Investigation of Fatigue Crack Propagation in Line Pipes Containing an Angled Surface Flaw

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Lichun Bian ◽  
Farid Taheri
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Surface Crack ◽  
Effective Strain ◽  
Crack Problem ◽  
Fatigue Crack Initiation ◽  
Stress Intensity Factor Range ◽  
Threshold Condition ◽  
Engineering Structures

The angled crack problem has been given special attention in the recent years by fracture mechanics investigators due to its close proximity to realistic conditions in engineering structures. In the present paper, an investigation of fatigue crack initiation and propagation in line pipes containing an inclined surface crack is presented. The inclined angle of the surface crack with respect to the axis of loading varies between 0deg and 90deg. Based on the concept of the effective stress intensity factor range Δkeff, the rate of fatigue crack propagation db∕dN is postulated to be a function of the effective strain energy density factor range ΔSeff. This concept is applied to predict the crack growth due to fatigue loading. Furthermore, the threshold condition for nongrowth of the initial crack was established and assessed based on the experimental data.

Fatigue Threshold Considerations During Crack Propagation

2002 ◽  
Author(s):  
Lichun Bian ◽  
Jae-Kyoo Lim
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Effective Strain ◽  
Crack Problem ◽  
Potential Drop ◽  
Fatigue Tests ◽  
Fatigue Threshold ◽  
Stress Intensity Factor Range ◽  
Engineering Structures

The angled crack problem has been given special attention in the recent years by fracture mechanics investigators due to its close proximity to realistic conditions in engineering structures. In this paper, an investigation of fatigue crack propagation in steel pipes containing an inclined surface crack is presented. The inclined angle of the crack with respect to the axis of loading varied between 0° and 90°. During the fatigue tests, the growth of the fatigue crack was monitored using the AC potential drop technique. Based on the concept of the effective stress intensity factor range, Δkeff, the rate of fatigue crack propagation, db/dN, is postulated to be a function of the effective strain energy density factor range, ΔSeff. Subsequently, this concept is applied to predict crack growth due to fatigue loads.

Modeling of Fatigue Crack Propagation

2004 ◽  
Vol 126 (1) ◽  
pp. 77-86 ◽  
Author(s):  
Yanyao Jiang ◽  
Miaolin Feng
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Damage ◽  
Fatigue Crack Propagation ◽  
Fatigue Crack Initiation ◽  
Cyclic Plasticity ◽  
R Ratio

Fatigue crack propagation was modeled by using the cyclic plasticity material properties and fatigue constants for crack initiation. The cyclic elastic-plastic stress-strain field near the crack tip was analyzed using the finite element method with the implementation of a robust cyclic plasticity theory. An incremental multiaxial fatigue criterion was employed to determine the fatigue damage. A straightforward method was developed to determine the fatigue crack growth rate. Crack propagation behavior of a material was obtained without any additional assumptions or fitting. Benchmark Mode I fatigue crack growth experiments were conducted using 1070 steel at room temperature. The approach developed was able to quantitatively capture all the important fatigue crack propagation behaviors including the overload and the R-ratio effects on crack propagation and threshold. The models provide a new perspective for the R-ratio effects. The results support the notion that the fatigue crack initiation and propagation behaviors are governed by the same fatigue damage mechanisms. Crack growth can be treated as a process of continuous crack nucleation.

Corrosion-Fatigue Crack Propagation Studies of Some New High-Strength Structural Steels

1969 ◽  
Vol 91 (4) ◽  
pp. 570-574 ◽  
Author(s):  
T. W. Crooker ◽  
E. A. Lange
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Salt Water ◽  
High Strength ◽  
Structural Steels ◽  
Stress Intensity Factor Range ◽  
Corrosion Fatigue Crack ◽  
Crack Growth Rates

Fatigue crack propagation studies were conducted on three new high-strength structural steels: 9Ni–4Co–0.20C quenched-and-tempered, 10Ni–2Cr–1Mo–8Co dual-strengthened, and 13Cr–8Ni–2Mo precipitation-hardened stainless. The yield strengths of these steels ranged from 176 to 193 ksi. Notched cantilever-bend specimens of each steel were cycled zero-to-tension in two environments, room air and 3.5 percent NaCl salt water. Fatigue crack growth rates were measured experimentally and correlated with the crack tip stress-intensity factor range. The results indicate that these new steels possess greater resistance to fatigue crack propagation and less sensitivity to environment than previously studied steels of comparable strength.

Fatigue behavior of an Fe48Cr15Mo14Er2C15B6 amorphous steel

2007 ◽  
Vol 22 (2) ◽  
pp. 544-550 ◽  
Author(s):  
D.C. Qiao ◽  
G.Y. Wang ◽  
P.K. Liaw ◽  
V. Ponnambalam ◽  
S.J. Poon ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Al Alloy ◽  
Test Environment ◽  
Sinusoidal Waveform ◽  
Amorphous Steel

Four-point-bend fatigue experiments were conducted on the Fe48Cr15Mo14Er2C15B6 bulk metallic glass (BMG), amorphous steel, under load control, employing an electrohydraulic machine, at a frequency of 10 Hz (using a sinusoidal waveform) with an R ratio of 0.1, where R = σmin./σmax. (σmin. and σmax. are the applied minimum and maximum stresses, respectively). The test environment was laboratory air. Fe48Cr15Mo14Er2C15B6 exhibited a high fatigue-endurance limit (682 MPa), which is found to be greater than those of the Zr-based BMG, Al-alloy, and high-nitrogen steel. However, the stress versus number of fatigue cycles curve of Fe48Cr15Mo14Er2C15B6 has a significantly brittle fracture mode. Some fatigue cracks initiated from the inclusions or porosities, and the fatigue-crack propagation region was large. However, other cracks initiated from the outer tensile surface of the specimen, and the fatigue-crack propagation region was very small. The mechanisms of fatigue-crack initiation are suggested.

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