors are used to account for key variables, such as strain hardening rate and bulging. The validity of the stress intensity factor calculations utilized and the effect of modifying some key parameters are discussed and demonstrated against available data from the published literature.

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.

Effect of Temperature on Fatigue Crack Growth in CPVC

2003 ◽  
Vol 125 (1) ◽  
pp. 71-77 ◽  
Author(s):  
Muhammad Irfan-ul-Haq ◽  
Nesar Merah
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Effect Of Temperature ◽  
Stress Intensity Factor Range ◽  
Crack Growth Behavior ◽  
Different Temperatures

This study addresses the effect of temperature on fatigue crack growth (FCG) behavior of CPVC. FCG tests were conducted on CPVC SEN tensile specimens in the temperature range −10 to 70°C. These specimens were prepared from 4-in. injection-molded pipe fittings. Crack growth behavior was studied using LEFM concepts. The stress intensity factor was modified to include the crack closure and plastic zone effects. The effective stress intensity factor range ΔKeff gave satisfactory correlation of crack growth rate (da/dN) at all temperatures of interest. The crack growth resistance was found to decrease with temperature increase. The effect of temperature on da/dN was investigated by considering the variation of mechanical properties with temperature. Master curves were developed by normalizing ΔKeff by fracture strain and yield stress. All the da/dN-ΔK curves at different temperatures were collapsed on a single curve. Crazing was found to be the dominant fatigue mechanism, especially at high temperature, while shear yielding was the dominant mechanism at low temperatures.

Mechanisms of Fatigue Crack Growth in WC-Co Cemented Carbides

2005 ◽  
Vol 297-300 ◽  
pp. 1120-1125 ◽  
Author(s):  
Myung Hwan Boo ◽  
Chi Yong Park
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Stress Ratio ◽  
Cemented Carbides ◽  
Stress Intensity Factor Range

In order to study the influence of stress ratio and WC grain size, the characteristics of fatigue crack growth were investigated in WC-Co cemented carbides with two different grain sizes of 3 and 6 µm. Fatigue crack growth tests were carried out over a wide range of fatigue crack growth rates covering the threshold stress intensity factor range DKth. It was found that crack growth rate da/dN against stress intensity factor range DK depended on stress ratio R. The crack growth rate plotted in terms of effective stress intensity factor range DKeff still exhibited the effect of microstructure. Fractographic examination revealed brittle fracture at R=0.1 and ductile fracture at R=0.5 in Co binder phase. The amount of Co phase transformation for stress ratio was closely related to fatigue crack growth characteristics.

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