Surface Characterisation and Fatigue Strength of Corroded Armour Wire

2014 ◽  
Author(s):  
Stig Berge ◽  
Ting Wang ◽  
Nina Langhelle
Keyword(s):  
Fatigue Strength ◽  
Surface Defects ◽  
Sea Water ◽  
Corrosion Damage ◽  
Water Flooding ◽  
Surface Characterisation ◽  
Electron Scanning Microscopy ◽  
Flexible Risers ◽  
The Wire ◽  
Fatigue Notch Factor

Tensile armour wire from two flexible risers was fatigue tested for assessment of SN-curves. Both risers had been subjected to sea water flooding of the annulus for several years. The wire was corroded in the form of pits, however, the cross section was not significantly reduced. Reference wire from the same batches of material that had not been subjected to corrosion was also tested. Testing was carried out in air, to investigate the effect of accumulated corrosion damage in terms of a fatigue notch factor. The fatigue strength of the corroded wire was significantly reduced, corresponding to a fatigue notch factor in the range 1.5–1.7. The wire was examined by optical and by electron scanning microscopy and the surface defects were characterised.

Corrosion fatigue strength of ship structural steel butt welded joints in synthetic sea-water

1999 ◽  
Vol 13 (5) ◽  
pp. 385-391
Author(s):  
Y Kobayashi ◽  
Y Tanaka ◽  
H Goto ◽  
K Matsuoka ◽  
Y Motohashi
Keyword(s):  
Fatigue Strength ◽  
Structural Steel ◽  
Corrosion Fatigue ◽  
Welded Joints ◽  
Sea Water ◽  
Corrosion Fatigue Strength

scholarly journals Affected depth approach to determine the fatigue strength of materials containing surface defects

2018 ◽  
Vol 346 (12) ◽  
pp. 1199-1215
Author(s):  
Anouar Nasr ◽  
Wannes Hassine ◽  
Chokri Bouraoui
Keyword(s):  
Fatigue Strength ◽  
Surface Defects ◽  
Strength Of Materials

Influence of Inner Surface Defects on the Fatigue Strength of Pipe Subjected to Cyclic Internal Pressure

1978 ◽  
Vol 100 (4) ◽  
pp. 360-368
Author(s):  
Y. Yazaki ◽  
S. Hashirizaki ◽  
S. Nishida ◽  
C. Urashima
Keyword(s):  
Fatigue Strength ◽  
Internal Pressure ◽  
Test Specimen ◽  
Surface Defects ◽  
Fatigue Crack Initiation ◽  
Internal Surface ◽  
Fatigue Tests ◽  
Inner Surface ◽  
Surface Notch ◽  
Medium Diameter

Cyclic internal oil pressure fatigue tests were carried out on medium-diameter ERW pipes of API 5LX - X60 in an attempt to determine the influence of surface defects on the fatigue strength. Experimental factors investigated were the depth and location of internal surface notch in relation to the axis of pipe. The specimen was subjected to cyclic internal pressure, the cyclic rate being 0.3–0.5 Hz. During the test, Acoustic Emission (AE) techniques were applied to detect the fatigue crack initiation. Along with the aforementioned fatigue tests, pulsating tension fatigue tests were carried out on specimens with the same surface notches as the cyclic internal pressure fatigue test specimen.

Effects of sea-water flooding of soil on growth of potted Bambusa multiplex (Loureiro) Raeuschel ex Schultes & J. H. Schultes

2014 ◽  
Vol 40 (1) ◽  
pp. 43-48
Author(s):  
Haruna INOUE ◽  
Kenichi NAKAGAWA ◽  
Takeshi TANIGUCHI ◽  
Fukuju YAMAMOTO ◽  
Norikazu YAMANAKA
Keyword(s):  
Sea Water ◽  
Water Flooding

scholarly journals The influence of Kanthal wire surface defects on the formation of Si nanolayer deposited by PVD method

2018 ◽  
Vol 36 (2) ◽  
pp. 264-269 ◽  
Author(s):  
Mieczysław Szczypiński ◽  
Kazimierz Reszka ◽  
Michał M. Szczypiński
Keyword(s):  
Surface Defects ◽  
Ion Beam ◽  
Erosive Wear ◽  
Optical Microscope ◽  
Dark Field ◽  
Expanded Polystyrene ◽  
Depth Of Field ◽  
Wire Surface ◽  
Transmission Microscopy ◽  
The Wire

Abstract The subject of this research is the structure of a Si nanolayer deposited on a FeCrAl wire surface by means of magnetron sputtering method. Si layer was selected as one of possible protections of the wire surface against excessive corrosive-erosive wear. In order to increase the power necessary for the DC discharge of the magnetron with Si cathode, a second magnetron with an aluminum disc as a cathode was used. The wire was attached to a carousel holder to ensure its rotation around the magnetron. The thickness of the deposited layers was about 150 nm. A wire surface examination indicated the presence of defects such as gaps between grains, cavities as well as severely deformed grains of surface layer. The research was conducted on the sample sections which had been prepared by focused ion beam method (FIB). The technique of transmission microscopy, which was used for observation, allowed us to obtain images in bright field (BF), dark field (DF), as well as in high resolution (HREM). The studies were also performed on the wire surface after the cutting process of the expanded polystyrene blocks. A metallographic optical microscope Nikon MA200 with a large depth of field was used for the examination which showed the presence of carbon deposit products. Additionally, a composition microanalysis was carried out along the line within selected areas of samples, with the use of energy dispersive spectroscopy (EDS). A large impact of wire surface defects on Si layer forming was found as well as a high direct homogeneous growth. The examination of the sections indicated the existence of a mechanism of defects sealed by Si layer, where directionality of grains growth in these areas revealed the tendency for vertical location relative to defects surface. Consequently, closed nanopores, i.e. spaces not covered with Si layer, were created. It is a characteristic feature of areas with defects covered with an oxide film created in a natural way.

scholarly journals Defect induced cracking and modeling of fatigue strength for an additively manufactured Ti-6Al-4V alloy in very high cycle fatigue regime

2021 ◽  
Author(s):  
Weiqian Chi ◽  
Wenjing Wang ◽  
Chengqi Sun
Keyword(s):  
Fatigue Strength ◽  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Surface Defects ◽  
Fatigue Crack Initiation ◽  
Projection Area ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Artificial Surface ◽  
Very High

Additively manufactured (AM) alloy usually inevitably contains defects during the manufacturing processor or service process. Defects, as a harmful factor, could significantly reduce the fatigue performance of materials. This paper shows that the location and introduced form of defects play an important role in high cycle and very high cycle fatigue (VHCF) behavior of selective laser melting Ti-6Al-4V alloy. S-N curve descends linearly for internal defects induced failure. While for artificial surface defects induced failure, S-N curve descends at first and then exhibits a plateau region feature. We also observed competition of interior crack initiation with the fine granular area feature in VHCF regime. The paper indicates that only the size or the stress intensity factor range of the defect is not an appropriate parameter describing the effect of defects on the fatigue crack initiation. Finally, the effect of artificial surface defects on high cycle and VHCF strength is modeled, i.e. the fatigue strength   σ, fatigue life  N and defect size area (square root of projection area of defect perpendicular to principal stress direction) is expressed as  σ = CN ( area)  for  N and  σ = CN ( area)  for  N≥N, where  C,  a and  n are constants, N is the number of cycles at the knee point.

scholarly journals Ability of multiaxial fatigue criteria accounting for stress gradient effect for surface defective material

2018 ◽  
Vol 165 ◽  
pp. 22032
Author(s):  
Wichian Niamchaona ◽  
Fabienne Pennec ◽  
Kévin Tihay ◽  
Michel Duchet ◽  
Bastien Weber ◽  
...  
Keyword(s):  
Fatigue Strength ◽  
Surface Defects ◽  
Stress Gradient ◽  
High Stress ◽  
High Strength Steels ◽  
Fatigue Behaviour ◽  
Multiaxial Fatigue ◽  
Integral Approach ◽  
Manufacturing Defects ◽  
Material Fatigue

New high strength steels are widely used nowadays in many industrial areas as in automotive industry. These steels are more resistant and provide higher fatigue limits than latter ones but they are also more sensible to small defects. Natural defects that outcome from metallurgy (as shrinkage, inclusion, void) are not considered in this study. We focus on small manufacturing defects such as cutting edge defects generated by punching or other surface defects due to stamping. These defects are harmful on the material fatigue behaviour due to high stress concentration at defects root. They also generate stress gradient that is beneficial from the fatigue strength point of view. This study focusses on the stress gradient (it does not account for the size effect) from cylindrical defect on specimen edge. Practically a normal stress gradient is added in multiaxial fatigue criteria formulation. Both critical plane approach and integral approach are involved in the present study. This gradient is calculated from stress states at defects root by using FEM. Criteria fatigue function at N cycles is used to assess the material fatigue strength. Obviously multiaxial fatigue criteria accounting for stress gradient give more precise fatigue functions than criteria that do not consider the gradient influence.

The Effect of Prior Surface Roughness on Fatigue Life of Nitrided Specimens

2020 ◽  
Vol 405 ◽  
pp. 271-276
Author(s):  
Marta Kianicová ◽  
Pavel Šandera ◽  
Jana Horníková ◽  
Daniel Kottfer ◽  
Jaroslav Pokluda
Keyword(s):  
Surface Roughness ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Surface Defects ◽  
Low Cycle Fatigue ◽  
High Strength ◽  
Case Hardening ◽  
Hardening Treatment ◽  
Initiation Stage ◽  
Almost All

The effect of surface roughness of virgin specimens (prior roughness) made of low-alloyed high strength steel on their fatigue life after the case-hardening treatment was studied by rotating bending tests of virgin and nitrided samples. In a whole range of S-N curves, the fatigue strength of virgin samples after lathe-turning machining (high roughness) was naturally much higher than that of samples after grinding (low roughness). As expected, the fatigue strength of nitrided specimens was higher than that of virgin samples when averaged through the whole fatigue life range. When distinguishing the rough and smooth nitrided samples, the low-cycle fatigue strength of rough samples revealed to be lower than that of the smooth ones and vice a versa in the high-cycle region. This could be explained by the fact that, in the low cycle region, the cracks in the rough samples nucleated from deep surface defects while, in the smooth specimens, they nucleated from shallow defects (or as fish eyes) which prolonged their initiation stage. Almost all cracks in the high cycle region initiated as fish-eyes but the extent of nitrided layers in the rough specimens was slightly higher than that in the smooth specimens. Therefore, the fish-eye centers were shifted further to the interior of the rough specimens which increased their fatigue life.

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