Experimental Study of Fatigue Crack Overload Retardation in X80 Grade Steel

2008 ◽  
Author(s):  
Qingquan Duan ◽  
Hong Zhang ◽  
Feng Yan
Keyword(s):  
Fatigue Crack ◽  
Crack Growth ◽  
Oil And Gas ◽  
Prediction Models ◽  
Pipeline Steel ◽  
Compact Tension ◽  
X80 Pipeline Steel ◽  
Oil And Gas Pipelines ◽  
Crack Retardation ◽  
Grade Steel

The tests of fatigue crack overload retardation were performed to gain a some what deeper understanding of overload retardation. We present an experimental investigation of fatigue crack retardation behavior caused by intermediate single peak tensile overload under constant amplitude cyclic loading. The compact tension (CT) specimens of API grade X80 pipeline steel were used in fatigue test. The results show there was an instant crack extension during overloading for the tested overload ratios. As soon as the overload cycle was removed, instant delay in crack growth occurred. The results should be of interest for fracture mechanics prediction models on fatigue crack growth under variable amplitude loading and overloading effect for oil and gas pipelines.

Applicability of SE(T) and SE(B) Fracture Specimens in Crack Growth Measurements of Pipeline Girth Welds

2012 ◽  
Author(s):  
Leonardo L. S. Mathias ◽  
Gustavo H. B. Donato ◽  
Claudio Ruggieri
Keyword(s):  
Crack Growth ◽  
Oil And Gas ◽  
Pipeline Steel ◽  
High Strength ◽  
Oil And Gas Industry ◽  
Crack Growth Resistance ◽  
X80 Pipeline Steel ◽  
Fixed Amount ◽  
Resistance Curves ◽  
Girth Welds

This work presents an investigation of the ductile tearing properties for a girth weld made of an API 5L X80 pipeline steel using experimentally measured crack growth resistance curves (J-Δa curves). Use of these materials is motivated by the increasing demand in the number of applications for manufacturing high strength pipes for the oil and gas industry including marine applications and steel catenary risers. Testing of the pipeline girth welds utilized side-grooved, clamped SE(T) specimens and 3P bend SE(B) specimens with a weld centerline notch to determine the crack growth resistance curves based upon the unloading compliance (UC) method using a single specimen technique. The shallow-crack SE(B) specimen provides an R-curve which, albeit slightly more conservative, exhibits levels of J-values which are relatively comparable to the levels of J corresponding to the deeply-cracked SE(T) specimen at a fixed amount of crack growth, Δa. This experimental characterization provides additional toughness data which serve to evaluate crack growth resistance properties of pipeline girth welds using SE(T) and SE(B) specimens with weld centerline cracks.

Detection of Fatigue Crack Growth in Aircraft Landing Gear, 4 Point Bend Test Specimens

2005 ◽  
Vol 293-294 ◽  
pp. 193-200 ◽  
Author(s):  
M.G. Baxter ◽  
Rhys Pullin ◽  
Karen M. Holford ◽  
S.L. Evans
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Compact Tension ◽  
Small Radius ◽  
Time Of Arrival ◽  
Aircraft Landing ◽  
Invaluable Tool ◽  
Point Bend ◽  
Grade Steel

This investigation considers the identification of fatigue crack growth in aerospace grade steel using Acoustic Emission (AE) techniques. Four specimens with small radius crack initiation sites were investigated under four-point bending (SENB4). A linear array of 4 resonant AE sensors was utilised to locate the crack growth. Detection and location of fatigue crack growth in aerospace grade steel SENB4 specimens using appropriate AE techniques was successful. Time of arrival (TOA) linear location has provided an invaluable tool for separating AE signals arising from fatigue crack growth from the notch from those emanating from the loading points. Analysis of the AE feature data from the notch has allowed initial categorisation of AE from fatigue crack growth. AE data from this research was found to correspond with that reported in previous studies [1] examining Compact Tension (CT) specimens.

Fracture Resistance and Fatigue Crack Growth of X80 Pipeline Steel in Gaseous Hydrogen

2011 ◽  
Author(s):  
Chris San Marchi ◽  
Brian P. Somerday ◽  
Kevin A. Nibur ◽  
Douglas G. Stalheim ◽  
Todd Boggess ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fracture Resistance ◽  
Pipeline Steel ◽  
Low Cost ◽  
Petroleum Products ◽  
Gaseous Hydrogen ◽  
X80 Pipeline Steel ◽  
Crack Growth Rates

Gaseous hydrogen is a convenient medium to store and transport energy. As existing petroleum-based platforms are electrified, such as with the growth of fuel cell systems, hydrogen is becoming an attractive fuel which must be distributed, stored and dispensed. Hydrogen is used extensively in refining of petroleum products, and often distributed by pipeline. However, there remains a need to quantify the mechanical properties of low-cost steels in gaseous hydrogen and to relate the measured performance to the variety of microstructures that characterize steels. This study is part of a larger effort to characterize a broad range of steels manufactured for pipelines and to measure their fracture and fatigue resistance in gaseous hydrogen. The fracture resistance and fatigue crack growth rates of two microstructural variations of X80 pipeline steel were measured in gaseous hydrogen at pressure of 21 MPa. The performance of these steels was found to be similar to the performance of other ferritic steels that are currently used to distribute gaseous hydrogen.

Corrosion-Fatigue Crack Growth in Age-Hardened Al Alloys: Examples of Failures and Explanations for Fractographic Observations

2014 ◽  
Vol 891-892 ◽  
pp. 248-253 ◽  
Author(s):  
Rohan Byrnes ◽  
Noel Goldsmith ◽  
Mark Knop ◽  
Stan Lynch
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Compact Tension ◽  
Al Alloys ◽  
Corrosion Fatigue Crack ◽  
Crack Tips ◽  
Corrosion Fatigue Crack Growth ◽  
Additional Support

The characteristics of corrosion-fatigue in age-hardened Al alloys, e.g. brittle striations on cleavage-like facets, are described, with reference to two examples of component failure. Mechanisms of corrosion fatigue (and explanations for fracture-surface features) are then reviewed. New observations of corrosion-fatigue crack growth for 7050-T7451 alloy compact-tension specimens tested in aqueous environments using a constant (intermediate) ΔK value but different cycle frequencies are then described and discussed. These observations provide additional support for a hydrogen-embrittlement process involving adsorption-induced dislocation-emission from crack tips.

Comparison of Fatigue Crack Growth Rates Between Different Specimen Geometries

2021 ◽  
Author(s):  
Yan-Hui Zhang ◽  
Matthew Doré
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Literature Review ◽  
Crack Growth ◽  
Compact Tension ◽  
Specimen Geometry ◽  
Single Edge ◽  
Single Edge Notch ◽  
Advantages And Disadvantages ◽  
Edge Notch

Abstract Most engineering components are subjected to cyclic loading in service and design against fatigue failure is often a key consideration in design. For fracture mechanics fatigue analysis, fatigue crack growth (FCG) tests are often required to determine the relevant Paris power law parameters for the material under the environment concerned. Standards allow use of different specimen geometries for FCG tests such as compact tension (CT), centre crack tension (CCT), single edge notch bend (SENB) and single edge notch tension (SENT). However, when selecting specimen geometry for fatigue crack growth rate (FCGR) testing, there is often doubt about which specimen geometry is more appropriate and whether they give similar FCGR. There is limited work to compare the FCGR between different specimen geometries. This paper first briefly introduces the guidance on FCG test specimen geometries in standards and compares the advantages and disadvantages of these specimen geometries. A comprehensive literature review is carried out to compare the FCGR data between different specimen geometries. FCGR tests are conducted on SENB, SENT and CCT specimens of C-Mn steel to investigate any effects of specimen symmetry/asymmetry and crack constraint on FCGR. Based on the literature review and test data, it is concluded that FCGR is independent of the specimen geometries examined.

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