Short fatigue crack behaviour of LZ50 railway axle steel under multi-axial loading in low-cycle fatigue

The deformation mechanism in reel-lay of corrosive resistance alloy (CRA) clad/lined pipes can facilitate defect tearing and low cycle fatigue crack growth in the girth welds. Pipe-lay after straightening will subject the CRA welds to high cycle fatigue. The permissible seastate for installation will be governed by failure limit states such as local collapse, wrinkling of the liner, fatigue and fracture. By means of a recently completed offshore project in North Sea, this paper discusses seastate optimisation when installing pipelines with CRA girth welds, from a fatigue and fracture perspective. The additional limiting requirement in CRA welds to maintain CRA liner integrity can lead to significant assessment work since all critical welds shall be examined. AUT scanned defect data were utilised to maximise permissible seastates based on fatigue allowance from a fatigue crack growth calculation. An alternative simplified approach to derive the crack growth based on a superposition method is studied. It enables a straightforward real-time prediction of crack growth and has the potential to be used during the offshore campaign to improve the installation flexibility. Post-installation fracture assessment under more critical seastates is examined for CRA partial over-matching welds. A comparison of CDF between conventional ECA procedure and 3D FE is provided.

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Rapid method for low cycle fatigue properties: thickness effect on the fatigue crack initiation life of welded joints

Fatigue & Fracture of Engineering Materials & Structures ◽

10.1111/ffe.12322 ◽

2015 ◽

Vol 38 (12) ◽

pp. 1492-1506 ◽

Cited By ~ 6

Author(s):

J. Raujol-Veillé ◽

D. Thévenet ◽

C. Doudard ◽

S. Calloch ◽

H. Minnebo

Keyword(s):

Fatigue Crack ◽

Crack Initiation ◽

Rapid Method ◽

Welded Joints ◽

Low Cycle Fatigue ◽

Fatigue Crack Initiation ◽

Thickness Effect ◽

Fatigue Properties ◽

Cycle Fatigue ◽

Crack Initiation Life

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LOW CYCLE FATIGUE BEHAVIOR OF Zn-22Al ALLOY IN SUPERPLASTIC REGION AND NON-SUPERPLASTIC REGION

International Journal of Modern Physics B ◽

10.1142/s0217979208050681 ◽

2008 ◽

Vol 22 (31n32) ◽

pp. 5477-5482 ◽

Cited By ~ 1

Author(s):

ATSUMICHI KUSHIBE ◽

TSUTOMU TANAKA ◽

YORINOBU TAKIGAWA ◽

KENJI HIGASHI

Keyword(s):

Fatigue Crack ◽

Crack Propagation ◽

Fatigue Crack Propagation ◽

Low Cycle Fatigue ◽

Fatigue Behavior ◽

Crack Tip ◽

The Other ◽

Al Alloy ◽

Cycle Fatigue ◽

Secondary Cracks

The crack propagation properties for ultrafine-grained Zn -22 wt % Al alloy during low cycle fatigue (LCF) in the superplastic region and the non-superplastic region were investigated and compared with the corresponding results for several other materials. With the Zn - 22 wt % Al alloy, it was possible to conduct LCF tests even at high strain amplitudes of more than ±5%, and the alloy appeared to exhibit a longer LCF lifetime than the other materials examined. The fatigue life is higher in the superplastic region than in the non-superplastic region. The rate of fatigue crack propagation in the superplastic region is lower than that in the other materials in the high J-integral range. In addition, the formation of cavities and crack branching were observed around a crack tip in the supereplastic region. We therefore conclude that the formation of cavities and secondary cracks as a result of the relaxation of stress concentration around the crack tip results in a reduction in the rate of fatigue crack propagation and results in a longer fatigue lifetime.

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